As of this writing, until a really clever slip-on type muffler comes along, something that is different than the stuff out there now, it really is apparent that just replacing the end caps on the stock muffler can is the best way to go for power, sound and cost.
So many people have the various end caps, from BestDualSportBikes.com now, that feedback from the customers directly, on the forums and reviews from the magazines, just hugely reinforce the fact that this is the best way to go.
I'm going to try to keep this as short and sweet as possible as to how and why it works and why it is better than other options at the moment.
Here is the stock muffler with it's rear section cut out to help you understand it.
The exhaust exits into the muffler through the core you see on the left. it exits into a more open chamber. This is a pretty good design, in that the exhaust can expand and cool down a bit, as well as some of the sound waves can rattle around in there and cancel themselves out.
The problem is, the exhaust exits into the chamber, where it becomes confined and backed up, until it finds it's way through the spark arrestor screen and into the exit tube, which you see on top of the tube. This design creates a lot of back pressure, and hence a big loss in power.
This is the outlet setup of our STE-2 End Cap.
You can see that the outlet tube lines up with the mufflers core now, letting the exhaust gas flow freely out of the muffler. On top of that, the inner diameter of the outlet tube is a larger 1.320", where the stock outlet is 1.100". Our tube also has 8 -.500" holes in it, which any extra pressure, that is built up in the muffler, escape.
The quietness of both of the caps, comes from the spark arrestor screen, and the fact that the holes are placed apart from each other, which seems to cancel out a lot of the exiting sound.
The free flowing design, is why you see such a gain on the dyno, with the BDSB caps, over the stock XCW end cap. The XCW cap doesn't have the perforated screens in the outlet like the EXC has. The power gain over the EXC cap is 6-7 HP. The cool part is, with all the work out into the sound part, it's as quiet or quieter, than even the stock EXC cap.
The STE-2 end cap, above, sticks out an extra inch, for an extra muffler volume and also has an otional quiet insert. The insert lowers the sound to less than the XCW cap and the EXC cap, but only lowers the bottom end power by a bit.
It still kills the stock caps. The extra volume the cap gives to offsets the extra pressure build up the smaller outlet causes. This is why the power isn't effected too much.
The STE-2 is lighter than the EXC cap. Sound tests are as follows
Per SAE sound test @4250 RPM. Stock EXC - 92 db. Stock XCW - 93. STE-2 - 92. STE-2 with insert - 90.5
In the end, the 250 and 350 bikes are good with either cap, the 450's, 500's and 501's are better off with the STE-2. And 80% of the users use with the quiet insert.
Opening up the exhaust flow will cause the bike to run leaner so using the TPS tuner and/or fuel rail is a good idea.
And just in case you wonder, how the end caps with the stock muffler stack up against the slip on mufflers that are out there, like the FMF 4.1 and the KTM powerparts mufflers, which are the 4.1's, you can easily see by the dyno chart here, that our end cap, for $160, smokes the $500 titanium muffler with carbon cap.
And this is at all rpm's. On the dyno, or by the seat of the pants, we win. The STE-2 end cap, is quieter than the FMF with spark arrestor insert at the same time.
So if you’re ready to improve your exhaust system, and gain the extra power, you can do so below.