DOH!! Good thinking!! I'm going to have to become less paranoid.


not-so-rednwhitecooperCowl scoop as in chevy cowl style scoop.

Rear facing.

Good suggestion, not-so-red! Seems to me it could be done in a way that would not even change hood structural integrity, much less harm it.

Especially if it could continue to use the negative pressure "close to the windshield" to "suck" hot air out. Just two questions (for whoever might know the answers):
1) Is the separation between cowl and hood in a position to take advantage of the negative pressure area? (this question applies to the proposed "stealth" vent's capabilities also) AND
2) Would the bubble/rise created by the rear-facing scoop change air flow so as to spoil the negative pressure in that area?

 

That would at least deflect the water away from the ECU, mine's wide open right now.

 

KOOL

 

Are you talking about the vents?
If so, thanks.
If not, then what the heck are you talking about?


I'm still waiting for pics of your custom offset wheels with the steamroller tires.

 

There is no negative pressure at the base of the windshield

 

With my new DF/CAI diverter, I notice there's air coming *out* of my cowl scoop, especially as the speed increases (tufts of cotton). I presume I have created enough air flow into the airbox that the cowl intake is now an exhaust...oh well.

cheers,

 

That may be possible I don't know. I was only remarking on the statement that there is negative pressure at the base of the windshield.

Normally there's positive pressure in cowl inlets as well.

 

The wheels are in the test forum My friend (motor mouth) posted it for me. My car is the BRG/W. Also TrickleX posted some of my pix in the alta turbo post too.

 

Thanks for straightening this out.

I had to prove to myself that I am NOT insane, though, so I went searching for old threads in which this topic was discussed at one time. I was glad to see that there were some authoritative sounding posts CLAIMING "negative pressure" in front of the windshield, so at least I know I didn't just imagine that it had been said. I also found that you (obehave) busted the myth then, too.

Based on that, cutting out the rear edge of the hood doesn't seem so likely to make an effective vent after all.

So much for "stealth" venting. Oh, well. I guess it's back to holes in the hood.

 

If you were to keep that air from exiting the cowl vent with a sealed air box, you could pressurize the system. yes? no?

 

Where the heck is Will?

 

Alright, I'll chime in. Carefully.

Is there negative pressure at the windshield? Yes. There's also positive pressure. Just depends on where you are measuring. We've done pressure measurements and confirm that there is higher than 1 ATM (~14.7 psi) pressure in the vicinity of the cowl vents (as long as the wipers are present/down). Does this make it an intake?

Well...no. Because pressure measurments at the cowl and in the box are really only half the story. Pressure differences are what cause flow. So, if you find that the pressure is higher inside the air box, which I think is the case most of the time, than it is at the surface of the cowl vent, then air is going to flow out of the cowl vent, no matter if there's positive or negative pressure (with repsect to "ambient" at 1 ATM) measured at the cowl vent. The difference is all that matters.

So can you open the rear of the hood and get venting? Very possibly, yes! As long as you are at a speed that produces a higher pressure inside the engine bay than is seen at the vent opening. Of course, there are two possible outcomes of opening up the rear of the bonnet. First, you could vent hot air at speeds. Second, you may end up drawing cool air in, and it will travel down over the header and out the bottom of the engine bay. I suspect, though, that both of these conditions will occur depending on the speed which you are traveling and how it changes the flow underneath the car.

 

Thanks for chiming in, Will. I knew you were still around here somewhere.

 

Having driven for 3 days now with the DF/CAI scoop and diverter, I am pretty sure the blast of fresh air from the front of the car going directly into the airbox is working! Will's analysis would reinforce the idea that I am pushing sufficient fresh air into the airbox to the following effect:
1. much more fresh air than is getting in through the stock duct that comes via a serpentine route from above the radiator, and
2. much more fresh air than comes in via the cowl inlet under normal (40-60mph) speeds
Anyway, I think it's a keeper. It certainly seems to have made a bigger single impact on the performance of my car than any other single mod, including the DFIC.
cheers,

 

Very cool(no pun), DrPhil.
Thanks for posting.
Maybe i'll hook the factory intake duct back up, and make an extension that will grab the air right from behind the grille slats.

 

I think this is a great idea, since I once did one of my "see through" photos with the bonnet open and closed and there's not much direct air getting into the OEM duct above the radiator--what air does get in there is simply finding it's way there behind the bonnet between the grille and the headlamp.

 

I had already experimented with this a little while ago.
I had an HAI for a couple days and got a piece of clear tubing from Home Depot, it was near the end of the roll so the tubing was somewhat oval shaped and curved already. I stuffed one end of it into the intake duct and let the other end hang down right behind the grille slats. I also "sectioned" the tubing behind the grille to act as a scoop.
The HAI filter was very cool to the touch after a good run.

 

DrPhil, can you post one of your "see throughs".

According to my rough measurements, the intake duct sits roughly where I outlined in this pic...

...an opening right here would be great, but might not look very nice.

 

Well, i think im gonna go for it with a cowl scoop.

I sound a 27 inch long x14 widex4 inch tall cowl scoop, mold on style from summit for about 60 bucks with my discount.

i think i'm gonna pick it up and just cut a big slot in my hood to get as much air out as possible.

i'll throw some pics up to give you an idea soon.

 

Partsman: Exactly! Your sketch shows the location very well--which I attempted to (rather poorly) explain in words (ah, those thousand word pictures...) Now there is space between the bonnet and the radiator-cowl where the airduct opening is, and as you've explained, a nicely shaped scoop could catch some serious fresh air and direct it up into the air duct. The problem is--the grille opening is smaller than the radiator as it is, so putting something in that grille area would be blocking some of the air to the radiator (is that a bad thing?)
Maybe remove the driver's side headlamp?...

cheers,




PS I will try to find my see throughs - I've done quite a few!

 

have any of you guys looked at if the stock CAI scoop (behind grill) could be enlarged? There seems to be room (to the left) to enlarge.

 

Here's a little PhotoChop for a matching Ram intake (sort of looks like a zit):


Bart: You could enlarge the intake hole, but then you'd have a job fabricating the duct to the serpentine tube...

 

Hey! What about the bumper? There's a lot of unused space behind that bumper cover.......

 

I took the filter off my AGS for cleaning and you wouldn't believe the crap that was on it

It looked like it was out in front of the bumper instead of behind the grill...

 

Yes, Sid, a good point! I am expecting considerably more grunge in my Alta filter now that I have a direct connection with the bugs and dust and other crud that goes in the very large hole I now call a scoop! Good thing we can clean these filters and we have obsessive compulsive personalities...