Late Model Stock car areo

[nolin78]

I have a question regarding aero effect on a late model stock car with an "ABC" body. These bodies have templates that require everybody to have the same dimensions. These rules leave the underbody of the car open to design. These cars are tube chassis and pretty much open to the air underneath. we have a 4 inch ride height rule that we have to follow. heres some pics of last rears car. it is not an "ABC" body but very similar to it.

http://www.ryannolin.com/highlights_subway_milton_carshow.html

that picture shows the basic body. You cant see it but there is a 5 inch spoiler at the deck lid.

With that said, i was wondering if you guys know if there is anything i could do underneath the car as far as areo goes that would increase downforce even if there is added drag?

Ive heard there is benifits to "skinning" the underside. I think this would help speed air flow, thus lowering pressure.

is that true?

thanks for your help

ryan

http://www.ryannolin.com

 

[swearingen]

You're right about speeding up the airflow underneath to decrease the pressure. Don't forget to take into account the center of this pressure. If you need more front traction, move the center of pressure forward and vice versa.

Don't discount drag, though. On a high speed track with high banks, the drag may outweigh the benefit of the downforce you get in the corners. On a tighter track or road course, it could be well worth your investment.

 

[sprintcar]

Smokey Yunick went to Daytona (back in the day) with a car that had styrofoam inserted between all the frame rail sections to provide a smooth underbody. It cut the turbulent drag significantly. Read his series of biographies and other books when you get a chance.

If you're running short tracks - the typical 1/2 mile or less, you can put your resources elsewhere since the actual gain would hardly be noticeable. It might help in the third decimal place during time trials, but during the race you run in the turbulance created by the other cars. If you play on bigger track, skin the underside of the car. If you need weight, use .031 steel, otherwise 0.040 aluminum with a number of axial stiffening ribs rolled in. Fair it in around the driveshaft area, but remember to make the area under the transmission and engine easily removable.

Instead - try to get rid of ANY unsprung rotating weight, followed by unsprung weight. You've probably got the weight distribution correct. Spend a practice session doing tire temperature runs until you have the same temp all the way across the front tires. Caster/camber changes will get max tire patch.

Shock absorbers are your best investment. We run Bilsteins on the sprint car and have a definite advantage in the corners.. If you don't have a contact for those, I can hook you up.

Run synthetic lubes - We use Royal Purple in the engine and QC rear. It frees up a BUNCH of power, runs cooler, etc. Ditto on the hook up.

When I ran dirt late models, I converted the radiator rock shield into a wing section and ran a "skid pan" under the fuel cell that was actually another wing.

"If A equals success, then the formula is: A = X + Y + Z, X is work. Y is play. Z is keep your mouth shut."
-- by Albert Einstein