Flow Through Front Fender Liners
 

Last weekend I gave my boxster a four hour spanking ....city, country, traffic. It seems that the LT T-stat really helps with cooling. The fans come much less often; the back end of the car feels like it has less heat load.

Even so this car get hot!!

I found myself thinking about the application of flow through front fender liners. Has anybody attempted these? Are their significant cooling benefits. Are there bolt on liners already available? Perhaps something with louvers to prevent damage from debris.

I have seen Boxster race cars with portions of the front of the wheel liner cut out (with wire mesh installed to block debris) to allow additional air flow to the brakes to improve cooling. I believe that these were custom fab'd.

I believe I have seen pictures of these on this forum, search.

Ahhh Eric has done it of course..http://986forum.com/forums/uploads01...1401829460.jpg

I am after better flow through the radiators....without damage. Currently the exhaust goes straight down in a sharp 90 turn. Brake cooling would be secondary for me.

It seem his mesh will offer some protection? Is it enough for a street driven car?

there are pics of this floating around. done to the early 996 rsr cars I believe. block the standard airflow path out the back of the rad and under the car and use a holesaw to drill holes from the back of the rad ducts into the wheel wells. I don't think the purpose is to improve cooling, I think it is to reduce the amount of air blowing down and trying to lift the nose at speed.

the next step would be to vent the fenders at the top just forward of the wheel centreline. aerodynamic analysis shows that this is the point of highest pressure, which can be converted to downforce if allowed to flow upwards out of the fender.

I've read that things run cooler if you remove the underbody panel just in front of the engine. otherwise, consider an oil cooler: ln oil filter adaptor - canton sandwich plate - two an hoses - canton thermostatic valve - two an hoses - setrab cooler mounted in the rear wheel well.

interesting that you mention lift........rolled over a dusty garage floor with fans blaring and created a hovercraft dust cloud....so I stuck my hands under the front body work and was surprised at the force of the airflow downward

I've done the fender-liner vents along with center vents in front of the hood ... And closed off ALL underbody vents. The temp still climbs in traffic, but once the car gets moving, temps drop quickly to right at 180.
http://986forum.com/forums/uploads01...1401838915.jpg

Any problems with damage to the radiators?

Can you show us a picture when you get a chance?

The factory and owners have been doing this to 911s for years .
The 73 rs had a lump cut out of the nose so air going through the front mounted oil cooler had a path under the car .
A few years later on the 935s they cut away the nose and had the path of air going upwards through the hood instead of below .
This was to aim it into the low pressure area above the front of the car .
Pretty much what you're seeing on a gt3 front bumper .
Another school of thought is to let it into the front trunk but exit through the sides into the fender arches so the air can be used to cool the front brakes .
This is pretty much what you are seeing in the pics of Eric's car , but with cutting into the tub .
I can post pictures if you like , but there are plenty out there on the interweb .

Okay...so as long as there mesh there we won't have damage occurring to the rads. I had wondered whether the mesh was enough.

To make things complete I would think the bottom exhaust route would need to be blocked...any pictures as to how these panels can made or bought? Sounds like I will have to make patterns and get hold of a pop rivet gun

there's this:

http://www.ebay.com/itm/380921775726?ssPageName=STRK:MEWAX:IT&_trksid=p398 4.m1423.l2649

but i think it's for a ruf front bumper. i was just going to use a hacked-up Rubbermaid container shot black and either plastic weld or hot glue in place. or perhaps some thin lexan from home depot.

Looks great if it fits up !

I think the 997 GT3 had vents behind the rads allowing air to flow through and into the wheelwell. Remember air going through the body creates drag reducing efficiency, especially over 50 MPH. Venting in and through the frunk seems crazy... If the car's not running hot, why mess with the aero? If it's lifting at speed or you're cooking your brakes then something needs changed. I had a Civic SI that I lowered and at around 80 MPH it actually OVERsteered because of it. If you occasionally get near the limit over 50 MPH changes to the aero can become REAL!

The 997 GT3 Cup car has very different airflow routing than Eric's modded 986. It would be interesting to see the different designs tested as airflow often moves in unpredictable ways. A lot of wind gets generated by tire rotation so the duct location is pretty critical to improve cooling.

Yes...exactly this is why I had envisioned horizontal "liner louvers" oriented/exhausted downwards so as to interact cohesively with the wheel rotation air...maybe there would even be a coanda effect to be had there! I would image that exhausting downward out the wheel well couldn't be any worse than in front of the wheel

This arrangement would prevent undue damage debris ingress to the back of the rads.....so I was curious as to what had been done for real on let's say a cup car. There's no easy way to test effectiveness without proper resources...so

if you search three's lots of physics around the behavior of air in wheel wells. from what I've read the air in front of the wheel actually travels upwards - fast moving air traveling under the car hits the front of the wheel and flows upwards. it meets air drawn up the back of the wheel at a high pressure area at the top of the wheel just in front of the wheel axis. this is why you often see wheel well vents in this location. effect is heightened by the fact that the airspace in the wheel well is larger than that under the car so air is drawn into the well by the resultant pressure difference. without a vent in the fender the air will try to push out the sides and create additional friction.

regardless, out the sides is better than straight down. I read someplace that venting the centre rad on the gt3 upwards instead of downwards created some huge amount of downforce that was said to be a big part of the initial gt3's handling prowess.

Okay! Will do.....I wont be venting the top of my fenders though :D. With net upward flow I am thinking the louvers should vertically orientated. I would be great to find 996 cup liner pieces that just snap in

I think the rsr liners were hand made, but google 996 tt fender liners - they appear to be vented and prolly a direct fit. another thing to look at is the 996 gt2 fender liners - they do something similar.

here's a fun read:

http://www.renntrack.com/forums/showthread.php?1949-Front-Fender-liner-Differences-GT2-Vs-996TT

check out the 997 brake duct bit at the end of the thread ...

one of the things about venting the third radiator upwards is that the act of changing the orientation of the third radiator interferes with the rad ducts on either side. so, to do it properly, one of the tricks is to change over to gt2 rad ducts (or, I presume, gt3 units). of course, that means a bumper cover change as well. i presume the wheel well liners can be swapped without all that, however. i think jfros approach with the third rad was to block the bottom vent and let the air travel down then up to the centre vent on the top?

here's the thread on the gt2 conversion:

Function GT2 Conversion DIY - 6speedonline.com Forums

I can post pics of 997.2 gt3 arch liners if you want ?
I have then sat on top of my beetle in the garage waiting to be fitted

The center radiator was sitting wrong and needed to be moved. IIRC, I flipped the bracket over to get the opposite angle, then move it towards the front of the car about 1".

did it interfere with the radiator ducts on either side?

the gt3 bit looks the best - designed to block the downward flow (and match the bottom profile of our bumper covers) and vent towards the brakes. combined with the 997 duct piece from the renntrack post should work well. the gt3 liner is two piece, however, so either trim your current one and hope there are suitable attachement points, or get the rear portion of the gt3 wheel well liner as well ...

http://www.autoteile-ab-lager.de/bilder/produkte/gross/Porsche-911-996-99650422391-8162.jpg

No, not at all. I did need to splice in extensions on the radiator hoses, though.

did a bit more checking. the gt3 uses the same radiator duct and bracket as the 986, so assume the gt3 radiator is the same orientation as the 986. assuming the body attachment points are the same, you should be able to just swap in the two-piece gt3 fender liner for the one-piece boxster unit. this will give you an oem blocking plate for the bottom of the bumper, and oem venting into the wheel well to aid in brake cooling. I think the gt3 unit allows a bit more room in the wheel well as well, should you want to run wider tires. these little babies should seal the deal:

997.575.231.91 and 997.575.232.91 brake ducts

jfro - did you have to trim the duct that joins the rad to the front bumper cover given you moved the rad forward?

I got rid of that all together. I tried to make it work, but it was just a non-fitting mess.
A new duct could be fabricated to force air to only go through the center radiator (not around it), but it already works well, so I've spent my time on other things.

probably by the time you've moved the rad forward there's not much of a gap between the rad and the front bumper cover regardless.

I'm willing to bet (over a few beers) that the **sell** is "brake ducts" to improve cooling (because brake ducting is *open* in the class) This is nothing more than helping to remove LIFT at the nose :) Why would I add 200deg. hot air to the brakes? :)

For the GT3 radiator to vent properly up and out of the top of the bumper, a stove pipe has to be built behind it. ALL air to radiators has to be sealed to the front bumper. Air will take the path of least resistance (go around the radiators if the guides are not in place and sealed to the front bumper.

Updates, discussion, More Pics?
 

TRK's comments reminded me of this thread. worth a bump. Brad's comment about adding 200 deg air to the brakes is something I had been wondering about - best to duct it to the middle and out the top of the bumper? I'm not afraid to cut a vent in the fender of my 2000 S, but would really want to have a valid model before I'd do it.

i've purchased the two gt2 parts from ************************* (hah, joke from another thread - auto atlanta) - the duct that mounts behind the third rad and vents up, and the duct that mounts between the rad and the bumper cover. for whatever reason, auto atlanta was significantly cheaper on these parts than anywhere else. otherwise, the rad has to be tilted and extended forward - my intent is to use the same bracket with some threaded rod to accomplish this. the two rad hoses will have to be extended - some hose, hose clamps, couplers (or you can go oem). there may be some interference with the front bumper bar - you could machine it or use small spacers to push it forward (there is an oem part for this also). final thing is to open up the top of the bumper. 997 'smile' doesn't work well here as doesn't follow hoodline. better jfros approach which is similar to 996 gt3 rs openings.

I may do this mod, and if so I may try to use the 997 upper brake cooling deflectors:

99757523191
99757523291

And fasteners: 99950778540

Significantly cheaper than the 996/GT3 versions or the fiberglass replicas sold by tunersmotorsports

Unsure how they would fit, and what tweaks/fabrication would be required, but if I do the flow through fender liners I am going to do this with it.

I read that 200 degree radiator air feels like AC to a 600-800+ degree rotor/caliper.

TRK can you share your part numbers for your part?

Edit: I see you shared those brake ducts like 2 years ago... Are those the two parts or are you talking about something else that helps the center radiator?

i was talking this:

99657514130

and this:

99657532530

Has anyone been able to get a vented 997 fender liner to mate up to a 9x6?

Also, check this thread re: brake cooling - DIY: Brake cooling upgrade for track junkies - Rennlist Discussion Forums

probably better to try and fit the vented 996 gt3.2 liners.