>>Vendors are making claims that the true cold air intakes which rely mostly on air coming from the cowl windshield area works better but we really need a head to head comparison to verify claims. The Webb airbox mod with drilled holes, although it lets in some additional SC sound may not be as good as thought earlier. Airflow back in the cowl area is just not very helpful for air intake in a meaningful way. Lets see some evidence that it really helps!


Vendors do make a lot of claims and I do think we need a head to head comparison... Unfortunately most of the "evidence" tends to come from dynos which are usually very subjective. Plus, a dyno where the car is sitting still with a fan blowing on it isn't the same as doing 60mph.

 

A CAI which takes air from the cowl vent does benefit somewhat from the ram-air effect of air pressure in that area. A positive pressure does form at the base of the windshield as the car is moving. It's the same principle used by Detroit musclecars of the 60s-70s era (think '69 Camaro hood scoop, etc). The reason why it's not used much except for die-hard performance applications is because the noise from free-flowing, unbaffled intake is brought closer to the passenger compartment, which some people find objectionable (this is not a problem for the performance-oriented types among us).

It would be possible to open up the bottom part of the stock intake into the cowl area and achieve some measurable gain, but these aftermarket intakes have a greater flow potential than the stock filter/hose setup has; you would derive more overall gains with the aftermarket pieces.

 

Thanks for the responses to this question.

There seems to be some disagreement over the amount of positive pressure in that cowl area. If I understand correctly, some people think that opening up that windshield vent to the intake only improves (i.e. increases) sound, while others feel that there's enough pressure to create a positive ram effect.

I'm wondering if anyone's attempted to mount some type of scoop above the vent there at the base of the hood. It seems that you could get a high pressure ram effect with air directly from the outside if you attached a funnel of some kind above that vent to direct the air down into the cowl and into the intake. (Obviously you'd have to do some plumbing to direct the air from that scoop into the intake.)

If such a thing exists, I'd love to see a pic.

 

Bump.

 

Here is these. I think they might better maximize if turned around (facing windshield)--as in earlier stated '60s era cowls.



_________________
-goin440 IB/IB MC

 

For the record, I installed my Alta and it pulls air from both the cowl and the front scoop. The car definately feels more responsive and has a little bit mroe pull at the lower RPMs, definately a little more peppy but nothing drastic, maybe 5 hp at the most. A piece of advice, DO NOT BOTHER WITH THE STUPID HOSE, it is a waste of time and money and needs a lot of cutting to fit properly. The hose is the sole reason the install took 1.5 hours, and while I finally got it on, it isn't worth the hassle.

 

According to Caddman, his scoops delivered an extra 2 psi!:

https://www.northamericanmotoring.co...5&start=50

Of course, he also made alot of other unsubstantiated claims. Take that with a grain of Sea Salt.

 

Thanks, that's just the thread I was looking for.