i time attack my car alot....would you suggest a single exhaust or dual.....i would think the single would save weight

 

Less weight is better. What exhaust type, size, and routing depends on the modifications to your engine and what the rules are.

On a normally aspirated engine, properly designed and tuned single exhausts tend to produce a bigger area under the curve (both torque and horsepower). Even high horsepower V8 engines can benefit from a big single exhaust. In the high horsepower era of TransAm, the cars ran 180 degree headers that merged into a 5 or 6" single exhaust that basically filled up the passenger side of the car and exitted out the passenger door. These elaborate exhuast systems added 40 to 60 more horsepower compared to the dual exhausts run previously.

Unfortunately, we can't fit something like that on the 350Z. But I still think a 3 or 3.5" single exhaust with a good merge collector and a Borla XR1 Raceline muffler will help the 350Z a bit more then any of the aftermarket dual exhausts out there. Hopefully I'll build one for my car later this year and test it.

 

BTW... the stock muffler on the 350Z helps generate a little rear downforce so keeping the same position/configuration with a replacement muffler is a good idea.

 

what about db level restrictions?

 

The 'downforce' from the aerodynamics of the stock muffler are minimal if anything. At most, it just cleans up the air under and exiting the car -primarily for drag/mpg purposes than adding downward force/grip to your car. You will not notice a difference at all if you change the design/shape of your muffler.

0.02

 

dB level restrictions depend upon the club/league and track administration, i believe.

 

dB restrictions are track related here in Ca with Laguna being the toughest. I have seen guys fail with new exhaust that they were assured would pass.

 

friend of mine races an 01' Trans-Am series Camaro at the Mitty at Road Atlanta every year. ive seen the exhaust routing when he was working on it and it is WILD lookin lol. incredibly loud car. I'm doin Solo II and Time attack events and I'm plannin on swapping over to a single 3 in. after I get a spare set of track wheels/R-comps.