Fast xfi rpm issue
 

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

Re: Fast xfi rpm issue
 

Sounds more like an Autometer issue.

Re: Fast xfi rpm issue
 

I agree, I think I will try another tach to see. Like I said, when it was a carb combo I really thought it was off then but I had nothing to compare it to

Re: Fast xfi rpm issue
 

Where are you picking up the tach signal?

Re: Fast xfi rpm issue
 

at the 7al2 box, tach terminal

Re: Fast xfi rpm issue
 

Is there an unused tach wire on the FAST harness? If there is, it would be worth trying before changing the tachometer.

Re: Fast xfi rpm issue
 

Have you tried the tack output in the XFI harness if I recall is the white points wire

Re: Fast xfi rpm issue
 

I have not had a tach in my car for a while now. I log & play back every pass. If I had a stick car, I would need one, wouldn’t I? Or a shift light. LOL

Re: Fast xfi rpm issue
 

That's what is firing the msd box. Seems the more people I talk to I am thinking it's a tach issue. Nobody seems to have this problem. And a Tach is a necessity in Stock. Foot brake, and reverse pattern ATI 350 means it's all on me lol

Re: Fast xfi rpm issue
 

I have used a digital hand held tach that uses a small piece of reflective tape on the damper to verify which is correct.
Ernie Neal
SS 354