I see mention of that being a more performance system.


Why? Seems to go against the free flowing idea?

 

Basically,the exhaust from one cylinder helps pull the exhaust from the other.


Explanation http://www.rbracing-rsr.com/exhausttech.htm

 

Man, that guy is long winded.

 

I just put a Patriot Defender 2 into 1 on my 1996 Ultra Classic FI. I am still working on getting the map right, but can tell that it has more power at lower rpms.

 

Pulses don't slam stagnate spent gases is what I understand which is what Schex is saying

True Duels are know for a torque dip in the lower rpms right where a Harley thrives, tougher on a big bike

 

I like the look and the sound. Little more ummph and smoother (for mine) at higher RPM's

WP

 

true duels are just a fancy way of saying drag pipes. the only way to get rid of the dreadful HP robbing dyno dip. is take those true duel/drag pipes off your bike and throw them in the trash. your bike will love you for it.

 

Every production vehicle on the planet with more than one cylinder, for many decades, comes with a 'siamesed' exhaust system, where the exhausts from each of the various cylinders are brought together. Further to Schex's comment, inertia draws both the exhaust plus fresh air/fuel out into the exhaust pipe, while pulse reflections from one of the other cylinders reverse that flow and push the fresh stuff back into the cylinder. Hence the cylinder is over-filled and performance is enhanced. A feature of cam timing is that the exhaust valve closes after the inlet valve, to use that pulse.

A single pipe, such as true duals or drag pipes, will achieve the same thing, but only at a narrow rev range, which for a racing vehicle may be just dandy, but for road use is not so useful. On a multi-cylinder engine with a collector set-up the torque range is improved across the rev range and increased in quantity.

I ran my S&S 107" for about a year with TDs, before swapping to my SuperMegs and had the bike dyno-tuned by the same shop and operator. Headline numbers for power and torque were very close, however where peak torque with the 2-into-1 occurred was very different. Max torque was just a little higher, however in the mid-range was 15% higher! The normal riding range was significantly improved, as well as the engine running much more smoothly, a bonus I didn't expect.

I suspect the current factory 2-1-2 set up has done similar things, relative to the older set-up our dressers came with for so many years. They also give more torque, compared with separate pipes.

My Buell has equal length pipes, which enables the engine to use wilder cams than with any other pipe set-up, plus increased CR, so gives significantly greater performance than a big twin of the same vintage, despite meeting the same EPA regulations. That is entirely down to it's 2-into-1 exhaust. It would make a great dresser engine!

 

 

Best bang for the buck for sure.

My 2-1 Supermeg and Big sucker gave me just over 15% HP gain and almost 11% Tq gain over stock.
Smoother, cooler and better sounding. I like the options that the Supertrapp system gives as far as sound and power.

Tuned with a Power Vision.