CLASS RACER FORUM - Fast xfi rpm issue

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Re: Fast xfi rpm issue

Quote:

Originally Posted by jamie2370 (Post 611839)

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

My car is in mothballs in the trailer so can't check without standing on my head. In a couple months will have a much better situation.
Believe you have the right set up. Don't expect the RPMs to match exactly a tach really is a volt meter depending on the quality of the device there may be inaccuracy. Plus there is noise that is tough to get rid of mostly from the MSD the 7AL2 is really bad tons of RF. If you wish to try to arrest some of it set up a Faraday shield around the box with aluminum expanded metal and ground it.
You should probably try a different tach again don't expect them to match exactly but they should be close enough that your staging and shift RPMs on the data log should make sense.

Re: Fast xfi rpm issue

Quote:

Originally Posted by jamie2370 (Post 611773)

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.....

Re: Fast xfi rpm issue

Quote:

Originally Posted by Rich Biebel (Post 611903)

Had an Autometer tach in my car for a while. Was wrong, just removed it. No tach now.