How much off are the stock tachs?

[youngcamarokid]

I'm sure it varries from production runs....but I have a '97 m5...and I want to know how off my tach is. I know it's off a bit...but it's crucial if I'm shifting at 5200 rpm or so that I'm not actually at 5650 or something...

Also, how could the problem be fixed, without buying an aftermarket tach?

[speedy-v6-camaro]

The only way to tell is to get Autotap. Thats really the only way to get accurate rpms. Shift lights will hook to the tach signal which is accurate if you are looking for a way to tell when you are at the max rpm you want to be.

[98Camaro3.8]

The tach lags behind the actual reading. If you're revving up fast in first gear, it'll be farther off than if you where bringing the revs up slower in another gear. So there's no set amount as to how far off it is.

[ June 27, 2003: Message edited by: 98Camaro3.8 ]</p>

[youngcamarokid]

I'm thinking maybe use my shop tach that connects to ground and feeds off the coil wire....only thing is i've never used it on anything but old cars with easy engine layouts and a distributor and coil right there.....i dunno, i'm just dumb :D