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GoosemanF7
09-03-2017, 13:36
Just talked an hour to a very interesting man.
He is a lifelong race-driver and a racing-instructor on the nürburgring.
He told me that the perfect downshift in a GT-car
(with sequentiel-gearbox, no computer-assistance syncing the gears, dog-clutch and a clutch-pedal for first gear and reverse)
looks like this:

-foot of the accelerator
-brake
-wait till revs are as low as possible without compromising lap-time
-press the clutch a bit (different in every car)
-shift down (with paddle of course)
-release the clutch immediately
-accelerate out of corner

This is done to go easy on the dog-clutch, because by just pulling the downshift-paddle
without using the clutch the (usually high) revs put a lot of stress on the drivetrain/clutch.
The same when shifting up: lift the accelerator a bit before shifting to reduce power
grinding on the clutch.

I never heard that before, but after googling a bit this is like most race-drivers do it.


NOW MY QUESTION:
Can anybody tell me if this is simulated in project cars?
Do you need to get of the accelerator for upshifts
and use the clutch for downshifts to reduce damage on the clutch?
Or can you just shift up and down without increased wear and tear?

Thanks!

RomKnight
09-03-2017, 15:56
Wear is simulated, yes but maybe not enough.

The autoblip/lift might be present in some cars and obviously not others and some just have auto-lift for flat shifting.

If you disable autoclutch you'll notice differences. Actually, driving with auto-cluch on as a negative impact on this for me because it seems to be tied with auto-lift/blip so it works against simulation (for me) more often than not.

Your call really but for me, auto-clutch OFF and the use of clutch will be dependent on the car even on H pattern cars assuming you get the timming correct and blip/lift yourself :)

hkraft300
10-03-2017, 06:12
Don't some cars have the ignition/fuel cut on shifts?
I thought modern race cars would have that to not necessitate the clutch/throttle lift.

ashasha
10-03-2017, 08:08
From what I understand after each race (or even a restart) the car's damage is reset to zero so unless you were doing hundreds of laps in a race you'd probably never have this particular wear become an issue.

GoosemanF7
10-03-2017, 09:08
Alright.
Thanks everyone!

Just tested a few GT3 cars.
In the BMW the downshifts are a lot less noisy when you use the clutch.
Hard to measure if your faster with it, but it sounds/feels better.

bradleyland
13-03-2017, 19:04
I think it's probably a bit difficult to describe, so take those words with a grain of salt. If you listen to the cars carefully at a race, you can hear that the drivers use far less engine braking (they downshift very late) than most of the players in pCARS. They wait until late in the deceleration zone, then blip of the downshifts rapidly.

I never knew they were floating the clutch, but it makes sense. Basically, that would allow for some slip on the input shaft as the gears engage, which dramatically reduces the reciprocating mass that must be dealt with. Even with automatic rev-matching from the engine, a dogbox downshift is a violent thing.

Understanding the mechanics of a manual transmission really helps. I wish a had a good resource for a really detailed review of how a manual works, but I'd really strongly recommend reading up on how a manual transmission works. Even if you learn about synchromesh transmissions, the mental leap to a dogbox is super simple; you basically eliminate the synchro cones and beef up the interlock sleeve.

Keep in mind that this really isn't going to improve lap times in pCARS. The reason actual race car drivers do this is because their team is paying to replace gearboxes, and that gets expensive. The profession of race car driving is about a lot more than just turning the fastest possible lap time. Sometimes it's about managing wear & tear. This technique serves that end.

From a pCARS perspective, I've never experienced a gearbox failure in hundreds (thousands?) of hours of racing with mechanical failures turned on, so it's less necessary. The only potential benefit — other than mitigating mechanical failures — would be increased stability of the car. Optimal grip comes when the car "settles in". Rapid changes in directional force disrupt the contact patch and reduce the grip available. That's why the whole "smooth is fast" thing is so important. The problem is that no simulation is 100% accurate, and pCARS tends to favor engine braking pretty heavily. If you use this technique in an online race, you're going to get out-braked in to the corners pretty bad. If you watch enough YouTube videos, you'll see that the really fast guys are leaning heavily on engine braking, down-shifting as early as possible in order to get that extra braking edge.

hkraft300
13-03-2017, 20:28
With mechanical failure on, smashing the limiter will damage the engine faster than the gearbox as far as I've seen.
In LMP cars you'll lose >50HP in a 30 minute race just upshifting with auto clutch on, where the clutch engages on up shifts and the revs spike. I'd imagine silly downshifting would have the same effect. Anyone notice this in GT cars?

poirqc
13-03-2017, 21:09
I think it's probably a bit difficult to describe, so take those words with a grain of salt. If you listen to the cars carefully at a race, you can hear that the drivers use far less engine braking (they downshift very late) than most of the players in pCARS. They wait until late in the deceleration zone, then blip of the downshifts rapidly.

I never knew they were floating the clutch, but it makes sense. Basically, that would allow for some slip on the input shaft as the gears engage, which dramatically reduces the reciprocating mass that must be dealt with. Even with automatic rev-matching from the engine, a dogbox downshift is a violent thing.

Understanding the mechanics of a manual transmission really helps. I wish a had a good resource for a really detailed review of how a manual works, but I'd really strongly recommend reading up on how a manual transmission works. Even if you learn about synchromesh transmissions, the mental leap to a dogbox is super simple; you basically eliminate the synchro cones and beef up the interlock sleeve.

Keep in mind that this really isn't going to improve lap times in pCARS. The reason actual race car drivers do this is because their team is paying to replace gearboxes, and that gets expensive. The profession of race car driving is about a lot more than just turning the fastest possible lap time. Sometimes it's about managing wear & tear. This technique serves that end.

From a pCARS perspective, I've never experienced a gearbox failure in hundreds (thousands?) of hours of racing with mechanical failures turned on, so it's less necessary. The only potential benefit — other than mitigating mechanical failures — would be increased stability of the car. Optimal grip comes when the car "settles in". Rapid changes in directional force disrupt the contact patch and reduce the grip available. That's why the whole "smooth is fast" thing is so important. The problem is that no simulation is 100% accurate, and pCARS tends to favor engine braking pretty heavily. If you use this technique in an online race, you're going to get out-braked in to the corners pretty bad. If you watch enough YouTube videos, you'll see that the really fast guys are leaning heavily on engine braking, down-shifting as early as possible in order to get that extra braking edge.

Let's just say i'm always super carefull on my manual shifts, in all of the cars i owned.

I would never do what i do in pCars, regarding engine braking and clutch splipping, on my cars! :D That's the beauty of simulation, i can trash my car without any 2nd thoughts! :D

GrimeyDog
14-03-2017, 10:27
Let's just say i'm always super carefull on my manual shifts, in all of the cars i owned.

I would never do what i do in pCars, regarding engine braking and clutch splipping, on my cars! :D That's the beauty of simulation, i can trash my car without any 2nd thoughts! :D

I keep Mechanical Failure on!!! I have Blow the Motor Many Times Down Shifting to Quick or Missing a Gear... Going from 4th to First Blows the Motor every time!!! LOL.... Practice make perfect tnough.... I Now have a Good Feel for the Shifter so even using VR i rarely Miss a Gear Now.

bradleyland
14-03-2017, 16:58
Just came across this IMSA video from this year's Rolex 24, which illustrates the concept really well:

https://twitter.com/IMSA/status/841663435322585088

Notice how late he's downshifting? It's fascinating how differently professionals drive real cars versus how the fast guys drive pretend race cars. You'll also notice that real professional race car drivers seem to hold the gear more often than not. This also preserves the gearbox.

In sims, there's very little penalty to jamming it down to 2nd, when an IRL race car driver would probably hold 3rd. You'll see this in a lot of Nurburgring 24h in-car footage as well. If you go by traditional recommendations, there's only two or three 2nd gear turns on the whole Nordschleife (Nordkehre, Wehrseifen, and Karussell). Yet, if you race online, you'll see plenty of people dropping to 2nd in places like Hocheichen, Adenauer Forst, Kallenhard, and Eiskurve.

hkraft300
14-03-2017, 21:01
Fuel consumption (as well as gearbox preservation) is also a factor. Choosing 3rd instead of 2nd in just those corners can save you .1-.2 litres/lap with bugger all effect on pace, help conserve tyres and that can equate to an extra lap or 2 of stint length which is incredibly important in an endurance race.
Although I'm not sure how much gearbox preservation is a factor considering the reliability of factory built off-the-shelf GT race cars.
What's also noteworthy is how often sim-racers bash the limiter even on upshifts vs RL. Just watch all the YouTube videos!
Also power-on exit stability. There are 2 schools of thought on this among race drivers especially in rain. 1 prefer the lower gear that they normally use in the dry, supposedly for better engine response, at the risk of power oversteer. The other prefer a higher gear for less torque output to the rear wheels.

Engine braking effect is conservative in the game. It's not easy to lock the rears on aggressive downshifts and spin. Unless you have reasonably rear-biased brakes like I do where the rears are near the limit and trail-brake+downshift sends the arse end wayward.
Even F1 and LMP1 driver onboard videos show they're late on the downshift to not be near the limiter.

bradleyland
14-03-2017, 22:11
FWIW, the #100 retired from this year's Rolex 24 on a dead gearbox. It doesn't happen nearly as often as it used to, but the risk of abuse still keeps drivers conservative in some cases.

hkraft300
14-03-2017, 22:24
FWIW, the #100 retired from this year's Rolex 24 on a dead gearbox. It doesn't happen nearly as often as it used to, but the risk of abuse still keeps drivers conservative in some cases.

To finish first, first you must finish!
I've seen some qualifying on-boards of GT3 cars and they don't do silly downshifts either going flat out. Forget endurance races.
Goes to show I reckon in RL there's very little braking/pace benefit to aggressive downshifting in modern race cars. Recently got me a 2014 Clio with a dsg and the engine+rolling resistance in that (when I've tried engine braking) is next to nothing and it's a turbo! Race cars would be even more so, with their free flowing exhausts and race tuning. I dare say it's pcars got it fairly close in that respect, though engine and gearbox should cop more damage from over-revs in my opinion.
TT isn't very representative in sim racing because turn off mech failure and you're stopping on a dime.

bradleyland
15-03-2017, 12:43
Engine displacement (relative to vehicle mass) and compression will have a lot to do with it as well. I had a MkV GTI with the DSG transmission and a 2.0t engine. Very little engine braking.

My last car, however, was an E92 M3 DCT (I live in the US, land of the cheap automobile), and the engine braking on that thing could unsettle the car. It was actually one of the very, very short list of things I didn't like about the car. It wasn't so much the engine braking as it was the fuel cut-out (modern cars cut the fuel when you coast).

So, let's say you're on a mountain road, running downhill. There are a lot of cases where you're going to be at or near zero throttle. You're kind of feathering it, never really going flat out. In these situations, I could feel the fuel cut-out constantly kicking on and off, and remarkably, the difference in engine braking between idle-fuel and no-fuel would actually buck the car a little. There were definitely mid-corner moments where it startled me a little. I would find myself intentionally coasting to the apex, even if I could have carried a little more speed, just to avoid it.

Not to mention, if you grabbed a high RPM downshift in that thing mid corner, it'd flat out break the rear loose (if you had stability control off). The throttle mapping was pretty robust, so you really had to try, but that car had engine braking like no other car I've owned. I can only imagine something like the Shelby GT350, with a 5.2L, high-compression, high-revving V8. That thing must be insane! :)

hkraft300
15-03-2017, 13:35
You'd reckon an M3, of all things, would have that behaviour sorted!

poirqc
15-03-2017, 23:54
I keep Mechanical Failure on!!! I have Blow the Motor Many Times Down Shifting to Quick or Missing a Gear... Going from 4th to First Blows the Motor every time!!! LOL.... Practice make perfect tnough.... I Now have a Good Feel for the Shifter so even using VR i rarely Miss a Gear Now.

Yeah, did that once on the BMW Pro Car. Wanted to go from 4th to 5th, but went to 3rd and dropped the clutch hard. Pouff! no engine.