Flow Through Front Fender Liners

[jaykay]

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.

[thstone]

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.

[BYprodriver]

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

[jaykay]

Ahhh Eric has done it of course..

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?

[The Radium King]

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.

[jaykay]

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

[j.fro]

Originally Posted by jaykay

Ahhh Eric has done it of course..

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?

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.

[jaykay]

Any problems with damage to the radiators?

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

[Ian c]

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 .

[jaykay]

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

[The Radium King]

there's this:

http://www.ebay.com/itm/380921775726?ssPageName=STRK:MEWAX:IT&_trksid=p3984.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.

[jaykay]

Looks great if it fits up !

[woodsman]

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!

[Topless]

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.

[jaykay]

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

[The Radium King]

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.

[jaykay]

Okay! Will do.....I wont be venting the top of my fenders though . 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

[The Radium King]

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.

[The Radium King]

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 ...

[The Radium King]

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?