Air circulation in the 'stock' engine bay.

[CFD]

Also something most don't take into consideration is that when your car is moving the air flow under the car acts a bit like a venturi and sucks the air out of the engine compartment

[The_Raging_Bull]

air coming in the front of the mail slot or the grills isnt going to just push out cold air, it'll push any and all air sitting in its way out the engine bottom.

The difference in hot and cold air is the density, but when a 60 to 90 mph airstream hits stagnant air, the higher velocity air is going to win > wheater its hitting cold or hot air. It'll also go the path of least resistance, i.e. towards the nearest open hole, so >> some toward higher openings, the rest towards the engine bottom.

Again, this is not a closed system; why over analyze it? If you want to spend 199.00 on this knock yourself out.


As the last commenter said, your're messing with the drag coefficients w/o knowing what you are doing. My point was Chevy DID wind tunnel testing, as the SS yeilds 160 lbs of upforce while the ZL1 has overall downforce (65?? lbs).

Frankly why mess with Chevy"s work unless it yields a way of feeding a CAI box directly, like the old shaker hoods, or directly to the TB thru a straight vararam style intake? That would get my money in a hurry.

[KBruno]

I never got an answer in their marketplace thread which was:

Originally Posted by KBruno

I love the idea of the mailslot being more than cosmetic but from the photos & renderings it looks like the air is diverted up directly into the rubber weather strip that seals against the hood & not down into the radiator area. Am I looking at it wrong? If the air is taken upwards do you cut the weather strip to let air into the engine bay or does it just flow around to the outside edges of the hood? Either way it seems the added function is purely cosmetic since either of those options wouldn't aid in cooling a water cooled engine in any way. Again, am I looking at it wrong?

Maybe it'll get read here or someone will pay attention. My opinion is that it's cute but should have been made to direct air into the radiator and not the hood seal. Also, a good extractor hood is good for both cooling & drag especially in conjunction with a belly pan (which shouldn't be used without the extractor). That's because the underside of the car is relatively 'dirty' aerodynamically campared to the top or sides of the car. But really, unless you drive at or above legal highway speeds for extended periods, aerodynamics play a very small part in overall drag.

[CFD]

Frankly why mess with Chevy"s work unless it yields a way of feeding a CAI box directly, like the old shaker hoods, or directly to the TB thru a straight vararam style intake? That would get my money in a hurry.[/QUOTE]

Utilizing the mailslot to feed a CAI is not that difficult, here are a couple of quick pics of how I did it

[Falundir]

Please excuse my ignorance, but wouldn't any vented hood also play with downforce?

[KBruno]

Originally Posted by Falundir

Please excuse my ignorance, but wouldn't any vented hood also play with downforce?

If well vented, and there are some poor designs out there, yes. But technically on the Camaro it'll reduce lift. It'll require more elements like the ZL1's complete aero package to get actual downforce.

[Synner]

Originally Posted by KBruno

I never got an answer in their marketplace thread which was:



Maybe it'll get read here or someone will pay attention. My opinion is that it's cute but should have been made to direct air into the radiator and not the hood seal. Also, a good extractor hood is good for both cooling & drag especially in conjunction with a belly pan (which shouldn't be used without the extractor). That's because the underside of the car is relatively 'dirty' aerodynamically campared to the top or sides of the car. But really, unless you drive at or above legal highway speeds for extended periods, aerodynamics play a very small part in overall drag.

I assume the goal is reduced underhood temps if you trim the weatherstripping. There's many Benfits to that for people who drive hard. And I don't understand your statement on aero doesn't play a role in drag, that's exactly what it does. A car at highway speeds uses 60% of its engine to counter drag so its extremely important. But the camaro has the aero of a Mac truck because their priority was retro design. So as I said a tiny opening will have negligible impact.

[geaux_tigerss]

Throw the overpressure idea out. There are too many outlets for this one little inlet to make any difference. Laughably so.

The drag thing is a non issue as well. Want to really change the airflow around a car? Open a window or sunroof. Much bigger opening.

[KBruno]

Originally Posted by Synner

I assume the goal is reduced underhood temps if you trim the weatherstripping. There's many Benfits to that for people who drive hard. And I don't understand your statement on aero doesn't play a role in drag, that's exactly what it does. A car at highway speeds uses 60% of its engine to counter drag so its extremely important. But the camaro has the aero of a Mac truck because their priority was retro design. So as I said a tiny opening will have negligible impact.

I fail to see any benefit at all with that little bit of air from the mailslot going over the radiator cap if you trimmed the weather strip. Through the radiator might help things that little bitty bit but since it's a water cooled engine it's not helping cool the engine when it's running and it won't cool the under hood when it's standing still. So what's the point other than cosmetic was my point there.

And I didn't say aero doesn't play a role in drag. I said "unless you drive at or above legal highway speeds for extended periods, aerodynamics play a very small part in overall drag". Depending on the car, tires including inflation pressure, road surface and other factors, an automobile uses more HP overcoming rolling resistance than aero drag up to anywhere from 40 to 60 MPH at which point they become equal. Above that point they both continue to rise, aero exponentially where rolling resistance is a liniar rise. Now, check your average speed on the information center. For most people that number is so low that aero drag played less of a roll than 1 or 2 lbs of tire pressure if that.

[edgehead2000]

Originally Posted by KBruno

Also, a good extractor hood is good for both cooling & drag especially in conjunction with a belly pan (which shouldn't be used without the extractor). That's because the underside of the car is relatively 'dirty' aerodynamically campared to the top or sides of the car.

Not following you on why using a belly pan without extractor is bad. Neither my old NA Chrysler Crossfire or their AMG tuned SRT6 had an extractor; regardless, it still performed beautifully.

[90503]

Originally Posted by edgehead2000

Not following you on why using a belly pan without extractor is bad. Neither my old NA Chrysler Crossfire or their AMG tuned SRT6 had an extractor; regardless, it still performed beautifully.

Yes, that's what I would like to know also...Of course the guy I bought the belly pan from said it's not a problem, but never heard it discussed here on the forums...So, I haven't put it on yet!...lol

[js19racer]

Have any of you guys actually looked at the front of your Camaro? Ever notice the size of the upper and lower openings? There huge! So opening up the mail slot wont make much difference. Especially at highway speeds. The only way you will see a difference is if you put it in the wind tunnel. If you open it up it will reduce front down force. Not enough for high way driving. It will let more air in so it would probably slightly reduce under hood temps.

[KBruno]

Originally Posted by edgehead2000

Not following you on why using a belly pan without extractor is bad. Neither my old NA Chrysler Crossfire or their AMG tuned SRT6 had an extractor; regardless, it still performed beautifully.

Again, it depends on the car & and the pan but a belly pan is to reduce turbulence of the air moving under the car and dumping all the air from the radiator/engine bay pretty well defeats that not to mention that it won't help overcome lift that way. Also if the pan is extensive enough there isn't enough space for that volume of air to exit effectively stalling the air flow. Probably wouldn't happen with the ZL1 pan but why mess with all the wind tunnel & CFD testing that's already been done by Chevy & others.

So the Crossfire fender vents (AKA extractors) were fake? That's well, disappointing but not surpising. Look at a real AMG or an SLR or an SLS. Hood & fender extractors are functional and the belly is smooth. Even as old as the 300SL MB was keepig radiator air out from under the body. Even more dramatic are some of the super cars. I'm not saying you have to go that far. Those kind of things only start to make a real difference about the time you start breaking the speed limit or for road racing. Look at the amount of vents to this engine bay http://www.sareni-united.com/en/. Drag racers on the other hand would probably be better served closing off the grills entirely if they're able to cool things quickly after 1/4mi squirt.

Never drove a Crossfire but I did see the Brit. Top Gear test and they hated it but they do get to beat on all the really cool stuff so they're a little jaded I think. BTW they thought the Camaro SS was a real kick.

[edgehead2000]

Kbruno, good explanation. Didn't mean to challenge your knowledge, just thought I'd bring it up before I purchase the ZL1's for my SS. After looking at some pics of it, the pan only covers the front half of the engine bay thereby still allowing hot air to exit and keeping the engine a bit cleaner.