GTR2 GET REAL PHYSICS MOD 1.3

SUMMARY OF CHANGES


DRIVETRAIN LOSS

I have implemented new method of simulating drive train loss which is modeled inside the engine file itself rather than via HDC file clutch friction parameter. The reason for this is that the game engine does not automatically adjust provided friction value (calculated for maximum torque rpm) but instead it applies fixed value across the entire rev range which is incorrect and results at drivetrain loss which is not consistent across the entire rev range. There is minimum affect on car performance if you stay inside power band however but standing starts and low rpm/high gear acceleration is improved. Braking stability will also be slightly increased because of this change in more powerful cars.

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SUSPENSION

I have provided more accurate wheel mass data together with corresponding changes to their inertial values. Original cars had all the same unsprung mass (except Lotus) and too small inertial properties modeled and this is now fixed. Similarly spin inertia and wheel/spindle friction values have been updated to reflect these changes. They take into account new wheel masses and tire radius to calculate new values which were shared across the board previously. Of course this now also has small affect on a total drivetrain loss simulated per vehicle.


CAR SPECIFIC CHANGES


Viper GTS-R - tweaked body drag value based on a new radiator intake size reference area

Morgan Aero 8 - fixed slightly too low body drag

Porsche GT3 Cup - removed splitter as its already taken into account in body aero calculations (very understeery car but very stable and easy to drive). New body inertia values which were shared before with GT3-RS.

Gillet Vertigo, Viper Competition Coupe - updated splitter downforce/drag and body inertia values. Particularly Viper CC had its inertia set way too low compared to its mass.

Mosler MT900R - updated splitter downforce/drag.

TVR 400R - overhauled aerodynamics, the car has significantly more downforce now on high downforce setting, but with splitter on setting 1 there is almost no front end downforce and minimal drag. This was done based on a car speed at Lemans and photo evidence. More realistic engine with 400HP.

Creation Lister Storm - more realistic engine spec with 557HP

BMW Z3M - now uses road car engine with 325HP, mass increased to 1375kg with corresponding inertia changes. This has shown much more realistic lap times than before and is within 0,5 seconds from 2002 lap times at Spa.

Lotus Elise - updated body inertia values


Install this on a fresh installation of the game or over version 1.2
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Newest version features updated aerodynamics, new realistic engines and improvements to the tire model and AI.

Aerodynamics

All the cars got refinements to the aerodynamics, on some cars differences are noticeable, on others not. With the help of the chatGPT I have redeveloped certain aspects of the sim such as drag coefficients for radiators/brake ducts and tires which results in slightly more overall drag in most cars. Body downforce is also very slightly increased now taking into account lower rideheight and wider body relative to the road version of particular car. I have updated rear wing center of pressure values which differ from previous ones very slightly.

Tires

You will immediately feel that the front end of the car bites more now as front tires and now identical in performance to the rears. In original physics they were downgraded in order to get car stable because of the shortcomings in tire model. I was able to unlock full potential of the tire grip with this new latest update and now they will feel better than ever. AI tire model also got updated and is more realistic, which brings their performance closer to player car.

Engines

Previously I held belief that original data is authentic for engine performance. But tests using new update have revealed that some cars were consistently faster than they should be. It turns out that many engines were too powerful. Here is the full list of cars with new spec engines:

Viper GTS-R (Force One remains the same)
F550 JMB and Wieth
F575
Lamborghini
Saleen
F360 GT + GTC
Nissan
BMW Z3M
Gillet Vertigo (2 versions)
Lotus
996 GT3 Cup
Seat

for which exact specifications can be checked in the game.

Updated documentation

Install this on a fresh installation of the game!

Version 1.1 brings many improvements across the board. The most important beeing new tire model. Cars will have better front grip and therefore corner entry speed due to corrected front tires grip values which were not modelled properly in original game. Same sized tires will have identical grip coefficents on both axles. Tire sizes were corrected for certain cars. There is significantly better control of the car under coasting.

I have updated aerodynamic data for all cars also. For example many cars use fixed splitter now. Rear wing lift and drag curve have been updated since Simbin used incorrect linear model. What this means is that you will have more downforce available at lower settings and more drag at higher wing settings than before. Overall minimum and maximum downforce values stay roughly the same. Cars have different maximum settings available now due to their aero configuration.

I have implemented more accurate brakes behavior for carbon and iron brakes separately. Cars are more stable under braking due to new thermal model. Carbon brakes now run significantly hotter than before with a peak temperature in excess of 700 degrees C.

Implemented real gearboxes for selected cars which incorrectly shared their gear ratios with other cars.

Updated drivetrain loss simulation logic. As a result acceleration performance will be slightly better.

Updated AI physics model and made additional setups for them. Some tracks grip values were readjusted. No longer will AI have better grip on certain tracks. This was possible thanks to overall physics improvements.

Updated documentation

If you are using old version of my mod delete it first and then install this!