Idle speed, acceleration, and top end issue ... SOLVED!!!

[mkov608]

Wanted to pass this on as lessons learned: I recently started a thread to get some help on a problem I was having. See the link below.

http://www.seadooforum.com/showthread.php?66954-Idle-speed-acceleration-amp-top-end-issue

Well, it turned out to be the j-pipe! I didn't think an exhaust leak could cause such a problem, but also understand Rotax has some secrets to getting horsepower out of engines and the water injection in the exhaust has something to do with it. Thanks Ski-doo (Jeff) for the advice and for the great price on a used pipe.

I've attached before and after RPM range scans. Now I'm hitting that upper band, 7050 RMP, and 61 MPH.

View attachment 22623

 

[Sportster-2001-951C-Stock]

Right, carbon monoxide doesn't burn well and a bilge full of it displaces oxygen needed for combustion, so an exhaust leak into the bilge will definitely create an issue.

 

[Coastiejoe]

Very good,,,,

Glad to hear you have it solved..

 

[mkov608]

You are spot on! I didn't think the exhaust lk was that bad, but for air breathing engines, O2 is much better than CO.

An interesting article here:

http://link.springer.com/article/10.1007/BF03227574#page-1

Looks like the water injection in the exhaust is to meet a US Coast Guard rule that exhaust system components must be below 90 deg C. I thought it was to improve horsepower output.

Right, carbon monoxide doesn't burn well and a bilge full of it displaces oxygen needed for combustion, so an exhaust leak into the bilge will definitely create an issue.