Rear brake cooling via rear 1/4 NACA duct?

widebody911 · widebody911's Garage

Has anyone tried putting NACA ducts in their rear quarters, just behind the doors, with a hose leading to the rear brakes? Something along the lines of the 930S, but with more of a NHRA look.

masraum · 11-13-2004, 08:53 PM

Wow, we go from famine to feast. You've really gone into top gear Thom.

Seems the tall slit vent like in the 930S or RSR's would be a better fit for the geography of the body in that area. Something like the fake vent at the same spot on a '69 Mustang.

911pcars · 11-13-2004, 11:44 PM

Some race regs. prohibit punching venting or duct holes in the body without pernalties. Not sure about yours.

Another altenative is to get some lexan or equivalent rear quarter windows, then install a NACA duct to each (pop-rivet or glue). Single duct per side can lead to rear brakes. Double ducts per side can provide air to the engine/air intake and to the rear brakes.

An inline electric blower will help the airflow.

Sherwood

robfike · robfike's Garage

In my present road race car, we have NACA ducts added to the lexan rear quarter windows. The air is routed to the rear brakes, and works very well. Our rules do not allow the addition of holes in the body if they were not factory.

armandodiaz · armandodiaz's Garage

Here's my answer to rear brake cooling:

JeremyD · JeremyD's Garage

Good grief - you can almost smell the brake dust!

widebody911 · widebody911's Garage

Yes Armando - kinda like that, but I was thinking just up a little, and horizontal. Looks like you're using the stock torsion bar hole.

armandodiaz · armandodiaz's Garage

I just molded a couple of nascar ducts to my rear rocker panels.

304065 · 12-09-2004, 07:14 AM

The NACA profile is unsuitable for high-pressure applications. Hang a piece of sewer pipe out there.

911pcars · 12-09-2004, 09:36 AM

"The NACA profile is unsuitable for high-pressure applications. Hang a piece of sewer pipe out there."

John may be right; the NACA duct/brake cooling scenario might fall under two different topics.

1. Free flow of air into a body panel with minimal turbulence
2. Adequate air flow to cool

The two may be mutually exclusive. One can look at CART, IRL and F1 pro racers whose typical terminal speeds (and thus air speeds) are way beyond the typical weekend racer and thus have less need for air pressure assistance. They also have scoops stuck in the airstream to grab cooling air, something not allowed (or wanted) on a street-type racer, although the rear wings on the GT-type rear spoilers use this method for intake or intercooled air.

Being such heavy beasts, the NASCAR types usually have inline blower motors to force air to the rear brakes and differential lube coolers. Compared to the front end, air pressure along the sides of the car are much lower. Lacking air scoops, some air pressure assistance like this may be needed for most effective cooling.

Sherwood

Neilk · 12-11-2004, 06:22 AM

Quote:

Originally posted by 911pcars
"The NACA profile is unsuitable for high-pressure applications. Hang a piece of sewer pipe out there."

Being such heavy beasts, the NASCAR types usually have inline blower motors to force air to the rear brakes and differential lube coolers. Compared to the front end, air pressure along the sides of the car are much lower. Lacking air scoops, some air pressure assistance like this may be needed for most effective cooling.

Sherwood

Now's the time to get out those two old E-Rams that you bought for your proposed twin-turbo, ahem, twin E-Ram setup.