Re: Fw: Fwd: Re: [T3] too much mind time

[sml214@casbah.it.northwestern.edu]

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 

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