I just installed the Carter Customs rear race diffuser on my S197 2011 GT track day car. First I had to move the vapor canister to the upper side of the wheel well. It sits in the well nicely but takes some plumbing to connect everything up. The diffuser is a well made unit even though its a little heavier than I would have liked. The one issue I had was that it did not come with installation instructions. It took a little time to figure out but I able to install it without too much effort. The problem I had with the design is that the forward edge of the diffuser ends at the mid point of of the wheel well. The wheel well has a large convex center section when looking from the bottom so there is a large gap between the diffuser and the wheel well floor. At speed this gap would create turbulence just as the air enters the diffuser where you want clean air flow. I addressed the problem by making a plate that enclosed the wheel well area so the air flow goes over a flat surface before entering the diffuser. See photos below. I had to limit width to clear exhaust. I'm hoping in conjunction with the Steeda wing the rear will feel more planted on high speed corner entry. I'm running at Homestead in February so I'll report back on how it works.
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