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On 4 Nov 99, at 18:04, Erkson, Toby wrote: > I was hoping someone else would clarify this question. I'll give it my best > shot as I know it and everybody else can correct me... Let me take a shot at this, too.... The cylinder firing order is 1432, which if you repeat it over and over again becomes 143214321432143214321... and if you look in there you can see that this could also be written 4321. Then note that while 4321 is the firing order, it is also the intake order. Now lets use a "V" as shorthand for an intake stroke because the air pressure gets sucked down and this looks like a down arrow. And we can represent no activity by a "_" representing just a blank. Thus for an intake order of: 4 3 2 1 the whole engine has the following representation: V V V V. But looking at just the right manifold the intake pulses look like: _ _ V V, and the left manifold looks like: V V _ _. If you look at these patterns and consider how they repeat, you will see that they look like V V _ _ V V _ _ V V _ _V V and the simplest repeating unit is V V _ _ , which represents 4 strokes or 2 revolutions of the engine. But if I could get all 4 cylinders to suck from the same manifold the pattern would be V V V V V ... for which the simplest repeating unit is just V, which takes 1/4th as long. Something that takes 1/4th as long has a frequency that is 4 times higher and would be represented by shock pulses in the intake manifold/carb that are 4 times closer together. This is just another way of saying that the wavelength is 1/4th as long. Since the length of the pipes leading to the cylinder can be considered similar to an organ pipe where the length of the pipe is shorter for a higher frequency, I can use shorter intake manifold runners if I can arange to make the intake manifolds think that the intake pattern is V V V V rather than V V _ _. The balance pipe helps that happen, especially at low RPMs where the frequency is already low and needs the most help. In the end it is exactly the same problem as a tuned exhaust with equal length headers. Jim - ******************************* Jim Adney, jadney@vwtype3.org Madison, Wisconsin, USA ******************************* ------------------------------------------------------------------- Unsubscribe? mailto:type3-request@vwtype3.org, Subject: unsubscribe