I did a bunch more research this week involving mufflers.

The 17702 part number vs the 17715 part number.

17702 is the number suggested by the track, and the benchmark for noise.

17715 is the part number for the 2.5 inch in/out muffler in teh same product line. Also the recommended muffler for WhipCity speedway that also has a very stringent noise requirement.  Besides the size of this muffler I havent heard of any major performance/reliability problems with it.

Some people (not all) have reported heat issues and performance loss with this muffler.

9 out of 10 of them are running 2006 or older motors. 1 person alone with a 2007 or newer motor has made claims also. I made some calls to Thrush and Walker racing exhaust, The manufacturers of the "thrush turbo" muffler to get some flow data. Here is are the numbers I recieved.

17702 has a flow ratin of 180

17715 has a flow rating of 410

What do these numbers mean? Well they couldnt give me an exact description of what a "flow rating" is. But its pretty clear that the 17715 flows 2.33 times better than the 17702. Attempting to get flow data from Yamaha, Suzuki, Kawasaki, Gravesport, Yoshimura, and Muzzy was a complete waste of a day. (Alhough hats off to Gravesport customer support for being the only one willing to actually try and help). A recommendation for one of their aftermarket installers was to go with 4 into 2 wit hthe collector and run dual stock exhausts with a crossover. Possibly the best performance solution possible. Good luck  fitting that on your left door. So if you are having problems with lean running or  high RPM restriction the larger muffler could be your answer while still keeping within the tracks required noise levels. Just be advised that its larger than the other, and you may have to prove your a racecar fabricator skills to get it to fit.

With any of these mufflers its in your best interest to get a 90 degree turndown on the end for further noise dampening and to deflect the heat off your LR tire.

 As always these are just suggestions. I am just trying to help with the transition, and get data so people dont have to incur engine damage or spend a fortune on a dyno with a power commander. The burden of having your car meet the tracks requirements does and has always been in teh hands of the individual teams, Not the ESDCA nor myself. The quiet dwarfcar act was not my idea, the 17702 was not my choice, and I didnt become involved with any of it until the third week of action by the track. So I would appreciate it if the one single team thats holding me personally responsible would STFU.

Jeff B