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mark houghton mark houghton is offline
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Join Date: Jul 2008
Location: Central Washington State
Posts: 3,775
Vacuum sensitive enrichment

On the topic of vacuum (or the lack thereof) triggering additional enrichment, I've got an idea that I can easily test out. First, some history: I've been running with an Andial system to enrich at boost (and recently modified to enrich at chosen rpm's instead). But, I just installed one of Brian Leask's adjustable WUR's and probably won't be needing the Andial anymore. But I'll leave it installed, just in case.

After reading your posts last night, my mind subconsciously worked on this all night and came up with an answer. Why not put a vacuum sensitive switch connected to a port on the intake manifold post butterfly (such as the line that goes both to the WUR and to the decel valve), said switch to have a normally open switch under vacuum....which will close in the absense of vacuum, and act as a ground to activate my Andial fueler? I had a spare pressure switch on hand and proceeded this morning to modify it to act under vacuum instead.

So, here's the deal: At idle, or at steady cruise when there is sufficient vacuum on the engine side of the throttle butterfly, the switch remains open. But as soon as you stomp on the gas and the vacuum goes away, the switch closes and activates the Andial fueler to richen things up. Of course this would lower the CP across the entire range while accelerating as well as on boost, so a person would have to dial back the WUR boost enrichment so as not to over enrich when on full boost.

Does this follow the logic of what you're trying to do...get more fuel at the onset of acceleration to improve torque and response?
Mark H. 1987 930, GP White, Wevo shifter, Borla exhaust, stock everything else. The result of a massive Pelicanite good will fire recovery effort. Truely an open book, ready for the slippery slopes to modification.
Old 03-15-2009, 09:30 AM
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