stock xb12 2 stage back pressure muffler does this really work?

[Stillonit]

I have a flat spot in the 3 to 5k rpm range and I am sure this is when the computer engages the higher back pressure valve on the muffler. I am in the process of trying to tune out this problem using tunerPro.
I disconnected the cable to make sure the problem isn't too much back pressure. It's still weak in 5k but seem better...should I make the new maps with or without the valve operational?...and your opinion if the valve is just a wishful thought by the Buell engineers? [confused]

 

[EricZ]

The exhaust valve actually provides an increase in torque over a stock muffler with the valve disconnected. Unless you are swapping to an aftermarket exhaust, the bike will have more power with the valve working.

 

[Stillonit]

why would you say this considering a aftermarket muffler is a very free flow muffler.... so the less pressure the better... consensuses on this?

 

[Stillonit]

Does anybody show this to be true in an independent dyno test and does hp go up as the torque increase in the range where the valve in engaged.

 

[Jimboni]

I have wired the exhaust valve open on my 09 X.
I heard that EB himself stated the valve was put in for EPA noise restrictions rather than torque. Unsure if that is true, but that's why I tried it.

It got rid of most of the low speed stumble, sounds a bit better, and there is no apparent loss in power. Just do the TPS reset after fixing the valve open.

I've been quite happy with the mod and was surprised that I couldn't tell a difference in power. Still does roll on wheelies shifting into second, and that's at altitude. I still have a flat spot in the 3500 rpm area, but I attribute that to the stock fuel map.

YMMV

 

[user_deleted]

agree with steve on the active power valve and i could tell a very slight loss in low to mid-range torque when my hawk muffler deleted it. at least on my 2007 Uly the deleted valve made the low and mid range lean surging even worse until i remapped the ecm with ecm spy and race map. now it's like a whole new bike and runs cooler and smoother...for what it's worth.