This is a brief tutorial on iRacing Dirt Sprint Car Setup Building. I’m not going to get into too much detail here. You can actually get what you need to build iRacing setups for the Winged Sprint Cars in my Sprint Car Setup Matrix that I made right after iRacing released the dirt content. Some of you may prefer to simply download a great setup, and I have plenty of those in the OSR iRacing setup repository.
I’m not one of those fast guys, but I am a thinker. I have a background in engineering and physics and I understand what certain changes to a race car chassis are supposed to do. Those things usually work in the real world if you do your calculations correctly. In iRacing, you never really know if it’s going to work or not. All you can do is try the change that is supposed to work. If it doesn’t, it’s really down to trial and error and that’s time consuming.
In addition to my background, I’ve been building iRacing setups for over four years now. I’ve learned a lot about how “iRacing physics” works. It’s not the same as real physics. Physics is a known law. There is no gray area. In iRacing, you just don’t ever know for sure.
It took me a while to really get a feel for any of the dirt cars. Now that I have just begun to be able to really tell what the cars are doing, I think I’m prepared to offer a little help in the setup building area, so let’s get on with it.
Let’s start with step one. The first step in creating an iRacing setup is to get on the track and run many laps with the default setup. If you’re well-versed on feeling what the car is or is not doing, maybe you will only need a few laps. This is a good time to do a fuel run. Run about 2o laps at race pace. Get a feel for the setup and see if you can tell what needs adjustment. Is it loose or tight somewhere? That what it really boils down to. For your fuel run, hit F4 when you finish your 20 laps to see how much fuel you have left. Subtract that from how much fuel you started with. That leaves you with how much fuel you burned. So let’s say you want a setup that will finish 50 green flag laps and you just burned 5 gallons of fuel in your 20 lap run. Here’s the formula:
Fifty divided by 20 times 5 is equal to 12.5. So you’re probably going to put 13 gallons in the car. If you depend on cautions in your Sprint Car and want to take a chance, you could put 8 or 10 or 12. But if it goes green all the way, you’re going to lose. So the formula goes:
#laps in race divided by #laps in fuel run times fuel burned or #racelaps/#lapsrun*fuelburned.
See, you don’t really need that telemetry after all. 🙂
So now you can set your fuel pretty close and maybe do another run later to make sure you got it right, and you should have some kind of feel for what the car is doing wrong that you want to correct. This is really where you want to refer to my setup matrix and make ONE change. Don’t stack the adjustments. Make one change at a time and test it, then move on. I’ll touch on a few adjustments and try to explain what they do and how they will affect the handling of the car.
Work with tire pressures in your setup for different track conditions. You need more pressure for a wetter, heavier track. If the track is dry/slick, lower your tire pressures a little, particularly on the right rear.
The right side tire is bigger than the left side tire. Anybody who has ever seen a Sprint Car knows that. That is tire stagger. Think of a plastic cup. It’s bigger on the top than it is on the bottom. Put the cup on a flat surface and roll it. The big end travels a lot further than the small end, and the cup won’t roll straight. It turns toward the smaller end. In a Sprint Car, one of the purposes of tire stagger is to make the car turn left. Front tire stagger doesn’t carry a lot of significance, but rear tire stagger is important. If your iRacing Sprint Car feels too tight, or doesn’t want to turn left enough when exiting the corner (that would be turns two and four) you can try raising the rear tire stagger. I have noticed that this also loosens the Sprint Car on corner entry (tunes one and three).
Torsion Bars and Torsion Bar Stops
If you have tinkered with setups that have springs, think of the torsion bar in the Sprint Car as the spring. It performs the same function. If you lower a torsion bar diameter it’s equivalent to softening a spring. The torsion bar stops should be adjusted to return the car to the original ride height after you change a torsion bar diameter. You can also use the torsion bar stops to change ride heights as a chassis adjustment.
Shock Absorber Bump and Rebound
Bump – How much force it takes to compress the shock. More bump means it takes more force to compress the shock.
Rebound – How fast the shock will “rebound” and return to its normal state. Keep in mind that a higher rebound setting actually makes the shock rebound more slowly. Rebound adjustments actually affect the opposite corner of the car. So if I want the dynamic weight to shift to the right rear of the car more quickly on acceleration, I might lower the left front rebound to make the shock rebound faster so that the weight will get on that right rear more quickly. Always keep that in mind and it will help you a lot.
There is only one wing that is adjustable on the iRacing Spring Car, and that’s the big one on top. It provides downforce which is what makes this car so wickedly fast in the corners. If you increase the wing angle or move the wing back, you get more downforce and it generally tends to tighten the car.
To get you started, run some laps, then decrease the right rear torsion bar diameter, then adjust the right rear torsion bar stop to return the right rear to the original ride height. Make some more laps. The car should feel a little tighter on exit. Now go back and raise increase the torsion bar diameter to more than what it originally was. Adjust the torsion bar stop accordingly. Run some more laps. The car should feel looser on exit.
Now you have some laps on the iRacing setup. If you don’t know what the setup is doing wrong, you need to run more laps and figure it out. What you’re looking for is something that is not too loose and not too tight anywhere around the corner. So, take a look at my matrix and start making one adjustment at a time, then testing to see what it does. In time, you will learn what works and what doesn’t work, and what works best for you. Good luck!