Testing Tach?
Thread Starter
Racer
Joined: Mar 2001
Posts: 327
Likes: 0
From: Southlake, Texas, USA
Testing Tach?
I have always thought the tach in the dash read high as I can peg it at WOT. Bought an Autometer to watch as I want to replace the dash with Digitial. Took it out last night and pegged it at over 8,000. This would be cool if right, but I have my doubts.
Any ideas on how I can verify this?
Thanks
Any ideas on how I can verify this?
Thanks
Melting Slicks
Joined: Dec 2000
Posts: 2,041
Likes: 0
From: Wichita, KS
Re: Testing Tach? (SprintCarDriver)
I just checked mine yesterday on the internet using a gear ratio calculator. I know that I indicated 3300 RPM at 70 MPH and I've got 3.55 gears and 1 to 1 transmission ratio. All that was left was to measure my tire radius from the ground to the center of the axle. With those numbers I was able to tell that my car should have been turning 3308 RPM. Close enough for me. Had I suspected that my speedometer was off I could have borrowed a GPS that has a speed readout or timed the car over a measured mile.
Good luck with it.
Good luck with it.
Team Owner
Joined: Jul 1999
Posts: 65,492
Likes: 230
From: Orange Park Florida
Re: Testing Tach? (SprintCarDriver)
The ONLY way to calibrate a tach is with a digital audio generator/oscillator...
that will give you a fine calibration of the exact freq output to feed into your tach....600 rpm will be only 5 cycles per second/5 hz for you newbies...
so 3000 rpm will be of course 25 hz..... and 6000 rpm will be 50 hz....
to calibrate a tach there is NO other way....
once you know the tach is accurate...you can then for sure do your calculations of tires, gears, tranny sending units/speedo's.....
OH, I happen to have one of those dig-it-all tone generators because I"m a stereo freak....McIntosh, etc.....
GENE
that will give you a fine calibration of the exact freq output to feed into your tach....600 rpm will be only 5 cycles per second/5 hz for you newbies...
so 3000 rpm will be of course 25 hz..... and 6000 rpm will be 50 hz....
to calibrate a tach there is NO other way....
once you know the tach is accurate...you can then for sure do your calculations of tires, gears, tranny sending units/speedo's.....
OH, I happen to have one of those dig-it-all tone generators because I"m a stereo freak....McIntosh, etc.....
GENE
Thread Starter
Racer
Joined: Mar 2001
Posts: 327
Likes: 0
From: Southlake, Texas, USA
Re: Testing Tach? (mrvette)
Ok then, calibrating is out of the question.. I have spliced the wire that goes to the orginal tach. Could I be getting feed back from the orginal tach. Is there another location that can be used. I have a HEI and hooking to the tach plug.
