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> MPS function, still tuning after these years
post May 16 2018, 10:23 AM
Post #1

can't remember

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From: Madison, WI
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Region Association: Upper MidWest

I have read and re-read PB Anders' epic work. Bought a Henry meter and everything , but there is one thing I am puzzled by. It looks like from idle to part throttle the pulse length is controlled by the contraction of the aneroid bellow. This produces a pretty straight vacuum- inductance slope. Which means that if you set one end of the curve for A/F ratio, say at idle, or part throttle, all of the other points on the line are fixed, based on the bellows and the spring rate. If you move a line with constant slope all of the points move by the same amount.

Nonetheless, there is some talk about setting mid throttle as though it can be adjusted independent of closed throttle. The reason I am asking is I have been chasing a partial throttle dead spot in the 2,000-3,000 rpm range under partial load. Idle is too rich (11-12) and at the dead spot the mixture goes way lean (16-17 or higher).

I can move the diaphragm stop (outer screw), but that doesn't change the range or slope of the aneroid, it seems to be mostly involved with WOT control (which works fine for me). So I cannot understand how that could affect partial throttle ranges.

Is there a way of adjusting mid-throttle independently from closed throttle?

I should add that it is a 2056 with 8.5 static compression and a Web cam 73 with so called Raby grind (can't blame Jake here, I ordered it without his help). I rather think it would work better as stock. But, I get really close.
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