View Full Version : PCARS- Physics Collection/Information to car releases by Casey

Thomas Sikora
04-03-2016, 17:21
The collection of current Cars of DLC releases posted by Casey Ringley

The Physics of US Race Car Pack


The Physics of StanceWorks Pack


The Physics of Aston Martin expansion


The Physics of Renault Sport Car Pack


The Physics of Japanese Cars Expansion


The Physics of Classic Lotus Expansion


The Physics of Old vs. New


The Physics of Audi-Ruapuna


The Physics of Racing Icons


Thomas Sikora
04-03-2016, 17:22
The Physics of StanceWorks Pack

Ford Falcon FG V8 Supercar

Super fun car. It's slightly heavier than a GT3 but with less tire, less aero, and +150hp. Vital stats are 1400kg & 635hp. Weight distribution is limited by the rules at max 46.5% rear but is nicely adjustable up to that limit to tweak handling balance.

Rear end is a spool axle so out of the corner it has great grip right up until you spin both tires and then doesn't have much at all. This kind of arrangement prefers a different driving style than some of you may be used to; there is more performance to be had by squaring off corners somewhat and using the power to accelerate out earlier. Sacrifice apex speed a bit for the coming straight.

Gearbox is an Albins ST6 6-speed sequential with a fixed set of ratios (cost reduction by the series) and a few drop gear options which are mandated by track being run. Longest one has the car topping out at just under 300km/h. Suspension is a simple double wishbone setup all around and points were available in the 3D reference for us to use on the game physics model.

The soft tires (yellow sidewall) are really very soft, and drop off extremely quickly. They tend to be a good 2-3 sec off brand new pace after only 15-20 mins. The hard tires last a whole fuel stint and lose a second or so by the end. Softs are 1 to 1.5 sec a lap quicker then the hards when new at a track like Ruapuna (this car is awesome at Ruapuna!), but there is a cross over point in races so the hards might win out on a longer stint if fuel isn't required. The claim from Dunlop is that they wear out in about 80km, which is roughly half a tank of fuel.

Anti-roll bars are adjustable in cockpit and it is a very important thing to tweak as the fuel burns off and tires wear down. The car changes balance a lot over a full-tank run and one click on the bars here and there can make a huge difference.

Motion Ratios: 0.79 / 0.72
Damper Transition, front: 60mm/s
Damper Transition, rear: 60mm/s
Unsprung mass: 50 / 55kg


Let’s talk about the elephant in the room first. :) This car is VERY difficult to drive and it was quite a cool challenge for us to model something so extreme in the game. Mad Mike and his team were fantastic is providing us the info needed to be sure we were getting an accurate representation done (and weren’t afraid to admit that the real thing is totally insane and difficult to drive). Some details about each of the sub-systems for it below.

tl;dr - Don’t think about using full throttle on this car, at least not until you have a good amount of practice.

The engine is a custom Mazda R26B with twin Garrett turbos. The R26B alone is good for nearly 700hp; default setup of 12psi (low) boost pushes it further to 1050hp. Rev limit is 11250rpm and that setting has you over 1000hp from 8000-11000rpm. Cranking it up to a high boost setting of 19psi gets you over 1250hp. We’re all fairly confident that matches the real car, but it’s difficult to say with 100% certainty as the real thing breaks dynos when they pushed it that far. Total madness. Power goes to the rear through a Holinger 6-speed sequential with a wide selection of ratios and drop gears and a 3.44:1 1-way locker at the rear. Haven't made the default setup a full locker, but more like a typical circuit racing diff with light power locking and more on the coast side. It can feel quite brutal trying to manage that much power when both wheels spin up so quickly. Good for initiating a drift, but not an easy way to learn the car.

Car weight is 2700lb per the FormulaD tire size-weight rule and there is little aero to speak of; just some very slight downforce from the rear spoiler to help stabilize things when sliding. The base car weighs much less than that 2700, so it is ballasted to 52.7% rear weight. Suspension geometry is all custom and based on a number of measurements I was able to get at the Orlando round. Steering geometry is interesting with zero caster, zero trail, and only a small amount of kingpin inclination. All about keeping the design simple for steering angle up to 78 degrees with minimal weight jacking and very basic feedback to try and keep the wheels pointed in the direction of your slide. It works quite well.

Suspension setup is very similar to what you'd find on a typical circuit racer. Wheel rates are kept quite even front to rear with no crazy toe or camber tricks, all with the intent to keep it predictable and balanced. Contrary to popular belief, pro-level drifting does NOT award you for using unorthodox and ‘bad’ car setup to make the car slide. The same rules as circuit racing, for the most part, apply.

New tires for it (Nitto NT05) are a modified version of our Nitto NT01 road tire with better behavior ‘post-peak’ to aid control when in a big slide. It works on some ideas which became apparent to our tire guru after getting to do some ride-alongs with Formula D drivers. Basically it adds lateral grip when sliding as a result of the tire surface turning into a gooey layer with slower response and balances with how it fades away from heat buildup.

Overall, this car is way beyond a handful. 1000+hp in an MX-5 takes a very light touch to manage and it is very difficult to do anything but slide around and spin in circles while trying to get used to it. I'd highly recommend practicing with the turbos essentially taken off the car (wastegate pressure=0) and building up from there. With no boost and the smallest air restrictor it can still make 520hp. That is plenty for an MX-5 to still get in lots of trouble. It's even pretty good fun to race around at that lowest power setting.

Motion Ratios: 0.66 / 0.76
Damper Transition, front: 51 / 75mm/s
Damper Transition, rear: 51 / 75mm/s
Unsprung mass: 39 / 41kg


KTM gave us a good amount of info and the most of the rest was easy to find on the interwebs.

It makes about 200kg downforce @ 200km/h. Pretty good for something that only weighs 790kg, but man(!) does it cost a lot in drag with the bodywork design they've used. It has 300hp, but is drag-limited to only 144mph; the BAC Mono, with similar power, can pull 170mph easily. That works out to more drag than the Formula Renault 3.5 needs to make 3x the downforce. Not the most efficient thing.

Engine is almost straight out of the A1 quattro with more boost to get it up to 300hp. Rev limit stops you at 7200rpm, but it's best to shift well before then. Dashboard display puts you in the redline at 6500rpm, and that's good shifting advice as power tails off above that rpm. Gearbox is also a variant of the original Audi 6-speed manual.

Suspension geometry direct is from the CAD. Nice, clean design. Simple double wishbones with just enough anti-dive/squat to let it run softer springs but not so much that it hurts the handling in mixed situations. There was also enough detail in the CAD to work out anti-roll bar wheel rates. Kinda neat. Default springs are standard from the X-Bow R and dampers tuned for typical circuit driving. Only unusual thing on the suspension is that they set up the car with some very long, progressive bump stops at the front. It gets into them at about 60mm ride height (from static of 100mm).

Set it to use the same tires as the Ariel Atoms. This whole bunch with the KTM, Caterham, Atom 300, and BAC Mono make a nice little group.

It's great fun to drive, supple and forgiving enough to let you use the weight transfer to your advantage and adjust the attitude of the car, but not so soft that it feels numb and slow to respond. Nice power to weight ratio, manual gearbox, and intense no windscreen open cockpit driving experience. Despite the low top speeds, I'm seeing times around 7:45 at the Ring and it could go faster.

Motion Ratios: 0.87 / 0.69
Damper Transition, front: 50 / 80mm/s
Damper Transition, rear: 30 / 80mm/s
Unsprung mass: 35 / 40kg

BMW 1-Series M-Coupé Stanceworks Edition

Here we took the modern time attack approach to stripping out the base car and doing mild modifications which all add up to a great track performance car. Engine is the same, but cranked up the turbo for 470hp and added an overboost feature when you go full throttle. It'll let you have 8s of 0.25bar extra boost and then 30s cooldown before firing again. That pushes it up to around 510hp. Gearbox is unchanged from the standard 1M. (Full disclosure: We missed that the 3D model had been changed to show paddle shifters even though it wasn’t in the plan to change the physics model over to a paddle shift sequential. Ignore the paddles for now and treat it like a normal H-pattern gearbox. We’ll get a full sequential installed on the car in the next update.)

Racing brakes and aero package are similar to the M3 GT4; suspension stiffness ranges from above average sports car to GT4 level and used the copy of Ohlins DFV dampers that have worked well on a number of other road cars recently. Set it to use that new Nitto NT05 tire by default. I like what this new tire is doing a lot; might be just slightly over-gripped for what it is, but not by a lot and the way it does post-peak handling feels super stable and fun.

Really fun drive and looks to be a good match for the Scion FR-S Rocket Bunny.

Motion Ratios: 0.96 / 0.57
Damper Transition, front: 51 / 75mm/s
Damper Transition, rear: 51 / 75mm/s
Unsprung mass: 58 / 66kg

BMW 2002 Stanceworks Edition

For this car, we decided to take the approach of tuning it up as if it were to race in Group 2 back in the 70s. The engine is swapped out to 2.0L M12/6 Formula 2 engine with 275hp @ 8500rpm. This was a common swap back in the day as a much easier and more reliable method of adding 100hp over the stock turbo unit. Those hadn’t developed quite as much as now where a simple ECU flash for more boost nets you easy power. Feels like a really good match for this car and does sound pretty damn cool up at 8k. Gearbox is the standard Getrag. Aero model adjusted slightly to represent the front air dam to reduce front end lift for a better balance. Suspension is lowered a bit and with a wider range of tuning to be had.

The tires we have it use are designed to be period correct, so it will be a match for (or slightly better than) the 300SEL at most tracks.

Motion Ratios: 0.95 / 1.0
Damper Transition, front: 80mm/s
Damper Transition, rear: 80mm/s
Unsprung mass: 39 / 41kg

Thomas Sikora
04-03-2016, 17:22
The Physics of Aston Martin expansion

Hands up all who forgot this pack was hitting the street today. (raises hand)

Four new cars this month, covering a wide range of history. Here are a few notes on what we found during the physics development.

Aston Martin DBR1: Working on these very old, very rare cars is always a fun experiment in research. A book by Anthony Pritchard on Aston Martin’s post-war cars proved incredibly useful in learning about the development and history of this Le Mans winner. We were able to find decent data for the engine and (terrible*) Dave Brown CG537 gearbox. The 2922cc straight-6 is good for over 250hp at 6000rpm, which isn’t half bad for 1959 and is really great for a car that weighs less than 900kg. Gear ratios are very close between 4th and 5th, I think to keep it near the top of the power band during the shift on Mulsanne alone. Suspension is trailing link front and de Dion rear. The trailing link front gives no recovery of camber loss in roll and also induces a fair amount of bump steer because the motion of linkages is in different directions. Very different front end to all our other cars; feels weird and definitely comes across as old fashioned when you drive. Could also be that a full fuel tank hangs 150kg of liquid way out behind the rear axle! It definitely changes balance by more than a little as the fuel burns off.

*If Stirling Moss is on record complaining about it constantly sticking in gear and being very difficult to downshift, you know it's bad. We’ve represented this in game by increasing in each gear the damage acquired from a bad shift. Take care of it if you are going for a long run or it might become increasingly difficult to get a working gear.

A new tire is available for use on this car and the Mercedes 300SL. There would have been a ton of tire development from 1952 to 1959, but letting them use the same rubber helps equalize the two (a bit) so matchups could be done at the right tracks with the right drivers. Should be fun stuff.

Motion ratio = 1.0 all around (torsion bars on the trailing links. Using wheel rate keeps it simple)
Damper transition speed = 70mm/s all around

Aston Martin DBR1-2 LMP1: 50 year after the DBR1, the folks at AMR decided to build a car to celebrate their win and the DBR1-2 LMP1 was the result. What started life as a fairly traditional LMP1 chassis took advantage of a rule which allowed use of a ‘production’ GT1 engine with a larger air restrictor to compensate for the weight disadvantage. And a very impressive engine they did use. It was based on a unit from the DBR9 GT1 car but with a restrictor 15% larger, which meant it was good for 670hp or more in race spec. By our usual calculations, this unit unrestricted would be good for over 960hp! All that power means a medium-high downforce aero package made sense to use even at Le Mans; something which hasn't really been practical since 2009 as restrictor and boost reductions cut power quite a lot. You can run downforce levels in the middle and still pull near 340kph in a draft while feeling very nice and stable through the Porsche Curves. The default setup is good for over 4000lbf of downforce at 200mph. Impressive stuff. Rest of the car is pretty standard LMP1, but man that engine...Overall performance is very similar to the Audi R18 TDI.

Motion ratio = 1.0 all around
Damper transition speed, bump/rebound (mm/s) = 30/60 front, 40/80 rear

Aston Martin Vantage GTE: A lot could come from the V12 GT3 version as they aren't hugely different under the skin apart from the drivetrain differences. The 4.5L V8 is quite evolved over the road model’s 4.7L and would be good for 620hp unrestricted. It is also mounted much lower and further back than the V12, giving a weight distribution sitting right around the ideal 50:50. ACO balance of performance has it breathing through two 29.1mm restrictors which cut it down to about 450hp. It has run anywhere from 2x28.3mm to 2x29.4mm in the last couple of years, so we entered that as the range of adjustment a player can fiddle with. End result is output from 435-460hp. Surprisingly low for a car of this class, but it finds speed in other ways by being much lighter, more fuel efficient, and having a very efficient aero package. Low drag setup is good for 290kph and just under 14 laps at Le Mans on a 95L fuel tank - all consistent with data from this year's race - and lower top speeds around 255 and 240 at Spa and Silverstone, respectively, as you put downforce on. Good car to drive. Feels much more composed than the GT3 version thanks to being 80kg lighter with the smaller engine mounted so much lower in the car. Makes a nice contrast in that it is down maybe 70hp but overall is faster around nearly every track.

Motion ratio = 0.71 front, 0.77 rear
Damper transition speed, bump/rebound (mm/s) = 30/60 front, 50/95 rear

Mercedes 300SL W194: Engine is strong from 4000-6000rpm, peaking at 180hp near 5200rpm. Quite impressive for 1952. Rest of the car, maybe not so much. Very low drag bodywork, but that comes with a fair amount of aero lift. Like the DBR1, there is a big fuel tank slung way out back, so handling balance changes dramatically over the course of a fuel stint. Weight distribution changes by something like 10% rear to front as that burns off. Huge change!

Suspension design is very old fashioned. Zero caster, camber or steer axis inclination at the front means steering often feels quite vague, and the swing axle rear is responsible for some spooky handling. It combines the fun of very high camber change with a very high rear roll center. Not exactly a recipe for the most stable rear end. The designer made lots of notes on this and the very late prototype W194/11 was switched over to a low pivot swing axle which, while still suffering the extreme camber change, at least brings the roll center down and improves rear stability. Same idea works amazingly well in our model, and it's tempting to use that setup, even if not strictly accurate. Shame it never raced as they shifted focus to F1; the notes out there on W194/11 make it sound quite impressive and it probably would have been a strong contender for a second Le Mans win. 90kg lighter than before, 35hp more from direct fuel injection, less aero drag and the improved rear suspension design. Hard to argue against the success they had in the W196 F1 car though.

Motion ratio = 0.59 front, 0.72 rear spring, 0.55 rear damper
Damper transition speed = 150mm/s all around

Thomas Sikora
04-03-2016, 17:22
The Physics of Renault Sport Car Pack

Personally, this pack was a fantastic surprise. I had high hopes for the Alpine A442B but didn't expect the others to all turn out as such unique and enjoyable drives.

Renault Mégane Trophy V6

This car is so much fun; what a surprise!!! Bear in mind that it is Mégane in name only. Suspension geometry was mostly present in the CAD files we used for modeling reference and provided a good start. It uses your standard double wishbones front and rear with nothing too strange or clever in the design; it makes for very predictable setup and handling. The engine is a Cosworth-tuned 3.5L Nissan V6 good for 425hp unrestricted and will run up to 8250rpm. You have air restrictor options to run it down to 330hp as they did early in its Megane Trophy life. Idle is strangely high at 2150rpm, but it doesn't matter much. Gearbox is a Sadev SL90 sequential with a ton of ratio options and flat shifting. Aero package is not amazing, but pretty good for a car with this body style that only weighs 1000kg.

Calling it a touring car is quite a stretch when it's a mid-engine silhouette built around a spaceframe chassis with very-much-race-spec double wishbone suspension front and rear. Not even remotely like the road car; more like a cousin of DTM. It has a slight better power to weight ratio than a GT3, perfectly balanced chassis and good brakes, yet tires that are much narrower than comparable GT cars. (only 21cm wide fronts!) You get to do a lot of steering on throttle with this and top speed is low enough that drafting is important on most long straights. Runs mid 2:20s at Spa, so a fast driver in this could compete with an average driver in a GT3. Great racing against the AI.

Motion Ratio:
Front= 0.87
Rear= 0.75

Damper Transitions: 50mm/s bump, 80mm/s rebound (front and rear)

Renault Mégane RS275 Trophy-R

Now this is more like what we think of when we think Mégane. :) I was a bit skeptical at first that this car would really be a major, or even noticeable, change from the RS265 we already have in game. There’s nothing too fancy here. It's the 265 with a bit more power, a bit less weight and different suspension tuning ranges. Dampers are matched to some Ohlins DFV shocks that should be the same as what's used on this car. Default setup for them is as recommended by the RenaultSport engineers. Numbers seem to make sense and it works pretty well.

All those small changes come together to make something really great. Definitely a lot faster than the RS265 Mégane! Seeing close to 8:05 at The Ring here while taking silly risks or honing the lap too much. Plenty more speed on the table. Still, that will put it on par with the new Mustang and some other cars which are much more powerful. Fun little thing.

Motion Ratio:
Front= 0.94
Rear= 0.86

Damper Transitions: 51mm/s bump, 75mm/s rebound (front and rear)

Formula Renault 3.5

This was a very cool little project as we ramp up to Indycar stuff. The FR3.5 chassis is made by Dallara and has an underbody with full tunnels which aren’t all that different from the DW12. We got some very good data for what this kind of underbody does over a wide range of ride heights and matched the game model to it all *very* closely. The changes in downforce level and center of pressure balance are much larger than you might expect. Getting your ride height wrong by 10mm can mean a loss of 10% of total downforce and a shift in balance that is enough to push it from understeer to oversteer. Fascinating stuff to work with real data like this. In general, it wants to be low - very low - and you tend to run it very very stiff to get that aero working.

The aero package also includes DRS, but it works in a very different way to what most of you are probably used to. Rather than reduce the angle of the second wing element, it flips UP a small flap at the trailing edge of the main element. This closes the slot gap and causes flow separation on the suction surfaces of the wing, stalling it out and reducing both downforce and drag. Similar in theory to how the old F-duct worked on certain F1 cars back before they added the DRS systems we now know.

Suspension geometry is from CAD. We did have to make one compromise in that the real car uses a monoshock front end: essentially one spring to hold the car up plus an anti-roll bar for lateral movements. Our current chassis solver doesn’t handle this elegantly. It works perfectly right up until it doesn’t and the car explodes off into space. :) As a compromise we’ve matched a traditional configuration of four ride springs + anti-roll bars to the standard setup on the real FR3.5 as closely as possible.

Engine is yet another 4.0L flat-plane V8 based on a Nissan block good for 530hp @ 9200rpm; this one being the Gibson ZRS03. Gearbox is the typical 6-speed sequential with flat shifting. In this case the same Ricardo unit as used in Indy Lights...somewhat interesting. Overall it's like driving the Indycar with 60% of the power and downforce, which is actually a lot of fun and a good challenge. Takes a good three laps to get the tires up to full temperature from cold as it doesn't work them very hard by being so light.

Top speed at Monza approaches 298-300km/h with another 10-15 added via DRS. Lap times are close to real: 1:34 Monza, 1:41 Nurburgring GP, 1:59 Spa. Pretty quick car for the specs!

Motion Ratio:
Front= 1.0
Rear= 1.0

Damper Transitions: 50mm/s bump, 80mm/s rebound (front and rear)

Renault R.S.01

Engine is a Nissan VR38DETT almost straight out of the Nissan GT-R GT3. Good for 550hp @ 6800rpm. Occasionally they run slightly lower boost for 500hp; not sure exactly how they decide. Power to the rear through a 7-speed Sadev sequential with flat shifting. Smart design using the 7 gears. It means there is no need to ever think about changing ratios for a given track; there is always one that will have you in the power band for each turn and an appropriate top speed. Suspension geometry is all from CAD points. Nothing to fancy there, but it is kinda nice how they've designed the rocker arms to give a near perfectly linear 1:1 motion ratio at front and rear. There was also enough detail in the CAD to estimate wheel rates for the anti-roll bars, which is cool. We almost never get that kind of data as pure wheel rate numbers. No official aero numbers yet, but vague PR-type numbers are floating around the web. Official website claims 1.7 metric tons of DF @ 186mph. This is very hard to believe as it would mean a lift:drag efficiency over 4.0 - better than some LMP cars. Other reviews are stating 1200kgf @ 190mph. This makes much more sense. It's essentially a GT3 car with LMP2 underbody venturi tunnels. If I put an LMP2-style underbody/diffuser on one of our GT3 models, it matches up to that number very closely and performance looks about correct. Tires are Michelin's standard GT3 set. No mention of what type of rubber compound, but I'd have to guess it's one of the harder versions. The WSR series seems to stress tire management with teams only getting 2 or 3 sets per weekend. Making them last takes some effort, too, because with more power, no driver aids, and much more downforce than a GT3 car, this thing really stresses the tires. It is very easy to overheat and cook them. It is very very fast; just off DTM pace, really. Fast drivers will be in the 2:11s at Spa, which could conceivably match up with an average driver in LMP2. Impressive race machine here.

Note that we did deviate from the standard RS01 suspension setup slightly for defaults. Numbers from RS indicate 900lb/in front springs and 1200lb/in rears with very low ride heights of 42mm front / 55mm rear. That works quite well at a fast, smooth track like Spa, but is a bit harsh for a lot of others like Oulton Park. Our default raises and softens it a bit to work better all around, but you will find some more pace at the fast tracks with the numbers above.

Motion Ratio:
Front= 1.0
Rear= 1.0

Damper Transitions: 50mm/s bump, 80mm/s rebound (front and rear)

Renault Alpine A442B

Interesting car to drive! This was right at the start of the turbo era and it comes across in the engine response and how many things are compromised for the sake of getting the power numbers. Engine is a precursor to the Renault V6 from our Lotus 98T but in 2L form and with a single, larger turbo. There is a good bit of lag and it takes about 100m out of slow corners before it builds up to the target 0.9bar boost. A N/A version of the engine was good for peak power around 12000rpm, but that rpm came well down with the changes to turbocharge it. Peak is around 540hp at 10,500 but it was geared to hit top speed around 10,200 and in 1978 they would only run it to 9,200 or 9,500 during the race to try and save the pistons. The gearing used meant that 9500 was still good for over 340kmh. Not too shabby. Has a very nice power band despite the lag issues; it will pull nicely from 6800 to 10200 without any unpleasant spikes or dead spots in the power curve. There is a ton of rubber at the rear too - 80cm total tread width on a car that is only 180cm wide! - so power oversteer isn't really a worry. Handling, in general, was something of a tertiary concern behind top speed and stability at top speed.

Weight distribution was somewhere north of 70% rear and what downforce it did make was very heavily biased to the back with the rear wing slung 1.3m behind the rear axle. No firm aero numbers available for the Alpine, but the Porsche 936 is similar enough and used it's 500lb downforce / 375lb drag numbers were used as a baseline. The car is so rear-biased that it will even pick up the front wheels for an instant on hard launches. Makes it very much a straight line car. No bad in corners, but being fastest in the tight portions of a track were never the intention.

Performance ends up strangely close to a modern GT3 car; somewhat faster than GT3 at tracks where top speed is important and just a bit slower at tracks where it isn't. Don't expect to hustle it through turns and it's a lot of fun. Runs around a 7:15 at Nurburging, 1:27s at Brands Hatch, and 3:55 at modern Le Mans.

There is a series of books (http://www.amazon.com/Alpine-Renault-Sports-Prototypes-1973/dp/184584226X/ref=sr_1_2?ie=UTF8&qid=1450805448&sr=8-2&keywords=renault+%26+alpine) out there which I highly recommend documenting the path of Renault & Alpine from the A110 through the A442B Le Mans win and on to the F1 cars. Such a fascinating era as turbos started making waves in the racing scene and the books have amazing detail of the testing and design, trials and successes and failures that made it all happen. Well worth space on the shelf.

Motion Ratio:
Front= 0.78
Rear= 0.87

Damper Transitions: 30mm/s bump, 60mm/s rebound (front and rear)

Radical RXC Turbo

Sweet little car.

Engine is a tuned 3.5L V6 Ford Ecoboost. Really good engine to drive with a fat torque curve peaking at 500lb-ft @ 3600rpm and then a very smooth drop to the power peak for 454hp @ 6100rpm. They have a new version - RXC Turbo 500 - boosted up for 537hp but tuned so it loses all that mid-range torque. Tried that boost curve on our model; Don't like it. The fatter power band is so much nicer to drive around a track. Power is to the rear through a Quaife QBE81G 7-speed sequential. It has three optional gear ratio sets and three optional final drive ratios; all available to mix & match in setup.

Downforce is claimed at 900kgf at the max speed of 185mph. That works out to a lift:drag efficiency of 2.0, which is perfectly plausible for a car like this. Experimenting a bit on this car with a much more aggressive model w.r.t. sensitivity to ride height and rake. It's a flat-bottom car with no front diffuser, and things like this tend to be very sensitive with a large penalty for getting either end too low to the ground. Airflow becomes choked and downforce vanishes in an instant. I think it is working well. Setup is quite important and there is a definite sweet spot where it likes to run. Slamming it down all the way to minimum ride height puts you outside of that window unless the springs are run so stiff as to be very unpleasant over bumps.

There were enough points our the scanned model and good CAD views on the web to draw up suspension geometry and work out motion ratios. Super-basic double wishbones; nothing special at all. The standard RXC I looked at had 50N/mm springs all around. Probably nice on the street but too soft on track. Ours defaults to 80N/mm instead.

Thing is fast! Don't have a ton of laps on it yet, but it's just about equal with the McLaren P1 with a much nicer balance between handling and power.

Motion Ratio:
Front= 0.90
Rear= 0.88

Damper Transitions: 30mm/s bump, 60mm/s rebound (front and rear)

Thomas Sikora
04-03-2016, 17:22
The Physics of Japanese Cars Expansion

Time is almost here for the next bunch of cars to go live! Some notes on their physics model development to keep you busy in the meantime...

Mitsubishi Lancer Evo VI T.M.E. - Cool little variant of the best looking Evo here. Done to celebrate WRC champ Tommi Makinen and built in something like a tarmac rally spec for street use. The 2.0L 4G63T engine put out a nice 276hp with very little lag and smooth power delivery through the 5-speed manual. Much nicer gear spacing on this one than the later Evo X FQ400! You won’t hate at all that shift from 4th to 5th like on that other one. Sadly, a lot of the detailed technical info on what exactly went into making a T.M.E. seems to have been lost to time. Good news is it’s a popular car (very popular) to tune, so I put in a range of suspension tune options that spans most aftermarket stuff I could find and stuck it in the middle by default. Seems to have worked pretty well. Everything about this car is nicer than the FQ400, IMO. Gear spacing is better, smaller turbo spins up better, lower weight feels (so much!) better. All around a great little car for turning laps.

Mitsubishi Lancer Evo IX FQ360 - F$%&^g quick, right? This car is actually quite closely related to the Evo VI TME above. The engine is still a 2.0L turbo and added MIVEC variable timing stuff plus 0.4bar more boost for a total of 360hp. We were able to pull a lot of other numbers from workshop manuals for gear ratios, front suspension geometry, etc. plus things like spring rates and damper dyno data from owner forums. Fun drive, splitting the difference between the Evo VI and Evo X FQ400. It’s a bit heavier than the VI, but still handles very well and the extra 80hp makes it about 20s faster around The Ring. Roughly the same pace as the FQ400, but with less turbo lag and a much better balance as that thing has another 160kg of fat added on.

Toyota GT86 / Toyota 86 / Scion FR-S - Gotta love these popular tuner cars. People tear them apart and measure every last thing we need to know to produce an accurate simulation model. Found useful shock dynos, ARB wheel rates, and spring rate info for stock and typical aftermarket, track setups. Put everything to stock by default; middle of the range on springs and dampers will match some popular Ohlins DFV units and typical track day springs/ARBs. Our reference car was laser scanned and could be used to get a good model of the rear suspension geometry. The FA20 is a nice engine, but there is a huge hole in the torque curve between 3500-5000rpm on all dyno plots; keep it between 5-7k for most fun. Added two popular final drive swaps as an option. Either one could be useful depending on the track and how you want to drive it. It really is as good to throw around a track as all the reviewers say. Just chuck it into every corner, floor the throttle and hold some angle through the apex. Awesome fun. I expect many of you will have some real world experience in the car to compare against, so it will be fun to see how you think it matches up.

Toyota GT86 Rocket Bunny - In playing around with the Rocket Bunny bodykit, we thought it would be cool to see how the package worked as a GT4 car. Long story short, it’s great! We cut about 100kg of weight from stripping the interior, etc; figured the body kit could change the aero from 200lbf lift to 90lb downforce; put on our standard GT4 tires with 23/64-R18 and 25/65-R18 sizing (one size smaller than the Ginetta G55 GT4); boosted the engine with a Cosworth supercharger for 335hp; racing brakes similar to the G55 GT4, and some very basic suspension tuning to put it at a similar stiffness to other cars in the class. Runs right on the same pace as the others but in a very fun, slidey kind of way since the handling is so nimble and neutral. Might be the fastest of the bunch at many tracks in qualifying, but it can wear through the tires faster since you are pushing so much harder in the corners to maintain speed. It is a lot of fun.

Scion FR-S Rocket Bunny - For this one, we took the approach of a more powerful street build that could be used for track days, some light drifting and showing off. We wanted more power than what the Cosworth supercharger alone and ended up using a twincharger type of system to boost the engine, which is kinda cool since we haven't done that on any other cars yet. Stage 1 is the supercharger, creating about 1.1bar boost and 150hp. Then for stage 2 there is a turbo added on top to bring it up to full boost and 500hp. The combination is much more driveable than some big turbo setups we tried where the overwhelming impression was just one of turbo lag. Having that supercharger in there first does a nice job at helping keep exhaust mass flow high for the turbo to work well.

500hp is a real handful in something so small and it does have some pretty good drift potential when you drop the tire pressures very low. That aspect will improve greatly in the near future with some STM R&D work AJ has underway, but it's surprisingly good right now...if a bit too difficult to transition out of a big angle. We might also have some other interesting cars coming which will be even better-matched for showing how tire rubber behaves in the transition from traditional slip angle vs. force model to a gooey/slidey rip grip model at the extremes of temperature and abuse.

Slightly modified the suspension geometry for this version of the car so it can be set with very low front steer axis inclination and caster angle, as I've noticed is the trend is pro drift builds lately. It helps in that the huge steering angles don't cause extreme jacking motion which destabilizes the car, but can soften steering feel through the FFB at very low caster...it's a trade off.

Standard tires for this one are Nitto NT01 in sizes 235/35-19 front, 275/35-19 rear. Good for 7:40s at the Ring if you avoid going sideways for the whole lap.

Toyota TS040 - For me, this car is the highlight of the packages. Just love working out the details for these hybrid LMP1s. Manufacturers never give out detailed technical info for current race cars (and rightfully so), so we have to go into full forensic science to sort out the details of how it works. The car is a hoot to drive. Where it’s main opposition, the R18 e-tron, is only mildly hybridized in the 2MJ class and drives mostly like a normal car, this thing has a Mario Kart Golden Mushroom on it. It is the fastest car with a low top speed that you'll ever drive. The thing with these hybrids is that getting the fastest lap is all about acceleration, not a top speed advantage. It's a strange feeling; when going for fastest laps you will have lower top speeds than a GT3 car, but getting to it so much more quickly means you are over 20s per lap faster at typical tracks. Notes on a few of the sub-systems below.

Aero: The car made news for having a (maybe...probably illegal) flexible rear wing system last year. We copied that here with via active aero system so it sheds about 300lb downforce and 60lb drag at typical Le Mans top speeds of 300kph. Efficiency drops a bit and balance shifts 4% forward when this happens. Numbers are just guesses, but should be in the right ballpark. I think this was much more significant to their performance than most realize. My own lap times around Le Mans dropped about 2s when adding this feature.

Power Unit: The 3.7L, naturally aspirated V8 is good for 520hp from 7000-8500rpm. Nice smooth engine. Hybrid motors add another 480hp (when over 300kph, below that speed they are torque-limited) split probably around 40/60 front/rear knowing the TS030’s rear-only MGU-K was good for 300hp. Configured the hybrid so that, driven normally, it uses all 6MJ of the energy at low speed for acceleration as that's best for lap times. Burning a full charge will take you from 60-280kph at an amazing rate and is about 3s faster over a lap of Le Mans than using it for top speed boost, even if top speed drops from 340kph to 300 when used that way. It is possible to use it for top speed on our model: Get up to 250kph or so without using full throttle and then give it full beans. That's when you'll see the power meter approach 1000hp and it will shoot up to 350kph in about 5s. Impressive, but only ever useful for passing slower traffic.

Gearbox: Slightly odd setup here. I can't find any evidence of 1st gear being used. It is always in 2nd even at 60kph behind safety cars, in La Source, Arnage, etc. 1st must be only for leaving the pits under electric power when the engine hasn't fired up yet. In Le Mans gearing, 6th gear takes it to 285kph, even if top speed in the most effective hybrid mode is only 295-300kph. 7th is purely for fuel saving and when they want to use the hybrid for a top speed boost. Then all of the extra hybrid torque means that 3rd/4th gear is fine for all but the slowest corners. Expect to be spending most of your time at most tracks in 4th-6th gear.

Some best laps turned in testing so far:
Le Mans: 3:23.5
Silverstone: 1:43.1
Spa: 2:00.5

EDIT: I goofed in the notes. The tire model update below wasn't done in time and will be happening for patch 6, not 5.

Last but not least, patch 6 includes some recalibration of tire heating models. Some folks in a G40 league here found an issue where a slight increase in pressure could cause an extreme amount of overheating in the tires. We tracked it down to a fix in a change in how the carcass generates heat at low inflation pressure, but this sent us down a rabbit hole of checking that no cars had completely broken tires with the change. Things are much better with the fix in place. Temperature balance front to rear looks more correct on most cars and it removes something of an exploit that was possible in car setup. You’ll need to take more care with setting tire pressures now and can expect a larger response from those changes.

With the fix, tires heat faster, more predictably, and will really punish you for poor driving and setup in a way they didn't before. A lot of tires could move to more standardized values without needing lots of extra calibration just to get the right front to rear temperature balance. Before, if rear tires started at a lower pressure, they could run up against a limit near ideal pressure and lose heat; ending up cooler than the front even if the handling balance was strongly biased to oversteer. Now they get nice, consistent heating and show a reasonably higher carcass temp than non-driven fronts, which then filters through to hotter tread. Generally the temps are feeling more representative of handling balance now. Cool stuff.

While in there recalibrating the heat, I merged in some ideas we've been playing with for pCARS 2. Biggest of those is that most slick tires (those based on our SLICK_GT3 template) now have a larger temperature range for the rubber of 0-200°C. This fits in with stuff we've learned from rallycross where tires under extreme stress creep up to 180C or more. This has a pretty cool result of accentuating the camber effects of a tire so the inside edge reads significantly hotter as it should. Implies that our the old cap around 150-165C was limiting heat gain on the inside edge but not the outside. Also does a very good job at punishing the driver for abusive technique.

Some tire sets also had slight wear rate recalibration to fit with changes brought on by the new heat model. Anything that did change stayed at the same starting grip as before, but some will wear faster now and with a stronger grip loss effect. Prototype work on the upcoming V8 Supercar helped to hone in the right reference point for grip loss on a heavily worn tire. Generally the cost is about 2s over a 2min lap at the end of a run. Go longer than that and you're likely to find yourself driving it off the performance cliff and losing heaps of time.

Thomas Sikora
04-03-2016, 17:22
The Physics of Classic Lotus Expansion

I think this is a really neat group of old cars from a time when design was moving very quickly. Hope you all enjoy them! Here are a few notes from the development. If you have any questions about them, ask below and I'll do my best to answer.

Lotus 51
Neat car here. It was a case of Lotus updating an older design to create what was the birth of Formula Ford racing as we know it. The engine is a 1.6L Ford Kent crossflow from a Cortina good for about 115hp @ 6500rpm. Very smooth and plenty of power for a car that weighs less than 900lb empty. Gearbox has a full range of Hewland Mk8 ratios to choose from; it was standard gear for the car after moving away from the (unreliable) Renault Gordini unit. Our reference car was laser scanned so the suspension geometry is new using the points that gave us. Surprising amount of pro-dive at the front, but it is otherwise quite similar to the Type 25 and works very nicely. Set it to use the same tire options as the Lotus 25. This was a beginner Formula Ford car from '67 and I think it is fair to assume that the tire tech available would have been equivalent to what went on F1 cars a few years earlier. It is not super sensitive to having great rubber anyway. 115hp doesn't tax the rubber, plus the chassis is so light and balanced that they barely have to work at all to put in fast times. Lovely (easy) car to drive and should make for some fun MP racing.

Motion Ratio:
Front= 0.67
Rear= 0.76

Damper Transitions: 500mm/s all around

Lotus 25
It's like a baby Lotus 49 - less weight, tire, and engine - and much better for it. There is good data available on the 1.5L Climax V8 and it is a peach. 200hp with a very smooth torque curve all the way from 6500rpm up to the limit at 10500. Not at all like the later DFV that hits you like a second engine turns on when over 7500rpm. It even made good mileage! averaging around 23L/100km at Monza. Very cool little engine for the time. Aerodynamics are typical early-60s stuff, with aero lift at speed but a low drag number thanks to tidy engine packaging. Expect top speeds up over 150mph when the track lets it run long enough. Gear ratio selection is from the original ZF 5DS10, which is to say somewhat limited. It wasn't the greatest unit and it's no surprise that restorations typically switch to a Hewland box. Doesn't work against you too much, though, as the Climax engine is happy at relatively low rpm and excessive shifting is unecessary. Suspension design is another fun look into very aged car design. It does most everything in a nice way, but uses high camber gain as a key design element - note the large angles on front top wishbone and rear top link. Means the car is plenty happy running right near 0° camber as it leans them into the turns under chassis roll. It does work quite well for cornering balance in testing here, but isn't lovely under braking and over bumpy sections. The large changes in roll center with suspension movement aren't highly desirable as roll balance can become out of sync front to rear. Both our Vintage Open Wheel 1962 and 1965 tires are available to use, with 1965 being the default. Redesigned the tire carcass and tread to a more convincing feel. They give a great view of how tires were developing over the life of the car, as the brands progressively experimented with softer and softer rubber. Tons of fun, whichever tire you choose.

Motion Ratio:
Front= 0.63

Damper Transitions: 500mm/s all around

Lotus 38
The 4.195L Ford Quad Cam is good for just under 500hp @ 8800rpm and is buttery smooth. Ford’s Cosworth DFV gets all the attention, but for the time this engine was every bit as impressive. It won just about everything from 1963-71, including 6 Indy 500s over 7 years plus one more in turbo form in 1977. Power goes through a ZF 2DS-20. Yes! that's a 2-speed version of the 5DS-20 that was common in other forms of racing. It's a very different feeling, but you won't really miss the gears because the engine provides good torque even down low. Means a little more work getting the right gears for each track, but you've only got two to worry about. A new rule in 1965 meant that 2 pit stops were required over the 500 miles, so fuel capacity was reduced to just 60 gallons. Tires could last the whole race.

The monocoque chassis has a lot in common with the Lotus 25, except it is shifted about 3.5cm left of center. This puts the lateral weight balance at about 52% left and means the suspension geometry is asymmetric. All points for that were taken from our scanned model. It doesn't ruin the car for turning right, but it does lead to some unusual behavior in how it puts down power and it does handle slightly differently in left vs. right turns. In general, it handles beautifully so long as you treat it with respect. There is a lot of power on tap.

Made a new tire for it from the Vintage Open Wheel base plus the new heat model ideas I've been working on for other cars. It's different enough from the F1 cars that this is needed, and Firestone did make something new specifically for this car.

Surprisingly, I’m turning low/mid 7-minute laps around the Nurburgring with it. It's really not that far off the Lotus 49 despite being a bit heavier and down 3 gears. Very good fun at historic Silverstone.

Motion Ratio:
Front= 0.6 (left), 0.7 (right)
Rear= 0.9 (left), 0.8 (right)

Damper Transitions: 500mm/s all around

Lotus 49C
There weren't huge changes from the 49 to 49C. Subtle changes to the suspension, monocoque, and wheelbase made the base package more refined. Cosworth worked on the DFV so it would run a higher rpm good for 430hp; the 1967 version could get that output at 10000rpm, but only for a couple of seconds before detonating. The big change, of course, was the addition of wings as aero was starting to be figured out. One of my books mentioned this particular aero package being good for around 450lbf downforce while cutting top speed to ~175mph, so that is what we've matched. Gearbox changed from a ZF to Hewland and the much wider range of ratios that comes with it.

Motion Ratio:
Front= 0.9
Rear= 0.9

Damper Transitions: 500mm/s all around

Lotus 40
This turned out to be a surprisingly cool car. Famous driver quote about it was ‘...Lotus 30 with 10 more mistakes’ but it’s actually a lot of fun to drive! Not exactly a perfect balance of chassis, engine, and tire, but it makes for an engaging drive. This was a classic case of taking a light car and finding some way to shove a big engine in it. Proper hot rod stuff, but in a sports prototype kind of thing. Suspension geometry could mostly be pulled from the scanned model. Tires are shared with the Ford Mk.IV. Set it to use a Hewland FG500 4-speed gearbox. Engine is a Ford 289c.i. V8 good for about 380hp at 7000rpm. Kinda like a race-spec version of what's in our '66 Mustang. These Type 30/40s ran any number of combinations for engine and gearbox, but this seems to give a good representation of how most of them ran early in life. Overall it's a good match for the Ford Mk.IV. Sharper handling, but down on top speed.

Motion Ratio:
Front= 0.6
Rear= 0.77

Damper Transitions: 150mm/s all around

Thomas Sikora
04-03-2016, 17:22
The Physics of Old vs. New

You all might have noticed some teasers of the next DLC pack going up on our Instagram @projectcarsgame - https://instagram.com/projectcarsgame/ (Are you following us on IG yet? Do it!) Thought it might be a good time to share a little of the work that went into developing the driving dynamics of each car you can expect to try in the imminent future.

BMW 2002 turbo
170hp with 0.55bar boost from the single KKK turbo. Getrag 235/8 5-speed gearbox is standard with a ton of rear end gearing options from the motorsport division and a 40% lock ZF differential by default. Suspension is made of struts at the front and semi-trailing arms at the rear; an arrangement not not all that different from the E30 Group A car used some 20 years later. Stock springs are around 275 lb/in front and 250lb/in rear and make for some lively handling. Found that they offered a 'special lightweight package' which cut kerb weight to 1035kg with a full tank of fuel, so went ahead and optioned that on to ours. Uses the same Faretti Superbelt vintage tire from our Escort Mk1 and '66 Mustang. Matches up surprisingly well with the Mustang despite the 100hp deficit. This car was really genesis for the idea of the light, nimble, turbocharged touring car and it’s really cool to see how that comes across in our systems.

We had a good starting point in the M3 GT4 and some very detailed technical manuals/setup sheets covering the differences needed to make it a WTCC car. The rules for both series require that the race car stays very close to the road car as far as bodyshell, suspension design, and aerodynamics. Fun fact: this is probably the only car we have where zero rear wing actually equals zero rear downforce. Plots in the manual show it goes from 100% front to 80% rear aero balance with increasing wing angle. (top tip: there is really no reason to run it lower than 4.0 in the setup. Real teams use a high angle even at Monza) It’s a lively car to drive. During research, I found it a little amusing to see that every other game with this or other WTCC cars has used only the FIA maximum rev limit of 8500rpm to design their engines. These really make max power around 6000rpm and you'll want to shift between 6200-6400rpm. A regulation limit of 2.5bar boost on a tiny 33mm intake restrictor means these engines are struggling for air at rpm any higher than that. That 8500rpm limiter exists, but it really is never used as the other rules around the engine are more strict. Still, it pulls *strong* for a little 1.6L unit and always feels like it has plenty of power. May have 100hp less than the M3 GT4, but it also weighs over 300kg less, has narrower, harder rubber and no TC or ABS. Can be a challenge getting the thing slowed down and out of a corner as fast as possible. Tons of fun racing in tight packs.

Ford Mustang 2+2 fastback
The Mustang was a huge hit from day one, and with models like this it’s not difficult to see why. We’ve opted for the K Code engine with 271hp, 3.0:1 rear end ratio by default as it's best for most track use, 135 lb/in rear leaf spring from the handling package, and stiffer than stock front coils as the standard 100 lb/in guys just can't handle in hard track use especially in AI hands (but they are available in setup if you want to try the car as it came out of showrooms). Lots of other little bits were able to be taken and modified from the Escort Mk1 with minor edits as the architecture is essentially similar between the two cars. Aerodynamics are not good, suspension is rough around the edges, tires are nowhere near modern standards, and that engine is well beyond all of the above, but man...Is the slowest car in game also the most fun to race? I think maybe so.

Ford Mustang GT (2015)
Independent rear suspension in a Mustang! Feels almost sacrilegious but you can’t really argue with the result. Chris Harris put out a video on the car recently and said something along the lines of ‘they’ve taken a very sophisticated car and tuned it to act like a hooligan’. I think that is about as spot on as you can get.
The nice thing about Mustangs is that hotrodders tear them apart the instant they get the chance. Means good data and numbers are already out on the interwebz that were useful to fill the gaps here. Stock springs and dampers show a significant rear bias, leading to oversteer and drifty behavior as the dominant characteristic. It feels, to me, like they have gone to some length to tune the new rear suspension so that it still has some of the feeling of the old generation’s solid rear axle. ‘Pushy-Loose’ is a term you might use for it. Not an altogether bad idea, but it does leave you feeling that some performance might be left on the table for the sake of fun dynamics. I guess that’s a choice we can stand behind, right? Plenty of room for a car to be designed for fun rather than getting that last 1s at the Nurburgring.
Decided to not use the optional 3.73 rear end in the default setup as it is useless on track. Makes 2nd gear too short to use on most tracks and you run out of 5th too early while 6th is too long for anything but highway cruising no matter what. The standard 3.55 is much better for track use if you then treat it like 6th gear doesn’t exist (Or 2nd for that matter. Run 3rd through 5th for best lap times and use the excellent torque curve to make up the difference).

Fun drive and faster overall than expected. Just heavy...

Ruf CTR ‘Yellowbird’
Engine and gearbox are all good to Ruf specs. Published power and torque numbers smell funny on this one; I think it really made a lot more than the 470hp they claim and definitely made a lot more than 408lb-ft in torque. Aero model has been roughly matched to data available for the Porsche 930 with a whale tail. Suspension is strut front and semi-trailing arm rear with spring rates I quickly found other people using on 930 Porsches. Didn't spend much time tuning it as we've got an expert amongst us in Doug, but it's already good fun.
Set it to use our Masculin tire set and it matches up quite well with the modern cars when running on those. Also added a 'CTR Denloc D40' tire to copy period-correct Dunlop Denloc D40s that originally came with the car and were used for the famous 8:05 Nurburgring lap; go watch the Fascination video on Youtube if you haven’t already. Bit of a handful, but I expect a lot of you here will like that.

Doug: Interestingly, I actually drove one of these cars (pretty sure it was a real one) at Watkins Glen back in the early 90's. It belonged to a well-off club member who was looking for an opinion on his driving.. The thing i remember most about it was not being able to get the throttle all the way down on the straights until just before the the braking area for the next corner. Saying it's handfull is an understatement.
We were talking more like 600 hp at the time in conversations. I thought it had adjustable boost, but that might have been added by the shop that was supporting this car.
Set physics to all the info i have from the years setting these types of cars up. Changed the brake power and bias, moved the weight bias back to 40/60, Adjusted the motion ratios to some direct measurements i've used setting up 911/930's. Casey’s spring rate and damper values were almost spot on. Some slight tweaks needed there. Added proper sized swaybars. It all works pretty well. Get your trailing throttle heads screwed on for this one

This is one epic car. If you’re on the fence about this DLC, IMO this is the car that should push you over.

Ruf Rt12 R
We could 'steal' a lot from the RGT-8 for suspension and basics. Aero package is more or less a mildly-tamed Cup car, so scaled down the aero package for a GT3 Cup we made many moons ago and used that. Good for around 400lb downforce at 150mph. Weird gearing on this one. Huge spacing in the first three and 3rd gear takes you all the way to 120mph, then 4th-6th are very evenly spaced up to top speed of 370kmh. For most tracks, that means you just put it in 3rd gear and leave it there for a long time; let massive mountains of torque handle the rest. It works out well, but it’s a slightly unusual technique for most drivers. AWD is an option on this car, and we opted to use it. The rear engine weight bias means not too much it sent to the front, but it’s enough to make a difference pulling out of corner exits, which it does in a strong way. Used our Audi R8 V10 plus method for sending roughly 15% of engine power to the front wheels. Really fun car. Very quick!

Thomas Sikora
04-03-2016, 17:23
The Physics of Audi-Ruapuna

Hey guys. The Audi A1 is available with patch 2.0 now and next set of DLC cars will be available soon, so thought you’d like to see some notes from the physics development of each one. Four great cars from the four rings this time. Very excited for you all to have a go in them.

Audi A1 quattro: Always tough working on these ultra-limited-edition cars as very often data on what was done to build them gets lost to time, but I think we’ve got a winner here. It’s another one of those weird Audi gearboxes with two final drive ratios in a slick 6-speed manual! Suspension for this car is mostly a parts-bin special from other hot Audi (TTS, S3...) cars, so I found good data on springs and some damper plots from a MkV GTI as a baseline and it works great. Engine matches as much detail as is available, weight and balance available from one of those nice Sport Auto Super Tests, and various other details plucked from various magazine reviews. Tuning ranges are close to typical aftermarket parts available for the S3, GTI and others from the same family. Super fun little car. Prefer it to the other small hatches we have by a long shot.

Audi 90 IMSA GTO: Some late-'80s madness here. Suspension geometry sketched up from our 3D model and photo reference; nothing too fancy going on. Gearbox is a mix of parts from the Group B WRC cars that came before it. Lovely little engine (coolest sounds ever) with little turbo lag and good for 720Nm / 720hp. Real car could be set up anywhere from 50:50 to 30:70 on the AWD torque split and I've used our hybrid system to land it somewhere in the middle. I know some people feel icky about doing it this way, but it really is a nice, effective simulation of AWD torque biasing that we can do now before spending the time on code for a fully adjustable, three-differential physics model. Aero is not lovely; typical mid/late-80s stuff here. While Group C cars were getting into underbody tunnels and crazy downforce numbers, the airflow management in GT was still quite crude and, at best, gave very modest downforce numbers. Means the car is very quick, but can feel a little unbalanced in performance. Not great in cornering, but it sure grips up and rockets out of the exits as few others can. Matches up quite well with the Trans-Am Mustang, or new GT3 stuff even. Huge power, light weight and super wide tires can do a lot for you.

Audi R8 LMP900: Nothing too fancy about this one, and maybe that’s why it was so dominant over its lifetime. Simple, effective suspension; aero package with strong downforce at expense of slightly higher drag; powerful engine with little to no turbo-lag. Can run fast laps all day long in this without feeling stressed. No traction control allowed when this car ran back in 2000-2006, so it’s all up to you to manage that 625hp. Great competitor for the Bentley Speed 8. Will have the measure of the BMW V12 LMR at most tracks - there was big progress in LMP900 performance from ‘99 to 2002 - but it could be a fun matchup with the right drivers.

Audi R18 e-tron quattro: This was a particularly exciting car to work on after it won Le Mans last year. The new hybrid regulations provide some very cool engineering challenges and the teams are, unsurprisingly, reluctant to share much data which could be used to work out where advantages may exist. That meant lots of work on our side to examine the data that was available and do some reverse engineering to figure out the details. Here’s an overview of all the essential areas and what we found.

Suspension: We got enough points from the CAD to work out steering geometry, anti-dive and such. General steering feel is a step up from the R18 TDI, IMO, and it handles the varying loads from downforce much better. LMP1 cars are lighter than before now by 30kg (870kg minimum), but the same basic suspension setup works fine from the TDI to e-tron. Not a big enough difference to throw out the basics.

Gearbox: 7-speed units now, and on-board telemetry that Audi broadcasted during Le Mans and other races last year was good enough to do basic speed vs. engine rpm analysis of the ratios. It's a pretty weird looking setup on paper, but drives really well since the diesel V6 has stupid levels of torque. First four gears are very very close together; I think as a plan to work in tandem with the flywheel hybrid system. Shifts were done at 4500rpm with very few exceptions.


Engine: 2014 regs meant no more air restrictor and a new boost limit of 4.0bar. I don't think they're going quite that high on this car it would go beyond the fuel flow limit with a 4.0L engine. Best guess is that it's running closer to 3.0bar like they used previously in the 3.7L version of the engine, and that's probably good for upward of 1100Nm torque. Slightly more than their 'over 800Nm' claim, but then that was always a 'No shit, Sherlock' kind of claim as the also-claimed 540hp means at least 850Nm@4500rpm. My best guess, using what we know from the previous engine, is that they are hitting that 540hp power peak early - around 3500rpm - and then using ECU boost/fuel control to hold it near constant power up to the shift point. Saves fuel (540hp is enough, really) and means that the operating rev range pretty much always has max power available.

Hybrid: This is where it gets interesting. The streaming video/telemetry was good enough to include a meter for hybrid energy storage. Without any other hard info, we have to rely on this to get an idea of how the system is working, and that ain't all bad. We know it's a 2MJ/lap system; watching closely and taking notes, it looks like they run through about 6 full charges of the system per lap of Le Mans. Easy math, then, to figure that in LM settings it is maxing out charge at ~330kJ. Official claims for system storage are over 600kJ and a few even stating up to 1.2MJ, but it doesn't make sense at Le Mans to carry that much at once if you have at least 6 good charging points around the lap and can only use 2MJ. Perhaps they use a higher level of storage at shorter tracks for the shorter races, but we don't have tons of info on that and LM is the main target anyway. Keeping the flywheel at lower speeds would be good for reliability unless you are absolutely certain that harvesting 4MJ per lap is reliably attainable. It seems they may be thinking just that for 2015 and I would agree that the 2MJ class leaves a lot of potential on the table. This year’s race also gave us some confirmation on the 330kJ number as Audi have claimed that they doubled their flywheel storage capacity to around 700kJ in their move to the 4MJ class.

Going back to the telemetry, out of chicanes on the Mulsanne, it is burning through that 330kJ in 5-6s and is emptied by the time the car is at 230kmh for an average system output of around 60kw (80hp). Maybe the system can do a full 170kW output as claimed, but perhaps that's only if used at maximum speed (340(ish)kph) and below that it is torque-limited so not to burn through the 2MJ too fast. We've got it modeled this way, so 170kW is possible but not ever really used as it isn't practical for performance over a whole lap. What you end up with is about the equivalent of an extra 200Nm from the engine accelerating through 5th gear, and that's not too shabby.

Aero: Very little 'official' data here, but a lot can be inferred. Audi have made public claims of lift:drag efficiency of 5:1, and we can be sure they are understating that. At top speed when ride height reduces under downforce load, it is probably closer to 6:1 (for those who aren't aero nerds, this is very very very good). What we do know is that top speeds without a draft at Le Mans were typically recorded in the 315-319kmh range. With a draft, closer to 340. Not very high in the grand scheme of things, and works out to something around 420lbf of drag @ 150mph in LM aero spec. Prototypes can drop 5% or more of their total drag compared to static ride height when squatting down under load at top speed. So what we'll do is take that 420lbf drag figure, add about 5% when at static ride height and figure the 5:1 downforce from there. If overall lap time performance is anything to go by, this has worked out quite well.

Audi were also kind enough to run both aero packages at Spa last year. #3 used the LM package while #1 and #2 used the sprint package with high drag/downforce. #3 was good for nearly 300kmh at the end of Kemmel straight, and our LM setup ends up matching that. Nice. Move to high downforce and top speed on Kemmel reduces to 275-279kmh while keeping similar efficiency. That's downright slow for an LMP1! These new generation cars are getting all of their speed in acceleration and hitting top speeds early on the straights. This is why the higher energy hybrid classes are the way to go and, IMO, were the key to Porsche’s victory this year.

What's it like to drive? Quite a bit different from the 2011-2013-era LMPs we've modeled so far. The narrower tires mean there is a lot less mechanical grip available and you end up hustling the car more at low speed. At the same time, the new aero/chassis rules mean more downforce on less mass, so high speed corners are an even more intense experience. Cruising to hit a good fuel number and maximize hybrid use is a very different experience and makes for a very interesting drive. Best laps here so far are a 3:26.3 at Le Mans, a 2:01.8 at Spa with high downforce and a 2:02.7 with low downforce. Can't wait to hear what you guys think of it

Thomas Sikora
04-03-2016, 17:23
The Physics of Racing Icons

Hope you guys are enjoying the new cars! Pleased we got to release a couple more Le Mans winners this week before the race; there will be even more added to the list soon enough. Thought you might like to see some of the internal notes we had during physics development of the cars. Do feel free to ask if you have any questions about these cars and I'll do my best to keep up with the thread for answers.

Bentley Continental GT3

- Initial pass getting all data from Bentley in place. We received good aero, engine and setup data plus suspension points from CAD and a good idea what the torque curve looks like without the FIA boost restrictions. Used that to model the effect of the 2015 BoP boost pressures and it all looks reasonable with a strong 540hp output near 6800rpm. Sweet drive. Over to Doug's shop now for finishing and AI work.

- Nice drive out of the box from Casey. Only adjusted default shock package for better turnin and corner exit response. Accepts the throttle better especially.

Bentley Speed 8

Lovely car. Might be my new favorite in the game. Much of the setup and technical info has been lost to time, unfortunately, but Bentley were able to get us a nice, old-fashioned blueprint for suspension geometry and basic layout. Mulsanne's Corner and some Peter Elleray interviews proved useful for the aero and the engine could easily be extrapolated from info on the 3.6L Audi V8. It's an awesome contrast to the BMW V12 LMR (and, soon, the Audi R8) with more power (+40hp) and about 30% more downforce but more drag, the coupe design means a higher CoG and narrower tires by 2 inches. Still a totally different experience to the modern LMP1 with their super wide tires and yet another 30% more downforce or so. Low downforce setup is good for 13 laps at Le Mans if you conserve and cruise in the high 3:30s. Le Mans plus the DLC with this group of cars is enough to make the whole game for me. Just awesome stuff.


- Initial pass at physics. Suspension geometry mostly from JF's very nice model. Very simple old car with no fancy suspension ideas or super high downforce. Just low drag, great engine, and a solid chassis with nice, predictable handling. Very different experience from our modern LMPs and, personally, one I much prefer. Super happy to have this car in game. It was a big part of one of my first mods for SCGT & F1C back in the day, so it's very cool to experience it on all our new tech.

- Some caster work and spindle inertia's increased. FFB re adjusted. AI speed rebalanced. Eyepoint was way off. Reset that so i could see out of the car

McLaren F1 GTR’97 Long Tail

- Initial pass at physics. Minor suspension geometry changes as were allowed in the FIA GT rules. Wild car. 915kg and 630hp with average-to-poor aero but a really nice suspension which actually ran quite soft for the performance level of the car. Strengths are acceleration and general speed. Weaknesses: sustained cornering. It just really struggle for front aero. Going to let it run at the claimed minimum weight and max power any team found in 1997 so that it can keep up better with the CLK-LM.

- Re balanced the AI speed. Did some caster work on the suspension. Some setup changes to balance. re adjusted the FFB. Moved the eyepoint back

Mercedes CLK-LM

- Initial pass at physics. This thing is absolutely a prototype in disguise. 940kg with a full-carbon monocoque, carbon fibre brakes, very advanced aero for the time, in-board suspension and the engine of a Group C car redesigned with a flat crank to be even better without turbos. If you compare it to LMP900 cars from the following couple of years, the CLK-LM was barely 1s slower at several tracks despite much narrower tires AND! considering that GT1 rules required a 30mm skid plate on new cars, so this one ran much higher than Mercedes would have wanted and they severely compromised the suspension setup as a result. Photo reference shows it using 230N/mm springs at the front on a 1:1 motion ratio, for a natural frequency upwards of 5.75Hz. That's practically formula-car-stiff so that it could stay close to the aerodynamic sweet spot. GT1 in the late-90s was bonkers.

- AI speed balancing to player. Raised collison mesh 30mm, eyepoint moved back and down.
Damper knee speed: 40/60 front and rear

- some caster work, spindle inertia's increased. Adjusted FFB, AI speed re-balanced. In my opinion the nicest of the LM lot to drive.

Thomas Sikora
04-03-2016, 17:23
The Physics of US Race Car Pack

Sorry for the delay in getting this up, guys. Hope you've all been enjoying the latest cars. Here are some notes from the production of each one.

Dallara DW12

We were fortunate enough to work directly with the Schmidt Peterson team on this car and their engineering team came through with a mountain of data for us to use in matching the game model to the real thing. Very pleased to say that our aero model matches the real car within 2% for drag, downforce, and aero balance over a full range of ride heights all the way from minimum to maximum downforce. Couldn’t be happier with how closely we were able to copy the real thing as aero is obviously a huge part of these cars. Important thing to remember in setup of a car with tunnels like this is that it doesn’t love a lot of rake. Ideally you want to keep it as low and level as possible for the aero to work at its best.

Our model was built from CAD, of course, so suspension geometry is pulled directly from this. All spring and damper values are done in wheel rate. The DW12 has adjustable rockers so motion ratio for each part is variable within the car setup. We adapted spring rates and damper force plots from the real car to cover the full range of motion ratio adjustment the teams have, so you can set it up as soft or stiff as they do. Default setup is aimed at a middle of the road thing, halfway between what a team would use for their minimum downforce track (Indy road course) and max downforce (Sonoma)

Engine is the twin-turbo 2.2L V6. I think both Honda and Chevy are being quite modest by still claiming 700hp for it in road course spec with 1.5bar boost. With the good aero data we could run it in similar conditions to the real car and match top speeds. This clearly showed that something closer to 750hp is needed to match speeds of the real car. Push to pass is then available in races for 10 shots of a 20-second / 0.1bar increase, taking it to 800hp. Lots of power from a little thing but only if you gear it to be up at the peak of the powerband.

Tires are a similar construction to what we have on the Formula Renault 3.5 - another Dallara chassis with similar design to the underbody aerodynamics. Primary (black sidewall) slicks will safely last you one tank of fuel without falling off too much. Alternate red tires are about 1s per lap faster but go off much more quickly.

Once we got all that baseline work done, the Mayor of Hinchtown himself gave it a good run and came back with a set of notes on areas to improve the car. We made a number of changes to the chassis balance, particularly due to engine braking, and tweaked the tire model for some added stability near the limit of grip (the Firestones they use are very sticky) and it now pretty much lines up with the feedback from Hinch. They gave it a second run at SPM HQ as well and agreed that it moved very much in the right direction. Really takes focus to push this one at 100%. Fun car!

Motion Ratios: 1 / 1
Damper Transition, front: 25mm/s
Damper Transition, rear: 25mm/s
Unsprung mass: 30 / 41kg

Chevrolet Corvette C7.R

Another car where we had the great opportunity to work with one of the real drivers; this time being Tommy Milner. We’ve actually known Tommy since he was a 14 year old kid just getting started in karts and fooling around with simulation games, so it is beyond cool to see where his career has gone. :)

Long story short, the C7.R is just a great package for endurance racing. The way it fits into Le Mans rules have it running at the standard class minimum of 1245kg (20kg more than the Porsche and Aston, which both get a break) and 2x29.1mm air restrictors which have making a healthy 500hp @ 6000rpm. The rear wing height and gurney flap size mean it pays a something of drag penalty for that power, but overall the aero package is excellent. The extra drag turns into a nice amount of downforce and general ride height/pitch sensitivity is low for a modern GT thanks to the short overhangs. It might not always be fastest over a single lap, but it’s super easy to push it at maximum for a long time.

LS5.5R engine would, amazingly, be good for upward of 750hp unrestricted. This matches up with some performance packages Katech produces for similar units you can run on the road. More amazing still is that they averaged 14-lap stints, same as the Aston, despite having a fuel tank 10L smaller. Direct injection making a big difference there. The torque curve is massive and, in restricted form, you are right up at 95% of peak power from 4900-6500rpm. It doesn’t need to rev out to the limit for max performance and the fuel savings benefit you get from using fewer rpm can be a big benefit in the long haul.

Tommy gave the car a run just before the Daytona 24 and said we were on the right track, but had the default setup too stiff. That instantly clicked with something I remember from the older C6.R and that Pratt & Miller actually ran that car on softer spring rates than the road car. The setup we’ve ended up with now is a much better match to how they run the real car. You can make it as stiff as the Vantage GTE or others, but there really is something to say for letting it roll around a bit more, and it can do that without so much penalty thanks to the docile aero.

Motion Ratios: 0.71 / 0.78
Damper Transition, front: 30mm/s bump - 60mm/s rebound
Damper Transition, rear: 51mm/s bump - 95mm/s rebound
Unsprung mass: 45 / 55kg

Cadillac ATS-V.R

Nice little racecar here. Official spec has the engine producing 600hp @ 7400rpm and 520lb-ft @ 5500rpm, but that makes it a very vague statement as neither restrictor size nor boost pressure are specified. So what we did was start by looking at the non-turbocharged road car plus 18psi boost (max for the ATS-V road car) and only light tuning was needed to make it hit those targets. Was just a case of holding that max 18psi boost up to 7000rpm rather than dropping boost as rpm rises to get a flat torque curve as appears they’ve done in the road car. A number of aftermarket tuners are doing ECU flashes with this same trick that instantly add 100+hp. Pretty cool, though you hate to see the standard car held back so much. Next we applied the boost pressure curve they must run in the PWC series and 2x40mm air restrictors to match. With that data, it fell nicely to 500hp with 445lb-ft torque and a super wide power band from 5700rpm right up to the limiter at 7600; perfectly matched to other cars in the class.

Aero package is fairly typical of a GT3 car. Decent efficiency with mostly an increasing rear bias as you dial on more downforce. Top speeds come in around 170mph at Road America, which is right on target for the race there last year.

You can sorta-kinda think of it like a GT-R GT3 with better natural chassis balance since it was RWD from the outset. 1315kg with weight distribution of 51% rear works really well for a car like this and overall it’s not difficult to see why it won the championship last year. Good balance and all the right elements around that.

Motion Ratios: 0.72 / 0.78
Damper Transition, front: 60mm/s
Damper Transition, rear: 60mm/s
Unsprung mass: 50 / 55kg

Ford Fusion Gen.6 Stockcar

I haven't paid much attention to these in a while and they are actually quite impressive now! The 5.866L (pushrod!) V8s can make well over 900hp now but, as of last year, they are using a mandatory 1.17” restrictor plate at all tracks. This limits the car to 750hp @ 8500rpm. Still a lot!

More impressive is the aerodynamics these simple shapes are making even without purely flat floors. Lift/Drag ratios are around 2:1, which is at or above what you might expect from a GT3 car. Mighty efficient for a car with 'simple' aerodynamics. The oval bodywork on their new cars is also designed to be asymmetric to produce upward of 500lbf of side force @ 200mph, taking a lot of work away from the tires at some tracks. Our model doesn’t rely on that as it is focused on road course racing, but thought it was worth mentioning as the lateral (heh) thinking going into the aero is pretty cool stuff.

Operating range for the tires is all the way up over 235°F, and Goodyear says to not worry unless they are consistently over 275! Tread rubber is only 3.2mm thick so it does heat, cool, and burn off pretty quick when pushing hard. There is the option to restrict it down to 480hp and I’d recommend that for learning the car. It can be a real handful jumping straight into something with so much mass, so much power, and relatively little tire.

Motion Ratios, front: 0.65 spring, 0.81 damper
Motion Ratios, rear: 0.84 spring and damper
Damper Transition, front: 90mm/s
Damper Transition, rear: 90mm/s
Unsprung mass: 61 / 102kg (note the rear number is per-corner, but solid axle means you have 204kg moving in unison there)

Aston Martin Vantage GT12

This is essentially a V12 Vantage GT3 for the road. Engine is a slightly detuned (but unrestricted) version of the GT3 unit good for 595hp @ 7000 with the rev limit just above that. Gearbox is a 7-speed automated sequential manual from Graziano which has been universally bashed for harsh shifting (sorry guys). That carries through to our model and you might want to take care during the shifts especially if in a situation where the chassis is unsettled. Slight lift on the throttle during downshifts isn’t a bad idea.

Aero kit does produce some downforce and is claimed at 7x the standard V12 S and 2x the Vantage GT4. Those are going to be multipliers on a very small number, though, and ours is set to produce a generous 400lbf @ 150mph with only mild sensitivity to ride height due to the car sitting above 100mm when static. Only thing it really doesn't like is nose up where that big front splitter loses effect and adds understeer. Drag added from the wing and stuff keeps top speed just under 300kph. It could probably push closer to 200mph, but the gearing holds it back as you're 1000rpm off peak power in 7th gear at 300kph.

Set to use our Faretti road tire set, same as many other supercars, with the soft 'track' tire by default. Very wide rubber with 265 fronts and 325 rear. More rubber than the Zonda needs with its extra 150hp. Grips *really* well and is good for mid 7:20s at the Ring here.

Motion Ratios: 0.72 / 0.78
Damper Transition, front: 50mm/s bump, 80mm/s rebound
Damper Transition, rear: 51mm/s bump, 95mm/s rebound
Unsprung mass: 45 / 55kg

Thomas Sikora
04-03-2016, 17:23
Project CARS - Pagani Nordschleife Endurance - Content

Thomas Sikora
04-03-2016, 17:25

Thomas Sikora
04-03-2016, 17:25

Thomas Sikora
04-03-2016, 17:36
hopefully block 13 :cool:

05-03-2016, 09:29
Moved to General Discussion subforum.

Jan Studenski
05-03-2016, 21:24
hopefully block 13 :cool:

hopefully block 14 ;)

Thomas Sikora
17-05-2016, 17:51
@ Casey,
any informations for the last few releases?

Jussi Viljami Karjalainen
17-05-2016, 18:09
@ Casey,
any informations for the last few releases?Seconded, really eager to add proper calculator information for the Mercedes-AMG GT3 and the new Paganis.

Thomas Sikora
05-06-2016, 11:56
@ Casey,
any informations for the last few releases?

Casey, any new on this side?

05-06-2016, 14:16
They must have him beavering away on pcars 2.

06-06-2016, 20:18
They must have him beavering away on pcars 2.

Joyrides in awesome race cars and kicking tyres in the name of SIM science ;)