No matter what you do - anything in the exhaust is going to reduce performance and change its sound. There's no way around it. "Tuning" an exhaust is really just trying to make sure those losses are somewhere outside of the useable powerband. As far as needing to be 'no closer than 2" from the end of the straight-pipe(header)' that's a load of bollocks. The farther away from the exhaust port you can put the baffle - the better. Why? Because the exhaust has had more of a chance to smooth out so instead of being short quick bursts of air that are easily restricted, it's a slower moving smooth stream and will restrict the movement of the piston less.

It has nothing to do with its placement in relation to the end of the header because headers are all different lengths and designs. It matters how far away you are from the exhaust port and the farther the better.

Greg wrote on 01/20/13 at 08:45:13:



I think it was Diamond Jim that had a thread about this a long while back. What he did was attached a handle to the end of the baffle, and while the bike was running held the baffle in the pipe and slid it around to different locations to hear how the sound changed, then later he bolted the baffle in place.

I'd also argue against Cavi Mike's statement that "anything in the exhaust will reduce performance," as exhausts need back pressure. There is a ton of science behind exhausts, so nothing is clear-cut though. Running without a baffle tunes your engine for a very high RPM that our engines can't hit, so while in racing applications you might not want a baffle since you're sitting on a hotrod engine at 10k rpm, on our bikes you are much more likely to be sitting at 3k rpm, so you want the torque curve of your exhaust to peak at 3k rather than 10k.

No engine "needs backpressure" not even 2-strokes. It's a complete myth that backpressure makes an engine run better. All backpressure does is physically slow down the piston on the exhaust stroke. You get a "smoother" idle with more backpressure because the engine would be spinning a lot faster if it wasn't being restricted. Your smooth 500rpm idle with backpressure is really a restricted 1,000rpm idle. The "more torque at low rpm" is your engine trying to force out more air than you're allowing it to. You're moving your torque curve lower in the range and limiting its top-end power.

Other than tuned-pipes on 2-strokes, the best exhaust is no exhaust. The only reason top-fuel rail cars have headers is to protect the exhaust valves and that's it. They're not performance pieces.

WD wrote on 01/21/13 at 15:15:37:

The fishtail is exactly what I am planning on doing. I would use the type that I have inserted at the bottom. How in the world would you weld it at the fishtail end?

Wire feed welder, go in through the fishtail. It's big enough. It will pretty much cook off the chrome at the weld line. I run the double flared 8" version like in your pic. Less chance for vibration to break the welds as the second flare holds the back end relatively stable. My exhaust has a 12" glass pack with no packing, just a bare core, and the stick stopper in the end of the pipe. Sounds like a L.O.A.C.H. instead of a UH-1 Huey.

I had to delete the airbox door and go up a size or 2 on the jets. I went a little fat with the jetting, so it runs a bit too rich, need to step them down a size since I'm only at 400' or so elevation now. Smokes like a 70s big rig until it warms up...

verslagen1 wrote on 01/21/13 at 21:42:36:

That's not backpressure, that's a tuned sound wave, and it's still not "needed" for a 2-stroke engine to run - it just bumps power in a small portion of the power band. A 2-stroke engine will run just fine without a tuned pipe or a muffler.

Coaxial wrote on 01/22/13 at 23:29:17:

Very informative. Thanks.