How accurate is the stock tach?

[EagleTalonTim]

Out of curiosity, I want to know how accurate the stock tachometer is in a 1g Talon. The reason I ask is because I have noticed in my data logger and some electronics I have made, when I shift at 6500 RPM in my automatic, according to the dash, my data logger and experiments show I am actually shifting closer to 7000. I have even seen the logs hit 7200 RPM when I shift at 6500 RPM with my shift box. I can feel the car shift and watch the tach never go over 6500 RPM, but when I check the data log, it is higher in 2nd and 3rd gear. Does this mean my dash tach is wrong or off? Is this a common issue?

 

[volcomsnow245]

Yea I noticed the same thing on my afc just a little off.

 

[brian9397gsx]

Its accurate enough of course your dataloggs will show different being as though the signal is not driving an electric motor. Mine are consistently off by a few hundred rpm, its just a good reference