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Originally Posted by jsteele22
Like I really need to be typing more ....
Or if the pipe was "too short" in the first place ? Wouldn't this accomplish the goal of allowing a shorter pipe distance from header to main cat and still having a favorably timed (albeit smaller amplitude) low pressure wave ?
I guess the one thing that's not clear to me is how "strong and sharp" the exhaust pulse is from a modern engine (like, say a Subaru ?) compared to the ancient beasts that Robertson, er, I mean Morrison, worked with. Maybe that's a factor that isn't considered in his work. But a sharp pulse reflecting off the closed end of an interference pipe will still produce a fairly sharp spike in the middle of the extended waveform travelling down to the resonator. It should be a copy of the original, more or less, reduced by half.
Cheers,
Jeff
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Development of resonate tuning in cars has been slow. I have been using it for two strokes engines for some time. It was started back in the late 40s by Walter Kaden at CZ. After the end of the war, CZ became MZ, and the resonate tuning was developed to a very high state.
The start of the wave is vital to the action of the wave. The faster the wave can be established, the stronger the effect. In strokers, we use a port with a very straight opening edge, to provide a sudden start.
The auto engines are getting the message, as the the quest for more power from the same capacity, is needed. The EG33 has very fast opening cam profiles, that can establish a strong wave action. This action intensity increases with engine speed. The faster the opening, the stronger the wave.
In the EG33 the resonate action becomes strong enough at about 4000 rpms. Below this rpms the wave action is weak. So the engine depends on the low. speed inertia action of the exhaust gas to pull a low pressure in the cylinder as the piston is rising. We don't have to worry about creating a low pressure at TDC (overlap) below 4000, as the Inlet Inertia system provides a positive pressure as the inlet valve opens.
The point is that you do need the longer header pipes to allow this action to operate. If you were to use the interference pipe to shorten the headers tuned length, you will lose the low rpm torque.
Harvey.,
