Dual exhaust versus h pipe versus x pipe- street motor

[cjperformance]

... but with long lengths there probably is more backpressure and losses involved. Not sure where that 115cfm flow factor comes from....

Exactly. The 115 CFM/" sq. was Vizard's flow bench finding re the flow through a one foot length of straight tubing, hence my assessment that a typical dual 3" system would ideally be used for less than the calculated 739 HP.

Yes a 1' length of straight tube is quite different to 12' of tube bent up to fit into a vehicle.

[Harleyoz]

I had a regular x pipe witha twin 3" system & recently changed to this setup, Apparently the V8 Supercars use it in Oz (http://www.v8supercars.com.au/)with success.

I can say it sounds really good & much more punchy than the x pipe setup. Its like a dual system that just "Kisses" for 10" or so.

http://planetsoarer.com/pdf/xfactorcolour.pdf

[Sandman]

Checkout Pipemax program. It gives sizes for exhaust systems, also ideal lengths.
It also give measurements back from collectors for X & H pipes. It depends on whether an X or H what the measurements are.

On my old car, I ran H pipe, 2 1/2" pipes and mufflers, after it went over the axle, I aimed them at the ground at about 45* angle. It sounded pretty good, without being overly loud when crusing, and good on the highway. It was still loud when you got into it.
I tried with tailpipes to rear bumper and it got a lot noisier.

[rfoll]

The h pipe on my 3" system cut my wot decibels at 100 ft. from 94 to 88. They measure at the track and boot you out over 90. My local muffler guy tells me he has too many problems with magnaflow breaking apart to recomend installing them.