Hood vent placement

[peapodf50]

Hello all,
I am thinking about putting hood vents in my car. I want to make sure I put them in the correct spot. I am going to be painting the hood soon and want to make sure that I get the vents in prior to the painting. I would like to put a vent right behind the radiator, but I have no way of measuring this as my cars front end is completely disassembled. Would someone be willing to measure how far the radiator is from the front of the hood? Also how much clearance is there between the hood and the engine? I was also thinking of doing two side vents. I watched a video and it said to put the side vents between 14-16 inches from the front of the hood. I really want to do side vents to help aid in the evacuation of the heat from the turbo charger area. Any help would be appreciated. Hopefully I gave enough detail of what I want. I know the vent behind the radiator is good for down force as well as cooler temperatures, but I think that ones further back can cause lift, I don't want to do that. Anyway thanks for reading.

Michael

[aeronaut]

My front clip and engine is out, so I can't measure much for you. But...you can measure from the radiator mount 'shelves'. Hard to see maybe, but plastic/rubber piece on each side of the frame. The center of that is where the center of the radiator mounts. You could also just sit your radiator in there and measure? If you're hood is still on, that is.

bay.jpg

[peapodf50]

7CDE67FF-7D20-46CC-8952-5F9F140436A6.jpg
I agree with you. Wish I had a front end on the car ��

[peapodf50]

Attachment 666363

[aeronaut]

Ohhhh yea, not much to measure.

[fbirch]

If I put a soft tape measure on the leading edge of my hood and run it up over the middle of the BMW roundel, the leading edge of my vent opening measures about 14.25" from the leading edge of the hood. At that spacing, the front edge of the vent hole is about 0.25" aft of the fan shroud, so just about as far forward as it can be without overlapping the fan shroud.

[peapodf50]

Thank you so much for the info. Now I can cut up my hood and get that part ready for paint

[fbirch]

Below are some pics, one prior too painting so you can see how far back it looks on the hood while actually being right on top of the fan shroud. Vent opening is actually about 14.5", although the hole underneath is a bit farther forward than that. Call it 14.5" to be safe
LW hood 1_low res.jpgTape measure.jpgFan shroud.jpg
BTW, this is a very effective location for venting air out of the engine bay. I once blew coolant out of the reservoir cap (head gasket failure overheated engine briefly) and every single droplet of fluid that came out of the coolant cap blew through the vent and onto the windshield. When I opened the hood, the engine bay was completely dry - not a drop of coolant anywhere to be seen!

[golgo13]

Can confirm 14" as that came with my instructions.

14.5" should be fine as well.

[aeronaut]

The hood bracing is spaced about 12" at that point on the hood. Are you guys cutting the bracing?

[BlackHawkRacing]

Race Louvers provides the following guidance on their site; see pages 9 and forward: https://racelouvers.com/content/hood-louver-guide.pdf

And since its semi-topical here is some wind tunnel data they just posted and a video:
https://racelouvers.com/content/Race...unnel-Data.pdf

[jakermac]

If one was to "duct" the back of the rad into the louvre in the pic above, does anyone think there'd be enough flow to adequately cool the rad or should I consider something with a bit more surface area/larger opening?

[fbirch]

I think it would be a challenge to duct the vent because it partially overlaps the valve cover and there isn't a lot of clearance in the zone of overlap (maybe 1 inch vertical clearance). The same company offers a very similar vent with a couple more rows of louvers, but that one would overlap the valve cover even more.

I can tell you that my car runs nice and cool in our hot local climate with no ducting and it does a good job of flowing incoming air out the vent - see comment above on coolant spray incident.

[fbirch]

The hood bracing is spaced about 12" at that point on the hood. Are you guys cutting the bracing?

In my case yes, I just cut the braces. I have a composite hood from MA Shaw which has less rigidity than the OEM Steel hood, but it's still ok after cutting the braces.
Under side 1_low res.jpg

Below is a shot after painting the hood and powder coating the vent
20180929_140018_low res.jpg

[golgo13]

The hood bracing is spaced about 12" at that point on the hood. Are you guys cutting the bracing?

Here are some pics of the kit installation and final install:












































I found this amusing:

[aeronaut]

Good info, thanks!

[aeronaut]

Race Louvers provides the following guidance on their site; see pages 9 and forward: https://racelouvers.com/content/hood-louver-guide.pdf

And since its semi-topical here is some wind tunnel data they just posted and a video:
https://racelouvers.com/content/Race...unnel-Data.pdf

I'm confused. Their PDF results mix and match measuring values. Focusing on the cooling results (page 4);

First, the chart is called 2 different things:
"Radiator Differential Pressure Percent Increase"
"percent change coefficient of pressure differential"

And I see numbers on the chart at 3%-12% increase in the above.
Then the text says "Race Louvers have up to 585% more airflow ..."

Confused.

[jakermac]

I think it would be a challenge to duct the vent because it partially overlaps the valve cover and there isn't a lot of clearance in the zone of overlap (maybe 1 inch vertical clearance). The same company offers a very similar vent with a couple more rows of louvers, but that one would overlap the valve cover even more.

I'll have significantly more room in front of the motor as the powerplant I'm swapping to will be lacking the front 2 cylinders.

[olemiss540]

You may want to consider tilting the radiator forward some by kicking the bottom away from the bumper? Nascar style? Am am sure there would be plenty of airflow for cooling purposes if you run a forced air system and would increase downforce I am sure.

[302blown]

I'm confused. Their PDF results mix and match measuring values. Focusing on the cooling results (page 4);

First, the chart is called 2 different things:
"Radiator Differential Pressure Percent Increase"
"percent change coefficient of pressure differential"

And I see numbers on the chart at 3%-12% increase in the above.
Then the text says "Race Louvers have up to 585% more airflow ..."

Confused.

Sorry a little late to this party but heres some useful info:

First pressure probes were installed in the front and rear of the radiator to measure the change in differential pressure across the radiator, higher differential pressure indicates more airflow thru the radiator, higher entry pressure and/or lower exit pressure. The wind tunnel records the pressures as coefficients. This is the most accurate way to measure cooling improvements as anamometer racks wont fit without effecting flow. Second the cooling chart shows the % gains over stock for various vents on the market and the 585% as noted in the pdf is the 'gain over the competition' and the competition referred to is trackspec. So in all of the data charts the 'recessed louver' data is actually the trackspec part. If you look in the above video at the 6:50 mark you can see the actual trackspec part as well as several wickers we added to it to try and improve but only saw minimal gains still not being better than the raised louvers or any of the race louvers. So the race louvers were 6 times better than trackspec.. We normally dont like to call out other companies which is why we list data by the design and not the company. It should be noted that this E36 rad pressures were on the low side as it had a small slim line fan with no shroud which doesnt restrict flow much at all while the audi wind tunnel car had higher pressures as it retained its full size shrouded fan which was very restrictive. Hope that helps..