Anytime you get a colder air charge into the intake you will get a power increase, even though it may not be much. Gotta admit that even if it doesn't increase power it adds a psychological effect to it.
Recently tests were performed to determine just that. The conclusion was that is does nothing....but it's way cool. I wouldn't call it failed marketing. Between Cowl Induction and the Pontiac Tri-Power, GM's marketeers created the most sought after misteque in muscle car history.
I don't know whether or not it really worked but Chevys intention was to get cool air from the high (air) pressure area right at the base of the windshield to boost HP at higher speeds.
The Nascar guys do it today on their cars for the same reasons but they run much higher speeds to take advantage of this effect.
So does it work? Probably not but the theory was sound. And it does look cool
In 1970 62,000 Chevelle SS cars were built and almost 29,000 came with the ZL2 Cowl Induction Hood. It may or may not work but it does look good, sounds great at wide open throttle and like everyone else says: IT IS WAY COOL.
The air induction hood on the 98 SS Camaro is worth 15 hp, the rating for the LS1 jumps from 305hp up to 320hp. The same theory works for the 70-72 Chevelles, Cool dense air makes more power than hot air.
John E. is right on the money. During a Fluid Dynamics class at NMSU, myself and a few friends looked into the benefits of what people refer to as "ram air" induction. We wanted to de-bunk the myths and see the numbers for ourselves more than anything. All you are doing is ducting high-pressure *cool* air from one of two optimum points - the front grille area of the car, or the base of the windshield. (we had a nice map of pressure points quantified by vectors along the profile of a sedan-type car..) Ducting this high pressure air into the intake has a pseudo-supercharging effect, which exists, but only at high speeds (100 mph+) (You have to overcome the demands of the motor before you can actually pressurize the intake.) The real benefit is the inductance of the cooler outside air as opposed to the hot underhood air. Colder air is denser air, rich in oxygen - which is what helps makes more power (when you have the right amount of fuel) The cold air has a bigger influence because we don't drive 100+ mph where ever we go.. (well, some of us at least..) So, yeah - the cowl induction has a function (did that rhyme??) but I think it exists to strike fear into the guy who lines up next to you.. Any little bit helps, and when GM uses what seems to be a gimmick (ram air Camaros?? should be *cold air* Camaros) most of the time they are preying on the hot-rod-engineer in all of us..
Here's a tidbit: Those drag cars with the huge hood scoop? They get an extra 150-200 hp from that huge scoop (thanks to the ram-effect), BUT it takes 80-95 hp to push that thing through the air.. Anyone wanna guess as to where they want to relocate that thing to get back that 80-95 hp??
With a 350 full roller sporting a tunnel ram and 2 holley four barrels, my cowl induction hood wouldn't close. So I had a 4 1\2" high steel one made to cover it. I don't know if it works, but Motorcraft and Mopar sure haven't came out with anything that looks that intimidating.
[This message has been edited by Rob M (edited 12-04-98).]
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