That same 18 to 22" from the end of the primary to the H-pipe can be used for collector length. Its a disruption in flow so from the harmonics same length.
Agreed. I'm just making the point that for it to work to its best effect the pipe diameter has to stay the same for that full 18-22" length of the collector. It's also possible to gain a little more bottom-end by making them even longer than 22".
When I get around to putting Doug's headers in my Duster in place of the Hedman shorties I'm going to redo the exhaust so it's 3" off the collectors all the way back to maybe 4-6" ahead of the mufflers and then have it go down to 2.5". I want to leave some length of 2.5" pipe ahead of the mufflers in case I decide to put in an H-pipe. I have an X-pipe now and I'm tired of the sound, too similar to modern muscle cars. I want that THUMP THUMP THUMP not just a BrrRrrrRrr if that makes sense lol
