Expert: Dan Liddy - 3/19/2005

Question
I was wondering if a flat underbody would increse downforce and reduce drag, or would a specially designed venturri style underbody be required to have any affect, thanks.

Answer
Hi Chris:

My understanding of it all is that a flat undertray acts to streamline the underside of the car and enhance it's ability to get down the straights. As to whether it would enhance downforce , I'm not sure, but I believe the effect would be minimal.

Forgive me for correcting you but the Venturi effect relates to air moving through an enclosed space, like a carburetor throat. What you are referring to is the Bernouli principal which speaks to air moving over a curved surface. It is what makes airplanes fly.

And with that in mind, a properly designed Bernouli undertray would be capable of developing a bunch of downforce over the chassis, added to all the wings and things they use topside.   Big trouble is that it plays hell with routing the exhaust, all the while trapping a furnace full of heat. And all that aero stuff requires zillions to develop.

Final comment about aerodynamics. All that foolishness you see on street cars is window dressing. NONE of it does much of anything at speeds under about 125 MPH.

I hope this answers your questions !!

Sincerely,

Dan Liddy
Sarasota, Florida