Hood Venting, NACA Ducts
 

I just ordered two Naca ducts or vents in my case to put in my hood. I want to suck the hot air out.
Question, where should they go? Front of the hood, middle, or back.
I am thinking right over the alternator and power steering pump. I'm trying to copy the efect of the hood on my Minibusa (pictured).

There has been some discussion about hood vents in this thread (mostly for FI applications, but some applicable to NA)

http://www.ft86club.com/forums/showthread.php?t=53580

Thank you, I read that entire thread last night, but didn't see anything about vent placement.

Wow, interested to see what you are going to do here. definitely keep us updated..

The only way to really know is by doing actual wind tunnel testing to find out whether there's a low pressure area. That's where you'd want to place an induction type duct. Without actual data, you'll be wasting your time and money.

The hole in that picture doesn't look like it's intended to suck hot air out. It looks like it's designed to suck more air through the radiator to make the liquid cooling more efficient. Hot air off the engine looks like it would still well up under the hump behind the fan with nowhere to go.

As for NACA vents, I believe those are designed to suck air in, not out. They're replacements for scoops to get cool air into the intake or to route cool air to the brakes. Usually if you're venting to suck air out, you use louvered vents facing away from the direction of travel, like so:

http://image.mustangmonthly.com/f/93...hood_vents.jpg

These give you lower pressure above the hood and higher pressure below, so that the hot air sucks right up through the louvers. You usually want them high up on the hood, since hot air rises.

NACA vents have the higher pressure on the outside, ramming the air in the wrong way for what you say you want to do. And I don't think turning them around the wrong way will help.

Actually no hot air under my Mini hood as the engine in mounted in back, mid engine.
Maybe I'm wrong about NACA scoops. I thought they would work either way.

Yesterday I removed the plastic inserts from my fenders. Using my hand held cut off wheel I cut an opening in the inner fender. Took the car for a drive, got it hot, and with the engine and fans running you could really feel a lot of hot sir blowing out. The air flow was enough to blow a Bic Lighter out at 8 inches away.

I have a friend who is a carbon fiber guy and he took my inserts and is going to make me screened, vented, carbon fiber inserts. I think this should help allot for removing hot air from under the hood.

NACA ducts are for moving air in.

Yes, NACA ducts are designed to suck air in from a flat surface that sees laminar airflow.

The slatted vents pictured above are called louvers, and are usually to let hot air escape.

The location of the inlet and outlet vents is somewhat important, can't just slap them anywhere. Need to consider high and low pressure, so an inlet vent is in an area of higher pressure, or the outlet vent is in an area of lower pressure, or both. You could have vents all over the place and surprisingly, they may not do much at all if they're not in the right areas.

A couple of members have done something similar to the fenders and they all commented that they could really feel the hot air pour out after a drive. Looking forward to how yours turns out...

Show us a vid, I want proof!

Really looking forward to see how this turns out.

Is heat a problem? I've had the car out in 36℃ 96.8℉ with the A/C on In traffic and never seen the needle go past the second line. Does it start climbing if you're in Texas per se?

The engine seems to be designed to run hot from the factory (its assumed this is for fuel efficiency), but put it on the track and things heat up beyond most people's comfort levels. If you have a turbo tucked under the hood somewhere, they generate a lot more heat at the front of the engine and the heat tends to pool in the engine bay. Enough heat is radiated to melt the radiator fans. Tracking a turbo car is an exercise in failure unless even more heat mitigation precautions are taken.

Here's a good thread.

http://www.ft86club.com/forums/showpost.php?p=680966

Also look for posts by @plucas @eric6 and @Hancha Group

They've done aero modeling to see the high and low pressure zones.


Sent from a secret volcano base using trained sharks

Will do in two weeks when I get home from vacation.

I've obviously been taking it way to easy my car! LOL! Yeah I'm glad I decided to stay NA, I don't have the time or ambition to deal with turbo troubles anymore. Used to have a little Omni GLH that I stage III'd with a turbo off a stealth.. had to put a Ford Taurus rad and fan on it. Don't miss those days, I could do a 2.5L head gasket in 45 mins flat. LOL! I love this car so much I don't have the heart to track it! I'd rather buy something used and build that up.

I think using the side plates as vents will probably work though. In conjuction with a low profile hood vent you could get a venturi affect going. I'm definitely going to keep an eye on this thread. ;)

Here's my solution. In traffic my view ahead turns wavy due to the heat coming out of them. Haven't had a heat issue since

Attachment 85637

Are those cut into the hood? Can you post a wide shot?

Been a while but i actually missed this thread, while creating one exactly bout the same topic. The hood vents.. did you make the rain caps or whatever else you said you were going to do. I wanted to do the same thing to my hood. Similar to what S2k's do to theirs. Any pics of the install? Thank mate. @Dipstik-sportech

I never installed them, the ones I ordered were a cheap piece of crap so I didn't install them.

No pics but all I did was the same thing the s2k guys do and job welded the aluminium mesh to the underside. I haven't been motivated enough to make rain caps as my car is parked inside when it rains but I will eventually.

My condolences to your car. Fitting user-name as well! What sort of conditions prompted you to redesign the work done by the dudes who designed the car?

Let engine heat escape. works really nice.
I got BRZ inserts, cut them out and installed gold painted mesh to match my gold wheels. I'm very happy with the results.

The outer fender is the cosmetic surface you see, the plastic inserts are another cosmetic item (they even look like a vent, but are nonfunctional). Behind these inserts is a part of the fender that walls off the engine bay. Cut a hole here, install vented plastic inserts, and you now have a new path for heat to escape the engine bay. Works quite well from what I've read, and exterior cosmetics are unaffected (depending on the inserts you use). Water ingress behind the exterior fender skin may be an issue, but I haven't researched that far.

All very nice. What overheating problems are you and OP having that you need to do this? Post oil temps pre and post mod if you have them.

I think overheating needs to be addressed with maybe a bigger radiator and a fanned oil cooler. The vents help release underhood heat but I cant imagine them making such a big difference. I actually touched my charge pipe right before the TB and it was pretty damn hot, was thinking of gold wrapping it.

So... what you're saying is there must be a prerequisite to do this mod? Namely oil temps? Lower under hood temps are nearly never a bad thing. On track my non-FI car saw coolant temps creep up a bit, it is possible this modification could help that. For what money he spent and the time he invested it seems like a great idea.

"My condolences" to you for being so traumatized by the fact that someone did what many see as a worthwhile mod. Your user name is even more fitting imo.

I've not done the mod, but I've looked into it and a friend is considering it. He tracks his car FAR more than I do. Either way, underhood temps get pretty toasty from even normal driving. I believe venting the engine bay helps in three areas:
1- Reduce heatsoak at low speeds/stops, this is especially important to anyone with FI.
2- Reduce heat-related degradation of all the neighboring components. Plastics can only be baked and heat cycled so many times before them become embrittled.
3- Marginally improve overall cooling efficiency by allowing radiator airflow to escape more easily (this is speculative, albeit logical). If the fender vent is in a low pressure zone at speed, then it can act as a soft vacuum to suck out hot air. It's also near the highest point of the engine bay so the heat will naturally want to rise and exit.

I have only one concern right now with cutting the vents and is not cutting it. I've arrived at the maybe incorrect conclusion that in order to extract the air based on some stuff that i can't explain.. the low pressure high pressure stuff, the vent needs to be around the front part of the hood. As you get closer to the base of the windshield the low pressure area wont allow for maximum "pull" effect. Now i've located two slots right over the front part of the hood which sit between the fans and the engine.. but also sits right on top of my turbine housing and downpipe so when it rains. i may not like it.

Vents need to go around the red areas on the hood.
http://hanchagroup.files.wordpress.c...11/frs_001.png

Neat pretty much where mine are!

I don't really know how much my fended vents help, if any, as I added a oil cooler and tranny cooler at the same time. What I can say is my engine oil and tranny fluid both stay below 230 degrees on the track and when pulling into the pits you can really feel the heat coming out of the vents. I'm sure they didn't do any harm. And I think they look pretty good.

I'm sure any vent in any location will help, so there's no wrong placement.

Sorry for this but being a auto detailing nut, you need to get those Spyder webs polished out of your paint.

Ya, I know I should.

I tell yah, if I was closer I would help you out, it is a passion of mine.
wax on, wax off

[IMG]http://i44.photobucket.com/albums/f2...ps0owiazse.jpg[/IMG]

[IMG]http://i44.photobucket.com/albums/f2...pszvbrnwrw.jpg[/IMG]

This is one of my master pieces.

So after cutting a whole in the fender, how did you attached the BRZ fender garnish?