Engine variables

I want to understand the parameters set in the .eng file.

In this line from the Ford GT40, I understand the first value, which is rpm, and the last, which is torque produced at that rpm. But what does the negative number mean?

RPMTorque=(1000 , -78.90, 280.00)

I assume it has something to do with engine braking, the degree to which the car will slow down when one 'taps off' at that rpm?

Hey Uncommen!

I think i dont know more about this files than you. Values for the Engine Power. I work on this file with Toms Engine Shop v1.2. look here:
http://www.esport-racing.de/include.php?path=download&contentid=2252

Greetings
Muddie

Thanks Muddie will check it out!

While I am hardly an expert at this either, I do know how to fix certain pratfalls that can happen using the Tom's Engine tool. What I have had happen many times when creating more powerful engines from existing files is that the engine in game may not drop rpms very quickly to the point of them climbing without touching the accelerator. The values you posted RPMTorque=(1000 , -78.90, 280.00) its always the centre value being too low that causes this. Here is a larger sample below so as to be easier to illustrate. This is an engine with a max rpm of 8500rpm. Note the centre values. If they are raised (meaning lowered numerically given being a negative value) the rpms will drop slower and if raised too much will cause the rpms to climb without touching the accelerator. If you look further down there is a line named as EngineBrakingMapRange. This also affects how fast the rpms will drop and is used together with that centre value. While you could have these centre values set so as the rpms climb by themselves and could be countered using this other line, its hardly practical. Another potential problem can occur if the rpms fall too quickly causing the drive wheels to lock up and stall the engine. In that scenario it means doing the opposite with the centre values. Sorry if this makes things clear as mud lol If so, pm me and I'll try to better explain.

RPMTORQUE=( 5000 , -120.10 , 292.1)
RPMTORQUE=( 5250 , -133.00 , 297.1)
RPMTORQUE=( 5500 , -145.60 , 299.9)
RPMTORQUE=( 5750 , -157.00 , 304.4)
RPMTORQUE=( 6000 , -169.50 , 307.6)
RPMTORQUE=( 6250 , -176.00 , 312.7)
RPMTORQUE=( 6500 , -184.70 , 314.5)
RPMTORQUE=( 6750 , -193.00 , 314.5)
RPMTORQUE=( 7000 , -200.20 , 313.1)
RPMTORQUE=( 7250 , -213.00 , 311.1)
RPMTORQUE=( 7500 , -226.00 , 307.5)
RPMTORQUE=( 7750 , -238.00 , 302.2)
RPMTORQUE=( 8000 , -252.20 , 293.7)
RPMTORQUE=( 8250 , -275.00 , 284.3)
RPMTORQUE=( 8500 , -298.80 , 274.2)
RPMTORQUE=( 8750 , -315.00 , 81.7)
RPMTORQUE=( 9000 , -330.00 , 10.9)
FuelConsumption=3.11e-5
FuelEstimate=1.20
EngineInertia=0.195
IdleThrottle=1.0
IdleRPMLogic=(1300.0, 1500.0)
LaunchEfficiency=0.5
LaunchRPMLogic=(6000.0, 7000.0)
RevLimitRange=(8500.0, 0.0, 0)
RevLimitSetting=0
RevLimitLogic=150.0
EngineMapRange=(0, 1, 5)
EngineMapSetting=2
EngineBrakingMapRange=(0.00111,0.00077, 6)
EngineBrakingMapSetting=4

Perfectly clear thanks very much!

How do we set the engine negative torque, in other words the braking that the engine offers if one throttles down (take your foot off the accelerator pedal)?

I see this:

EngineBrakingMapRange=(0.00111,0.00077, 6)

But what do those elements mean? What does each parameter define?

I have found the Toms Engine tool to seemingly lack adding enough negative torque so it needs to be done manually in Notepad or whatever you use to open those files. Its a bit of trial and error to get it right.

The EngineBrakingMapRange=(0.00111,0.00077, 6) again, to say definitively what exactly each is, I would look dumb trying to someone that knows the proper terminology. What I can say is this...the left value is like a base amount of positive torque. If you find the engine rpm dropping too fast you can add the positive torque in the garage and in this example it can be added 5 times...why it says 6 yet only 5 in the garage I don't know.

Yeah I use Notepad++

The reason I am asking all this is I want to correct the Mirage (the JW Automotive Gulf GT40) performance in GTL; it is way off the pace it should be in comparison to the LM_CLASSICS cars. I tried reducing the weight and changing the aero cd and even put the Mk IV engine in it; almost no difference.

I have considered the possibility that if there is no .svm for a given track, the car will not have the right ratios, so at Le Mans it will not be able to take advantage of the long straights. I took the GT40 for a test and it hit redline very early; once I changed the final drive ratio it was fine, and I think maybe the sim cannot enable the right ratio without the .svm for that track while AI is driving?

Thanks for the input; always appreciated

The middle value is the engine brake torque at that very engine speed. The value can be read in two ways: its the torque you have to apply to the engine from the outside to keep the engine running at that speed, or the torque which will decelerate the car if you close the throttle.
To make it more visual, imagine travelling in a car on a decenting road. Depending on the gear you're in and the slope, the car might decelerate, hold its speed or even go faster, when you take the foot of the pedals. In the first case, the braking torque produced by the engine is larger than the forces produced by rolling down the hill, in the last case, the forces by rolling down the hill are larger than the engine's braking torque. If the car maintains its speed, even though the throttle is closed, the forces of engine and the car rolling downhill are even. On highly compressed engines, the torque can be so high, it'll lock up your driven wheels (and send you off track) if you do not carefully match the engine speed while shifting down.

Rule of the thumb, it'll be larger on bigger and more powerful engines, and it'll be larger on higher compressed engines.

Uncomman wrote:

Yeah I use Notepad++

The reason I am asking all this is I want to correct the Mirage (the JW Automotive Gulf GT40) performance in GTL; it is way off the pace it should be in comparison to the LM_CLASSICS cars. I tried reducing the weight and changing the aero cd and even put the Mk IV engine in it; almost no difference.

I have considered the possibility that if there is no .svm for a given track, the car will not have the right ratios, so at Le Mans it will not be able to take advantage of the long straights. I took the GT40 for a test and it hit redline very early; once I changed the final drive ratio it was fine, and I think maybe the sim cannot enable the right ratio without the .svm for that track while AI is driving?

Thanks for the input; always appreciated

While I do have GTL and have used it in the past it was very limited so I can't speak from experience regarding the ai or svm file. I'm much more well-versed with GTR2. Something you might want to look at if the ai is too slow for the field is in the tyr file assuming the tyr is the same for each game.

This value...

AIGripMult=1.010 You can adjust it without affecting how the tire performs when you drive it.

There is also these lines in the hdc...

AIMinPassesPerTick=2 - raising this will make the ai drive much better but can make a performance impact to your pc if its fairly old. 15 is the max and may reduce lap times by as much as a couple seconds depending on the track.

These lines can also make quite a difference to the ai's performance too.

AIEvenSuspension=0.7
AISpringRate=0.7
AIDamperSlow=0.5
AIDamperFast=0.5

The good part is these setting have no impact to when you drive.

0fflabeluse wrote:

The middle value is the engine brake torque at that very engine speed. The value can be read in two ways: its the torque you have to apply to the engine from the outside to keep the engine running at that speed, or the torque which will decelerate the car if you close the throttle.

Thanks Offlabeluse - I had assumed correctly then when I said I thought this was engine braking on throttle release. I have a very technical understanding of vehicle dynamics and variables in the real world; I am trying to gain an understanding of how those dynamics are represented in this modelling methodology.

Much obliged!

hmmguy wrote:

While I do have GTL and have used it in the past it was very limited so I can't speak from experience regarding the ai or svm file. I'm much more well-versed with GTR2. Something you might want to look at if the ai is too slow for the field is in the tyr file assuming the tyr is the same for each game.

This value...

AIGripMult=1.010  You can adjust it without affecting how the tire performs when you drive it.

There is also these lines in the hdc...

AIMinPassesPerTick=2 - raising this will make the ai drive much better but can make a performance impact to your pc if its fairly old. 15 is the max and may reduce lap times by as much as a couple seconds depending on the track.

These lines can also make quite a difference to the ai's performance too.

AIEvenSuspension=0.7
AISpringRate=0.7
AIDamperSlow=0.5
AIDamperFast=0.5

The good part is these setting have no impact to when you drive.

Understood - thanks! I've had a closer look at those settings and while I agree they will help, in this case the problem was causing a difference of around 16 seconds a lap and these would only have incremental effects. Interestingly, they had already been set as you specified anyway.

I finally fixed it by changing the final drive ratios; the GT40 was redlining about 15% into the Mulsanne straight, which meant it could not go faster than the 242 km/hr in its original specification. So it was getting around the track some 30 seconds slower than the leaders. In the 1967 Le Mans, the Mirages (which were lighter than the original GT40) and GT40s qualified about 12-15 secs slower than the fastest mk IV Fords, so once I changed the final drive, took a little weight off, and changed the aero cd, it is now qualifying in the right area, competing with the Lolas and Porsche 907s.

Now my field is ready to run the entire 1967 WEC series.

Thanks for the help

Uncomman wrote:

hmmguy wrote:

While I do have GTL and have used it in the past it was very limited so I can't speak from experience regarding the ai or svm file. I'm much more well-versed with GTR2. Something you might want to look at if the ai is too slow for the field is in the tyr file assuming the tyr is the same for each game.

This value...

AIGripMult=1.010  You can adjust it without affecting how the tire performs when you drive it.

There is also these lines in the hdc...

AIMinPassesPerTick=2 - raising this will make the ai drive much better but can make a performance impact to your pc if its fairly old. 15 is the max and may reduce lap times by as much as a couple seconds depending on the track.

These lines can also make quite a difference to the ai's performance too.

AIEvenSuspension=0.7
AISpringRate=0.7
AIDamperSlow=0.5
AIDamperFast=0.5

The good part is these setting have no impact to when you drive.

Understood - thanks! I've had a closer look at those settings and while I agree they will help, in this case the problem was causing a difference of around 16 seconds a lap and these would only have incremental effects. Interestingly, they had already been set as you specified anyway.

I finally fixed it by changing the final drive ratios; the GT40 was redlining about 15% into the Mulsanne straight, which meant it could not go faster than the 242 km/hr in its original specification. So it was getting around the track some 30 seconds slower than the leaders. In the 1967 Le Mans, the Mirages (which were lighter than the original GT40) and GT40s qualified about 12-15 secs slower than the fastest mk IV Fords, so once I changed the final drive, took a little weight off, and changed the aero cd, it is now qualifying in the right area, competing with the Lolas and Porsche 907s.

Now my field is ready to run the entire 1967 WEC series.

Thanks for the help

I think you misunderstood. Those values were merely for demonstration as to where I meant they could be found and not necessarily set as shown.

About the gearing issue, that is of course nothing to do with what I was referring to. No matter what values are used if the ai car is bouncing off the rev limiter it won't fix it. Same with the tyr aigripmultiplier setting. Those were mentioned to help dial in desired ai performance without affecting how the car is for the user. .svm files are the typical way to get ai to use certain setups for a given track though not the only way. Of course that is dependant on the grb file having the capacity to be adjusted for any given track.

Glad you got it sorted.

No misunderstanding, but I did give the impression I had not, sorry. I figured that it was for demonstration.