Holes in engine lid?

[widebody911]

I had the hole saw out today, and I was tempted to put a series of holes across the back of the engine lid. Kind of like this, but not so extreme. Advantanges? Disadvantages? Thoughts?

[Wil Ferch]

On my street 85 Carrera....I have two holes like shown on the bumper ( alongside the "3R" for reference)...these two holes fit "just" behind the rear license plate. Offers a degree of cooling while on the street ( plate does not fit tight against the holes), and removing the plate during track days is nice too.

I'm undecided what the "net" effect is if you put holes on the underside of the rear wing. Probably not a thing to do if you still run an A/C condenser there.

- Wil

[widebody911]

I already have holes behind the license plate, and yesterday I added a 3" one on each side. This is a 90% track car. I didn't know if having holes back there would be a good thing or a bad thing; with all of the aero threads lately, I'm kinda sensitive about the whole thing.

[Moses]

Originally posted by widebody911

Thom, I know a guy who makes a pretty cool carbon fiber RS heater tube. Dresses up the motor nicely.

[widebody911]

That's an old picture, but it was the only one I had available that showed the license plate holes

[Plavan]

I have been told that those holes were not just for cooling. Its also an aerodynamic aid. The rear bumper acts as a big "Sail" and alot of air gets trapped in the rear of the car. Putting holes there helps releave the pressure. Kinda like the cars that put big holes in the rear lexan windows.

[IROC]

Yeah, there would be a negative pressure area under the wing right there, and I suppose that these holes would allow the air to flow somewhere, but I bet one of the main reasons for the holes is weight reduction.

Mike

[widebody911]

So, you think I should do it, or not? I could always save the cutouts and glass them back in.

In other news, I installed pins back there, and removed the latch and pull cable.

[randywebb]

You could do it and then use smoke injection or even wool tufts to characterize the flow. If it looks ugly, you could seal them back up.

[widebody911]

Originally posted by randywebb
You could do it and then use smoke injection

Would the smoke coming off the headers from the leaking valve covers work?

[kach22i]

Thom, is this the tail you are currently running?

[buster73]

The holes can indeed reduce the total drag of the car. The rear bumper acts almost like a parachute (if not covered at the front). Not sure about the 911 aerodynamics in this case, but holes in the rear bumpers are quite common on the drag strip - and they save some weight too.

[kach22i]

Why don't you remove the reflector and put in some mesh like the white car - I think you have enough holes (for now).

[widebody911]

Yes

Originally posted by kach22i
Thom, is this the tail you are currently running?

[kach22i]

I found this - not holes but slots. Very poor pictures, not sure about this guy.

http://www.mintercreek.com/ndn/prj-71-porsche.html

[kach22i]

I'll give you all a good laugh today - think out of the box for a moment.

One big hole will solve everything- think big!

Feed the fan directly from the outside - no waiting.

I'm calling this one "Cool-Port-1" in honor of the "Cool Duck" series I did a while ago.

It just gets crazier from here - all the good ideas have been done. Just like all the good songs have been written.

[widebody911]

I like the drawings!

I'm going to go ahead and try it.

[fredmeister]

The rear wing is exactly that, a wing. Where you drilled the holes is a low pressure area which you want to keep separated from the high pressure area on top of the wing. By drilling holes there is no longer a separation or surface for the pressure to act upon killing the effect of lift on the wing. Just my opinion, but I would seal them back up.

[randywebb]

See... this is why you need to test it...

[jyl]

In Jack Olsen' "poor man's aero" threads I suggested reversing the engine fan to draw air from the underside of the engine and exhaust it out the engine lid, behind the tail in your case

Take it from a high pressure area, creating some ground effect (maybe). Exhaust it in a low pressure area, reducing turbulence and drag (maybe). Be unique and daring (definitely).

Hey, remember the F1 "fan car"