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is it necessary to disable/disconnect the stock tach, in order for an aftermarket tach to function properly, or can they both do their thing without interfering with each other?
It doesn't matter do it either way.....use one, two, or none. I use the stock atari gauge along with a shift light that's connected/piggybacked to the same "stock" tach wire right before the main cluster connector. You will notice that the stock atari gauge is pretty accurate - until you really get on the throttle and hop on the RPMs there is a serious momentary "lag".
Last edited by engle1147; Mar 18, 2011 at 10:12 PM.
Reason: pics
that momentary/permanent lag is why I am asking...who needs a tach unless they on on the gas,
and since the Atari fails to keep up, it gets a big "F" for fail, as in my case, I hit my fuel cutoff set at 6200, and the tach shows 5200 rpm, way too slow and death to a motor.
don't want to hang another thing on the cockpit, but this is just a bit of insurance...thanks for the info...
The tach light installation pictured is installed on an '89 auto' that spins up pretty damn quick for a L98. I can data log a run and it will shift right @ 5200 consitantly...when my shift light comes on (set @ 5K) my Atari RPM gauge only reads 4700 - 4800.
If your drive your car "hard" I would highly recommend a seprate shift light for any Atari clustered 'vette using a manual transmission....I'll bet your shifting 300 to 600 rpm higher than you think your are.
well a modded engine does want to spin faster, I swap out of a zf6, I kept the dana 44 with the 3.33, with the my built 700r4 first gear, or second or third, i can hold it till it blows.
secondly trying to figure out what rpm I am experiencing valve float, right now I just don't have a clue, to determine if my valve springs are letting go incrementally lower as they age.
I had a blue glowshift light just like yours when I had the stick, and sold it afterwards, I am getting the glowshift digital tach with the shift light, cheap and small, should do the trick
I followed your build back when you did it...it is kinda soon for weak springs. Your sure it is "float"? Over reving and going "lean" by surpassing injector duty cycle will cause a similar kind of "noise".
I must have missed the trany swap you did thought you were still a manual.
Any way try the shift light and watch the stock gauge at the same time...you'll see the difference...it will scare you a little.