RE: whats the different between tune muffler and tune pipe?
Pé,
I cannot agree with you about the last statement.
The power addition from installing the MVVS tuned silencers on engines, is much too great to be only a result of suction (more complete exhaust scavenging and quicker induction).
The RPM difference on the same prop size, like an 11.5x6 Bolly on the .49/8.0 engine, is ~2,000 RPM, to 13,600; compared to the #3245 muffler.
This is an addition of no less than 61% in HP compared to the base number, which cannot be accredited solely to better scavenging.
There is definitely a positive pressure boost; supercharging, as compression begins and the exhaust port closes.
A very good muffled tuned-pipe installation, can only bring a gain of 300-400 RPM over that number.