Vented hoods

[Capt. Obvious]

I really like the look of vented hoods and there are several out there for our cars from different manufacturers. Does anyone know anything about the different options and which of the hoods have the best vent placement?

I'm assuming the lowest pressure spot on the hood is somewhere near the center? Or is it more towards the front or maybe back the back of the hood near the windshield?

Would two louvered vents or maybe NACA ducts on either side of the hood be the best option? Or would a big opening in the middle of the hood (like on an Evo) be the best choice?

[A4Rob]

I run a vorsteiner hood with the center louver vent. I do believe it is effective. At stoplights I can see heat pouring out the louver.

[Johnnys4]

Heres what I have. Just a stock hood with a NACA vent. This is about as far back as you can put it. Sits rite above air filter.

[TighTT]

Like Rob, I too have a vorsteiner hood on my A4. I personally would skip the whole vent idea. My bay is constantly wet/dirty.

[wdbdy2000s4]

does the vorsteiner have a rain tray?

[TighTT]

does the vorsteiner have a rain tray?

Nope...just vents. Dont get me wrong...IMO its the absolute highest quality hood available for our cars...which is why I bought it. Also my A4 generates some serious heat...so its nice to have. The downside is when it rains...my coils get soaked, etc, etc.

[omgwtfbbq!]

Low pressure area on the hood?

wat?

[*Blue-Angel*]

Isnt there a hood out there that has vents on both sides.

[Capt. Obvious]

Low pressure area on the hood?

wat?

Aerodynamics. As air goes over the hood of the car it causes a low pressure zone. If a vent is located right below that spot on the hood, it will pull hot air out of the engine bay as you drive.

[omgwtfbbq!]

You will have an area of lower pressure immediately aft of the headlights, but everything else is exposed almost directly to the air flow, and will be under quite a bit of high pressure. The original engineers did design these cars with heat flow in mind, punching holes in the hood would tend to cause turbulence, effectively heat-soaking the air under the hood, decreasing cooling effects and creating possible heat concentrations. The best method of heat dissipation would be routing more air through the radiators, through the engine bay, and down the underside of the chassis, like the original design. You could do that a number of ways, the easiest of which would be flat-bottoming the car.

And if you try to tell me a forward facing naca duct is going to suck heat out of the engine bay you are high.

[julex]

Aerodynamics. As air goes over the hood of the car it causes a low pressure zone. If a vent is located right below that spot on the hood, it will pull hot air out of the engine bay as you drive.

And you can start saying that you have a heated windshield as well!

[Dimcorner]

I think the vent is the actual cause of the low pressure and not the hood. You might have one right behind the headlights and right in front of the windshield by the hood since it has a lip.

[Capt. Obvious]

What options are there for vented hoods?

I know of the Seibon and the Vorsteiner, any others?

[veggiemonster]

why don't you space the hood like honda people's so you have an "engine bay" vent the size of the bay. the added turbulence would suck out heat, and you wont have to worry about water.

[Dimcorner]

These kind of vents worked very well on the RX-7 (and that is one HOT engine). Kept water out pretty good as well. I think this kind of vent (not same size or number, just the style) would work ok. I think the new Aston Martin has vents on the hood as well.

[Capt. Obvious]

why don't you space the hood like honda people's so you have an "engine bay" vent the size of the bay. the added turbulence would suck out heat, and you wont have to worry about water.

Two reasons.

1) I don't think that looks good.
2) I don't think it will work very well with our hoods since the hood includes the front grill and wraps over the front of the car.

I'm not worried about water in the engine bay, there's plenty of ways to keep it out while still allowing venting.

I really like the B7 RS4 Vorsteiner hood:

[RolledMySTi]

What options are there for vented hoods?

I know of the Seibon and the Vorsteiner, any others?

Every Seibon hood I have seen is total crap. I would never waste my money on their cheap Chinese carbon products.

[veggiemonster]

OP, just throwing it out there. thought about it for myself as i'm sick of spending moniez on the s4, and i don't have a EFK with my FMIC. i'll test it myself sometime in the future.

[Capt. Obvious]

I feel ya there with spending more money on the car, I'm too busy replacing every sensor on the engine since I seem to need a new one every other week...

My hood is kinda messed up (been repainted half a million times), so I'm thinking about just sacrificing it in the name of Idontgiveafuckanymore and cutting vents into it and fabbing up a removable rain tray for each vent. If it looks like shit, I'll buy a carbon hood.

[veggiemonster]

i would have no problem doing that with mine either. especially if yours comes out looking even half decent.

mine has more rock chips all the way through the 3 coats of silver and 2 primer coats (at least). lol they are big enough i can tell its been repainted a couple times. and i wouldn't mind a "reason" to get a carbon hood...i just can't do the "but i want it" shit anymore with this thing

[Avant Fetish]

Is there a reason the vents are placed so far up front? Doesn't the majority of the heat gather towards the firewall where the turbos are?

Has there ever been any tests where under hood temps were measured? Seems like the vents are more cosmetic??

[Capt. Obvious]

Has there ever been any tests where under hood temps were measured? Seems like the vents are more cosmetic??

That's basically what I was trying to ask with this thread. Cosmetically, I like vented hoods and I want one. But if I'm going to get a vented hood, I might as well get one that is functional. If none of them are truly functional, I'll just get the one I like best.

[Avant Fetish]

I remember Mugen actually wind tunnel test their front bumper and hoods.

You might as well just pick the hood you think looks best. IMO...the vents on the Audi hoods are nothing more than cosmetics.

If you are going to cut your hood...maybe check where the E46 M3 vents are placed...

Its actually something I've always wanted to do to my Corrado...but never had the cojones to cut up a good hood!

[omgwtfbbq!]

Just get the one you like best.

[hellrot98m3]

i sort of like this one because its simple. i have the vented vorsteiner hood on my m3 and the quality is of the best that ive seen.



http://cgi.ebay.com/ebaymotors/SEIBO...ht_3913wt_1165

[Tormented]

i sort of like this one because its simple. i have the vented vorsteiner hood on my m3 and the quality is of the best that ive seen.



http://cgi.ebay.com/ebaymotors/SEIBO...ht_3913wt_1165

You do realize that hood is not vented right? It's simply a CF hood, the OP asked about vented hoods.

[Capt. Obvious]

A more technical discussion on the topic:
http://www.honda-tech.com/showthread.php?t=2766239

I'm going to be putting my vents just after the radiator. I'll try to do some before/after logs too.

[golfrsi]

I'm going to be putting my vents just after the radiator. I'll try to do some before/after logs too.

remember you also need to work around the framework of the hood as well or you risk making a floppy hood as flat sheet metal is very pliable.

[NishadJoshi]

^I REALLY like that hood too, super clean. I wish they made one with a similar style (dual vents) for the B5.

[SummitS4]

Has no one really mentioned the fiber images hood? Friend of mine said it kept the engine 150* cooler on the track.

[Capt. Obvious]

No way it kept it 150 degrees cooler, did you mean 15?

[Avant Fetish]

What about placing the vents towards the rear of the hood like the E46 M3...or even vertical vents like the mk2 golf?

The majority of the heat comes from the area of the firewall where the turbos are...no?

or does the heat from that area gets pulled out from the bottom of the car?

[Capt. Obvious]

Having the vents towards the front of the hood allows the most air to be pulled out best because that's where the pressure is lowest. As you move closer to the windshield the air pressure gets higher as the air "stacks" against the windshield.

Also, having the vent more towards the front will pull the hot air that has just traveled through the radiator up and out of the engine bay.

[Avant Fetish]

When I pop the hood after city driving...the back of the motor seems to be generating most of the heat. Wouldn't it make more sense to dissipate the heat from that area instead of the radiator that already has air hitting it? At least at lower speeds...the heat will have somewhere to go.

When the car is moving, the engine bay is under vacuum anyways. Driving home from my girlfriends place is mostly highway. When I get home, pop the hood...the intake and engine covers are cool to the touch. The front of the bay may have the lowest pressure...but it seems to generate the least amount of heat also.