So my car sat for a few months and the battery died. I have since got it running again and the rpm's are off. I have a Apexi Neo. They are about 500-700rpm lower than the actual tach and get worse as you go up. What could cause this? None of my other settings were messed up. I think it has a function that keeps your settings even if the battery dies. So what could be the problem? Thanks

 

Its the stock tach that is off. The all versions of the safc read the rpm correctly.

 

Definitely a tach problem. The AFC is more accurate than the tach

 

Well it wasnt off this bad before???

 

how do you know the stock tach read more accurate before?

 

Well because I used to watch them both. Its wasnt really off below 3grand but now it is. So I shouldnt worry then and just go by the safc? Also what would make it do this all of a sudden? Thanks

 

Mine varies how much its off. It can be 100 or up to 500rpm off.

I think the stock tach just needs to be recalibrated but I have no idea how. I heard about using a battery charger some how to calibrate it.