What is the resonator? What does it do? What is resonance?
What the hell are they talking about? And what’s that got to do with ‘back pressure’?
No four-stroke engine needs or uses backpressure. Defined as a residual ambient pressure in the header pipe.
The term ‘back pressure’ is erroneously used to describe the action of sound pressure waves that operate in the exhaust. These pressure waves start with the opening of the exhaust valve. This positive pressure travels down to the end of the pipe, where it is replaced with a negative wave that travels back up to the cylinder to reduce the pressure.
This pressure wave moves inderpendant of the gas flow, moving through the gas changing the pressure as it goes. It does not move the gas, it just changes the pressure in the gas.
It’s like when you drop a stone in a pond, the pressure waves travel out to the edge of the pond, to be reflected back to the centre. It does not move the water, it just changes the pressure and as water can not be compressed, it formes ripples on the surface.
Resonate waves may not seem to be all that important but it is this technology that has transformed the two stroke from a 50hp/lt. Weakling into a 400hp/lt. Superstar.
Subaru used this technology in both inlet and exhaust systems to design a very efficient engine. There is not much that you can do to increase the torque output, without resorting to No2 or forced induction.
Harvey.
