
Originally Posted by
wobbly
. . . In a reed valve setup,tuned for peak power around 12000 rpm, we find that the best tuned length is around 135mm from the reed tip, to the end of the bellmouth works best.
What this does is hard to explain but easy to show you.
The wave bouncing up and down the intake length, when its "in tune", will arrive at the reeds as a + going pressure ratio, at the same time as the case drops below atmospheric, due to the piston rising - plus the pipe diffuser sucking like hell on the Ex Port around BDC.
When this happens the reeds have + on one side and - on the other.They open real fast, with little "flow energy" being waisted, and Hp is made big time for free..
With this & Frits advice on keeping the tract as short as I could(ish) I have flowed a control reedblock (the differing epoxy makes it look like there is a bad match but I used Kneedit as its easy to form & then Devcon over the top to smooth it out. Then I ground & sanded it back. Needs more but will do for now. Next block will incorporate a fin & test against this one.
But then I measure it & it is 160mm from reed tip to bellmouth (photo makes it hard to see but it is squared up).
I want to peak faster still than 12, probably 13,000, but I'm no where near even 135mm to the Bell mouth. I could perhaps find a shorter manifold rubber, but only by a few mm & mill into the 10mm ally plate. But I'd only find 10mm tops. The manifold is only about 30mm long. Going to the 36mm PWK makes the assembly even longer.
currently an early TZR block (only just fits) with VJ21 32mm Mik.
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