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Old 02-11-2014, 04:27 PM
kurtnkegger's Avatar
kurtnkegger kurtnkegger is offline
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Join Date: Jan 2011
Location: Denver Burbs
Posts: 841

I got this information by googling engine vacuum at elevation...I've understood there would be a 1" drop for every 1000ft of elevation.

When testing manifold vacuum, it’s important to remember that if an engine idles at 22” Hg at sea level, it will idle at about 17” Hg at 5,000’, 14” Hg at 8,000’ and 12” Hg at 10,000’ altitude. Variations from the calculated standard, of course, are the weather conditions, the engine design, and how well the engine management system adjusts spark advance and air/fuel mixture to correspond to a change in barometric pressure.
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