something fishy with tach

[Auto[BoT]_GTS]

what should i trust the shift light or the tach......cuz i put the 7600 in and it comes on around 74-7500.....then i put the 7800 and its comes on around 76-7700 what should i trust the tach or the light....its an autometer pro light

[Auto[BoT]_GTS]

does anyone know?

[marcus_GTS]

I don't know for sure, but I would give the nod to the shift light, especially in lower gears. The tach is a needle that needs to move in response to a change in engine speed. Even good tachs have some amount of lag. I think the Celica's tach is decent, but not the best.

A shift light, on the other hand, only has to do one thing: Light up when the RPM reaches a certain number. This takes significantly less time than moving a needle. Of course, this assumes your shift light is hooked up properly.

One way to try this is to accelerate SLOWLY up to the RPM you've got set up for the shift light. That way, the needle has plenty of time to react to the change in engine speed. Of course, your tach might still be a little off, but I think it will be a lot closer than if you're accelerating quickly in first or second gear.

[Auto[BoT]_GTS]

ok ill try that anyone else?

[kaioshin]

If you have a S-AFC that will tell you the right RPM's too. Usually my tach is a little off, so I would go with the shift light too. But, if you aren't bouncing off the rev limiter you might want to try a higher setting on the shift light.