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Old 02-05-2013, 04:21 PM   #26 (permalink)
beatr911
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Join Date: Feb 2008
Location: West Coast, USA
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B2300 - '96 Mazda B2300 SE

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About carbies and late intake closing/massive duration.

Does anyone have actual experience with constant velocity carburetors and very long duration cams where the intake closes, say 90* ABDC? Interested in the peculiar effect on the carbs at various speeds/loads. My understanding is the reversion would cause air to be metered three times causing an extreme rich ratio, but only at some engine speeds. I'm guessing idle and low speeds to be affected most.

As manufactured, he 997cc Concours has a 275* duration, and intake closes about 54*ABDC. Though this is what is usually considered a long duration cam and closing is pretty late, the four individual carbs meter just fine.

Just wondering if there is some knowledge as to the upper limit of intake closing ABDC that individual constant velocity carbs can tolerate.
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