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Posted by D. Sherman [24.32.202.83] on Monday, January 18, 2010 at 23:05:59 :
In Reply to: tach-o-meters posted by Dave Royal [76.182.149.93] on Monday, January 18, 2010 at 22:47:54 :
You're right, it will read high. Another way to think if it is that by the time there have been 8 sparks in a 6 cylinder motor, the crank has turned once around plus another 2/6 of a turn, so it's gone 1/3 farther than the tach thinks it has. Once I worked on an engine that sparked each cylinder twice per revolution, so it sparked on the exhaust stroke as well as the compression stroke. I can't remember what it was, probably some small air-cooled engine. That would double the tach reading.
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