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Hey Jim- One other thing... > Result: > V*(720-ECD)=24*W*N*L > > Let's plug this in: > L=20.625 in > V=15000 in/sec > ECD=210 degrees > > For N=1, W=15455rpm. For N=2, W=7727rpm. For N=3, W=5151rpm. Something else to consider: obviously, the N=3 pulse is the one, if any, the engine *could* be tuned to. The -3db point of the wave is at N=2.875 and N=3.125, right? That is 4945rpm-5375rpm. The weak N=4 pulse (usually only 2 and 3 are considered because the signal is progressively damped out) would be N=3.875 and N=4.125, which is 3747rpm-3988rpm. We can also consider when the resonance effect decreases performance. This corresponds to the valleys of the cosine wave, when N=1.5, 2.5, and 3.5. Those correspond to 10303rpm, 6182rpm, and 4416rpm. That last one is interesting: the -3db range of that valley is from about 4263rpm-4579rpm. Here there is a DECREASE in performance thanks to the runners, which is where the stock 1600 T3 engine has its peak. Between this and the unequal-length runners, I don't think that the VW engineers were too concerned with resonance when they designed this system :-) Not that it matters all that much... the engine is restricted otherwise anyway (i.e. exhaust and t-body). Take care, Shad ------------------------------------------------------------------- Unsubscribe? mailto:type3-request@vwtype3.org, Subject: unsubscribe