Aero question - vent wheel well liners?

[Roadhouse]

@roadhouse Yes, that is exactly what I'm envisioning.

How did you attach it to the fenderwell? Just use the existing two screws on each fender, plus the splitter attachment? Any other pictures or notes?

Yes, I fastened the spat to the two existing screws on the fenders. It's been awhile, but is there a third screw that is further inside the fender at the bottom? If so, I used that one as well. I just can't remember what it looks like.

I used a cheapo "L" bracket to attach the spat to the splitter. You can see bolts/nuts in the pictures above. I didn't spend much time making this look pretty but it held together at speed. I'm sure you could make something a little more visually appealing

I used 1/4" ABS plastic for both the splitter and spats. It's cheap and relatively easy to work with. Once you get a few of the screws going along the fender line, the spat will start to bend with the fender as you tighten them. I was really surprised how well it worked and looked. I'm sure some heat could help the spats relax a little more.

I may have these still in my garage. If I run across them I'll be sure to send you a picture.

Hope that helps!

 

[Roadhouse]

Too much for your car? Nah. If you weren't lifting the front tire, then maybe.

LOL...Ok it's coming back!! Downforce...I need it all

 

[Grant 302]

LOL...Ok it's coming back!! Downforce...I need it all

Seriously, you are the perfect example of why the front spats are needed. They act the most on the inside tire to increase the pressure on the splitter. And it would still transfer all that downforce to the outside tire when you go into tripod mode!

 

[Roadhouse]

Seriously, you are the perfect example of why the front spats are needed. They act the most on the inside tire to increase the pressure on the splitter. And it would still transfer all that downforce to the outside tire when you go into tripod mode!

You make a good point... May need to cut up a new set!

 

[twistedneck]

The spats that (I think) Drew is talking about should help kill a little lift too. Making the air follow around the top of the arch will have a downforce component along with creating a low pressure area that would suck some wheel well air out. These are some small ones I used to have on:


Many racers are restricted from doing such aero mods, or can be costly from a point count depending on the organization.

But back to the main topic...I think the more air you can vent from the fenderwell area, the better for killing lift and increasing engine and brake cooling.

One more effect that that *excellent* hand drawing is missing, is that air moved by the top of the wheel and tire is a turbulent mess and better off vented. Oh and btw, for those that didn't know, the top of your tire is moving at exactly TWICE the speed of your car. So when I round the ROVAL at 145+, the top of my tires is moving at 290+. So anything you do to help control the air moving at near 300 mph will help!

One other thing that many have not notices is that our fenders have a piece of foam/batt insulation/bulkhead thing toward the back just in front of the door. I pulled both of them out. Strangely, they aren't fastened by anything an they can be pulled out by hand intact. This allows some of the air to escape between the fender and the door and at the top of the fender by the cowl and A pillar. I'll try to find a pic of them later.

I'm removing that batting also, but once its gone where does that passage lead? is it a dead end for pressure to build up? It could either vent to the bottom of the car and that would be bad, or it could vent out the side - good.. or vent out the top? best - possible vent into the cabin if you had a race only car with ducting.

This seems like it would do wonders.. especially when combined with the thin fender extensions and the front spat.

http://thmotorsports.com/i-1791956.aspx it would let the air out of the wheel well and create a nice cushion of air along the side of the car just like the extensions do..

its an ugly piece and I will not even think about putting it on but for pure pace it might help down force.

Finally, what if we could put a very thin 1/2" flat plastic duct there and then vent that through the hood somehow? is there a path? I don't think so - but the ducting idea might be the easiest to implement in our wheel well. flatten out this 2.5" duct http://www.mcmaster.com/#55125k18/=vi3tml then poke that through the wheel well someplace.

all in the name of increased front grip.

 

[DGRacing]

I'm putting my fender vent in that rectangular section on the top/side of the fender so I don't mess up the C stripes. Just need a little one.

 

[Grant 302]

I'm removing that batting also, but once its gone where does that passage lead? is it a dead end for pressure to build up? It could either vent to the bottom of the car and that would be bad, or it could vent out the side - good.. or vent out the top? best - possible vent into the cabin if you had a race only car with ducting.

This seems like it would do wonders.. especially when combined with the thin fender extensions and the front spat.

http://thmotorsports.com/i-1791956.aspx it would let the air out of the wheel well and create a nice cushion of air along the side of the car just like the extensions do..

its an ugly piece and I will not even think about putting it on but for pure pace it might help down force.

Finally, what if we could put a very thin 1/2" flat plastic duct there and then vent that through the hood somehow? is there a path? I don't think so - but the ducting idea might be the easiest to implement in our wheel well. flatten out this 2.5" duct http://www.mcmaster.com/#55125k18/=vi3tml then poke that through the wheel well someplace.

all in the name of increased front grip.

My thinking is that with the foam/batt piece out that the next available venting would be at the fender/door joint. The APR vents are a bit ricer fugly, and there are vented CF and FG fenders that would look better. I think Trucarbon is one of the manufacturers.
http://www.vortechsuperchargers.com/images/1421.jpg

I wouldn't remove that complete back half. Otherwise the rear of the fender would become more of a parachute. I plan on making louvered/slotted holes and covering with wire screen to help keep the clag and gravel out.

I have the sides of the rubber seal out and left about a foot in the center to help stabilize the hood! Just don't leave it off all the time...I think the heat from the vented air is ruining the lower windshield rubber trim that's attached to the two plastic cowl halves.

I've tested that it vents rearward, but that's with relatively open grilles like the 302S and Steeda. Not 100% sure how it would do with a stock grille but I suspect it would still vent.

I think the pressure at the cowl has always been a bit overstated. With the bulb seal in place, the cowl area has a lot of stagnation an is probably mostly turbulent to slight vacuum/drag at the rear facing surfaces.

I have to eat some of my words here. Looks like my previous test was skewed by the piece I left in the middle. With a center, left and right wool yarn tuft right at the back edge of the hood, all 3 stayed in the airstream. That was with the Saleen grille. I have a stock Boss grille on now and repeated the test with 3 tufts. When I took the center section out, the center got sucked in and stayed there whenever the car was in motion...even sub 5 mph. I put the center ~1 foot seal back on and tested on the sides of the 'power dome' and added a dozen tufts to the back of the hood. Most of the ones on the power dome sides got sucked in and the ones on the left and right sides were showing lateral/out flow. Added back the seals at the full width of the 'power dome'. Then all the tufts on the dome stayed in the airstream and the sides were mostly lateral venting out/up.

You have to be careful when allowing air to enter at the rear of the hood.

Sounds strange but there is positive pressure at the base of the windshield. Removing the seal on the hood should add air to the engine compartment. Adding air at the windshield area when we are trying to remove air may be counter productive.

You were right! I should have been more careful and diligent with my original testing. My final modification only removes the outer 8" of bulb seal on either side.

 

[TMSBOSS]

Grant302

No worries. Cowl induction has worked for yours.

Thanks for the update and the info from your experiments.

TMSBOSS

 

[theamsoilguy]

Sorry to revive a dead thread. I put vents on top of the fender and a vent behind the wheel. It was suprisingly easy to put the vent behind the wheel. Cut the fender, folded the sheel metal in and filled that with two pieces of metal. I will put the rear fender liner back in and cut a hole in it and duct it to the vent I made,. I think this is as complete a solution as can be done. I dont need spats as my aftermarket front bumper covers the tire.