Grand Tourer Road Car to GT Race Car.

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CarBastard

CarBastard

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GTP_ARP93
Hello GTPers :gtpflag::

Like a week ago I saw the video of Hans Joachim Stuck driving the Nordschleife in his BMW M3 GTR and decided to try it myself. Trouble is, GT5 has no E92 BMW M3 GTR (And the Standard E46 is well...a hideous Standard with generic sound and no cockpit view). So I looked for the Specifications of a GT class racing M3, and I found the ones of the M3 GT2 that raced this year at Sebring and Le Mans (It was something around 450HP and 2745 Lbs, which I took as 1375Kg, according to this link.).

I bought a new M3 E92 and I gave the car everything from the Tunning Shop (Except a Turbo), re-painted it, change the rims to some RAYS ones (Like on the real M3 GT2), added a front splitter and a huuge rear wing. I also bought for it all sets of Tyres but sticked to driving on Racing Hards (as I suppose they're the "most realistic" ones for a Race Car). After adding the necessary ballast and limiting the engine power so I could get the exact HP and Torque numbers, I just adjusted a little the Transmission and Suspension to my taste and went for the Nordschleife. And boy it was amazing!!!

I was quite happy with my little project car that I had taken from a Grand Touring road car to a Green-Hell racing GT Class racing beast, so I decided to try my hand with another car of this type, and bought a Jaguar XKR which received the same treatment. And then another, and I bought a 458 Italia which received the same treatment. And then another, and I bought a DB9 and...you get the idea. And I want more. But I found trouble when the sources I use in different websites say they all have different HP and Weight and Torque ratings. What standard should I use then?

For example, my BMW M3 "GT2" is the slowest of them all. I also have a Jaguar XKR "GT2" (a la ALMS Rocketsports Jaguar) which comes stock with a Supercharger, and given that I can't remove it I decided to upgrade it as well (It's a race car after all, everything gets upgraded! :D) and now it gives a humongous and unfair amount of torque, but on the other side weighs way to much than the other three cars. With the 458, I couldn't find any specific data regarding it's Power/Weight/Torque, and with the "DBR9" I found some specifications that suggest 600HP and 1100Kg, which is way overkill compared to the BMWs power and it's a weight the car in GT5 can't achieve despite full weight reductions.

So dear GTPers, my question, after all this wall of blabber, is: How to make a realistic GT racing car from a road car?

A cool bodykit is obvious. A resembling paint scheme is as well. But what about the power/weight/torque? (What do rules say nowadays regarding the power in the GT category wether it's FIA or A.C.O?) What about the tyres? (Is it too easy/overkill to use Racing hard tyres?)

Please guys, I need a little help here. I absolutely love GT race cars, but sadly PD has given us NONE OF THEM and a veeeery few amount of Race Modifications. I really want to keep turning road cars like the 458, the M3, the DB9, the XKR, the Gallardo, the GT-R, the Corvette, etc, into their racing counterparts (458 GTC, M3 GT2, DBR9/DBRS9, XKR GT2, Gallardo LP600 GT3, GT-R GT1, C6.R), and try them all around the Nordschleife, but first I need some realistic data to model them to represent as accurate as possible their real world counterparts and not just be a "fully-tuned" GT5 car.

Thanks in advance! :sly:
 
hawkeye122
I know that I already made a thread relating to this 2 months ago...
Click to expand...

Your thread doesn't adress my questions but whatever...

Could a Mod please merge this thread with this other one ?

Anyway, I've worked out a way of establishing 3 (fictional, but real world inspired) classes which should prove competitive between the cars of each category given that they're balanced with their Power/Weight ratios, which should also make the categories different enough from one another too feel they actually are from a different category, even if they're based in the same car. I'll post more info when the threads are merged 👍.
 
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Just relating to the original Stuck statement. Isn't that qualifying lap with the E46 GTR? we have that in the game.

I too have tried making GT2/GT3 racecar-esque vehicles, but I just can't get that high level race car feel or look to them(they have more aggressive ride heights/splitters and arches).
I think I'll turn to FIA-GT4 style for my race car dreams as this seems more achievable. I think the Camaro RM might be close to the FIA-GT4 spec, though I will look into that more as it would be good to use as a benchmark.
 
Well, as promised, here's my solution to the issue. In my intention to have some GT race cars to have fun with, and extending my help to the GTP community, I give you the three classes of the "Gran Turismo GT World Championship" :D.

Trying to replicate real-life specifications of modern GT racers in GT5 cars proved to be hard. First of all, not all of GT5 cars that have a real-life racing counterpart are able to reach the horspower or the weight of the race specifications, a problem apparently encountered by many. Second of all, due to the ever-changing specifications of the F.I.A and the A.C.O , it's also hard picking a specific real-life category in which all of this cars in GT5 can participate and are able to compete with realistic, competitive, specs. I still gave it a try anyways, as realism was the aim of my project, and started with two cars that are competing in the same category this year.

I began with the 458 Italia and the Lotus Evora, which are both racers in the A.C.O LMGTE PRO category. What caught my attention about their specifications (according to the internet) is that both weight the same (1245 Kg) and have almost the same power (470HP in the Lotus, 465 in the 458), and thus have the same Power/Weight ratio, which might work as a way to equal performance in all cars across a category. Both this cars of the 2011 A.C.O GTE specification have a Power/Weight ratio of around .37 BHP/Kg.

With the idea of a established Power/Weight ratio to equal all cars within a category, I browsed for the specs of the now-gone but glorious A.C.O GT1 car class. This was the class with the Corvette C6.R and the Aston Martin DBR9. Interestingly, I found that both of them also have a similar Power/Weight ratio, .55BHP/Kg for the Aston and .52BHP/Kg for the 'Vette. Given that the Aston in GT5 can't even get close to those specs (600HP for the DBR9, which can be matched in GT5, but 1100Kg, which is around 300Kg less than the minimum weight of GT5's DB9) it seem apparent that I needed a middle category if I wanted to include this mythic (and gourgeous racer). So, what's between .37 and .5X? .4X!

After this thinking, I stablished three fictional classes for GT5 cars that would be representative of both the modern A.C.O GTE specs and the old A.C.O GT1 specs, with a middle point to make things more interesting and also to fit a wider range of cars. I equaled things among the cars with a mandatory Power/Weight ratio for them, as I previously said. The categories are GT3E, GT2C, and GT1A, being GT3E the lowest tier and the one resembling 2011 A.C.O specs, and GT1A being the highest tier based on old GT1 specs. The mandatory BHP/Kg specification for the categories is: .37BHP/Kg for GT3E, .47BHP/Kg for GT2C, and .57BHP/Kg for GT1A.

Now, back to GT5 territory.

All cars are fully modified and then de-tuned with the use of engine restrictors and ballast. Here's the parts list:

GT Auto:
Full Aero (As many aerodynamic parts as possible. For downforce and "RACECAR!!!" factor).
Styling changes (As desired by the car's owner).
Oil change (Only when necessary to meet a HP rating and there's nowhere else to go. Shouldn't be done when a car doesn't need the extra HP).

Tunning Shop:
Full Weight reduction (Stages 1, 2, and 3).
Increased rigidity.
Lightweight Windows.
Carbon Hood.
Full engine tunning (Stages 1, 2, and 3).
Modified ECU.
Modified Intake manifold.
Racing air filter.
Titanium racing exhaust.
Modified Exhaust manifold.
Modified catalytic converter.
Supercharger (Depending on the category rulings. See below).
Turbo Kit 1/2/3 (Depending on the category rulings. See below).
Fully customizable transmission.
Fully customizable suspension.
Twin-plate clutch.
Semi-racing flywheel.
Carbon driveshaft (Where available).
Torque sensing center differential (Where available. Must be set to 10 in the front and 90 in the rear).
Adjustable LSD.
Full compliment of Racing Tyres.

However, with "fully modified" came the issue of turbochargers/superchargers, which I decided to solve this way: GT3E cars aren't allow to use any turbochargers/superchargers unless the car comes stock with it, in which case it can't be modified from it's stock form to a custom turbocharger/supercharger. GT2C cars aren't allowed to use any turbochargers/superchargers unless the car comes stock with it, in which case it can be modified from it's stock form to an upgraded turbocharger/supercharger (It still has to meet Power/Weight ratio regulations). GT1A cars are allowed to use any turbochargers/superchargers if available, even if the stock car doesn't have one (It still has to meet Power/Weight ratio regulations. This is done to truly make it the fastest and most brutal category). Other problems I found were how to adjust the Weight and Power of the more flexible cars to fit in certain category without allowing too much of an unfair difference, so I also stablished a minimum weight for each category, and how to deal with 4WD cars which will, as in real life, be forced to run as RWD as possible.

Here's an explanation by class:

Class GT3E
Based on: 2011 A.C.O GTE specifications
Power/Weight ratio: 0,37751004016064257028112449799197 (The one of the Lotus Evora GTE, 470/1245. Shortened to .37).
Minimum weight: 1245 Kg.
Turbocharger/Supercharger rulings: Not allowed unless fitted in factory form. In case it has one, it can't be upgraded or modified from it's stock condition.
4WD Rulings: 4WD cars are not allowed.
Competing cars: Ferrari 458 Italia, Aston Martin DB9, Lotus Evora, BMW M3, Ford GT.

Class GT2C
Based on: Middle point between GT3E and GT1A, pre-2011 A.C.O GT2.
Power/Weight ratio: 0.47 BHP/Kg.
Minimum weight: 1290 Kg
Turbocharger/Supercharger rulings: Not allowed unless fitted in factory form. In which case it's allowed to upgrade/modify them as long as the car still complies with the
BHP/Kg rating.
4WD Rulings: 4WD cars are allowed but trough the use of a custom center differential they must send as much power as possible to the rear axle (10/90 distribution).
Competing cars: Aston Martin DB9, Corvette Z06RM, Dodge Viper SRT10, Ford GT, Jaguar XK-R, Ferrari F430, Nissan GT-R.


Class GT1A
Based on: A.C.O GT1, Polyphony Digital "Dream Car" class.
Power/Weight ratio: 0.57 BHP/Kg.
Minimum weight: 1100 Kg
Turbocharger/Supercharger rulings: Allowed where possible, as long as the car still complies with the BHP/Kg rating.
4WD Rulings: 4WD cars are allowed but trough the use of a custom center differential they must send as much power as possible to the rear axle (10/90 distribution).
Competing cars: Lamborghini Murcielago LP670SV, Ford GT LM Spec II Test Car, Corvette ZR1 RM, Dodge Viper SRT10, McLaren F1.

Later on I might add the specs of my cars as suggestions, but the beauty of this system is that cars can be adjusted at will and still be competitive with the others in it's category. Throw in PD made race cars and RM cars like the Vette and the GT Test Car just to show who's best, if PD racing or GTP racing. Give the Vettes and the Vipers the same specifications to finally decide who's king. I don't know, go nuts!!! Above all, have fun!!!

Comments and criticizm very much appreciated 👍
 
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hawkeye122
Can the M3 be modified to be that light?
Click to expand...

Nope, but it can be given extra horspower to achieve the same Power/Weight ratio as the Lotus and the 458 Italia. Same goes for the DB9 in the GT3E category.
 
This is scary man, I have been trying to turn the M3, the Z4, the SLS, the 458 and the Evora into their counterparts from Le Mans and the Nürburgring 24h for the last few weeks :)

You put a lot of work into this, great! I'd love to race you online in these things one of these days if you're interested.
 
i've been doing the same thing scince this years Le Mans, although my cars just look like GT cars, i havnt got round to tuning them properly.
 
In my experience, basing classes around ONLY power-to-weight ratio will not work. It is, however a good starting point. Factors to include are

*Torque Curves - A torque Viper V10 will likely destroy a F430 because of the torque curve. Do you add more power to the Ferrari or add weight to the Dodge to compensate?

*Straight-line speed - BMWs have never been the most aerodynamic cars, and usually have a disadvantage on long straights. This should also be taken into account.

*Intangibles - Some cars are just "better" than others. You'll never get cars to be exactly equal (as shown in the real world ACO's "balance formulae" or in GT5), but you can get close. The only real way, however, is to test them. And test them. And test them some more.

I tend to take any set of cars I'm testing on a short-twisty course like Autumn Ring, a medium course like Trial Mountain, and a long fast course like Fuji. Then, based on their fast-lap times, I tweak horsepower, weights, or even parts, and do it all again. Even use different tracks to get a good feel for what the cars can do across the spectrum.

Food for thought.
 

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