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SAFC2 lower rmp reading than tach

Old 08-02-06, 09:23 PM
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SAFC2 lower rmp reading than tach

I hooked up my [email protected] and the rpms on the display are lower than the tach reads. Tach reads about 1000, SAFC2 reads about 900. But when the tach reads about 4000 the SAFC2 reads only 3500. That seams to be a lot of difference, and i have not even tried to see what it would read by redline.

What do u think is wrong?
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Old 08-03-06, 03:57 PM
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i have the same problem also!!
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Old 08-15-06, 10:08 AM
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The stock tach might be off...
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Old 08-15-06, 09:16 PM
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i have the same problem....i know someone here has figured out what causes that to happen...come one guys lets dust off this safc section i know no one ever checks it
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Old 08-16-06, 09:50 PM
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On the setup menu use the 4cyl mode if you use 2cyl it will read wrong
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Old 08-21-06, 10:40 PM
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that seems to be normal discrepency, as i notice this also. the stock tach is not all that accurate. i don't think it is a "problem".
Mazda also seem to have made the speedo read a little higher than actual...
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Old 08-23-06, 02:07 PM
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even in 4cyl mode with the air point to the up and right my tach safc have different reading teh up at 8000rpms my sfac rads 7200 rpms

yeah if some one could post up their fix that would be great and awesome
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Old 09-01-06, 06:46 AM
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I read on the SAFC2 manual that this is normal. If I have a chance today I will find out what page this info is on.

Looks like it does it on other cars with analog tach too. :\
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Old 09-01-06, 06:01 PM
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The factory tach is the discrepant part. Take a digital meter with the capability to read rpm and you'll find the SAFC is closer to the truth.

I see this difference on a 86 n/a I have and I'm sure it's the stock tach thats wrong.. I'm *pretty sure* I checked this out in the past with a meter. Might check it again soon.

Even a meter with Freq should confirm it. Back probe a fuel injector wire (primary) and read the output in freq. It should correspond to rpm. The compare the tach to your meter.

I think my 86 is off a bit more than 100 rpm.
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Old 09-13-06, 06:43 PM
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Yeah me too, my safc-2 will always read a true rpm versus the 20yr old tachometer. Mine stays anywhere from 80-150 rpms above the tach all the time.
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