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Fender rear engine vent: optimizing performance

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Discussion starter · #41 ·
Fast Willy said:
The fenders are partly hot because of the outside temps from the sun.
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Um...the roof is not hot. It's cloudy here right now and rainy. The fenders are completely open to the engine bay and get almost all the heat the hood sees. The lower rear fender vent pulls the engine air across the fender wells and it really settles at the higher areas of the hood and fenders when you slow down. This is why i wanted to do fender vents, so at lower speeds there would still be descent engine bay ventilation.
 
#43 ·
I am glad to hear that you atleast track your car. Doing all of this to a car that never sees the track would be pointless.

I am glad that you are doing the R&D on this development. That way when my car becomes a dedicated track car in the future i can just refer back to this. :tup:
 
#45 ·
hillhucker said:
I've seen quite a few race car that use top fender vents, like ALMS type cars used to a couple years back.
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The purpose of the vents on the tops of the fenders on those cars is for aero, not heat dissipation. I'm not saying don't do it- it's probably way worth it for a track car and I've considered it myself, but you have to complete the connection from the wheel well to the top of the fender. The idea is that the wheel well is a high pressure area at the front and top of the spinning wheel, while the top of the fender is a low pressure area. Venting air from the former to the latter should increase downforce. For another reference, TiC just added them to their WRX.

I also applaud your effort on the rear-of-fender vents. I noticed that rubber flap on mine when I got my car and I've never returned to the issue to make them more functional. I guess I should look into the engine bay to see where the other end of that space is to see if that needs modification as well. Removing the flaps should be a no-brainer if it works.

Frank
 
Discussion starter · #46 ·
caveguru said:
The purpose of the vents on the tops of the fenders on those cars is for aero, not heat dissipation. I'm not saying don't do it- it's probably way worth it for a track car and I've considered it myself, but you have to complete the connection from the wheel well to the top of the fender. The idea is that the wheel well is a high pressure area at the front and top of the spinning wheel, while the top of the fender is a low pressure area. Venting air from the former to the latter should increase downforce. For another reference, TiC just added them to their WRX.

I also applaud your effort on the rear-of-fender vents. I noticed that rubber flap on mine when I got my car and I've never returned to the issue to make them more functional. I guess I should look into the engine bay to see where the other end of that space is to see if that needs modification as well. Removing the flaps should be a no-brainer if it works.
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That's interesting about the fender downforce, i was not aware of that function. I'm going to have to research more into that.

The GR STi fenders are completely open to the engine bay, this is why fender vents work so well on this car.
 
#49 ·
I just took mine out, going for a test drive now and will report back with the differences. I'll also repeat the test with the seal remove at the back of the hood and compare as well. (10 seconds to remove the hood seal and about 10 seconds per side for the rubber things in the fenders)
Cheers,
Chris
 
#50 ·
Definitely cooler...

Didn't have time to test with the hood seal off but the trusty old hand on the intercooler and intake manifold noticed a difference for sure. :)

(That's with the fender rubber strips removed only)
 
Discussion starter · #51 · (Edited)
I would say it might help, but that piece of rubber is not flush to the exterior hole, so in stock form i would guess it flows just fine with it on with the stock holes. The stock holes are just ridiculously small, enlarging them is the key to this mod. If you saw the 24 hour car early in this thread, they completely cut out that whole section of fender and the fender cover. I would really doubt removing the rubber by itself would increase the efficiency of that vent at all. In the stock form more of the air actually exits through the gap in the door and fender, not the vent. This is because of the great amount of restriction by the little fender holes. (recently i enlarged the holes even more then what is posted in this thread. Every bit helps.)

-To really test your theory, get your car hot enough to kick the radiator fans on and have one rubber piece in and one out, then feel the air flow.(the best way would be with mounted temp gauges while driving, but not a common item in the garage). When my fans kick on there is a huge amount of air exiting the fender vents.
 
#52 ·
I've been meaning to respond to this thread for a while. I cut (4) 1 inch and a quarter holes (w/ a hole saw) into each side just where hillhucker cut out his vent. I thought the hole saw might be easier to control. I removed the rubber piece also.

As far as I can tell, the stock setup does absolutely nothing to vent engine heat. There is two small factory holes that get completely covered by the side vent plastic piece. The only place for the hot air to go is the front of the door (where the electrical connections go into the door). If you have everything apart you'll see what i mean.

Now onto my findings: This works hands down. I was going to hook up thermometers to see the before and after but the results speak for themselves. After a drive (when the engine is at op temp) I pull over and turn on the AC (fans forced on) you can feel the hot air blow onto your hands. Also if you feel the area of the door where the vent discharges, its very warm.

I'll post up pics tonight.

If you do this, make sure you paint/touchup any bare metal or rust will appear.

I don't know why the factory piece doesn't have "vent holes" in it. My only guess is that in extreme cold (like here in Canada) it would keep the engine out of operating temperature. If thats the case I could always put the rubber pieces back in for the winter.
 
#53 ·
^^^^ I was planning on taking temperature readings inside the eng bay and out by the vent of both before the mod and after but havent gotten arround to it.........whenever I have time to do it Ill post results
 
#54 ·
Did the test with the engine running and AC on. Can feel the warm air coming out of the vents...(not strong but there)
Removed the hood seal and tested again...It's noticeably cooler than before. Very large difference...My only concern is if there is any airflow impact to the intercooler as a result of the rear hoodseal being removed. I had the AC on recirc so no issues with odour etc. (It's so easy to put back in you can reinstall it if it rains)
 
#55 ·
Subsribed to see any empirical data. Lowering engine bay temps is something I've been looking into since I like the TMIC.
 
Discussion starter · #56 ·
Increasing the airflow OUT of the engine bay could only have a positive effect on tmic performance. One, your lowering engine bay temps. Two, you are decreasing engine bay air pressure, so this would allow the air to flow faster through the tmic.

- I also removed the back hood seal earlier in the year. I doubt rain would pose any concern with it removed.
 
Discussion starter · #57 ·
Fujiwara said:
Subsribed to see any empirical data. Lowering engine bay temps is something I've been looking into since I like the TMIC.
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I wish i had the time. I just also did the first step in installing my automatic tmic sprayer. I installed the Cusco sprayer nozzle, and have it just connected to the rear washer pump. It's just manually operated by the stalk switch right now, but i'm in the process of purchasing a mechanical pressure switch to make it boost regulated when activated. It really makes a difference holding it down during forth gear pulls in this hot weather. Smoothes out the pull a lot and holds torque much better. Can't wait for the auto setup!
 
#59 ·
hillhucker said:
Increasing the airflow OUT of the engine bay could only have a positive effect on tmic performance. One, your lowering engine bay temps. Two, you are decreasing engine bay air pressure, so this would allow the air to flow faster through the tmic.

- I also removed the back hood seal earlier in the year. I doubt rain would pose any concern with it removed.
Click to expand...
Yup agreed...I was just thinking about dust / dirt etc :)

Cheers,
Chris
 
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