The Fixer

The Lighweight's hood louvers look to be solely for intake temperature cooling.
They are too forward to be an actual fresh air intake, also rain would have grounded the car..

The Fixer

Due to hatch pins and drilling, water can enter the hatch frame and must be directed to the appropriate area to drain. Thought i'd share this.
Matt

The Fixer

Couldn't end the day with the horrible hatch drains, will look ok when painted i hope. Hood pins are perfect, placed them exactly where they are placed on the GTR. Getting ready to cut opening for louvers. No hood drilling to be done, the holes are bugging me already in the hatch. Oh well.
Have a great night everyone.-Matt

jorj7

My hood vents are right over where the intake to the air box is. That's as far back as you should go to still be in the low pressure area of the hood. So it looks like where you positioned the vents will work out well.

George
90 S4 Grand Prix White (Murf #5)
94 GTS 5-Speed Midnight Blue
06 Cayenne S Havanna/Sand Beige (PASM)
http://928.jorj7.com

BC

For Hood vents to work as Heat vents, we would need to figure out where the air is moving to, when there is proper flow at speed, as well as where it exits at the bottom of the engine bay. The S4 bottom covers - how would a hood louver interact with this?

The Fixer

Ok good, and thanks for getting back. I looked closely at the Daytona lightweight. Also seeing the intake tubes when looking closely in the daylight would be nice. Kind of wish i designed the louvers a little bit scales up.

The Fixer

I am guessing there is a lot of pressure build up under the hood and air will be forced past the intake tubes and out. I don't have an S4 it is a MY '83.

I have an electric cooling fan set up which works very well, when you'd shut down the car it would still run for about a minute or two. I would examine where the hot air escaped, much escaped at the long hood seams on either side. The rest below the car.
I could do a video possibly to see how the louvers work. (old HVAC trick with tissue paper)
Wish i could devote more time to this, need to get some work done that pays bills..

Will test fit front splitters tomorrow though and begin removing more bits for paint. Door glass will be ditched for lexan ala 924 GTS
-Matt

Tony

As George said..the lowest pressure is as close as you can get to the windshield. There is a diagram floating around of it somewhere? Kibort??
Bottom line is... the velocity picks up at the base..so the pressure drops at the change in direction.

jorj7

Tony,

The base of the windshield is a high pressure zone. The low pressure zone is from the headlights to a little after the rear of the wheel arch. The main reason to have it as far back as possible and still be in the low pressure zone is that the air pressure inside the engine compartment builds up at the fire wall, so you want the max inside pressure and the lowest outside pressure. Then the air will move out of the engine compartment in the desired direction. May people put the vents right after the radiator to expell the air from the engine compartment the quickest, but letting it pass over the engine the exiting air will removes heat from the radiator (200ish degrees) and the engine (400ish degrees), at least that's the theory.

George
90 S4 Grand Prix White (Murf #5)
94 GTS 5-Speed Midnight Blue
06 Cayenne S Havanna/Sand Beige (PASM)
http://928.jorj7.com

Rob Edwards

Here's the wind tunnel pressure diagram:



At some point pre-Carbon fiber intake, Mark Anderson played around with cold air intakes at the rear of the hood:






There's still a cutout in the underside of the hood today:





Just for grins, here's the hood pin setup on the Zombie:




And some opportunities in lightening the doors:

Rob Edwards

EDIT: dp

jorj7

Rob,

That's the diagram from the 83 928S sales brochure that was taken by me with my Olympus camera, and reposted many times. It agrees with what I stated earlier...


George
90 S4 Grand Prix White (Murf #5)
94 GTS 5-Speed Midnight Blue
06 Cayenne S Havanna/Sand Beige (PASM)
http://928.jorj7.com

jorj7

Rob,

Oh wow, it uses the stock door hinging mechanism, at least it won't be that hard to get to when it breaks...

George
90 S4 Grand Prix White (Murf #5)
94 GTS 5-Speed Midnight Blue
06 Cayenne S Havanna/Sand Beige (PASM)
http://928.jorj7.com

Rob Edwards

Hi George-

Yep, I remember it in a thread about NACA ducts for the hood. Didn't realize you'd taken it. Holler if you'd like me to take it down.

jorj7

One other note about the air pressure diagram. Notice the extreme low pressure zone at the top of the windshield at the front of the sun roof. That caused some major issues with early attempts to exceed 200 mph in a 928. The sun roof would pop open and cause some consternation within the cabin....

George
90 S4 Grand Prix White (Murf #5)
94 GTS 5-Speed Midnight Blue
06 Cayenne S Havanna/Sand Beige (PASM)
http://928.jorj7.com