Author Topic: Fox Tach Error  (Read 1148 times)

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Matthew

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Fox Tach Error
« on: October 09, 2013, 07:14:43 PM »
The factory tach in the Fox Mustang is pretty widely known to be out but I think that many guys don't realize how far out it can really be. I sometimes shoot cell phone video of the tach on the dyno so that I can show customers how bad their tach actually is, and I thought you guys might be interested as well so I shared one typical example on my youtube channel. In this case the car was run to 6286 RPM and the tach goes all the way up to 7000 making it about 700 RPM too high at that point. This type of error is typical, but often results in short shifting by guys who don't realize it. It just goes to show why you need an aftermarket tach if you ever plan to race your car. Enjoy!

<a href="http://www.youtube.com/watch?v=G1CwOzks_KQ" target="_blank">http://www.youtube.com/watch?v=G1CwOzks_KQ</a>

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crzyhrs

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Re: Fox Tach Error
« Reply #1 on: October 09, 2013, 08:32:35 PM »
Wow, that is a huge difference.
I've noticed my auto meter tach to read about 200 to 300 rpm higher than the factory tach. The tweecer digital value is the same as the factory tach. So is the factory tach error introduced in the electronics or the physical gauge sweep? If it is in the electronics, then I have to assume both the tweecer reading and gauge reading are both out, or my auto meter tach is out. At idle the factory tach and set point are around 900 rpm but my auto meter reads over 1100, judging by sound, I would think 900 is more correct though.
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PurEvil

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Re: Fox Tach Error
« Reply #2 on: October 13, 2013, 02:32:44 PM »
Did the mustangs ever come with a dash that didn't have a tach but still had the rest of the gauges?
89 Mustang GT