I've had a few PM-comments about the intake / plenum
but I'll take it to this thread, as I'd be glad if someone more knowledgeable
than me (shouldn't be hard to find) could offer competent comments:
We're talking about the need for a certain size plenum
to create a "pressure-reservoir", to 'bridge the gap' between
the constant/even-pressure delivery from the blower.
and the intermittent demand because of the 'un-even' (V-twin) firing order.
(On a single-cylinder the problem would be worse. On a multi it would be much less)
My calculations for the plenum-size is based on
Maurice Brierley's ( sixties supercharged Vincent drag-race hero)
book "Supercharging Cars and Motorcycles",
and an exchange with Jeff/"Panic", of Victory Library fame
( I tried to linkto the supercharger-part of his site,but they seams to have vanished (
and a few other sources.
Their seams to be an agreement, partly different depending on blower-type,
that the size of the plenum should be from 150 to max. 200% of the engine-displacement,
on a V-twin.
My engine is 600cc and my plenum is approx. 1190cc so that's pretty darn close to max.
(I just re-checked it, by filling it with water).
Theoretical there's a bit difference depending on the 'firing pulse'
which in my case is 42 degrees, so the phase/wave formation
is slightly different than, say, a 50 degree V-twin.
This is mostly theoretical but:
...despite the plenum/(boost-storage-tank), the two cylinders
because of the 'un'even' firing, will receive slightly un-even quantities of "supercharge".
Because of this, some folks, like Brierley, will run slightly (half a ratio) different compression-ratios
on the two respective cylinders, to ad up things.
Apart from all this; my plenum is not perfect by any means,
as I'm not able to make it perfectly 'stream-lined' inside
to avoid what Brierley refer to as "aerodynamic fungus"
...but I did my best, considering the means I have available.