• For street performance on Harley-Davidsons, the best performing exhaust will be-
• 1.75" diameter from the cylinder exhaust ports
• Will be equal length pipe front and rear cylinder
• These pipes will come into a merge Collector
• The exit from the merge Collector will be 2" diameter, AND no longer than 8 inches.
• Low back pressure baffles can be used, if needed for sound volume reasons
• W Series Thunder Torque Inserts should be used
  

Are these accurate statements pertaining to HD exhaust systems?



As far as the collector is concerned, it can be no longer than 8" ??

This certainly does not take into consideration the length of the muffler/pipe after the collector, does it? Or are they strictly referring to their style of exhaust systems? Most 2-1 exhaust systems have a muffler that is at least 20 inches long.

 

All looks good to me, but then I am not an exhaust designer. The expression 'collector' refers to the short piece of pipe between the two separate pies and the muffler. Having equal length pipes is a given, for optimum performance, and relates to most engines and applications. Bringing them together into a single outlet or collector, prior to the muffler, goes without saying! Making that no longer than 8" may have a scientific explanation, or be based on hard experience. The actual length of the two pipes, the collector and the design, size, length of muffler, will each influence the end results. I'm sure that other designers of 2-into-1 exhausts may have slightly different criteria that they use, but yield satisfactory results - there are many subtle ways of achieving similar results!