Another issue with true duals is scavenging. If you look at the front pipe, the distance the exhaust has to travel is nearly twice that of the rear.

 

deleting duplicate post.

 

The RH Slimline duals are not a true dual. True duals have a separate pipe all the way from the header to the muffler.

Rinehart does make a true dual however.

The Slimlines, AKA H pipe have a short pipe between the two under the branding plate shown in the image on their website below making an H shape. http://rinehartracing.com/exhausts/true-duals/100-0450

The Vance and Hines power duals AKA X pipe also have a crossover between the two pipes.

I am going with the Rinehart H pipe just to keep the whole exhaust the same since I already have the Rinehart 4" mufflers, and reports show they dyno the same anyway.

 

Fuel moto 2-1-2 is the only way to go.

 

I just ordered d&d fatcat 2:1 with the ghost pipe. Gain performance without losing the dual look.

 

Thanks Raider Fan! Dumbass here finally gets it. If I want to use my new slipons that came on the bike when purchased, I need to go with the RH H pipe or some other crossover dual looking header pipes. Their $1100 true duals are one piece and hence the higher $$. That sound right?

 

I'm not sure if you can get the true duals without mufflers or not, but I would assume you could. You're right, unless you want to replace your mufflers too, all you need is the header regardless of which type you choose to go with.

 

The lose of power is due to loss of scavening not due to lack of back pressure. Any type of exhaust could be designed to have little or not back pressure

It has always been my understanding that "Scavenging" is the exhaust gases from one cylinder helping to pull the exhaust out of the other cylinder. This allows the exhaust to be designed to help broaden the power-band. Therefore you would have to have either a 2-1 or a 2-1-2 to get any significant scavenging. A 2-1 works best and a 2-1-2 is a compromise between the two allowing the traditional look

A previous post stated that you don't see any 2-1-2 or 2-1 on Drag Bikes... This is BS as a 2-1 would be the preferred exhaust on lower/slower classes where the bike still needs to be streetable.
On Higher/Faster classes they do run one pipe per cylinder but this is because their only interest is in maximum horsepower in a very narrow power-band... there is no partial throttle and from launch to finish the engine is at or near it's peak RPM. Fine for Drag racing, not so much for any other application where you need a broader power-band and need to quieten down the exhaust...

 

The goings on in an exhaust system are complex! A pressure pulse is generated every time the exhaust valve opens. A well tuned exhaust draws the spent gases into the pipe, plus a measure of fresh unburnt mixture, which the reflected pressure pulse pushes back into the cylinder, before the exhaust valve closes (a 3-cylinder 2-stroke works especially well).

All multiple cylinder engines in most applications use siamesed pipes in some combination, depending on the application. Drag engines are an exception, as they are intended to operate in a very narrow power band, hence a V-8 drag car may have 8 separate short pipes, but a V-8 racing engine from a different racing class will use two 4-1 or 2-2-1 set-ups etc.

Harleys haven't used separate pipes in production since the late 70s IIRC. That is partly related to noise emissions, but also to provide us with improved torque for road riding. Using two separate pipes, no matter what name they may be given, is giving up low/mid range performance. It is a retrograde step as I myself have discovered and proved!

 

i may go D&D 2-1 soon. Want the low and mid back.