Setup for top speed run?

Howard Jones

Supporter
Neil, We both know what we are trying to say without scaring Michael out of dipping his toes into a mile style event. At this point, it's really up to him how to proceed.
 

Neil

Supporter
That is true, Howard. The summary of our advice is to approach it cautiously and in steps, not just go out and make a Banzai run.
 
I 100% agree with you, Neil.

As someone who has run these cars at very high speeds in a road racing environment, I would highly recommend that you move slowly from a high downforce setup to a moderate or low downforce configuration. You don’t ever want to find yourself in the position of not having enough well-balanced DF at these speeds. Be careful about assumptions especially regarding how much front downforce you’re actually generating.

From my experience, I would say that starting in a low DF configuration could be very dangerous at high speed (+160mph). From what I've personally seen with the QRP 25 hour car and with the Raver Motrosports car, the SLC has a tendency to pack air under the nose and front wheel arches causing front end lift in certain conditions. The front end DF or lift would certainly be a concern to me at 200 mph especially with a stock body car without canards, fender vents, flat underbody, side-skirts and race splitter. Keep in mind, that you cannot fully control variables like wind speed, and direction. A gust at the wrong angle at these speeds can go from a pucker moment to a catastrophe in the blink of an eye. Too much rear DF can also be an issue if the distribution of downforce on the car is heavily rear because this can cause the rear to "squat" at high speed, causing more air to be caught under the nose. As the attitude of the car changes, you can go from making decent DF to having significant lift very quickly. I would not underestimate the power of the air moving underneath the car at around 200 mph.

We’ve done a lot on our cars to try and minimize the risk of a Mark Webber/Posrche style backflip. That starts with improving the balance of downforce, specifically by making changes at the front of the car. Since we’re doing a lot of high-speed cornering too, high front end DF is more important than in most applications but it shouldn’t be ignored in this environment either. Controlling the airflow into and out of the wheel wells is really important at these speeds. The potential for the nose to come up and cause the car to take flight is the reason why modern LMP and DPi cars have the top of the front fenders cut away. After that Nissan GTR G3 flew into the crowd at the Nurburgring a couple years ago, anti-wheely strategies were also developed for a number of motorsports control systems what will automatically cut power if the front shocks begin to extend past safe levels. The idea is to cause the weight to transfer back onto the front end driving it downward. We employ this fully automated strategy on the Raver car but I pray we never get the opportunity to test it’s effectiveness.

I’m not saying don’t go run any high speed events. I’m not trying to scare anyone, and I think the car may shine in this environment if properly setup. I would not shakedown a new car in this environment but it sounds like you’re car is past that stage. Like anything else in racing, I would approach it with caution, making small changes to your already vetted and tested setup until you get to a place where you’re happy with the high-speed setup. Once you get that setup dialed in, then you can go for a full throttle, all-in pass with greater confidence in your machine and minimize the associated risks.
 
Good advice. Especially to proceed gradually and with caution. I'd like to do one of those events at some point and will refer back to this thread.

A friend of mine's brother in-law participated in the Texas mile a number of times. He spent $20,000 on a roll cage, which ended up being a wise investment when things went sour for him there one year.
 
... I plan on removing the rear race wing and the front canard winglets. Any other suggestions? SLC WHP East
Sorry for the late reply. I've run Texas Mile after some high speed on-road racing. I removed the wing also.

First time I had run over 60mph w/o the wing. Over the years I've been dialing out more and more AOA on the wing, so probably don't have a huge amount of downforce now.

I still found it VERY disconcerting running w/o the wing. The car MOVED around. Took several runs to get comfortable with it. It was not at all un-safe, just totally different. I run the huge end plates which may contribute to stability as well. By Sunday, I could comfortably make the corner at the end of the run at 140-150.

I had lots of engine issues, a few driver issues... So no real speed. But did see 175+ on six cylinders (two pistons holed).

Be careful on the painted bits. Down two cylinders I could still light them up in 3rd across the markings.

My suggestion for a first timer: Your goal is to take your time and have fun. Don't set a MPH or license goal.
 
In relation to Hill's comments, I should mention I have front fender vents, run the car at 3"F, 3.5"R, Street tail with the whole back end of the the tail removed (from taillight to taillight and down to the bottom).
 
Caster 6, camber 1, toe we measure in inches, with nose off. 3/8” front toe in as measured from back of tires to front of tires (is that clear?). Sorry for the toe in inches, but we are dirt guys 90% of the time. Was only a few years back that we stopped eye-balling the toe ;).

rear we are running same camber, 1/8” toe in.

IMHO, not much handling difference between 1/8” toe in and 3/8” unless you have some flex up front. Though for open road racing it will help keep some heat in the fronts between corners.
 
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