Re: Anyone know anything about exhaust design?
 

The OD's would be great. If you want to take a little extra time and figure out the lengths of each section of pipe that would be even better... but I won't whine if all I get is OD dimensions.

I plan on leaving the first 4-8" of pipe in the factory sizing, so I don't' have to try and manufacture a flange to fit the exhaust port. I might change that later, but for now it seems the best bet. I believe the factory pipe is 1.5" OD. I'll step that up to 1.75" all the back to the collector... where it go 1.75"(x2) into 2"(x1)... the pipes will be relatively equal-length based on head-loss (I'm going to do a hand calculation for the flow restrictions in each pipe) and then install a cross-over pipe about 6-8" upstream of the collector joint. I'm going to do some additional research on cross-over piping... that's the bit that runs between the two header pipes right before the collector.. which tends to broaden the torque band a bit in the mid-range by allowing the two flows to balance each others pressures ahead of the collector.

If you care to, take a measurement on how far before the collector the M4 system installs that bit and I'll see if I can figure out why they put it there versus where the stock system install it (there is one on most of the 2003+ year models).

Thanks again.
Johnny

Re: Anyone know anything about exhaust design?