edomund

First off I searched!
I got a Greddy FMIC and need to vent my engine bay now.

I'm doing all the cooling mods, upgrade rad., ducting etc.
But I haven't found a thread asking about covering the turbo scoop. I have the CF speed machine one so I don't want to go to a NA hood.

I'm going to cantilever my hood at the back probably.
Should I leave the scoop open, duct it somehow, or close it off. Remeber the hood will be proped at the back to let hot air exit.

thanks
ed

classicauto

iTrader: (3)

I can't see that blocking it off or leaving it open is drasticalyl going to effect you either way...

If it was mine I'd run it open, if I hit any problems with cooling issues then I'd cross that bridge when I got there.........just my opinion

edomund

I do have some cooling issues I have a big *** FMIC that blocks a lot of air. Any cooling help I can get will help.

88t2romad

is your ac condensor removed? What fan are you using?

bacek

ummm im no physics major but wouldnt the air coming in from the tmic vent help pull hot air out if you cantilever your hood? i mean air will keep on moving so wont it move in through the vent and out through the back?

im getting this idea from vmounts and vented hoods.... the air thats getting sucked in needs to move out thats why they need vented hoods. so if there is an opening (t2 vent) pulling air in wouldnt it just aid the escape of hot air through the raised rear of the hood?

again i suxor at physics so if someone knows more chime in

edomund

AC is there.
Stock fan (soon AWR radiator and stock fan and shroud)

Thats what I was thinking bacek, but I thought I heard some people a while ago saying something about blocking the scoop or using NA hoods.

CrypticApathy

wait, are you getting to cold or to hot? My impression is your running to cold.

Wankel7

I jammed a big *** piece of foam in the scoop. You can't see it from the outside. I was going to leave it open but it was making my engine bay dirty and when it rain water is just going to pour in there.

I have the koyo, greddy fmic, no ac, stock fan/shroud and no cooling issues.

James

adrock3217

Propping the hood in the back (cowl?) is supposed to pull air in, contrary to popular believe...

Wh1t3 C0m3t

very true, it draws the turbulent air where the hood meets windsheild.

edomund

Yeah I've heard this debated on other threads many times.

Well even if I dont prop the back of the hood should I block the scoop?
I've heard the scoop sucks in air and creates turbulence and disrupts air flow through the engine bay.

Black91n/a

There's a high pressure region at the base of the windshield as is evidenced by the attached picture that shows the pressure profile of the car. The cabin air intake for the heating and cooling is at the base of the windshield there. If you're not convinced set the fan to off and the vents to the top ones only and drive along a highway, there'll be air coming in at you.

Raising the back of the hood will let air out when you're stopped or going slowly, but once you get moving more than maybe city speeds then it'll pull air in, making the rad and intercooler less effective (the air's having to flow against a higher pressure than before, thus reducing the amount of flow going through).

As for the hood scoop it's probably better to close it off from a radiator and intercooler point of view, but leaving it open will help bring the engine bay temps down.

NZConvertible

Do not prop up the back of the hood! Apart from the obvious frontal impact dangers, this will push air into the engine bay, not let it out. All those fools you see doing this have zero understanding of aerodynamics and are achiving the exact opposite of what they want.

You should definitely block off the hood scoop if you don't need it any more. The best way to improve airflow through the radiator (and now FMIC too) is to improve airflow leaving the enigne bay. That's what properly positioned bonnet vents do. The hood scoop performs the exact opposite of that. Pushing air into the engine bay makes it harder for air to flow through the radiator and FMIC.

Remove the rubber TMIC seal under the hood and replace it with a piece of sheetmetal with foam around the edges to seal it to the underside of the hood.

edomund

That is a helpful aero picture thanks.

So with a FMIC and a turbo hood where does the air escape the engine bay? Throught the bottom of the bay?

What do you suggest I do to vent the engine bay to move more air through the fmic and radiator and then out the engine bay?

edomund

^Sorry late post I posted that while nzconvertible was posting and answered my question.

edomund

So where do properly placed bonnet vents go?

I'm assuming further forward on the hood as to stay away from the back where air is sucked in due to the pressure zones.

NZConvertible

Yep.

Correct, the low pressure zone is always towards the front of the hood. Look at factory placements for evidence of this, e.g. WRX and Evo.

If you were to install you own you should take pressure measurements above and below the hood at various points to find the point with the greatest pressure differential. That'll result in the greatest airflow.

elnots

What about installing an RE Amim hood scoop on it? I haven't seen the flow charts from it but it looks like it's blocking off the hood scoop from elements if that is a concern. Anybody have anymore info on that?

NZConvertible

That vent is probably better than nothing, but AFAIK nobody has ever performed the pressure testing I mentioned on FC's so nobody knows if it's in the ideal spot.

And it does not stop rain getting in. If it did it would be completely pointless as a vent...