Re: GT4 - Redline Specifications

[Tomte]

Well, I think, cause we are in early development yet, we can slow down the car. It's not a good start to have the Test Mule already breaking the "speed wall" of other real GT4.

We noted for quite some time that cars are quicker in Redline than in real life, with some notable exceptions. While top speed can be matched somewhat easily, the acceleration is mostly too good.

After doing some quick laps with some road cars (968 turbo S and CS, Z3 M Coupe, 911 CS, XLR). It appears to me that the turbo S is a class above the others on this track, probably due to the higher torque.

So I thought I have a go at another test mule, based on Andreu's BMW Z4 M Coupe. For this car, some real numbers exists.
Still, I managed a 2:00 on the third lap....

So I guess we need to go down with the tire stickyness (0.15?) and the downforce (0), but I'm not sure if this will make a lot of difference.

[theSnail .@y]

So I guess we need to go down with the tire stickyness (0.15?) and the downforce (0), but I'm not sure if this will make a lot of difference.

I have tested a .car for Nissan 350z with numbers close to real life (when I could find them) and when I reached a handling that pleased me it was faster than the real thing up to 8 secs on all the tracks where I found real lap times. I checked the length of the tracks in reality and RL - they matched
I have tried a higher front air resistance (and lost about 2 secs ?).
I have lowered the torque but this significantly changes only the 1st lap time ...
Downforce was already 0.
Tire stickyness is 0.17 as you told me to do.
I weakened the brakes and lost some time again (2 secs ?) since I have to brake (and go slower) earlier before the turns.
I'm still too fast even though with such settings I now have difficulties reaching the real top speed on most tracks (I can't reach it on "official" GT4 european challenge tracks).

Of course I'm no expert in .car files but the 350z is fine to drive (for me at least) and these are conclusions I made 2 weeks ago ...

Cu this evening on IRC to discuss the matter Tomte

[DonaemouS]

there is a value we didn't touch in all the .car file.

the wheel friction. May this value change how the car handle? (maybe making slower, increasing tarmac resistances, and so on)

[Tomte]

there is a value we didn't touch in all the .car file.

the wheel friction.

I don't understand wheel fricion enough to be willing to change it at this moment. Right now I leave it at 10, but I remember that there where already some discussions about it while balancing the performance of the TCC cars.

On another note, I rechecked the downforce/lift values given on Mulsanne Corner. The model 2000 Porsche 911, the similar aged Audi TT and Mazda RX7 produce lift in the area of 90 to 270 kg at 240 kph, which would translate into lift coefficients between 0.30 and 0.92 in total.
Given that most cars in GT4 don't have any wings which would cancel out or reduce the lift, my assumption of using -0.1 to 0 was probably a wee bit off
Now, we also know that in Redline, gravity is not up to what it used to be, so I wonder how much this influences our discussion here.

In any case, if we don't find a good and comprehensible way of bringing the GT4's performance down to real life, I'm prepared to accept a standard which is reasonable in comparison with Redline GT3, TCC and road cars.

[C14ru5]

I don't understand wheel fricion enough to be willing to change it at this moment. Right now I leave it at 10, but I remember that there where already some discussions about it while balancing the performance of the TCC cars.

How about looking at the test that I did on the matter a while ago?
Car's physics and setting: wheels.friction
Result: a road should have wheels.friction close to 50, if that value is to represent all the power loss after the gear box.

Changing wheels.friction for a GT4 car will have little effect on lap times, because it only is noticable at low speeds. At high speeds, the air resistance becomes the most important factor.

I think the better-than-real-life performance comes from the suspension, sway bars, load sensitivity and tire slip ratio. No easy way out of that mess, I'm afraid. But I agree - test driving a car in any simulation game should result in slower laptimes than in real life, as we're not as good a driver as the race drivers that set the lap record we're comparing it to.

[Tomte]

Another idea I'm having is to limit the power to the wheels to say 98% or so (by setting wheels.powered to 0.49 instead of 0.50). This mainly acts on the top speed and a bit on acceleration and costs me some 2s per lap.
But then again, what's the top speed of a GT4? That depends on the gearing obviously.

For now I have 3 test mules in the works, 2 with 6 gears, one with 5. I spaced the gears so that the cars reach about 270-280 kph on a flat road, but on most tracks these cars hardly reach 245 kph. As this mostly equals 5th gear, I wonder if a top speed of 250 - 260 isn't sufficient.

EDIT: I just tried the 98% thingy on the two other test mules. It really cripples the top speed, but not in a consitent manner. Some cars are just a bit affected, others seriously. Seems to depend on the amount of torque available... It was probably a crap idea....

[C14ru5]

I just tried the 98% thingy on the two other test mules. It really cripples the top speed, but not in a consitent manner. Some cars are just a bit affected, others seriously. Seems to depend on the amount of torque available...

The consistency has to do with the differentialLockCoefficient (which has to do with difference in torque). I found that out last year in the early stages of the Ford RS200 development. If the diffLock is above a certain value when the sum of wheels.powered < 1, top speed is crippled.

[djpimley]

Another idea I'm having is to limit the power to the wheels to say 98% or so (by setting wheels.powered to 0.49 instead of 0.50)

I would hate to see a kludge like that. Have you played with the engine's friction settings? I don't think it makes any significant difference but perhaps a very large increase in RPM and base friction would take the edge off acceleration.

[Tomte]

I wouldn't like to play with the friction settings for the simple reason that I use these settings to control the off-throttle and coasting behaviour through corners.
And I think you would need an awful lot of friction to do that, I already tried that once. Of course, one could compentate a bit with engine inertia, but this often has other side effects.

Maybe it has less to do with acceleration but with cornering ability (or wheels.stickyness).

I think I will not follow the wheels.powered settings any further, better to leave them alone. Instead, I'm more and more thinking "what the heck, as long as the performance difference is reasonable to the GT3 and TCC cars, it will be ok."

[C14ru5]

Maybe it has less to do with acceleration but with cornering ability

That's what I believe. For instance, low sway bar settings easily adds two-three seconds to a lap time. (I'm not saying that low sway bars are correct, just that they have a great impact on performance.)

[Tomte]

Interesting idea.
In the meantime, I updated the GT4 test pack, now including another old banger of mine and the Z4 M which Andreu was kind enough to share.

3 test mules
Please have a go.

[Tomte]

I'd just like to know the development status of the GT4 class.

For what I know, we could have the following cars:
BMW M Coupe (Z3)
BMW Z4 M
Cadillac XLR
Chevrolet Corvette Z06
Ford Mustang FR500C
Nissan 350Z
Porsche 968 turbo S

For now, I have the .car of 4 cars in the works, still trying to slow them down.
While getting the cars down to parity (which is more difficult than I imagined), I'd like to keep them different enough, so that they all have their character. Specifically, I don't want them all to behave tomte-like.

- The BMW M Coupe should be quick, light, but not easy to master.
- The BMW Z4 M is for now very quick, with reassuring understeer.
- The 968 is again just difficult to balance. While having the lowest power/weight, it has one of the best torque/weight ratios. On some tracks it flies, on some it's just last.
- The XLR is the heaviest car with a short transmission, understeers noticeably, but is overall an easier drive than, say, the M Coupe.

On most tracks the Z4 M is the fastest car, sometimes beaten by the 968.
Actually, the Z4 M is annoyingly quick, I will need find some new different ways to slow it down some more. I'm thinking FAR at the moment, which would therefore be above factory specs.

I'd like to get a consensus on the performance vs reality level of the GT4 class:
I see the following options:

1. Lap times as close as possible to real life times, even at the cost of using lower than published specs
   
2. Factory specs all the way thought, the cars just end up where they end up.
   
3. Balance the cars that they are reasonably slower than GT3 and close/faster than TCC, depending on track)
   

Personally, I'm in favour of option three.

Apart form that, I noticed that the UV-Map of the M Coupe is not in a state to easily make a race skin for it, I will need to redo that.

NNB and I agreed that for future Redline Race Classes, the naming format should be: Race class - Manufacturer - Model Name (for example 'GT3 Laborghini Gallardo'), as these cars are meant to be driven against each other, be it LMP1, GT3, GT4 or TCC cars. We think that this should only apply for race cars, not for road cars, trucks or the like.

Feel free to say 'nonsense' or that I overcomplicate things.

[Aleksi]

Is there any built-in cars that would fit into class with some modifications? I don't have any modeling skills (yet)

[Tomte]

Is there any built-in cars that would fit into class with some modifications? I don't have any modeling skills (yet)

I'd say the Audi TT could fit, maybe with a tuned VR6 engine (no turbo/supercharging, just classic tuning like the BMW Z4 M). Which leads to the question if we allow AWD. I would be against it, as in GT3 (where the Gallardo and the Audi R8 had to be converted into RWD only).
Apart from that, a performance limited Viper might be in order as well, but it would need to be severely resticted, similar to the GT4 Corvette C6 (which runs with 390 hp in this series).

[Superslow]

a performance limited Viper might be in order as well

NOOO!

Vipers should always be about raw power IMHO.

[Tomte]

maybe if we disable the left cylinder bank? It would still be a 4.0l 225 hp inline 5.... with 400 Nm.... ok, bad idea....

[Aleksi]

Is there any built-in cars that would fit into class with some modifications? I don't have any modeling skills (yet)

I'd say the Audi TT could fit, maybe with a tuned VR6 engine (no turbo/supercharging, just classic tuning like the BMW Z4 M). Which leads to the question if we allow AWD. I would be against it, as in GT3 (where the Gallardo and the Audi R8 had to be converted into RWD only).
Apart from that, a performance limited Viper might be in order as well, but it would need to be severely resticted, similar to the GT4 Corvette C6 (which runs with 390 hp in this series).

Audi TT? Is that all? I'd like to see some older machinery as well, Charger, Mustang, Vette or even Pickup truck. And Maserati 3200 GT would be also good.

[djpimley]

Charger, Mustang, Vette or even Pickup truck. And Maserati 3200 GT

I just ate some crushed glass and stuck a hot butter knife in my eye socket... but it wasn't as painful as reading this sentence.

[Tomte]

In search of a somewhat realistic performance envelope, I revised the GT4 Redline Specifications slightly.
Same as with GT3 (even if not all of us cared), please add 100 kg for fuel and driver to the weight you find on the Fia GT4 pages. I presume that the stated homologation weight refers to car+all fluids except fuel.

Thanks.

[Tomte]

Good Morning,

I added the Redline GT4 specs to Wikispaces (link) for better visibility.
We can continue to discuss the development of cars here or at ASW.
The specs are still open for discussion, the balancing will be hell compared to TCC because there are many more factors involved now, so bring it on!

[Tomte]

New Test Pack released.
The pack includes the
GT4 BMW Z3 M Coupe
GT4 BMW Z4 M Coupe
GT4 Cadillac XLR
GT4 Porsche 968

The zip file contains 4 standalone redplugs (i.e. the original redplugs of the base cars are not needed anymore). The names of the redplugs are indiviual for easy update later on.
I'd like to see some MP action and have some comparison feedback here. Leo, could you make the Test Pack available on LOL?

GT4 Test Pack 1

Everybody who downloaded the earlier test packs, please delete the following folder in your plug-in directory:
Porsche_968_GT4

[leoantix]

yummy yummy and done

[theSnail .@y]

Please download the plugin here

[Tomte]

Looking good! Gotta test it later.

[theSnail .@y]

Thx Tomte - C14 did a pretty good job with this model

To make it short : yesterday we had several races on different tracks (often full house). The overall feeling seemed to be that the cars already have close performances in race. The best laps were often similar and the fights were really tight. We still have to get used to the new vehicles, but that should give us a good car class to have fun with.

PeSt had an issue with the gearbox of a bmw (I dont remember which one - I'm sure he will do), while Lippa was ok with it - both on keyboard - strange.

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