Here is a simple DIY mod for the guys running GT2 fender liners. These fender liners have a solid face with a small opening in the inboard side of the fender liner. Air flows through the large side opening in the nose of the bumper over the side radiators and then via this small opening in the fender liner into the wheel well where it is directed to the brakes. The problem is the simple fact that the size of this fender liner opening is significantly smaller that the opening in the front of the bumper the result of which is a bottle neck which will reduce the flow of air past the side radiators thus slightly reducing the ability to extract heat from the radiators. All the later generation cars starting with the 997GT/Cup cars and continuing with the 991s have significantly enlarged the opening in the front fender liners thus aiding air flow though the side radiators. The byproduct of enlarging the fender liner opening is that you are increasing air flow over the front brakes (assuming you have the complementary upper air guides) thus increasing front brake cooling.

What I have done here is simply enlarged the opening of the front of the GT2 fender liners roughly doubling the open area. This reduces back pressure and aids the air flow past the radiator. The fender liner opening area is now almost the same size as the opening of the bumper air inlets. You can see in the picture below the stock unmodified right GT2 liner on the right and the modified left liner on the left. I added aluminum mesh to this opening to keep rocks and pebbles from flying into the front of the wheel well. I sprayed the front of the mesh flat black to make it blend in. I got the mesh for $20 on ebay here:

https://www.ebay.com/itm/CCG-UNIVERS...53.m1438.l2649

The aluminum mesh is easy to mold to the shape of the liner and I secured it with small 1/8" aluminum rivets as can be seen in the second picture of the back of the liner. It also helps to trim away part of the metal radiator cross brace to aid in the flow if air. I did this with a grinder in a similar fashion as detailed in my radiator bracket mod DIY.

I only had a chance to run two sessions since doing this mod so I do not have solid data as to the effectiveness of this but initially it does appear that both water temps and oil temps dropped bout 5-10F under hard 30min track sessions. One I get more data running in 100F conditions next year I will be able to fully validate this. Either way, any improvement of flow of air past the radiators is clearly a good thing in extracting more heat. Cheers....

[url=https://flic.kr/p/ZaRBrU]

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Looks OEM, as usual for your mods

Also these pics give a good view on the final shape of your liners from the radiator bracket mod in case anyone is looking at doing both.

 

Good idea, looks clean.

 

I just did it myself. Its really easy to do. I just used a different (smaller) mesh.
I guess i will use the 6GT2 air ducts. They fit almost plug&play. But like John said, they are expensive.