NASCAR Pavement Modified Ground Effects

[modhauler]

I run a NASCAR Wehlen-type pavement modified on road corses such as Watkin Glen, Lime Rock, etc. I am considering putting a full belly pan on it and was wondering 2 things:

1.) Should it be totally smooth or have downward facing louvers to draw air out of the engine compartment forced in through the radiator opening as well as accelerate the air going under?
2.) Will a "NACA" style duct function "backwards"? I mean, if installed with the "wide opening end 1st" leading the narrow opening end, will it draw air OUT of the inside space vs. push air in as normally used? I would like to use something like this to "evacuate/bleed" air out of the trapped ares (wheelwells, etc.)

Thanks in advance for any help...

 

[MikeHalloran]

1. I don't think there's a simple general answer beyond 'see the rule book' and 'spend some time in a wind tunnel'.
2. I think a NACA duct works by tripping the boundary layer at its leading edge and rolling it into a vortex, rather two vortices, that stay tucked inside the bodyshell. It has to work very differently going backwards.



Mike Halloran
Pembroke Pines, FL, USA

 

[modhauler]

The class that I run in for SCCA (SPO) has no restrictions on this type of enhancement. I was just wondering... Thanks for the response..

 

[lemans]

yes a complete belly pan.if you can upswept in rear or lower in center.

 

[mactem]

lemans, can you elaborate on the belly pan issue? What does "lower in center" mean. I'm building a sports car to do landspeed racing. (straight line for 1-5 miles highest speed) I'll be running between 180 and 200 mph. I can have a belly pan the full length of the car. I can also have side skirts and front air dam. Is a belly pan advantageous with those two? Thanks
David

 

[lemans]

Looking at the side of the car.if you make the belly pan lower say in the middle of the car picture a one pc. flat belly pan kinked in the middle down.This creates a nozzle effect,if you could also seal the sides to the ground the car will make more down force.I dont think you would want this on a l.speed car, MS.