Exhaust Back pressure II - Two Bros vs Stock

[Yukonf3]

A while back I was able to test the stock exhaust for back pressure. ( http://www.spyderlovers.com/forums/showthread.php?98322 )

It's been cold here for a while but finally got a chance today to put the Two Bros exhaust on for a few test runs. I then added the P1X tip. I also put the stocker back on and tested it again, so that the digital manometer set up was identical and the external factors such as wind and temp etc were close for comparison.

Here is what I got...

Two Bros
3K steady state: .1 psi
4K steady state: .08
5k steady state: .1
WOT to redline : .5

Two Bros with P1X tip
3K steady state: .1 psi
4K steady state: .12
5K steady state: .15
WOT to redline : 2.9

Stock
3K steady state: .07 psi
4K steady state: .1
5k steady state: .19
WOT to redline : 3.7

Steady state runs were done in 2nd gear. WOT was done in 1st and 2nd.

Gotta say the Two Bros flows phenomenally well all the way to redline. Race systems strive to get under 1 psi, so 0.5 is fantastic. It also shows you that BRP did their home work on the collector sizing. Regarding steady state, I suspect there is less pressure at 4k than 3k due to more velocity and likely less turbulence in the perforated bore.

There is a rule of thumb that for every .5 psi of reduction you can pick up 1 hp if the tune is right. So theoretically this pipe could be good for 5-6 hp over stock. But many feel it's noisy and add the P1X to quiet it down. The P1X is called a power tip but it's really just a flow restrictor that also reduces power. So if you use one, enjoy the Two Bros lighter weight and tone, don't count on any noticeable hp difference (1-2 max over stock).

Still to come are my tests with a cat delete and various baffles. Plus I'm building a lighter weight primary muffler that should reduce noise but keep back pressure to a minimum. All this will likely have to wait for testing next spring as it's time to winterize.

cheers,

[jcthorne]

Good work. Please keep posting the real data as you determine it. I do look forward to what you have planned.

Thanks!

[Minister]

This is great info, Thanks.