wushunut

This is a question for all the racing and aerodynamics gurus out there. I noticed that a lot of the high end performance cars, and many race cars, feature an underside that's completely covered and flat. My basic understanding is that this helps create a venturi effect and helps increase downforce by a significant amount.

My quesiton is whether something like this can be done (is worth trying) on the 8? Is it even feasible without windtunnel testing? Underbody heat (trapped) issues? Could you end up flipping your car a la Mercedes LeMans racer?

Inquiring minds want to know. :p

wushunut

oops...maybe I'll search first next time.

for others who want to know... https://www.rx8club.com/showthread.p...ight=underbody

so anyone try it yet? Results?

Paul_in_DC

Heat would be a major issue with the Renesis. What speed would you be going that it would make any difference to the aerodynamics of the 8?

wushunut

Not really thinking of doing it for myself. Just intellectual curiousity. I think the other thread mentioned that just 50mph would be sufficient to produce downforce. I just wonder that having a flat underside that is poorly designed could cause lift instead!

mikeschaefer

Having nowhere for the air to go but straight through would cause the air to have a high relative velocity. High velocity equates to low pressure so you would be sucked to the road. The only way to induce aerodynamic lift is to increase velocity above the car higher than below the car (lower pressure above the car than below the car).

wushunut

Ah..i see. Makes sense. Bernoulli's principle? It might be an interesting experiment if I wasn't so paranoid about the heat issue with our cars.

Blue87Sport

I believe that reducing aerodynamic drag is a larger consideration for most cars than downforce. Aero drag is usually the limiting factor on top speed. Downforce is easy to manage through wing, spoilers etc.

KYLiquid

right, while aerodynamic forces act on anything as it moves, they really come into play around 55+ mph.

You could plate the underside of the car up to the exhaust pipe...on either side of it, so the pipe was 1/2 exposed to open air, it has a pretty straight shot front to rear something like this : _____||______ the plating runs on both sides, tight to the pipe....almost touching.

The other ways to solve the heat issue is heat wrap around the pipe....something most race cars have anyway...ect

other things to consider, if you seal off the whole underside of the car, you would really want to now adress the cooling of the trany and diff, they would no longer have airflow near them, so you would need to install oil coolers for them, with pumps to circulate the fluid thru them, again this is something most race cars have anyway. Trany temps can get VERY high in WOT accel, esp in a car with a lot of power and grip...theres a ton of friction in there, I think the McLaren F1 hit 400* when it was going for a top speed run, in the trany!!!

If you can weld, you could get some aluminium sheeting, and construct your own undercarige aero-package, using factory bolt holes to hold it in place, later if you were really serious, you could find a way to mount it withough the bolts being exposed, or use things like carrige bolts (smooth top)

beachdog

There is an aftermarket kit for the c5 Corvettes. It is a combination aero cover and structural reinforcement for the underside. It covers most of the bottom from the rear of the front wheel wells to the front of the rear wheel wells. They don't do anything about heat. It covers right over the exhaust pipes through the midsection of the car.

Paul_in_DC

Yikes! I can just imagine sitting at a stoplight in traffic as my center console starts to melt...

Moonrover333

yeah under trays are nice but not really cost effective for streeting and minor track use though some company in japan made one for a very overlooked car the GT4 (celical all track here in USA) it took the car from 60 lbs of lift and 100mph to 470 lbs of downforce at 100mph so yeah they are pretty kool

mikeschaefer

470 lbs of downforce? so being conservative and saying about 235 front and rear... I hope they put on stiffer springs!

Moonrover333

yeah it was really crazy lookin pan had all these scoops and whatnot it was for "full race applications and like i said it only made that much at 100mph and in all honesty if your going 100 in that car your an idiot that is a born/ breed rally car but i'll see if i can find it

yiksing

Lower your car, put side skirts on (prevent air from getting under the car from the sides), front spoiler (for down force, better yet prevent air from going under the car), rear top wing approximate height of roof for downforce, rear underside kit for helping air to get out from bottom of car.