How to test tach?? - Team Camaro Tech
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post #1 of 8 (permalink) Old Oct 2nd, 03, 02:39 PM Thread Starter
 
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Got my new OER repro tach today, how can I bench test it to make sure it works? I only have 30 days to return, but the car will be down much longer, so there has to be a way to bench test prior to install.
Thanks,
Jerry
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post #2 of 8 (permalink) Old Oct 3rd, 03, 07:03 PM
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You'd need one of two things. A) an accurate signal generator of some sort or B) a frequency counter. The signal generator could be used to generate a known frequency signal for the tach which could be verified on the display. The frequency counter could be used to measure the frequency of a running engine and translate the result into a tach signal. Although, you'd have to protect the frequency counter from ignition spikes. For a V8 motor, RPM = Freq(Hz) * 60 / (Ncyl / 2). An AC power line could be used as a signal generator if you know how to do so safely. 60Hz AC would generate a 900RPM signal. You would need a resistor network which would limit the voltage to the tach to a half-wave-rectified voltage of less than 30 volts peak or so.

-dnult

Dave
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68 Coupe, 350 w/ Edelbrock Performer RPM heads, cam, intake, 700R4, Dave's small body HEI
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post #3 of 8 (permalink) Old Oct 4th, 03, 02:45 AM
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You can do a quick hook up to a running car, preferably to a points type vehicle. No need to bolt it down or anything. Just a couple of wires. You might compare the reading to a known good tach while you are at it.

-Mark.
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post #4 of 8 (permalink) Old Oct 4th, 03, 03:59 AM Thread Starter
 
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Thanks guys....Dnult, I consider myself somewhat technically inclined...aerospace wise atleast...but I had to read your response 3 times and I'm still sitting here saying how the hell am I going to do that? [img]graemlins/clonk.gif[/img] So to make it simple I am going to trust that it is new and install it as is.

I am still amazed at the knowledge present here...I'll just go away and play with my helicopters now...
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post #5 of 8 (permalink) Old Oct 4th, 03, 06:23 AM
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Quote:
Originally posted by sherr20:
...but I had to read your response 3 times and I'm still sitting here saying how the hell am I going to do that? [img]graemlins/clonk.gif[/img]
Sorry about that, I was trying to compromise between giving an over-view and a dissertation. I'm sure I could have done a better job.

-dnult

Dave
========================
68 Coupe, 350 w/ Edelbrock Performer RPM heads, cam, intake, 700R4, Dave's small body HEI
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post #6 of 8 (permalink) Old Oct 4th, 03, 07:52 AM Thread Starter
 
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No probs, I just realized I dont have access to any of the things that you mentioned, and I would probably burn out the new one trying to test.
Thanks [img]smile.gif[/img]
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post #7 of 8 (permalink) Old Oct 4th, 03, 02:13 PM
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Stingr's advice is the way to go them. It's a version of method B - using a frequency counter. Except the reference tach becomes your frequency counter. Calibration of a tach isn't all that critical anyway (+/- 50 RPMs or so). So as long as it's wired and setup correctly (8cyl vs. 6cyl etc.) it should be plenty close.

-dnult

Dave
========================
68 Coupe, 350 w/ Edelbrock Performer RPM heads, cam, intake, 700R4, Dave's small body HEI
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post #8 of 8 (permalink) Old Oct 6th, 03, 07:58 PM
 
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If it's done Stingr's way. From my limited knowledge of tachs, I'm assuming there should be +12V, -coil, and ground... Anyone know which post is which on the OER repro tach?
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