Everyone says the factory tachs are off quite a bit. I can't remember which way. I'm going to quess and say they are on the slow side, is this correct? At 6,000 rpm how far off is it? Thanks.

 

I know that right now my idle is set to 875 (confirmed by Datamaster) and the tach shows idle at ~1000. So, at least at idle, my tach reads fast.

 

At idle tach shows 200 more thanis and while driving it shows 100 rpm more than it is.

 

Mine is 200 high.

 

Well, as usual I guessed the wrong way. The good news is, I need to have my shift points changed. I'm probably off by at least 3 to 4 hundred rpm. I hope it helps my times. Thanks guys.

 

They vary. Mine is within 50 rpm at all times.

 

That's why I need an aftermarket tach installed to go along with the other gauges I've been sitting on. This summer is for fine tuning what I have before raising the bar.

 

Why are they so off and why do the aftermarket ones read accurately? Is it just a cheap tach or do they have different methods to read the rpms?

 

I dont know why they are so often off, but I plan to correct mine by pulling the needle off and sticking it back on in the right place. I have a scanner I can use to verify its accuracy afterwards, and assist me in gettting it on correctly.