Fast xfi rpm issue

[Rich Biebel]

Originally Posted by jamie2370

Fast xfi, analog 7al2, fast dual sync dist. My autometer tach is roughly 500rpm less than what fast data shows. Fast at idle shows 1100 while tach is around 600. Is this normal or if not, what is the fix. I honestly thought I had a low reading tach before I put on efi, just now I have another reference that should be super accurate since its dual sync

My last stocker, a number of years ago had an Autometer tach that was off by 500 at higher rpm and about 200-300 at lower rpm...

That was not the first Autometer tach I've had that was off but was the most inaccurate

I used an MSD ignition tester to fire the ignition and it reads rpm right on the tester. It can be used to test many items rpm related including a tach.....