89FX3

http://vettetube.com/view_video.php?...2c9d4db0c6bbe4

Vette Fast

Depending upon your application, hood vents do work. With out starting an argument, why do some new OEM vehicles come from the factory with hood vents?

hardlight

This is my 91 Z-07 with the ones from Mold Kraft. Work well, they vent a boatload of heat. I have a 383 with Stainless Works headers and I noticed a difference right away.

http://www.greenwoodcorvettes.net/gc4/louvers.htm

$355

http://greenwoodvette.com/options.htm

$299 cheaper from Mold Kraft and same thing, I think he used to make them for Greenwood and he seems like a nice guy. Thats where I got mine.

Lrod

Not wanting to poke you with a stick, but why didn't your car come with them in the first place? I'm not a design engineer or anything like one, but it seems that there would have been wind tunnel test to prove out the final design.

Vette Fast

I would agree, however perhaps they were not added because of the added cost. Does a stock corvette need hood vents? Probably not.

As I said in my earlier statement “depending upon your application, hood vents do work.” My Vette is no longer stock and the vents in my hood work two fold. The vent on the passenger side of the hood evacuates engine heat. The vent on the driver side allows the supercharger access to cooler air.

Aardwolf

Some I am sure are for looks only and are not even functional.

Vette Fast

True. I should have written -why do some new OEM vehicles come from the factory with functional hood vents?

hardlight

The ones on my car can be bought either way, show or go. I paid $100 more to get the rain diverter baffles for the inside of the hood. I know that at 120+ on the straightaway at the track they are pulling loads of heat off the engine and I run cooler water temps.

For an original equipment design with a properly sized cooling system you generally don't need them. But you will notice that most racers have extra venting on them somewhere up front.

Aurora40

When GM wanted functional heat extractors, they put them on the side of the hood:

http://deliquescence.net/~tyler/prototype/active3.jpg

In fact, on many cars they have put them in that area, must be something to it...

redrose

from the early Grand-sport racers (the real ones, in the 60's) to the latest factory hot rods (the yellow things), escape of heat vertically is favored by the GM high perf crew...vents on the top are not good if the vehicle will sit for extended periods in rain/snow.

Aurora40

True, though I suspect they do a lot of testing, they don't just toss vents on a hood. And not all of those are for the same thing. The C5/6-R has that huge opening where air from the radiator comes out, i.e. it isn't venting underhood air, rather the radiator is sort of by itself. And some are over the wheel housings, I believe this improves aerodynamics.

What I meant was when GM puts heat extractors on real production cars, they put them on the sides. As to the active-suspension C4 in specific, one would think they put them where they did because it really worked. Those hydraulics apparently created a ton of heat. So if one was wondering about where a scoop might actually pull out hot air, there's one place where I'm reasonably sure it would.

BrianCunningham

There's a lot to aerodynamics on high speed cars

You need to analyze the pressure zones, you could actually wind up with something that flows backwards from what you think it does.








There's a high pressure zone at the base of the windsheild, musclecars used it for "cowl induction"

RICEKILA

With the hood louvers / cut back hood gasket - except over the distributor / side gills / real 2" radiator / 160* therm. / BMAD and Z-51-ish air dam in the last 1 & 1/2 years the temp. has never gone over 205*

And at speed - "Zero" - front end float

Coconut

If you're moving, then air is moving. Forget whether air is going in or out of louvers, cowls, & etc just for now. When you get stuck in traffic for a light, a wreck, or whatever (& are sitting still), heat will rise out of the louvers, through the back of the cowl (unless sealed up), or through whatever holes you have available for heat to rise out of. When you move again, the air will obviously cause different things to happen, but heat will rise out of louvers when you're stuck in traffic. I don't know how significant it is, but some is better than none, I guess.

91 black convert

So are you saying that cutting out the cowl seal will help get hot air out from under the hood? But then I hear that the base of the windshield is a high pressure area, which is why cowl induction hoods work. So would cutting the cowl seal let hot air out or force cold air in? (I guess either one would be cooling the temp down.)

Also, why is the cowl seal there in the first place? Maybe to stop rain from being forced in? I'm confused!

Inquiring minds want to know...


BTW, I like the looks of the hood vents even if they are not letting hot air out.

Jim S.

redrose

nobody knows for sure, at GM all such decisions are made by "committee", all those people are long gone.

most likely, to stop all that ugly engine noise...maybe to preclude hot engine compartment air from entering the cockpit air intakes at the base of the windshield and messin' the missus's 'do.

Aardwolf

Yeah the air intake is there for cabin air. I noticed when my car was stock that the fan took awhile to bring temps down. There isn't a lot of places for the air to go. I didn't want it all blowing on my trans making that hot either. So the seal is trimmed on mine. I've been thinking of adding vents for aero reasons. Yes that area is high pressure when moving. At idle is when I didn't really like the air flow. I'd like a no weight vented hood one of these days!

hardlight

these are the ones I got from

MOLD KRAFT MANUFACTURING, INC.
1683 Beardall Avenue #101
Sanford, FL 32771
Phone : 407-321-1016 Fax :407-324-3646
E-Mail Us at info@greenwoodvette.com

edit......cheeze, I just noticed that I previously responded to this thread over a year or so ago

Coconut

I actually have a functioning cowl hood, because I converted my car to a carburetor. Using a sealed cowl at high speeds, air is sucked into the air cleaner do the the high pressure build up. If it was not sealed, hot air would blow out at idle, & then suck air in as speed is increased. Therefore, for a daily driver, there is probably more benefit for a non-sealed cowl so that heat can escape at idle, & even bring in some cooler air when going down the interstate. For a race car, use a sealed cowl for air induction.
I hope this clears things up a bit. A street car, & a 100% all-out racecar are totally different beasts with different setups.

Coconut

Check out this Corvette that has a sealed cowl & a hole in the front of the hood to get radiator heat out!





Here's the link:
http://s64.photobucket.com/albums/h167/Tazio_Nuvolari/