[HO455]

Originally Posted by LockDoc

It is a set length depending on your driving habits and RPM of the drone. Mine needed to be 28.25 inches long overall. There are charts in some of the writeups. I will see if I can find one.... If I do I will edit this post and add it.

Edit: Here is the chart. All I did was drive the speed I most often drive, note the RPM at that speed and check the pipe length at that RPM on the chart. I don't drive interstates much so I just set it for the RPM at 60mph and it seems to work pretty good for all speeds. If a person is concerned about multiple speeds the second picture shows an adjustable pipe.

LockDoc

Thanks for posting this LockDoc. I have spent at least half a day reading up on it. I had heard of Helmholtz's theory years ago but not in this application. This explains the strange tail pipes on a 1968 GTO my friend had back in high school. The stock tail pipes had a one on each side tucked up behind the rear rocker panels next to the frame.