Well...i tried to add pictures, but it says i can NOT add attachments. Not sure why.

 

try a hosting site like photobucket and just post the

 

These are the vent holes before with my pointless cut lines for my new holes. As you can see there is little area for air to flow, and these openings are covered mostly by the lower fender vent panel.

This is the vent before with air block.

Here is the airflow block rubber piece.

Vent after block removal. (you can just slip the rubber around the metal clips. No need to remove the clips.)

This is the fender with my new super high flow hood vents. (before i cleaned the lines of the cuts up.)

Closer up

Finished job out in the sunlight. After my hard work of cleaning up the cuts, you can't see the holes after all.

 

Overall, this modification should increase the performance of the engine venting dramatically. With that air block in the way, the low pressure created on the exterior of the car, when moving, could not exert the same force as it should. Also, the larger fender vent holes will provide a much larger and more efficient flow of hot engine air to the vent. Oh...for the cutting i just used a dremel with a cutting bit. I also used a standard drill for the pilot holes. Let me know if you have any questions.

 

Strong work on improving the aero.

 

Thanks man. I wish i had some before and after data to back it up.

 

OP: I was thinking about this today. Weird. The first time I took the side vent plastic pieces off, I thought the holes in the fender we're big enough to move enough air. It looks like in stock form the majority of the hot air gets "blown into" the front of the door. Which doesn't do anything to vent out hot air. One of the reasons I haven't cut the fenders the way you have is because I haven't figured out what the best way to keep the cut fenders from rusting.

I cut the stock mesh out and installed new stuff in to match the mesh I used in the front grill. I think I'll remove the inner rubber piece when/if I enlarge the holes in the fender.

 

That mesh looks really nice! I forgot about rusting. I guess i'll go back with some rustolem or plasti dip stuff. Those stock holes get mostly covered up by the vent trim piece, so they don't do much good. With these new hole and removing the rubber block, the low pressure can really pull out the high pressure, hot engine air. Today after driving hard, i was cruising about 30-40 and reached my hand down behind the vent, and i could really feel a lot of hot air coming out. I didn't try this before, so i don't have any comparison on how much it changed.

 

Thanks. Funny, I would reach down after a hard drive and I didn't really feel a much heat around that area. In stock form I'd figure it would stay pretty warm if it was indeed venting underhood air. I think there is room for improvement.

I think you're on to something here. I know the Nurbugring 24 hr Challenge car has the side vent cut and what looks like dryer vent coming from the hood to the side of the car. I guess the stock setup didn't cut it for them in a racing application. I look for that pic of the car and post it later.

 

I have actually already ordered premade louvers that measure 15.5 x 2 inches from this off road site. I am going to fabricate them onto the top of the front fender arches by dremeling out the opening then riveting them to the fender. This should give me quite a bit more cooling too.

-i will not be leaving them silver though. Flat black, i believe, is the choice i will go with.

 

Great idea guys. I'm going to look into this some more.

 

That site actually offers those already powder coated matte black FYI.

Nicely done, btw. I admire your ambition. If you manage to get some good results, I may have to copy & slightly modify your idea!

 

wheew! i just looked on their site and saw that! i just called and got my order changed before it shipped!

 

Ok, that's a good start....

How do we know if that airflow is actually detremental to the overall Aero though? This would only really show if the vents are capable of dissipating extra engine bay heat.

 

Ok, that's a good start....

How do we know if that airflow is actually detremental to the overall Aero though? This would only really show if the vents are capable of dissipating extra engine bay heat.

Look into the new ferrari "F599xx" motortrend article. Gives more insight as to why this mod would help in heat disapastion in the engine as well as give more down force to the car. They have an extensive article on it's aero design...very impressed

Makes me interested in this mod as I like efficiency over looks.

 

I'm sure the aerodynamics of a 140mph beer keg are TOTALLY different than those of a 200mph cruise missile.

I will definitely check out that article here in a minute though...

 

haha...of course. I mean you definitely see better performance from aerodynamics at 100+ mph speeds, but i also did this mod to decrease under hood temperatures, which will decrease intake temperatures so i can have more consistent power output.

Even at normal highway speeds correct aero should play a role into the handling of your vehicle, and also the acceleration of your vehicle. If you can lose that under hood/car extra turbulent pressure to above/outside the vehicle, there will be less overall resistance by the vehicle. Another GREAT car to look at this on is the Ferrari Enzo...Amazing aero from ducting properly.

 

Oh...i like that race venting! That fact is you don't want extra air under your car than what normally passes below the front lip. You wanna reduce that under chassis pressure and give the below car air the greatest velocity compared to the air above the vehicle. The only issue with these vents is they work off of pressure difference between higher under hood pressure and the lower, velocity induced pressure on the side. So at lower speeds this system does not work well, because as we know heat rises. This is why we see hood or upper fender vents. I am trying to stay away from the hood vents because of the extra wear the engine components would be subjected to. But i am going to do upper fender louvers from genright.

 

So i got the Genright louvers in...i bent them in to the shape of the fender and just have some scotch tape holding them on. I think i like the way they make the car look, but i'm not sure. They will definitely increase engine bay venting performance though. Tell me what you guys think.

 

So i got the Genright louvers in...i bent them in to the shape of the fender and just have some scotch tape holding them on. I think i like the way they make the car look, but i'm not sure. They will definitely increase engine bay venting performance though. Tell me what you guys think.

hillhucker... Subaru must have notice your top fender vents...

http://www.iwsti.com/forums/subaru-news-rumors/212627-sti-nbr24-2011-a.html

 

Hmmm... Not a big fan actually.

I was thinking something like this would be kinda hot:

 

yeah, i'm not sold on the way they look yet. I couldn't do chrome on my subie.

 

I don't like either one especially the chrome ones. However you will be making a cosmetic sacrifice for better performance. Is it worth it? What type of racing will you be doing?

 

Just 1 or 2 track days a month, but i am wanting to reduce my under hood temps by as much as possible for better engine performance, plus higher speed handling. I am thinking of another modification to the rear fender vent, where i will cut/fab the top above the STi badge thing, and make it match the lower factory vent. This might be a better option.

 

Your original idea of the bigger fender holes and remove the plastic flapper is great and I applaud you on it. With that said I think you are getting a little carried away and missed the bigger picture that you are about to mess your exterior of your car permanently for maybe a few less degrees under the hood. My .02 is DONT DO IT.

It;s a fine line between innovating and doing crazy things.

 

I agree that the pic I posted above would look better in carbon fiber or matte black... I just couldn't find a picture on short notice, and these were the style that I was thinking of.

 

I'm not too worried about messing up the exterior since fenders are not that expensive and it's just a body panel anyways. But i don't wanna do it if i'm just going to want to change it back to original a week later and dump 200-300 for a painted fender. Thanks for the input!

 

I don't have that rubber block behind my fender vents. didn't ever have any on the car...

 

That's kinda strange...i guess your car was meant to be fast.

 

What year's your car? Anyone else with an 08 that doesn't have that rubber part blocking the fender vents?

 

Mine's an 08 also.