[justpete]

Originally Posted by shirtpants_

You're suggesting that you let more of the wheel well pressure/air mix with the engine bay air? No idea how that would go.
There should be a significant amount of pressure built up inside the wheel well, I would think even more if you have extra ducting to the rotors. But I don't recall where in the wheel well it is. There are probably different ways to go about relieving this pressure depending on it's location.

Maybe ill check out what the wheel well pressure looks like.

Probably not worth looking into as it turns out. An opening there would allow in all sort of track debris, not a good idea. Duh to the duh power... :/

[tetsuo111]

Originally Posted by justpete

I was thinking given the frontal area and high pressure in front of the radiator that the pressure in the wheel wells would likely not be as high, seems like it couldn't be. Would be great to find out some real world numbers though.

Here you go. Different vehicle but the principals are the same.

http://www.autospeed.com/cms/article.html?&A=113177

[feuer]

Originally Posted by justpete

Probably not worth looking into as it turns out. An opening there would allow in all sort of track debris, not a good idea. Duh to the duh power... :/

Perhaps something similar to BMW M8 v12. The fan shroud is like a funnel that seals the hood where it vents out right between the radiator and the engine.

[justpete]

Originally Posted by feuer

Perhaps something similar to BMW M8 v12. The fan shroud is like a funnel that seals the hood where it vents out right between the radiator and the engine.

Not sure I follow, any drawings, pictures, etc.?

[feuer]

Originally Posted by justpete

Not sure I follow, any drawings, pictures, etc.?

This:

[bNks334]

After getting into a huge debate over n55 iats and intercoolers I've been doing all sorts of logging of temps across the engine bay. It appears there is a massive amount of heatsoak occuring under the hood. Intake tubes are hitting 200f in 70f weather. Cold side chargepipe was 200f. The intake box was 156f. Even the air scoops were 140f. The intercooler on this 70f night was showing only 72f...

I came to the conclusion I need to find a way to excavate more heat from the engine bay... not buy a big ass intercooler for no reason...

Can anyone speculate on the effect of either adding a Cowl dam to remove heat (and placement) or a hood slot to force air in to increase airflow (and placement)???

I don't see any well designed aftermarket hoods...

[shirtpants_]

Ok, I got to do a little more testing. This time I measured the pressures of the engine bay, and the wheel well.
All testing was done on the same road as before, and at the same speed (51 MPH).
All other measures were identical, except the placement of the end of the tube.

I put the tip on the edge of the engine cover, right between points 3 and 4 on my original pictures.

All measurements were in INWC(Inches of Water Column) just like before.
Engine Bay
MIN Max
.61 .75
Most common reading: .63

The most common number I saw was .63, so I think It's fair to assume that that is the average.
Since I have an open intake, I think it's possible that that may have lowered the pressure in the engine bay. I didn't feel like swapping it for the stock box, but all testing was done with cruise control on, at low rpm in 6th gear, so it shouldn't matter too much.

Now the wheel well testing was done by feeding the end of the hose through one of the few holes between the engine bay and the driver's side wheel well. I believe the wheel well pressure builds up in the back, closest to the driver. I could not get that far with the hose without it just flopping around, and I think I'd have to get the car up on jackstands to secure the hose where I want it, since there's no room to do so when the car is on the ground.

This reading was more stable than the engine bay reading as well.
Wheel well
Min Max
.28 .34
Most common reading .31

So,
Engine bay: .63 INWC PSI=0.0227 (rounded to 4 decimal places)
Wheel well: .31 INWC PSI=0.0112 (rounded to 4 decimal places)

It's weird that the wheel well pressure is just about half of the engine bay pressure

It was a little damp when I did the the testing, and my rear tires are pretty much bald, so I didn't have the nerve to try any testing at higher speeds. I'll see about re-doing all of these tests at higher speeds after I get new rubber(and new wheels!) next Friday.
Pics:

[shirtpants_]

Originally Posted by feuer

This:

This is almost exactly what I had in mind. Duct the radiator to the the vented hood. Maybe add another vent on either side of the center one if you still need to reduce engine bay temps even further.

[shirtpants_]

Update:
Got a chance to do some testing of the underhood pressure again. This time at just over 100 MPH.

I used the same location for the end of the tube for measuring.

I ended up with a much more stable reading than any of the other tests.

Hovering right around 2.23 INWC the entire time. This is over triple what the pressure was at 50 mph.
This equates to 0.08048 PSI. I would have done it at higher speeds, but even at just under 110 I was getting an overflow message, which basically means that the readings were going over what my unit is capable of measuring.

I tried to get more data for the over hood pressures as well, but I was getting an underflow message at anything over about 60 mph. So the pressures were below (as in negative pressure) what my unit could read.

This is pretty much the end of any aero testing I'll be doing. My unit cant read anything higher, so this is it.

[bNks334]

Originally Posted by shirtpants_

Ok, I got to do a little more testing. This time I measured the pressures of the engine bay

I am Considering buying Duraflex 108970: https://www.carid.com/duraflex/eros-...FcxWDQodGmYEjg

Looks like the ducts should help extract air as that area is high pressure under hood and low pressure above the hood. Goal would be to relieve under hood temps and enjoy the weight savings of fiberglass...

any thoughts on whether they will actually be functional? Placement is similar to a louvered hood like this: http://n5tuner.com/index.php?main_pa...4#.WCIxyk10yWF

but it's cheaper and looks better (in my opinion). wont water just pour ino the engine bay with EITHER of these options?

[shirtpants_]

Originally Posted by bNks334

I am Considering buying Duraflex 108970: https://www.carid.com/duraflex/eros-...FcxWDQodGmYEjg

Looks like the ducts should help extract air as that area is high pressure under hood and low pressure above the hood. Goal would be to relieve under hood temps and enjoy the weight savings of fiberglass...

any thoughts on whether they will actually be functional? Placement is similar to a louvered hood like this: http://n5tuner.com/index.php?main_pa...4#.WCIxyk10yWF

but it's cheaper and looks better (in my opinion). wont water just pour ino the engine bay with EITHER of these options?

I only did testing on the center of the hood, but I would assume the results would be similar on the sides.
I think the biggest source of high pressure is the air coming from the radiator.
Yes, Water will just pour into the engine bay if you are stopped during a storm.
I think the best way to go about this would be to duct the vents to the radiator. A lot of hot air comes out through the radiator.
Ducting the radiator to the vents would definitely improve it's efficiency, by the pressure difference giving the radiator air somewhere to go,
instead of building up in a "wall" in front of the engine. By using ducting, you could also make some channels for the incoming water to go,
to keep it from going places you don't want it to. Without ducting, I would be worried about the possibility of water getting into the intake, if you have an open intake.
If you planned on using ducting for that hood, it would probably look similar to the E46 m3 GTR. Although those vents are much bigger.
The engine bay in the 1 is kinda crowded though, so I don't know what you could make work.

[tetsuo111]

shirtpants_ Thank you for your efforts. At the last track session my car overheated and limped home. I prefer passive cooling to active due to simplicity and weight, but I do have aux oil and diff cooling in the queue this winter.

I bookmarked this pressure map of a Miata hood:


The pressure gradients and distribution are similar on every similar pressure map (regardless of model) I've seen. Pressure is negative on the forward third, increasing aft until the base of the windshield / cowl intersection. This is why cowl induction works. Pressure also generally falls when moving from the hood centerline towards the left and right sides. Interesting to see how the "power bulge", similar to the M3, actually creates lift in the local region.

I agree with your conclusion - locating the vents in the forward third, directly aft of the radiator exhaust ought to enhance both cooling efficiency and downforce. Even more so with radiator ducting. Sadly, there's very little room to fit a radiator duct in between the fan and the front of the motor.

I bought these functional vents today. They measure 10" x 10" x 6", and come with AL screens.



Based on your data, and similar pressure maps, I'll locate the pair directly aft of the underhood bracing, or simply "re-engineer" the brace to fit.

[soursamo]

Where did you order those vents from?

[tetsuo111]

Originally Posted by soursamo

Where did you order those vents from?

Sourced from Anvil Auto, camaro 70-81:

http://anvilauto.com/products/camaro...ood-vents.html

The vents were delivered a couple of days ago. The fab and finish quality far exceeds my expectations.

I'm looking forward to cutting holes in the hood and having these installed in the position marked on page 1, behind the red line, similar to (but slightly fore) the DBS, optimized for heat extraction from the radiator exhaust. I expect improved cooling and less front end lift. Will need to buy a manometer to verify.

[Ruddigger]

Cut those holes yet? Need to borrow a can opener?

[tetsuo111]

Originally Posted by Ruddigger

Cut those holes yet? Need to borrow a can opener?

Lol - I really want to do this one myself, for the simple joy of cutting sheet metal. At the same time, my responsible inner-voice recommends finding an adult with skills since any blunder will be front and center visible. Also need to decide whether to "modify" the under-hood bracing to locate the Anvil vents further forward to a lower-pressure zone.

[Ruddigger]

I was wondering if the structural supports on the underside of the hood would interfere with your preferred location. Sounds like they do? I would go after that hood with a die grinder and a cut off wheel.

[brodan]

Originally Posted by tetsuo111

Sourced from Anvil Auto, camaro 70-81:

http://anvilauto.com/products/camaro...ood-vents.html

The vents were delivered a couple of days ago. The fab and finish quality far exceeds my expectations.

I'm looking forward to cutting holes in the hood and having these installed in the position marked on page 1, behind the red line, similar to (but slightly fore) the DBS, optimized for heat extraction from the radiator exhaust. I expect improved cooling and less front end lift. Will need to buy a manometer to verify.

Did you ever wind up installing these? I'm about to pull the trigger and buy some vents.

[tetsuo111]

Originally Posted by brodan

Did you ever wind up installing these? I'm about to pull the trigger and buy some vents.

Sadly no. Lost the car.

I will do the project on the next car, but have many more urgent things vying for attention first.

[sirdaft1]

Originally Posted by brodan

Did you ever wind up installing these? I'm about to pull the trigger and buy some vents.

Originally Posted by tetsuo111

Sadly no. Lost the car.

I will do the project on the next car, but have many more urgent things vying for attention first.

I'm currently in touch with John from Track Spec Motorsports to try and get a vent kit developed for my e90 335 track car/the e90 chassis similar to the ones they already have for the e46 platform. I'll keep you all posted.

http://trackspecmotorsports.com

[bbnks2]

Originally Posted by sirdaft1

I'm currently in touch with John from Track Spec Motorsports to try and get a vent kit developed for my e90 335 track car/the e90 chassis similar to the ones they already have for the e46 platform. I'll keep you all posted.

http://trackspecmotorsports.com

I like the front vent, but I am not sure I see the value in the cowl induction vent near the windshield... I also think the two side vents are a bit overkill. They are so large that they cover areas of both high pressure and low pressure. I'd go for vents that were smaller by about 30-40%. Having 4 big ass vents like that is more for looks than for the performance benefits/science of removing air from under the hood (IMO).

[sirdaft1]

Originally Posted by bbnks2

I like the front vent, but I am not sure I see the value in the cowl induction vent near the windshield... I also think the two side vents are a bit overkill. They are so large that they cover areas of both high pressure and low pressure. I'd go for vents that were smaller by about 30-40%. Having 4 big ass vents like that is more for looks than for the performance benefits/science of removing air from under the hood (IMO).

Keep in mind the one near the windshield is from the factory on the e46 m3. For the 335, turbos are on pass side and the DCI's pull from the drivers side, so any additional airflow will be a net win - especially on the heat soaked N54.