Quote:
Originally Posted by Buddy Seat
As far as the smaller Ex valves & less flow. The official HD Training Manuals (don't ask how I get 'em) are noted that HD was trying to increase Ex port velocity & anti-reversion.. That kinda worked, but with side effect..Big heat diff...
Sure changing heads, or porting em is an option. But you shouldn't have to do this $$ to a brand new bike to lower running temps IMO...I've been at long redlights with TC w/95" kit & cams in Fla.. And I felt like I could fry eggs from the tremendous heat..
Mission Accomplished (as was posted)..
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Interesting, thanks.
I understand reversion to be exhaust flowing back into the cylinder as a result of a pressure wave inside the exhaust pipe. I'm thinking it is something that happens at certain rpm ranges (and at different ranges based on the characteristics of the build & exhaust system). By making the port & valve smaller they increased the speed of the gasses and that is what fights the pressure wave (or pulse) by the fact that faster moving gasses have more momentum to keep going the right direction even in the face of a pressure wave coming upstream. The trade off is the smaller port/valve also inhibits flow, especially at higher rpms. Thus, the loss of peak HP.
Am I close to understanding this correctly?
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