Computer Diagnostics and Tuning Technical discussion on diagnostics and programming of the F-body computers

How accurate is the stock tach?

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Old Nov 24, 2010 | 07:37 PM
  #1  
TT350's Avatar
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From: Picayune MS
How accurate is the stock tach?

96 T/A 100k miles bone stock.
Leaving it in drive the tack is showing 6500 shift points.
This can’t be right, can it?
Old Nov 24, 2010 | 10:16 PM
  #2  
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Re: How accurate is the stock tach?

Check it with a datalog. Tachs vary by individual car.
Old Nov 24, 2010 | 11:25 PM
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Re: How accurate is the stock tach?

Originally Posted by TT350
96 T/A 100k miles bone stock.
Leaving it in drive the tack is showing 6500 shift points.
This can’t be right, can it?
In your opinion, does it seem to stop pulling near 6000-6500rpm? A stock motor usually runs out of steam past 5500rpm for sure.
Old Nov 25, 2010 | 11:04 AM
  #4  
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From: Picayune MS
Re: How accurate is the stock tach?

It pulls good all the way to the shift points.
No complaints with the performance, I just know
that the stock cam is not much good past 5500.

I knew it was off, just wondered if it was a common thing with these cars.

I may send it off and have it calibrated.
Old Nov 25, 2010 | 02:38 PM
  #5  
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Re: How accurate is the stock tach?

Typically, they read 100-200rpm higher than actual enigne speed, and in extreme cases 400rpm. Since the stock rev limiter is set for a bit over 5,800rpm, yours would have to be reading 700rpm high if the car is truly "bone stock". Never saw one off that far.
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