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Re: Cowl induction... (archive)

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Posted by kwillmorth on April 20, 2000 at 15:46:46:

In Reply to: Cowl induction... posted by Justin on April 20, 2000 at 12:27:22:

Jeez, you're age is showing.

1. Cowl induction is about INduction (se Zandir's notes). Everyone with a mid sixties to mid seventies (my days of wrenching every weekend and evening) hotrod knows about cowl induction. It uses the high pressure at the base of the windshield to force air into the intake. The carb intake was usually sealed off to the underside of the hood, with some form of pan or plate. Because the area at the base of the windshield is HIGH pressure, it cannot draw air/heat from under the hood...etc.. If it does, the cars aerodynamics are awful, because it would mean pressure under the hood was higher than at the base of the windshield...not good at all.

2. You are unlikely to ever see a real cowl induction system on a modern car. First, the area at the base of the windshield is almost always used to force air into the car, which is counter-indicated with cowl induction. Having one vent area sharing air with the inside of the car and the intake for the engine was never a good idea. In the old carb days, the inside of the car could get stunk up pretty good from this mixture.

3. While the E46 M3 has a cowl induction hood look-a-like. Which begs the question Why?

Finally, who really cares. The car isn't even being produced yet (counter to claims that they have been seen all over the east coast and here in LA at the beach!). The Frankfurt cars were prototypes (according to BMW Car Magazine). We might see them in September. At which time, I can guarantee I'll be giving one the boot and making real subjective evaluations. Between now and then, it's all just fun talk.

: Cowl induction isn't usually an intake method, but simply an air system using the vacuum effect created by air travelling over the car. As the air travels over the car, a vacuum is created around the car (thus explaining why a piece of paper can be "sucked" out of an open window).

: A cowl hood simply creates an opening near the windshield in order that this vacuum effect can actually "suck" the hot air from under the hood, out... thus being replaced with cooler, atmospheric air from any frontal source.

: I've never known anyone that thought of cowl induction as an intake method... kind of an interesting thought, though. I am pretty sure that the point of most cowl "induction" systems is to keep ambient engine temperatures low.

: I suppose perhaps you were confused by the term "induction"...? It doesn't mean the same thing here as in the term "forced induction". Cowl induction is inducing air into the engine bay, not NECESSARILY into the engine.

: I suppose, though, on the older American blocks, it was able to accomplish both with the top-side, cylinder intake systems of the early hot rods. However, that was primary a coincidence. Cowl induction, now-a-days is primarily used to keep engine temps down... it's been that way since the inception of modern fuel injection and throttle bodies.

: Justin

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