stock tach accuracy

[spederman]

Anybody know how accurate the stock tach is when the motor is being revved up really really quickly? I have heard that the tach can climb quicker than the engine is actually revving when your boosted and can over rev and be off by a lot (like 500rpms).

 

[san~man]

You can always set the instrument cluster to diagnostic mode and change the display to show the tach reading electronically. Match that with what the needle on the dash tach says and see how far (if any) it's off.

 

[Stang|ess]

It's slightly off, just like the speedo.

 

[BurningRubber]

I dunno, I got the tach to read around 6300 RPM once, but I never hit the rev limiter.

I missed a shift so the engine revved very fast, if its true then I guess it flung over a little more than it was actually revving... or else I dont have a rev limiter for some reason.

 

[LaserRed01GT]

When I go through the gears, I can watch both my stock tach and my Autometer 5" tach and in the upper RPM's (over 4500), my stock tach is about 300-350 RPM higher than what the Autometer shows. I know the Autometer is more accurate because my rev limiter is set at exactly 6400 and if I ever bump the limter, I can hit recall on my Autometer and it will show exactly 6400 RPM. My stock tach will show close to 6750 when I bump the limiter.

 

[spederman]

good to know. I thought it might be off because if i tap the gas to the floor and let off right away in 2nd, the tach jumps all the way to redline 6300-6500K or so but my shift lite doesnt go off which is set at 5800k. So i figured since thats tied into the ecu, the tach must be just revving to quick.