Do vented hoods actually work?

[gearhead55]

Do vented hoods actually bring down temperatures inside the engine bay? I'd like to keep my RB cooler since it is going to be the daily driver now and i'm wondering how effective vented hood actually are. Real data would be appreciated but i guess i will listen to fact-less opinions too...

[slideslidegnarslide]

Think about it heat rises. Stock hood doesn't let it out vented hood does. I have an rb too and I've always rocked vented hoods. I don't have evidence but there was an issue of super street were they proped the back of the hood up and it was 10% cooler so imagine vents.

[MisawaJason]

In theory yes
Do allot of companies just throw a vent on a hood without any R&D on how well it performs............yes

[Def]

Yes. I dropped my coolant temps about 5-10 deg F depending on the day with a vented hood over the stock one on track. Seemed like less drag on long straights too.

[Sleepy_Steve]

+1, it will do wonders if you do a little bit of homework first.

While you're at it, maybe do some ducting of the air passing into and out of the radiator if possible. Very cool stuff once you get into it. (assuming you like somewhat technical things)

[gearhead55]

Alright cool, thanks for the info. Interesting what Def said about less drag at high speeds, i would have never thought about that.

Guess its time to buy a vented hood.

[ROOSEY]

correct me if im wrong but proping your stock hood up in the back can also help cool everything down. hence why lots of drift cars have them propped up in the back. it acts like a cowl hood. and it looks cool....or like youve gotten into an accident lol kinda like hat slideslidegnarslide said. its deffinitly more efficient with a vented hood depending on your budget of things

[Def]

Originally Posted by ROOSEY

correct me if im wrong but proping your stock hood up in the back can also help cool everything down. hence why lots of drift cars have them propped up in the back. it acts like a cowl hood. and it looks cool....or like youve gotten into an accident lol

You're wrong. The base of the windshield is a high pressure area at speed. It will force MORE air into the high pressure underhood area.

[dawagarage]

Originally Posted by Def

You're wrong. The base of the windshield is a high pressure area at speed. It will force MORE air into the high pressure underhood area.

this is what ive heard from a lot of ppl that track their cars. however ive also heard (& speak from experience) that @ a stop, ie traffic light & 'pit stop areas'.... vented/raised hoods do help to allow hot air to escape from under the hood.

[hOngsterr]

its like saying its hot in your car, you have no windows, theres a sunroof, if you open it, does it vent out the heat? lol

[gearhead55]

Originally Posted by hOngsterr

its like saying its hot in your car, you have no windows, theres a sunroof, if you open it, does it vent out the heat? lol

what is like saying that?

S14DB thanks for the info. I guess i'll start fabbing some cooling panels

[hOngsterr]

que?

vents should work, but DB explain it even more,
but basically what im saying

is you crack your sunroof cause its hot, thus letting the hot air vent out.

technically same as a vent on a hood.

[murderrsirenss]

damn, learned a lot from reading this.

[slideslidegnarslide]

With vented hood that high Preasure area wouldnt matter cause yOu have vents so propin may not work but this thread is about vented hoods and they clearly work

[21Nemesis]

Just make sure the vents aren't over any critical components, like the MAF or spark plugs. The vented hood I have, Seibon DV, has a vent directly over the MAF. During the rain, the MAF shorted out from all of the water that came into contact with it. However, I placed a make-shift cover underneath the hood that now protects the MAF.

[gearhead55]

good point.

[DirtyMick]

I’ve been looking for a CF single vented hood for a while now and all I can find is the multi vent. I had one on my old s-3 back in the day. It was a D1 style with just one vent. I guess I could go with the multi vent to help my RB but I’m just not a fan of the others. Any ideas guys?

[brndck]

Originally Posted by DirtyMick

I?ve been looking for a CF single vented hood for a while now and all I can find is the multi vent. I had one on my old s-3 back in the day. It was a D1 style with just one vent. I guess I could go with the multi vent to help my RB but I?m just not a fan of the others. Any ideas guys?

sI'm assuming you still have an s13 with pop ups?

VIS make 2 styles

[BlackZenkiS14]

Hood vents work, but you have to make them work correctly, and direct airflow through them. Sealing off the underside, and providing correct ducting for airflow through the FMIC, Radiator, Oil cooler, etc...

[jr_ss]

As mentioned above, in order for them to function correctly, the components being vented must be sealed underneath and directed out said vent. I plan on cutting and 03’ cobra style vent into my hood behind the radiator and ducting that up and out.

[Kingtal0n]

The second most mis-understood aspect of combustion engines besides PCV is heat flow.

The engine itself needs to be insulated. It should have thick, cast manifold, plastic intake insulation, blankets, exhaust wrap, coatings, shields, covers. The OEM does more and more of this as the years go on. The temp rise created by burning fuel is your $$$ from that fuel so to conserve the heat and insulate the engine/exhaust is to save money on fuel and get the most from the fuel in terms of shaft power.

Power plant engineering fundamentals always revolve around conserving heat, insulating the power plant, getting the most from the fuel.

If you start ripping that heat away by removing the exhaust wrap and removing the hood (extreme example) you are ruining the engine efficiency, lowering fuel economy and increasing the amount of fuel that needs to be sprayed by injectors to maintain the same temperature steady state.

Its like opening the cover on a propane grill, now you need to turn up the propane gas (fuel) to compensate.


Vented hoods can be used effectively in performance applications, but they should NEVER be used to directly cool an engine, or exhaust system. Those parts need insulation and to be wrapped up tight to conserve energy. Exhaust gas velocity increases as it warms up, it expands and takes up more space (it can move a turbine better at higher velocity, or move to the exit quicker) the hotter it gets.

If you need more info ask questions I dont wana make this into a huge long post
basically the engine bay should be kept cool by insulation, not a vent. Its okay to vent whatever is left but the vent should not be a first line defense.
The radiator needs to deal with the waste heat, and insulation makes sure that all the waste heat makes it to the radiator, and if the rad has trouble THEN you upgrade the radiator, fans, make sure the panels are intact and functional, and finally add a vent to help the radiator as needed.

[BlackZenkiS14]

Originally Posted by Kingtal0n

The second most mis-understood aspect of combustion engines besides PCV is heat flow.

The engine itself needs to be insulated. It should have thick, cast manifold, plastic intake insulation, blankets, exhaust wrap, coatings, shields, covers. The OEM does more and more of this as the years go on. The temp rise created by burning fuel is your $$$ from that fuel so to conserve the heat and insulate the engine/exhaust is to save money on fuel and get the most from the fuel in terms of shaft power.

Power plant engineering fundamentals always revolve around conserving heat, insulating the power plant, getting the most from the fuel.

If you start ripping that heat away by removing the exhaust wrap and removing the hood (extreme example) you are ruining the engine efficiency, lowering fuel economy and increasing the amount of fuel that needs to be sprayed by injectors to maintain the same temperature steady state.

Its like opening the cover on a propane grill, now you need to turn up the propane gas (fuel) to compensate.


Vented hoods can be used effectively in performance applications, but they should NEVER be used to directly cool an engine, or exhaust system. Those parts need insulation and to be wrapped up tight to conserve energy. Exhaust gas velocity increases as it warms up, it expands and takes up more space (it can move a turbine better at higher velocity, or move to the exit quicker) the hotter it gets.

If you need more info ask questions I dont wana make this into a huge long post
basically the engine bay should be kept cool by insulation, not a vent. Its okay to vent whatever is left but the vent should not be a first line defense.
The radiator needs to deal with the waste heat, and insulation makes sure that all the waste heat makes it to the radiator, and if the rad has trouble THEN you upgrade the radiator, fans, make sure the panels are intact and functional, and finally add a vent to help the radiator as needed.

I dont know anything about you or your backround, but everything you just wrote made me feel so good about the choices i've made to build my car, and all the mods I've done during this off-season. Thanks lol

[kanyedian]

Love all this tech talk. Leaning heavy toward a TA style hood for kouki S14 front on my S13 vert.

I confess the reason was to lower the engine bay temps a bit. I do have my downpipe wrapped with DEI mummy material and a turbo blanket. The 1JZ is so long and my bay small that the dual electric fans fit one centimeter from the serpentine belt and I can't run a radiator shroud nor properly duct the waste post-radiator air up and out. My thought was that the low pressure area behind the rad would draw some warm air out. I do also like the look.

[OBEEWON]

Yes. I also noticed adding back undertrays and fender liners helped too. Basically keeping the factory ducting plus a hood vent = better cooling.
Folks often make the mistake of putting the vent too far back though. As close to the rad as possible is ideal.
Source: Neil DeGrasse Tyson

[Ryan_H]

Yes they work.

They work even better if you can direct the air to them and are best served on ambient engine bay and cooling packs.

The area over the hood when you're moving is for all intents and purposes negative, so air is sucked out the hood.

But as has been said, ambient engine bay temps that are low are good, but engine components should be nice and hot.

[Kingtal0n]

Hey I remember this thread

Heres my engine bay currently



Plastic intake is an insulator, it runs 135*F
Exhaust Downpipe is wrapped and double shielded
Radiator ducted with shields and flow separated from intake plumbing
Stock hood closes tightly with OEM rubber seal at the back
Heat shield separates exhaust crossover and downpipe from exhaust manifolds

I have a couple shields that aren't shown in the pictures because I'm just being lazy. But the idea is basically reflect as much of the radiant heat back into the exhaust while insulating as much heat as possible into the engine while keeping the components such as coil packs, injectors, electrical stuff cool. You measure their temps with the infrared temp gun, the coils should not really exceed the temperature of the valve covers and the valve covers should not exceed the temperature of the oil and if you have done your job correctly the oil should not exceed the temperature of roughly boiling water at atmospheric pressure- near 210 to 220*F max temp oil is ideal for daily drivers. The coolant needs to stay near the temp of the oil as well, I run 195 to 205*F coolant and 200 to 215*F oil temps almost all day everywhere no matter what the situation is.

This car sits in daily driver traffic bumper to bumper high noon, it sits in drive through, it cruises highway for 200 miles, it does stoplight stuff, the fans kick on and off sitting in traffic.

Have some video fun

Tire chirps video
https://www.youtube.com/watch?v=RswyLY1kqac

Un-cut un-edited drive
https://www.youtube.com/watch?v=1y09lYL4Now

0:05 get on highway cruise note 16's
3:38 note 15.8 to 16.0:1 still cleaning plugs @ 65mph in traffic
5:18 kick out of lockup and small boost in 4th to move up in traffic
6:29 step down lightly into lockup for some boost in 4th
7:18 get off highway
8:23 downshift rip the tires loose at 50mph
9:12 slowing down for stoplight
9:20 Showing A/F Stopped at stoplight note 14.7 to 15.0 open loop steady
10:51 leave light, turbine whistle
11:30 cruising 15.6 to 16.0 housekeeping plugs
12:18 rip tires loose at 50mph 'spool character'
13:05 stopping for traffic light
13:10 show a/f for traffic light stop 15.5 walking into 14.7 to 15.0 open loop
13:52 2nd gear chirp coming leave light