jorj7

If this is a race car, then just put a hose on the hole in the firewall and route
it to a hole through the sunroof. No need for the cool suit. Just make sure
the hose is fire proof...

heinrich

Am I reading wrong George, wouldn't a hose exiting the roof actually be less effective than a simple hole at the base of the windshield?

jorj7

The negative pressure at the sunroof will "suck" air out of the engine compartment.

Jim M.

If I remember correctly didn't Devek try a full underbelly pan and found the handling got really touchy at speed.

Lizard928

Any suggestions on how to add that hose and make it look half decent George?

Lizard928

Jim, you do yes have to be very careful with a full belly pan, if it is not done correctly it can make things worse

ew928

Pair of double layer fire-proof (don't want any engine compartment fumes or fire to enter passenger compartment) tubes running up the A pillar. Attach the tubing along the front A-pillar part of the roll cage.

Probably never pass tech as I'm not sure if the safety guys want to see any large connections like that past the firewall.


Is that why they call it a firewall. Wall to keep the flames outta the passenger cell.

jorj7

If you didn't have all the climate control stuff in the passenger side behind
the fire wall and removed the glove compartment, then I'd plumb it there and
route the hose up the passenger side A pillar to the roof.

jorj7

If you did it right, you wouldn't need to "cut" the firewall, just remove the
seal between the firewall and the heater vent intake area. Seal up the
regular vents to the outside there, and then use the hole for the AC stuff to
get into the passenger compartment. Then connect that to the hose going up
the A pillar. The hose can be boxed or formed so it doesn't look like a hose if
need be.

ew928

The hose can look like part of the roll cage.
Got it.

But don't most race organizations require sunroof closed for their events?
So the trick would be to remove seal around the sunroof and vent engine compartment out around the sunroof.

dprantl

This is also the number I recall for the S4/GT. You have to remember, though, that lowering the ride height will lower the frontal area.

Dan
'91 928GT S/C 475hp/460lb.ft

atb

"negative" pressure is higher, otherwise correct. The high pressure areas are at the front vertical surface (point 3) and base of the windshield (point 13) and then at the rear spoiler (point 30).

FlyingDog

I've been waiting for somebody to bring this up, although the responses so far are pretty much what I expected.That crash had very little to do with the belly pan and more to do with the rest of the aero.

I am planning a full belly pan with diffuser for my car. The radiator will be inclined at a steep angle with a vent in the hood. There will be other venting, but nothing will go into the cockpit. As much as certain people claim that it's foolish not to run 305+ wide tires on a race 928, I'm sticking to 275-285s due to drag. It will be interesting to see how it fairs vs BMWs weighing 100-300lb less with 245-255s and Vettes weighing 100-500lb more with 315-335s.

Louie928

I talked to Marc T. about the underbelly pan & rear diffuser. It was stored in his shop "attic" along with a bunch of other neat experimental stuff. He said that it did supply rear downforce in a goodly amount. Handling became squirrelly above X mph. The thought was that it lightened the front. Possibly adding more aero bits to the front would have helped, but I don't know.

mark kibort

why is that? less tires being seen? thats the only thing i could see effecting frontal area and as it is, that would be fairly small. 1" lowering 10" tires, 10sq" x 2 or almost .13 sq-ft??

mk