Step 11: Fix the Performance

Remember all the problems you had in the last step? In here, you can fix them.

First, I found the torque curve to be weird, so I took it and raised the torque peak.

That's better, don't you think?

I also noticed the drag coefficient to be a little high for this car, so that came down too.

Then, I took it for a test drive, and discovered the engine mass to be too high (slow revving!)

I got everything the way I wanted it.

Matt has a wealth of suggestions for getting your car almost exactly like it is in real life. So here's Matt.

1. Use the dragstrip and back the car up all the way to the beginning. Drive the car all the way down the strip and when the car reset complete the lap and press <Esc> & <End race>. You now have the cars exact topspeed. Change the rolling resistance to tune the cars topspeed. Note: Don't forget to use full springs, no toe-in or spoilers (if any) and that cars with low torque/power rpm peak might be faster with lower gearing!

2. Run the car down the strip again trying to accelerate as fast as possible from 0-200 kph, when you reach 200 kph try holding it there or preferable a little over 200 kph then try to deaccelerate as fast as possible (200-0 kph). You can now use the replay/analasys/speed to check the cars acceleration/deacceleration. Simply use the fast forward button to scroll forward until you see the speed change from 0 to 1 mph. Read the timer (for me it always reads 4.8 seconds so I don't have to check this time every time). Momorize this number (or write it down on a piece of paper) and scroll to let's say 62 mph. Now read the timer (let's say it says 8.8 seconds). You're car does 0-62 mph (100 kph) in 8.8-4.8=4.0 seconds! Easy huh? You can keep scrolling to what ever speed you like; 100 mph (160 kph), 125 mph (200 kph) etc. Now scroll to the very moment you start deaccelerate. On the way down when the speed hit 200 kph (125 mph) read the timer (let's say it reads 15.0 seconds). Memorize this number or write it down on a piece of paper. Now scroll forward until the speed says 0 kph and look at the timer (let's say it says 20.3). You car deaccelerates from 200-0 in only 20.3-15.0=5.3 seconds!

You can adjust the acceleration and deacceleration in many diffrent ways, with transmission inertia and variouse of settings in the .tir-files etc. Weight also affects the acceleration figures a whole lot. Personally I prefer tuning a car so that it matches it's real life counterpart instead of just using real life values and hope that the game engine will create the perfect car for you (it will never happen!)

3. You need to test the car around a track you know the car's real life counterpart can finish in a certain time. You can also compare the topspeeds if you have access to all of this. Most often it is very hard to find information about things like this.

4. Test the cars re-grip by sliding it a little bit throughout some corners during diffrent speeds. A more powerful re-grip will be achieved by making the diffrence in tire grip front/rear bigger. If you know how to tune .tir-files you can adjust the speed of lateral movement and a whole lot of things. I you want alot of control you should try raising the inertias to let's say 50000/60000/20000 and change the cp_height to maybe 35.0. This will make it possible to powerslide the car like crazy. Using these settings together with really low grip (needs to be set in the .tir files) and you're close to building a really cool rally-car. Remember that a heavy rear end will make the rear brake out easier but also make the car harder to control during high speed... Don't make the car too heavy at the rear or it will be too hard to powerslide it. You can make sure the cp_height is not too far off normal by driving the car really fast and the spin it around by putting in the reverse. If the cp_height is too high the air underneith will lift the car up in the air and if it is too low the car will roll over. Higher cp_hight means more control and higher cp_long means more general understeer... don't go too high on that one either (I personally use 45 compared to the original vipers 51)

5. Do some dougnuts and "jump" over some curbs in some tight corners to make sure the car doesn't flip over. This will happen with certain settings in the .tir-files and/or if the car is too light.

I could go on and on about performance editing... there's simply so much more info than we can ever put in a turtorial. Only by changing the .tir-files you can do all of this...

Change the overall tire friction.

Set how much energy that will be lost into the body/chassis of the car instead of pushing it forward and that way alter the cars performance in the mid-range speed.

Set how much the rear-axle torque of the car will affect the grip.

Set how much and how easily the car will slide sideways before the tires re-grip.

Set the tire rubber harder or softer which will affect the "control" and "snap"

Set how much the chassis will respond to tire grip for example doing wheelies etc.

Change the tire air pressure which affects how much grip will be lost because of bumps on the road or when you brake.

Change how much skids the tires will leave because of bumps on the road.

Change the longitudal grip.

Change the speed and range of lateral movement when grip is lost.

...but in case I come to think of anything else that is essentional to changing a cars performance I will post here. Unfortunally I have promised some of the more important persons in the VR community not to say too much about the .tir-files at this time so I will have to post a more exhaustive turtorial for that at another time. For more info on performance-editing send me your questions at

If the torque-curve is too flat or not flat enough:

1. Raising the maximum torque amount will lower the amount of torque at low rpm's and give you a more pointed torque curve.

2. Lowering the maximum torque amount will raise the amount of torque at low rpm's and give you a more flat torque curve.

3. Raising the torque peak rpm will lower the amount of torque at low rpm's and give you a more pointed torque curve.

4. Lowering the torque peak rpm will raise the amount of torque at low rpm's and give you a more flat torque curve.

5. Lowering the power peak rpm will raise the amount of torque at low rpm's and give you a more flat torque curve.

6. Raising the power peak rpm will lower the amount of torque at low rpm's and give you a more pointed torque curve.

7. Lowering the maximum power output will lower the amount of torque at low rpm's and give you a more pointed torque curve.

8. Raising the maximum power output will raise the amount of torque at low rpm's and give you a more flat torque curve.

Please note that cars with a very low power/torque output will tend to get flat power/torque curves no matter what you do.

It is also possible to tune these power/torque curves so that you will experience something like a turbo kicking in at a certain rpm. However the effect will be quite powerful and resemble that of a dirtbike (I had a Kawasaki KX 80 as a kid) but also force the power output higher than the value you've used in the .cf-file. Maybe I could explain how to do this another time.

The car revs too fast or not fast enough:

Try this formula for the engine inertia: max. torque (lb-ft) / 36. If this doesn't work try raising or lowering the value a little bit until you get the result you are looking for. A car with higher torque/power will need a higher engine inertia or it will rev too fast and the other way around. Please note that cars with low engine inertia, very low torque at low rpm but loads of power at high rpm will rev really slow at low rpm but really fast at high rpm.

P.S. If the torque/power curves seem really screwed up the diffrence between the maximum power and torque is too big or not big enough - - or - - the diffrence between the torque and power peak rpm is too big or not big enough. Setting the power peak rpm lower than 5252 can also screw things up. I have created many diffrent calculators but none of them has been good enough in my opinion so I have never shown them to anyone, but here's one of them if you would like to try it out: (right-click and choose "save target as") P.P.S.

Once you are happy with your performance, you can move ONWARD.