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Old 06-18-2012   #2
Paul Workman
 
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Join Date: Nov 2007
Location: Squires (near Ava MO in the Mark Twain N'tl Forest) - Missouri
Posts: 6,466
Default Re: Tach way far out!!!!

Quote:
Originally Posted by 1963korvette View Post
Hey? My tach is sooo far out. When I'm at idle according to my snap on scanner it reads 675 rpm. The tach reads 2300. Aside from the obvious what other problems could this cause? I've read something about a rev limiter? Is this is real does it redad from the tach or the computer?
Thanks
Rich
The rev limiter is independant of the tach, so there's no problem there.

As for DIY tach calibration, it isn't a big deal, if you can solder a few resistors. But, I must say an error of over 300%...is quite a bit! Usually the error is much lower. Mine was off 20+%, and I've heard of a couple a bit more (e.g, near 30%).

Usually the error increases over time; a function of deterioration of a printed resistor circuit. But, in your case, I wonder if the ground on the voltage divider isn't lifted (or the like).

I can dig up the calibration procedure, if you want to try it yourself. Who knows...the calibration process might just fix a lifted ground problem too.

P.
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