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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > N54 Turbo Engine / Drivetrain / Exhaust Modifications - 335i > Vented hood or ducts (ST users)



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      07-14-2020, 06:10 PM   #23
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Originally Posted by nicky dj View Post
Is the OEM hood aluminum? Also the underneath of the hood is not resin covered, its literally plastic. Only the top side of the carbon fiber is the resin part.
High tensile steel, not aluminum.
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      07-15-2020, 03:59 AM   #24
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Originally Posted by FEDE/E92 View Post
This is what I have, vent is right next to Turbo, wish they were bigger but they definitely let some heat out.
The vents are just above turbo, like the hood i have in mind.
What about rain and car washing?
Do you have any problens?
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      07-15-2020, 05:13 AM   #25
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Quote:
Originally Posted by nicky dj View Post
Is the OEM hood aluminum? Also the underneath of the hood is not resin covered, its literally plastic. Only the top side of the carbon fiber is the resin part.

The carbon fiber material used should be a composite of carbon fiber in resin, otherwise will be a bit....floppy. Thermal conductivity is very very low.

Even iron is over 10X more conductive, so whatever steel's used is going to reject heat far better than carbon fiber, and sure enough our stock hoods are much warmer after a drive.

Interestingly the most conductive material by far is carbon....as diamond! Who knew?
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      07-15-2020, 12:05 PM   #26
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Quote:
Originally Posted by CALWATERBOY View Post
Quote:
Originally Posted by nicky dj View Post
Is the OEM hood aluminum? Also the underneath of the hood is not resin covered, its literally plastic. Only the top side of the carbon fiber is the resin part.

The carbon fiber material used should be a composite of carbon fiber in resin, otherwise will be a bit....floppy. Thermal conductivity is very very low.

Even iron is over 10X more conductive, so whatever steel's used is going to reject heat far better than carbon fiber, and sure enough our stock hoods are much warmer after a drive.

Interestingly the most conductive material by far is carbon....as diamond! Who knew?
Okay Bill Nye the science guy. This is the underside of the hood, it feels like plastic and is not resin based, even the support brackets and molding is plastic. And it's so lightweight that I can bend it side to side but doesn't loose it's shape (front to back it's solid).

I can touch the underside of the hood after a spirited car ride and it doesn't feel hot at all.

No way this hood conducts heat over the heavy steel pot cover.
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      07-15-2020, 12:46 PM   #27
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Quote:
Originally Posted by nicky dj View Post
Okay Bill Nye the science guy. This is the underside of the hood, it feels like plastic and is not resin based, even the support brackets and molding is plastic. And it's so lightweight that I can bend it side to side but doesn't loose it's shape (front to back it's solid).

I can touch the underside of the hood after a spirited car ride and it doesn't feel hot at all.

No way this hood conducts heat over the heavy steel pot cover.
This is basic heat transfer... conductors get hot, insulators do not. Typically you don't want an insulator for a hood, but I'm sure the vents help dissipate the heat.

Edit: I don't see any vents on your hood so nvm.

Last edited by lwgrenier; 07-15-2020 at 12:48 PM.. Reason: I don't see any vents on your hood so nvm.
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      07-15-2020, 03:17 PM   #28
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Quote:
Originally Posted by lwgrenier View Post
Quote:
Originally Posted by nicky dj View Post
Okay Bill Nye the science guy. This is the underside of the hood, it feels like plastic and is not resin based, even the support brackets and molding is plastic. And it's so lightweight that I can bend it side to side but doesn't loose it's shape (front to back it's solid).

I can touch the underside of the hood after a spirited car ride and it doesn't feel hot at all.

No way this hood conducts heat over the heavy steel pot cover.
This is basic heat transfer... conductors get hot, insulators do not. Typically you don't want an insulator for a hood, but I'm sure the vents help dissipate the heat.

Edit: I don't see any vents on your hood so nvm.
Another theoretical... I don't think you get my point. The is constructed in 2 parts; a bottom layer which is a plastic sort of material that is fused to the top side carbon fiber. It appears hollow in between.

And yeah I don't have vents never stated I did, but I did state that I do have the cowl removed and the BMS cowl filters so the heat just flys out the back side. I literally "see" the heat waves on the bottom of my windshield.

So explain this to me smart guy. How come my engine oil temps with the steel hood would reach 260+ with 15 minutes of spirited driving, but once I replaced the hood my engine temps barely reach 250 on 30-1hr of spirited driving now? No other modifications have been made.
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      07-15-2020, 03:31 PM   #29
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Playing devil's advocate here......but there are a lot of other factors that could attribute to a 10 degree swing in oil temps.

Ambient air temp the same?

Was is the same section of road?

Was the humidity the same?

Was is cloudy/sunny out?

Same brand/weight of engine oil?

10 degrees isn't a very big change..... ambient air temps alone could do that....if you want to get scientific about it.
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      07-15-2020, 03:49 PM   #30
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Quote:
Originally Posted by nicky dj View Post
Another theoretical... I don't think you get my point. The is constructed in 2 parts; a bottom layer which is a plastic sort of material that is fused to the top side carbon fiber. It appears hollow in between.

And yeah I don't have vents never stated I did, but I did state that I do have the cowl removed and the BMS cowl filters so the heat just flys out the back side. I literally "see" the heat waves on the bottom of my windshield.

So explain this to me smart guy. How come my engine oil temps with the steel hood would reach 260+ with 15 minutes of spirited driving, but once I replaced the hood my engine temps barely reach 250 on 30-1hr of spirited driving now? No other modifications have been made.
Not trying to start an argument, just stating why I think a steel hood would be much better for transferring heat to the outside air. Doesn't matter if you have a layer of plastic on the bottom of the CF, there is still CF (an insulator) separating the hot air in the engine bay from the cool air outside. But there are other factors too--maybe the shape of the new hood allows for better airflow, etc. Everything is anecdotal at this point.

Edit: The same would be true in reverse as well. If your car was sitting in the sun all day the engine bay would probably be warmer on startup with the steel hood than the CF.

Last edited by lwgrenier; 07-15-2020 at 04:02 PM..
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      07-15-2020, 04:05 PM   #31
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Quote:
Originally Posted by nicky dj View Post
Okay Bill Nye the science guy. This is the underside of the hood, it feels like plastic and is not resin based, even the support brackets and molding is plastic. And it's so lightweight that I can bend it side to side but doesn't loose it's shape (front to back it's solid).

I can touch the underside of the hood after a spirited car ride and it doesn't feel hot at all.

No way this hood conducts heat over the heavy steel pot cover.

My hood's very warm....fairly sure no plastic liner but it's not here now.

Your year? Mine's '09
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      07-15-2020, 04:07 PM   #32
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Quote:
Originally Posted by nicky dj View Post
So explain this to me smart guy. How come my engine oil temps with the steel hood would reach 260+ with 15 minutes of spirited driving, but once I replaced the hood my engine temps barely reach 250 on 30-1hr of spirited driving now? No other modifications have been made.

Cowl filters removed both runs?
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      07-15-2020, 04:49 PM   #33
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Quote:
Originally Posted by CALWATERBOY View Post
Quote:
Originally Posted by nicky dj View Post
So explain this to me smart guy. How come my engine oil temps with the steel hood would reach 260+ with 15 minutes of spirited driving, but once I replaced the hood my engine temps barely reach 250 on 30-1hr of spirited driving now? No other modifications have been made.

Cowl filters removed both runs?
Yes first thing I did when I got the car. Guys, I don't think the direct heat being conducted/reflected by the surface of the hood is the issue here but the encapsulated hot air by the heavier hood.

My theory is that the hot air has the ability to escape much easier due to weightless hood.

I'll give you an example. After heavy spirited runs for 30 min, my OEM hood would be on fire on the touch, after popping it open really quick I would walk away because of the immense heatwave/air was so hot and intense. Now that's not the case, obviously the hood is not nearly as hot and when I pop it open I don't feel a whoosh or air, just a typical hot BMW engine.
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      07-16-2020, 10:11 AM   #34
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Quote:
Originally Posted by nicky dj View Post
Yes first thing I did when I got the car. Guys, I don't think the direct heat being conducted/reflected by the surface of the hood is the issue here but the encapsulated hot air by the heavier hood.

My theory is that the hot air has the ability to escape much easier due to weightless hood.

I'll give you an example. After heavy spirited runs for 30 min, my OEM hood would be on fire on the touch, after popping it open really quick I would walk away because of the immense heatwave/air was so hot and intense. Now that's not the case, obviously the hood is not nearly as hot and when I pop it open I don't feel a whoosh or air, just a typical hot BMW engine.
Weight of the hood makes no difference (for heat), only thickness would have an effect. Your CF hood must allow more heat to escape through the cowl, etc. Regardless, only thing that matters is your car is staying cooler and a few pounds lighter.
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      07-20-2020, 12:08 PM   #35
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Quote:
Originally Posted by chiefsotos View Post
The vents are just above turbo, like the hood i have in mind.
What about rain and car washing?
Do you have any problens?
I don't do carwash but I had no issues with me washing it myself, as far as rain Im in California so it hardly rains but the times that I got caught no issues.
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      07-21-2020, 09:27 AM   #36
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thanks for the reply
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      07-21-2020, 11:10 PM   #37
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If you have DCI and not a factory air box, vents on the hood will be a problem when it rains. Hydro locking the engine anyone?
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