Geoffrey

I'm in the process of fitting an undertray to my Race car (seriously) and I run one on my street car. It does not touch the silencer if we are talking about the secondary muffler. There is enough movement in the mounting of the secondary muffler to move it slightly.

garrett376

I keep mine on the race car, and my street car... there are specific rules in racing that keep earlier 911's from having underbody paneling to improve aerodynamics... but the 964 came with it so why not keep the advantage. Ever see the underside of a 959?

boxsey911

Yes I meant the long, cylindrical one across the back*. I'm guessing mine touches as the car has been lowered a lot and therefore the mounting for the muffler needs adjusting. I took my tray off because the result of it touching was that the car smoked when on track (probably due to oil drips caught in the tray). I'll probably get round the touching problem by replacing it with a cup pipe but will leave the tray off in the summer to keep the weight down.

*I didn't mention primary or secondary as I've heard some refer to it as a primary on the basis that the cat is not a muffler.

Wachuko

With it off you really keep it (the engine) cleaner, at least I do. Since you have better access to the area under it. The tray is more like an dirt/oil trap...

As far as aerodynamics... my 996TT can go up to 190mph... no engine undertray in that car...

Anyway... no tray here, nor secondary muffler... better access to the plugs when maintenance time comes around...

Geoffrey

My purpose is to build a difuser to create downforce under the car since I run a stock rear wing.

911addict

Removing the undertray saves weight, I read 6kg.