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View Full Version : [ANSWERED] Is there a glitch with the slipstream on Project CARS 2 ?



TX3 StorM
07-05-2018, 21:47
I really wonder if there's something wrong with the slipstream on Project CARS 2. This needs to be seen as much as possible. I explain EVERYTHING in a video available on my YT channel (unfortunately, I can't share it right now because my account is too young and the spam protection system blocks my post when I directly put the link of the video so...). I had made a previous video, but it is less complete.

Tbh I don't know if this was intentional from the developers, but to my current knowledges I have never seen this happening IRL.
I'm obviously not saying this is a glitch and so on... but I'm quite disturbed by this phenomena. I mean... 6 tenths of a second, with the exact same settings. I don't know what to think about this.

So... was this intentional or not ?

simsimsheree
07-05-2018, 21:54
Without the video, this needs a fuller explanation to make any sense at all...

TX3 StorM
07-05-2018, 21:58
Yeah I know man, but I need someone else to post it unfortunately. :(

TX3 StorM
07-05-2018, 22:00
https://www.youtube.com/watch?v=SULfe2aSl28 : Here's the video FINALLY ^^
https://www.youtube.com/watch?v=SS8pNTyFjp4 : Here's the second video (actually the first I made which is as I said not very complete)

ACR_Glacc3751
07-05-2018, 22:06
Dear developers,

Recently a number of racers did research about a possible weird slipstream effect (possibly glitch, we're not sure)
In the first video above you can see that a car has better speed when someone is drafting behind them. (the same test has been done with LMP2 at Spa, the second video link of Storm) We want to know if this was done on purpose because it is also true in real life (if so, we would like some explanation on this fact)
If this is not on purpose and this should not be the case, then now you know this is a thing in PC2. If this does not represent real life racing, we as a racing community ask you to solve this. Thank you for replying and working together with us

(also, there have been reports slipstream affects the car behind when he is on the other side of the track, further investigation is needed for this)

cluck
07-05-2018, 22:14
That's quite normal, yes, that a following car will reduce the aerodynamic drag of the car in front. pCARS2 models this, as well as side-drafting.

MaXyM
07-05-2018, 22:14
IMO in slipstream both cars can go faster. If I'm not wrong the effect is called 'aero push'
The reason is, while going alone the air flowing over the end of your vehicle generates forces dragging your car back. With two cars, the air don't flow down at the back of your car. Instead it drags back another car.
However I cannot confirm if the gain shown on your video (about 10kmh) is correct or not

TX3 StorM
07-05-2018, 22:18
@cluck and @MaXyM : Well the gap between the 2 tests is quite huge, knowing I felt understeer, like if I was following a car... well in the slipstream of a car ahead. ^^

And the thing is when you compare the laptimes, Couffi's time is just 1 tenth quicker than mine. Then if both cars have pretty much the same slipstream... I don't really know what to think. And I even talked about what you just said in the video. So I took that into consideration when I analysed the data provided by the test.

And if as you say the aerodynamic drag is reduced, why is it globally reduced (knowing that there's nothing in front of the car so the front wing should work at 100%) and not just on the rear ?

cpcdem
07-05-2018, 22:40
Some of the drag a car has, is due to the turbulence of the air just behind it (because of the movement of the car), which causes low pressure that "sucks" the car back. When there's a car just behind, then there's not enough space available between the two, so there's not much turbulence in there, causing drag to be reduced. But I would expect this to happen only when the car behind is maybe half a meter back, not one or two car lengths back...

TX3 StorM
07-05-2018, 22:40
However I totally understand your points guys. Indeed that seems perfectly logical. Nevertheless, someone found this : https://cdn.discordapp.com/attachments/193001948478308352/443178125455654926/SmartSelect_20180508-003128_Samsung_Internet.jpg
It is precised 'in NASCAR and ARCA racing' or something like that.
Indeed those cars race so close to one another that there's not even half a meter and even less between the cars, which could be aerodynamically considered as one piece. So yeah the cars in front can see their pace being bettered. But what about LMPs and Indycar ? It's so far away from this kind of racing, yet the models make the cars to react the same way, which I don't understand.

TX3 StorM
07-05-2018, 22:43
@cpcdem that's what happen in NASCAR. The cars are so close that turbulence aren't present as much as they would do if the track was clear behind.
But here as you can see, I'm gaining 10 kph when the car following me is like 10 meters behind me, like an actual slipstream which is I think much different than what we have talked about. It's really like I had a car in front of me, causing first higher top speed and then understeer, even with LMP cars.

Zaskarspants
07-05-2018, 23:03
"On the faster speedways and superspeedways used by NASCAR, and ARCA two or more vehicles can race faster when lined up front-to-rear than a single car can race alone. The low-pressure wake behind a group's leading car reduces the aerodynamic resistance on the front of the trailing car allowing the second car to pull closer. As the second car nears the first it pushes high-pressure air forward so less fast-moving air hits the lead car's spoiler. The result is less drag for both cars, allowing faster speeds.[2]"

https://en.wikipedia.org/wiki/Drafting_(aerodynamics)#Motorsport

Konan
08-05-2018, 04:57
I think we can establish he understood/agreed on that...what he is questioning is if it happens that extensively in other classes...

Sankyo
08-05-2018, 07:21
IMO in slipstream both cars can go faster. If I'm not wrong the effect is called 'aero push'

A quick web search revealed that aero push seems to be the term for the trailing car losing front downforce/grip. Does anyone know what the 'inverse drafting' is offically called? :)

MaXyM
08-05-2018, 07:55
I think we can establish he understood/agreed on that...what he is questioning is if it happens that extensively in other classes...

or for cars being in such distance as in his example

blankfile
08-05-2018, 07:59
Bump drafting? its basically the same hehe

TX3 StorM
08-05-2018, 10:36
Yeah my point is :
Yes the phenomenon exists IRL, and it seems to be present on the game, I'm not contesting this at all. I'm even very happy that SMS pushed the level of the aero physics that far.

However, what I'm doubting is the strength of this effect on cars such as Indycars and LMPs, because as you can see you can easily crush any of your laptimes only because a car is less than one second behind you. I prefered to show this with an Indycar at the IMS because if it ever existed I would get a huge gap.

But if you watch my video at Spa, my mate is pretty far away from me and yet, with a lower tire pressure on the first test, I managed to improve the top speed by 4 kph which represents a tenth and a half ! And I also had a bad run through Raidillon so the speed gap would have been even bigger.
Besides that, I talked to someone on the PC2 discord channel, and explained him exactly what I felt.

The thing is when someone is within one second of me, I start to feel understeer but I gain in top speed, as if I was actually behind a car, not in front. That's why I slightly hit the wall at the exit of turn 3 on the IMS in the second version of the video, because I expected more grip at the front. It really feels like I was behind a car, slipstreaming it, whereas I'm actually ahead ! That's my point.

If the 'retro slipstream' (let's call it like this lol) is present on this game, if a car follows me from a pretty close range, let's say 5 tenths, maybe the maximum speed I will reach would be only 2 or 3 kph, not 9 or 10 which is HUGE on a track like the IMS, a lap is completed in just over 40 seconds !! (it's 6 tenths at the end of the lap, just saying...), but I shouldn't feel understeer at all because this would mean that the level of grip produced by the front of my car would be lowered, which can't be logical as I'm the leading car and I have a clean air flow on my front wing.

Hopefully you guys got my point, because as I'm french sometimes my English is quite limited and I can mistakes that can totally change the meaning of my sentences... ^^

sas5320
08-05-2018, 11:22
You are correct and your English is fine.

This will be another thing that will require mountains of evidence to get any action or response.

TX3 StorM
08-05-2018, 11:26
Yeah, we would need many people to show the same potential issue, if it is, because we don't know if this was intentional or not from the devs.
I also have several of my collegues that report the same thing. The car in front suffers from a sensitive lack of grip in the corners, but higher top speeds.

cluck
08-05-2018, 11:34
In the interests of fairness, I should add that I've not watched your videos, my initial reply was only because I thought you were questioning the very act of aero-push, side-draft etc. A few members of our league noticed a very evident aero-push effect in the GTE cars in our last cup season but what none of us know, of course, is whether this effect is true to real-life. Certainly, I would expect a level of induced understeer from the aero-push effect but from how far back it can affect the car in front, and to what extent, that's the thing I suppose we need some real-life data on to conclude whether this is expected or unexpected behaviour.

My like for your post above was because it was well explained and stuck to the point. It's a good lesson in how to report findings.

TX3 StorM
08-05-2018, 11:42
I'm absolutely not questioning the aero push or the side draft at all. Indeed it seems to be very strong on cars which imo shouldn't be very much affected by the aero push. We are talking about a 10 kph sometimes ! at IMS it represents 6 tenths per lap... PER LAP !
That's what I show in my second video (the V2.0 one).

TX3 StorM
08-05-2018, 19:05
More thoughts on this ? We need to know if this was made on purpose or not.

Sampo
08-05-2018, 22:49
Yeah my point is :
but I shouldn't feel understeer at all because this would mean that the level of grip produced by the front of my car would be lowered, which can't be logical as I'm the leading car and I have a clean air flow on my front wing.


Couldn't the understeer be there because you're going too fast into the corner with the push?

Max Torque
08-05-2018, 22:58
In my understanding, the car ahead benefits from drag, too and it is also logical. But: the car behind should profit more as it does not "hit the wall" - it only will upon leaving direct slipstream. This corresponds with my observation when watching Formula 1 overtakes in the "good old times", before aerodynamics where close to perfection. These "good old times" should be closer to current e.g. GT3-realitiy than modern Formula 1.

DECATUR PLAYA
09-05-2018, 04:46
Couldn't the understeer be there because you're going too fast into the corner with the push?

^BINGO!!!!!!!

All cars can draft each other. The way that they draft or slipstream is highly dependent on the design of the car. For instance NASCAR drafting and IndyCar drafting is not the same. Cars are not designed the same so the air coming off the car in front is different therefore the draft effect is different but the same if that makes sense.

The cars get a draft effect much further away than you may think and dirty air is no bueno. Dirty air can have disastrous effects on the cars handling. This is represented in the game.

TX3 StorM
09-05-2018, 23:20
Sampo -> Absolutely not. I always pay attention to my pace in the corners and believe it or not but when a car is within 1 second I lose pace in the corners, so when I say understeer I mean my word, I feel understeer.
Decatur -> Obviously all cars can draft each other, and obviously following the design and the body work of the car, the draft and the way the air flows on the car is different. That's the reason why the 2018 F1 have so much trouble to overtake, because they move a pretty huge amout of air and create turbulences, causing the car behind to not work to its full potential.

sas5320
10-05-2018, 01:18
The only form of racing I knoe where a _trailing_ car can remove rear aero from a leading car is NASCAR. And even there they have to basically be almost touching.

DECATUR PLAYA
10-05-2018, 04:44
Sampo -> Absolutely not. I always pay attention to my pace in the corners and believe it or not but when a car is within 1 second I lose pace in the corners, so when I say understeer I mean my word, I feel understeer.
Decatur -> Obviously all cars can draft each other, and obviously following the design and the body work of the car, the draft and the way the air flows on the car is different. That's the reason why the 2018 F1 have so much trouble to overtake, because they move a pretty huge amout of air and create turbulences, causing the car behind to not work to its full potential.

The last part of what you said is what we call dirty air in NASCAR but you just explained it in Formula 1.

DECATUR PLAYA
10-05-2018, 04:45
The only form of racing I knoe where a _trailing_ car can remove rear aero from a leading car is NASCAR. And even there they have to basically be almost touching.

^He just explained it in Formula 1.

TX3 StorM
10-05-2018, 10:30
That is what I read. The only kind of racing where the leading car can actually gain a bit is the NASCAR & ARCA racing. For the rest, I have never heard of any form of aero push, so it must be insignificant compared to the slipstream effect.

CoproManiac
10-05-2018, 11:48
The more I read about this, the more I get confused.

Bump drafting seems to have nothing to do with the car in front gaining speed from reduced air resistance that forms behind the car which gets removed by having a car closely behind him.
Bump drafting is literally BUMPING into the car in front to PUSH him forward.
https://en.wikipedia.org/wiki/Drafting_(aerodynamics)#Bump_drafting
"Bump drafting is a tactic used at Talladega and Daytona. The technique was initially popularized by the Archer Brothers in the SCCA Sportruck series during the late 1980s.[5] It begins as normal drafting, but the following car pulls up behind the lead car and bumps into the rear of it, pushing the lead car ahead, to maintain momentum."

This is what it looks like in single seaters, notice how he actually touches the car in front and pushes him forward:
https://wtf1.com/post/teammates-bump-draft-overtake-spa/

Aero push has nothing to do with the car in front gaining speed from reduced air resistance either. It's an effect that affects the car that's in the slipstream of the car ahead.
It's basically an effect which removes front downforce due to the lack air pushing down on the splitter, because it's not receiving said air due to the slipstream.
Explained in this video at aobut 4:25:

https://www.youtube.com/watch?v=v52XXzK0MQ0

Anyone knows the correct term for the effect that's being discussed here?

Zaskarspants
10-05-2018, 12:03
Two cars one behind the other will go faster the closer they are.

A thought experiment may help that removes all but the essential elements.

Two cars are traveling side by side. Each car has say 300 hp and say 1 sq meter frontal area, so you have 600 hp and 2 sq meters of drag producing frontal area.

Now imagine the cars are very close, imagine them physically joined. Now we have 600 hp and 1 sq meter of drag inducing frontal area, so a faster top speed as drag is reduced.

Clearly this is a limiting case with the complexity removed but that is in principle why push aero is a real effect that applies to all objects moving in a fluid ( air and cars in this case).

MaXyM
10-05-2018, 12:14
We know such effect exists. What is being reasoned here is a scale of this effect achievable in PC2.
I want also add that following a car being in dirty air seems to me exaggerated too. I mean for example GT3 or GTE cars following each other more than half a second away. I suspect the this phenomenon is simulated in very rough way due to it's natural complexity. This is why there are cases which might be way off.

Zaskarspants
10-05-2018, 12:28
^^^ I was explaining the front car will go quicker as the previous post appeared to claim otherwise, from Copromaniac. It does seem counterintuitive so I was trying to show how it happens.

I am sure you are right about the complexity of simulating this.

IIrc aero effects such as this were increased after a patch as people observed slipstreaming was not effective enough. I think it was an early patch.

CoproManiac
10-05-2018, 12:32
I'm not denying that the effect exists, I was just hoping someone could tell me what the actual term for this effect is so I can research it better as aero-push and bump draft don't seem to be the correct terms.

I just found this which might explain the increased understeer: https://auto.howstuffworks.com/auto-racing/nascar/nascar-basics/nascar-drafting4.htm
"The Archer brothers, Tommy and Bobby, made their mark in the Sports Car Club of America (SCCA) when they used a technique called bump drafting, also referred to as impulse momentum in engineering circles, to steal the lead from the competition. The technique involves the trailing car driving up and actually hitting the lead car's bumper to shoot it ahead while pulling the trailing car behind it.

Dr. Jerre Hill said he was skeptical about the process, and that the math and physics didn't quite mesh with the reality. But whether it works or not, the technique is impressive -- and dangerous. The trailing driver needs to hit the lead car in precisely the right spot and at precisely the right angle. Failure to do so can lead to disaster. Hill said as the trailing car comes closer to the lead car the air stream under the car, the downforce, is disrupted. As this happens the nose of the lead car begins to raise a little adding an upforce to the equation. The lead car's tires have less contact with the track and can often slip entirely even before the bump is made. Drivers will often take advantage of this in the last laps by getting close to a lead competitor in exactly the wrong spot and unsticking their tires by manipulating their downforce stream. They may also add a small bump and just that fast, a potential first place finisher moves to the back of the field."

sas5320
10-05-2018, 13:26
In NASCAR this typically results in oversteer for the lead car as primarily rear aero is removed. If the lead car (in game) is getting understeer push, I don't have any explanation.

TX3 StorM
10-05-2018, 13:43
sas5320 -> this is what I feel though, and many other esport drivers report the same things I reported earlier on the topic. It actually feels like you are in the dirty air of a car, taking the slipstream of it.... but you have nobody in front !!!
That's quite strange to be honest, and you have the proof in the videos I put on the first page.

CoproManiac
10-05-2018, 13:43
In the info I found it says the nose of the lead car raises a little, adding upforce. So less downforce on the front equals more understeer.
Anyway, in game it certainly adds more understeer instead of oversteer. If in reality it should add more oversteer then I'd say the effect in the game is incorrect.

"Hill said as the trailing car comes closer to the lead car the air stream under the car, the downforce, is disrupted. As this happens the nose of the lead car begins to raise a little adding an upforce to the equation."

CoproManiac
10-05-2018, 13:46
sas5320 -> this is what I feel though, and many other esport drivers report the same things I reported earlier on the topic. It actually feels like you are in the dirty air of a car, taking the slipstream of it.... but you have nobody in front !!!
That's quite strange to be honest, and you have the proof in the videos I put on the first page.

I agree, I have a harder time driving the car when someone's behind me than when I'm in the slipstream of someone else.

TX3 StorM
10-05-2018, 14:20
So what to think about this guys ? Is it an actual issue of the slipstream not behaving like it should or is it wanted from the game devs ? That's what I would like to know, because we can give many reasons for that but we need to know what the developers think about this.

MaXyM
10-05-2018, 14:30
Devs are reading. Apparently. Though

But I wouldn't hold a breath.

Mahjik
10-05-2018, 15:13
As cars follow, it adjust the exit of air from the front car. How this affect the behavior of the car is a little hard to know which factor creates which behavior. The front car will travel faster along with the car (or cars) behind. This is because the air exiting the rear of the front car is not as disturbed. This will also make the lead car faster into a corner which can and will give the impression of understeer. i.e. it's not the effect of the draft that created the understeer but the fact that the car entered the corner faster.

I personally have experienced this in real life. During a time trial session, a car in my class tried to draft me for a faster lap. As I entered T1 for the track with him directly behind, I almost went straight off the track. I didn't account for the slight increase in speed during braking which caused my car to push as I entered the turn. The driver following me really thought I was going straight off the track but I was able to scrub off enough speed and get the car rotated enough to stay on the tarmac.

I'm not saying this is exactly what is happening in this thread, but I wanted to provide some real world examples of what can happen.

DECATUR PLAYA
10-05-2018, 16:03
Bump drafting is when you actually make contact with the other car.

Aero push has to do with the manipulation of the air or vacuum of air between 2 cars. Thats why it can be hard to catch guys because as you run in his dirty air you are pushing him faster by pushing on the vacuum created behind his car. You can also move guys cars around a lot by crossing this vacuum of air when the car is weightless. As a cars weight transitions from one side to the other for a fraction of a second the car is weightless. If you cross a guys slipstream at this exact moment you can almost spin him out. This is represented in game.

What we refer to as aero push is simply entering the corner faster than you normally would and not adjusting your braking point causing the car to push on corner entry. Understeer.

Bump drafting is a dangerous technique because it requires a feathery touch from the second car as he brings in his car to make contact.

CoproManiac
10-05-2018, 18:20
Bump drafting is when you actually make contact with the other car.

Aero push has to do with the manipulation of the air or vacuum of air between 2 cars. Thats why it can be hard to catch guys because as you run in his dirty air you are pushing him faster by pushing on the vacuum created behind his car. You can also move guys cars around a lot by crossing this vacuum of air when the car is weightless. As a cars weight transitions from one side to the other for a fraction of a second the car is weightless. If you cross a guys slipstream at this exact moment you can almost spin him out. This is represented in game.

What we refer to as aero push is simply entering the corner faster than you normally would and not adjusting your braking point causing the car to push on corner entry. Understeer.

Bump drafting is a dangerous technique because it requires a feathery touch from the second car as he brings in his car to make contact.

Nope, that's not what Aero push is :p I also thought it was what you say, but when I googled it, it appeared it's not the effect what you're talking about.
I posted a video in post #31 which explains Aero Push.

I'm not sure what the correct name is of the effect that causes the car in front to gain an increase in speed. I would like to know it though.

Aero Push:
When following another vehicle closely, the airflow off the lead vehicle does not travel across the following one(s) in a normal manner. Therefore, downforce on the front of the trailing vehicle(s) is decreased and it does not turn in the corners as well, resulting in an "aero push." This condition is more apparent on the exit of the turns.

CoproManiac
10-05-2018, 18:39
As this site explains, the effect that give the leading car an increase in speed is indeed called bump drafting:
https://www.racingjunk.com/news/2017/03/29/slipstreaming-aero-push-and-maintaining-tires-on-the-oval/

Bump drafting:
"When they’re upon the back end of their competitor’s car, the air between the two can drastically alter their performances depending on where they’re meeting. If the two cars meet on a straighter portion of the track, and they’re closely matched in straight-line speed, the rear car can actually use the air cushion to push the car in front. Therefore, the leading car can accelerate faster than it could running alone. Known as bump drafting, this technique can be used by two teammates willing to cooperate temporarily to break away from the pack."

Aero Push:
"Because high-speed cornering relies on the airflow over the body (and the wings, in the case of a sportscar/formula car), the passing car needs to be completely free from the passed car’s wake so that clean airflow will press the four wheels firmly into the asphalt. If they fail to break free of the wake, their tires won’t turn as much as they want, and they’ll suffer from what’s called “aero-push.”

"If the passing driver does not make it ahead by the corner entry and follows too closely, they can use the air cushion which propelled theiradversary on the straight to gain an advantage. In the middle of a corner, that air pressure will push the leading car into an oversteer, or “aero-loose.” It’s a crafty tool, if a slightly dirty one – though NASCAR isn’t for the meek."

So it should actually result in oversteer while in PCars it gives understeer?

DECATUR PLAYA
10-05-2018, 20:09
Nope, that's not what Aero push is :p I also thought it was what you say, but when I googled it, it appeared it's not the effect what you're talking about.
I posted a video in post #31 which explains Aero Push.

I'm not sure what the correct name is of the effect that causes the car in front to gain an increase in speed. I would like to know it though.

Aero Push:
When following another vehicle closely, the airflow off the lead vehicle does not travel across the following one(s) in a normal manner. Therefore, downforce on the front of the trailing vehicle(s) is decreased and it does not turn in the corners as well, resulting in an "aero push." This condition is more apparent on the exit of the turns.

Aero push for the lead vehicle to fast corner entry.

Aero push for the trailing vehicle is no downforce on the front of the car.

You get Aero effects on corner entry, corner exit, and straights. All having different effects.

You cant bump draft without the bump. The whole act of drafting is sometimes identified as bumpdrafting but you cant bumpdraft without the bump.

sas5320
10-05-2018, 20:25
sas5320 -> this is what I feel though, and many other esport drivers report the same things I reported earlier on the topic. It actually feels like you are in the dirty air of a car, taking the slipstream of it.... but you have nobody in front !!!
That's quite strange to be honest, and you have the proof in the videos I put on the first page.

Not denying your report Storm, you are great pilot and I watch your fights with Jardier every Tuesday. If trailing car is cause understeer on lead car in the game then the game model physics is incorrect. Only oversteer (rear aero loss) can occur for the lead car and only understeer (front aero loss) can occur to the trailing car.

TX3 StorM
10-05-2018, 21:11
@Mahlik -> thanks for the report on real stuff, interesting to read. Unfortunately, the only thing that is different between my situation in the game and yours in real racing is on Project CARS 2 we are talking about gaps of 5 tenths and even a second, possibly a second and a half, which not only was not your case, but also is nowhere near NASCAR racing where aero push/bump drafting is supposed to occur.

@sas5320 -> Thanks buddy for the kind words, indeed I've had some close battles with him, sometimes I had the edge, some other times he had it. But I can confirm that the trailing car cause understeer on lead car in the game. That's what many drivers have reported in the esport community when I asked them if they ever had things similar, and almost 95% of the time, it was : understeer and higher top speed...
The remaining 5% was just because they couldn't tell if this was understeer or a sudden lack of grip... I actually think the understeer causes a lack of grip, that's why some told me that.

Mahjik
10-05-2018, 21:42
@Mahlik -> thanks for the report on real stuff, interesting to read. Unfortunately, the only thing that is different between my situation in the game and yours in real racing is on Project CARS 2 we are talking about gaps of 5 tenths and even a second, possibly a second and a half, which not only was not your case, but also is nowhere near NASCAR racing where aero push/bump drafting is supposed to occur.


To be honest, I don't know how close the car was to me during that incident. I know he was behind me but I don't know the exact distance. I was too focused on trying to slow the car down and not fly off the track! ;)

TX3 StorM
11-05-2018, 12:14
Or you just maybe braked a little late... Idk
Maybe you entered the corner with too much speed.

Mahjik
11-05-2018, 20:02
Or you just maybe braked a little late... Idk
Maybe you entered the corner with too much speed.

Naw. I have hundreds of laps at that track. Missing a brake zone is not a thing. Braking too early may happen, but not missing a brake zone. There is no denying that two cars can travel faster together than apart so I know the speed was increased. That is just science and proven.


The draft is when downforce and drag, as well as a few other factors, come together on the track. Drag and downforce are affected by airflow coming off of cars driving close by -- usually within a car length, though effects can extend up to three car lengths away.


The two-car draft is the most basic draft pattern and the one most often used by a team. Pulling within a car length of a lead car benefits the trailing car by reducing drag. That same reduction also benefits the lead car as the presence of the trailing car reduces the pressure drag off the back of the lead car. The result is a speed increase for both drivers.

Keena
11-05-2018, 20:19
Every days a school day..
"The draft is when downforce and drag, as well as a few other factors, come together on the track. Drag and downforce are affected by airflow coming off of cars driving close by -- usually within a car length, though effects can extend up to three car lengths away. In common drafting situations, the lead car breaks through the air in front of the line, or pack, and reduces the friction drag for trailing cars. But the trailing cars play a role as well. In addition to friction drag, there is pressure drag created by the low pressure behind the leading car. By staying close to the lead car the trailing car interrupts that low-pressure system and cuts down on its effects. The end result is about a 5-mile per hour (8-kilometer per hour) increase in speed for each car in the draft."

Depending on your background, you may find it easier to understand it in terms of induced drag rather than pressure drag..

3 mins in
https://youtu.be/70s1Zycr_x0

MaXyM
11-05-2018, 21:08
So it looks like PC2 simulates this effect too early (with much more distance between cars)
Of course mentioned figures are rough examples and the effect depends on aerodynamics of cars as well as their speed. But still...

Keena
11-05-2018, 21:48
Yeah- its my understanding that for the car in front to benefit they have to be really really close.. the youtube link shows that quite well i think. There is a potential for a reduction in induced drag from the car in front as the aerodynamic effect of the following car intrudes upon the aerofoil airflow of the car in front, but i would think the effect of this would be minimal compared to the primary effects demonstrated in that link at the 3 min mark. In my job induced drag is a commonly understood concept but the only thing that we are concerned with is fuel efficiency, so my understanding might be slightly off for this application. Fair play if its modelled though- quite impressed if so. If its a bit inaccurate, who cares. Its all about the immersion ;)

TX3 StorM
20-05-2018, 19:24
Well I did a race just a couple of minutes ago and having cars both behind and ahead is terrible. You first suffer from the dirty air of the car in front and you also suffer from this thing that we have tried to give an answer to.