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Originally Posted by Kurlon  If your theory was the only method of explaining how an exhaust works, throttle position wouldn't matter. Partial throttle, WOT, based on the amount of impact you're saying pipe harmonics have you'd never see anything other than sawtooth power curves zigzagging up and down.
That theory is only one way of looking at a pipe's operation. It doesn't fully describe the system though. |
I'm not sure you don't see sawtooth curves for the +/- 10% torque being added (or taken away?). I don't know. I can't really say how long the length of that sawtooth wave is. Maybe it's not jagged, maybe it's long. Maybe it's long enough that it covers most of the area under graph while it's "up". I hadn't thought of that before.
Maybe there's something I am missing, there surely is. I will admit I really can't describe something that complicated.
From the "serious" stuff I have seen on intake and exhaust tuning, diameter and length, that's what it is. It's Heimholtz. It's resonance. It's actually tuning. That's why I always thought the Yamaha tuning fork logo was cool, even though it's not what it means. Motors really do hum at some level.
Are you racing the CRF? I'd like to find something really little worth tuning. Somthing cheap enough to fool around with, something with gears that will support a 180 pound adult. I rode and very much liked some little two stroke things in Europe way back, Zundapps? The Puch fell in my lap and there's a lot of cheap performance kits for them, oddly enough. I'd be very happy tuning that if it only had gears.