Exhaust scavenging.

 

I love this forum, you guys most of you realy know your stuff. Now I can talk and understand more intellegently about these issue's to others. Thanks.

 

XTROOPER beat me to the V8 response. In the car world crossovers give the best overall performance. I do like the look of true duals though.

 

It's not so much a matter of the exhuast pipe length as it is the exhaust pipe's internal volume. The internal volume need to be within certain measurements specific to the engine it's attached to.Volumeof course can beincreased by length but also from diameter. Notice the 2 -1 pipesgenerally have a larger diameter. Problem is at some point an exhaust pipe beings to look stupid if it's too fat. Look at that god forsaken thing on the Yamaha Road Warrior.[:'(]

 

I like the look and sound of tru duals. I can't tell the difference in power either way.

 

A lot of what you're saying is correct, but it gets a little more complicated. There is an optimum pipe length, but I'm not going to look it up right now. The biggest detriment to scavenge is reverberation. That's actually the pressure wave caused by the exhaust pulse exiting the pipe (you know, that sound we all like). It travels back up the pipe & interfeers with the low pressure zone at the exhaust valve (scavenge). It's also the reason for stepped headers (each step interfeers with the reverb pulse). Two to one exhaust systems, or cross over systems, use the exhaust pulse from the next cylinder to both aid the exhaust velocity & diminish reverb.

 

This is the right answer, and the OP posed the right question of why HD would use a x-over on all models when they added expense. No "true-dual" system will perform as well as one with a x-over, all other factors being equal. Those who show more HP/TQ over stock are likely making other changes, like EFI controllers, AC, etc. at the same time. The best system for performance is a 2-into-1, but Fuel Moto has a custom baffle setup for Rush mufflers that achieve the same effect with asymetrical baffle sizes and a reversion cone inserted in the left side. These are used on stock head pipes, which amount to 2-into-1 performance for a much lower price.

 

I have true duals because I like the look and sound. Can't get into it with performance because never tried the stock pipes. I really don't know many friends that left the stock exhaust on. HD dealers really makes some extra bucks by selling or installing new ones. Most people on the forum have changed pipes $$$. It's like why do you pay $20K plus and not have a windshield trim??? $$$[/align]

 

I would not trade my Rinehart 2 into 1 for any true dual system. The torque in 2nd & 3rd gear at 4000-500 RPM's is incredible. I have to lean forward and hold on, I love it.

 

True duals are much easier to tune, and to some of us it has to be that way.Love the sound of true duals!!!!!!!