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.

[Def]

Originally Posted by hotboiblaze

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.

Just one question... how would an aerodynamic high pressure zone form at the base of your windshield when the car is NOT moving?


So yea, I guess it "vents heat" when you're stopped, but when do you want more cooling when your car is stopped and less when it's moving? Engine running hot as you're creeping to the local hard parking spot?

[S14DB]

Originally Posted by hotboiblaze

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.

Yeah, it will let heat out when the car isn't moving. But, will force air in when moving. Fighting the air coming trough the radiator. I'm sure it works great for Drag and drift where you do a quick run and the radiator doesn't heat up. Then cool off in the pits.

Vents in the hood should be behind the radiator and in front of the engine. I have seen a ton of vented hoods for the 240sx over the coil packs or core support. Just because they look cooler there on the out side.

Also, mentioned earlier. Make sure you have a under tray/panel from the front bumper to the subframe/crossmember. As air enters the bumper it will look for the easiest way out. If there is no panel between the bumper and core support it will hit the FMIC/Radiator and go straight down. There is low pressure in the engine bay from the air rushing under it. If you block off the front half from the ground it will suck air through the radiator then out behind the subframe. No panel behind the radiator and you will get air coming up spoiling the low pressure zone.

[ROOSEY]

well i learned something today thank you for the correction!

[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.

[dawagarage]

Originally Posted by Def

Just one question... how would an aerodynamic high pressure zone form at the base of your windshield when the car is NOT moving?


So yea, I guess it "vents heat" when you're stopped, but when do you want more cooling when your car is stopped and less when it's moving? Engine running hot as you're creeping to the local hard parking spot?

'when do you want more cooling when your car is stopped' = in the shitty bumper to bumper traffic that LA and san diego provide us with, especially on hot days. im speaking in regards to a dd, non tracked car. on the highways/not in traffic/etc, the inrush of air through the radiator negates the 'base of the windshield' problem.

[S14DB]

Originally Posted by hotboiblaze

on the highways/not in traffic/etc, the inrush of air through the radiator negates the 'base of the windshield' problem.

No, it won't. The pressure in the cowl area is greater then the air in front of the radiator. The airflow through the radiator is reduced.

[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?

[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...

[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

[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.