They have gotten their explanation about intake pulse tuning slightly wrong. Here is a better description from Heywoods "Internal Combustion Engine Fundamentals":matt21 wrote:The trumpet length is depending on the rpm where you want to set the resonance frequency of the inlet tract.
This gives you a slight charging effect.
You can influence the power and torque curves with that.
So basically you chose the rpm where you want the highest effect and set the length for it.
Here you have to take into account the rpm, speed of sound, valve timing.
http://www.autozine.org/technical_schoo ... haust.html
https://nwmobilemechanicdotcom.wordpres ... se-tuning/
http://www.exx.se/techinfo/runners/runners.html
"As the piston moves downward during the intake stroke, a reduced pressure occurs at the inlet valve relative to the pressure at the open end of the inlet pipe. A rarefaction wave travels down the intake pipe to the open end and is reflected as a compression wave. A positive tuning effect occurs when the compression wave arrives at the inlet valve as the valve is closing."
This is basically the same, but opposite from what is happening during exhaust pulse tuning. When the exhaust valve is opening a compression wave is formed, which travels to the collector in the exhaust manifold and is reflected as a rarefaction wave and travels back the exhaust valve again, preferably arriving when the exhaust valve is about to close.