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Fender Vents, General aero Questions

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So Ive been planning my modifications to the front end of my car.. Car is lowered a couple inches, fyi.


Heres the plan


- Enclose radiator opening, seal the airdam to the bottom of the intercooler, etc


Old setup




Now I have an intercooler so Ill need to redo it.




- Seal the bottom edge of the air dam to the bottom of the core support.


Like this...




I can attach directly to my supports.




Extend it up the sides a bit enough to cover my wheels




-Make some sort of panel to direct air away from the front of the tires. See thread..




Its not a good picture but imagine something like this (bottom left of screen) but larger and closer to the ground.




Im thinking about using some sort of plastic, imagine something like the garden edging stuff so it could actually scrape the road. It would be flexible enough to not snap off but stiff enough to actually redirect air. It would go all the way across the car in a arc, wheel to wheel with the middle further forward.


- I originally planned on just having a filter direcly on my holset but im thinking of incorporating an intake duct that will scoop up cold air from under the car. If you can imagine the area behind the radiator and in front of the sway bar, thats where the duct would be. Id get alot cooler air and a little bit of a "ram" affect. Should be good for 50hp, assuming the ducting is chrome as well. haha


- Lasty it comes to my primary question, regarding venting the engine bay. I relocated my battery so now both areas under the inspection lids are open. I have a vented hood already and was considering modifying my inspection lids to have a vent. Im not sure how much venting it takes to avoid air going out of the bottom of the engine bay but I suppose too much isnt bad. haha Given that, I was looking into how Id setup fender vents.


There are a few factors that come into play. I dont have fender liners so the battery tray area is directly open to the fender well. If I just install a vent on each side of the engine bay where it just vents to the fender *WELL* would that be effective? With my other modifications wouldnt the fender wells likely be a lower pressure area? Second option is to actually vent from the engine bay through a closed duct and actually out the fender, completely bypass the fender well and vent air to the outside of the car. I was even thinking about the possibility of running two small fans in the ducts to help evacuate air even at low speeds.


See this thread for more pics and discussion.




Of course all of this will be paired with equal attention to the back although I havent considered what Ill do as much. For now its just VG, and hopefully a SDI 5.25 inch spoiler.


Any comments and discussion is appreciated. I think this stuff is super cool, hopefully Ill be able to apply some of the what I learn in fluids this semester.

Edited by Challenger
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Did fender vents on my old S30, cut holes though the inners near the front together with vents in the outers behind the wheels. Of course the inners are structural so any holes cut through them have to be reinforced. I see you are thinking of a complete aero package which is good, with my S130 the approach was a bit different to the S30. No holes in the inners because I wanted to use the wheel well low pressure area for oil cooler venting purposes. The S130 has a lot of bonnet (hood) venting instead, see pic.

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post-185-073047100 1283123859_thumb.jpg

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This setup didn't work. Huge aero understeer at speed - almost drove off the track on the second lap. A splitter needs to be no more then 2" off the ground if you want it to work as a splitter. You can alway angle the splitter down and just have it work as a spoiler.




(The car looks like its about 6" off the ground but there's a jack under the car behind the door)

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I wanted to find something like that but couldnt.. What is it made out of exactly? What kind of plastic?


I have no idea, I buy 50 foot rolls from speedway motors and a local hole in the wall supply shop carries the same plastic in flat sheets.



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I was putting alot of thought into venting the inside fenders close to the firewall and using the exterior vents from an 03' Hyundai Tiburon on my 73' fiberglass subtlez kit. I thought these would fit proportionatly and have a nice fish gill appearance. I decided against going through with it though and got muy inspection lids vented, and had a stock 82' turbo naca duct welded into my stock unvented hood. It sits flush just like a zx stock hood would. Some pics to show what I am talking about.

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post-736-022808500 1283307053_thumb.jpg

post-736-024631800 1283307080_thumb.jpg

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  • 1 month later...
  • 4 months later...


What tool do you use to make those chamfered holes? I wanted to do the same thing to make my engine bay -to- outer fender vents but wanted to maintain structural integrity.

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There is an interesting bit in this month's Racecar Engineering about fender vents. Actually it's really about dive planes, but there are about 2 sentences on fender vents that say that they got more downforce from the vents than they did the dive planes, and their vents were apparently "engineered" with a cut off wheel...

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Thanks guys!








There is an interesting bit in this month's Racecar Engineering about fender vents. Actually it's really about dive planes, but there are about 2 sentences on fender vents that say that they got more downforce from the vents than they did the dive planes, and their vents were apparently "engineered" with a cut off wheel...


Are you talking about fender vents ducting air from the engine bay or just air from under the fenders themselves?

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They looked like they were just holes in the fender behind the front wheels, and like I said, the article didn't focus on them, it was focused on the dive planes, but it did say that they cut holes in the body panels with a cutoff wheel, so it didn't sound like any "engineered" attempt to get air out of the engine compartment.

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  • 1 year later...

Bringing back this thread with a question or two. I revisited my thoughts on using the Hyundai tiburon side vents and ended up getting a used set to tape up and visually see if it would work for me both functionally and aesthetically. My question is in regards to venting the trapped firewall air. Would anyone see a problem by routing it through a sealed, triangulated tunnel through the firewall into the cabin exiting out the side vents, as opposed to the way some have done in the past by putting holes in the structural sides and out the side vents. Here are some very, very quick and crude visuals. I would intend on keeping the vertical structure intact at the firewall and making a sealed tunnel for the air coming directly at it to vent out.

Edited by Nelsonian
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