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tach output

Old 02-19-08, 02:37 PM
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tach output

I'm trying to hook up a G2x Datalogger to my FC racecar, and to get the RPMs to read I need to find a 12v square wave tach output from the ignition. It would basically be the same process as hooking up an autometer electronic tach to the car. Has anyone done this before? Any input on where I could pull this from? I suck at electrical, and any help would be great!
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Old 02-19-08, 04:25 PM
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Use the tach output wire off the trailing coil. Configure the logger to 4 cylinder mode.
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Old 02-20-08, 10:06 AM
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Thanks for the response Ludwig! I've gotten it hooked up...after poking around the wiring for a bit I found a tach output I could tap into on the back of the stock cluster. The instructions on the G2x specify that you not hook it up directlly to any coil, so it worked out fine.

I have it set to 4 cylinders and it seems to be reading alright, but I'm showing +/_ 230 rpm low than what it should be. Do you guys have any idea what the ignition on an rx7 sends out signal wise? Would I be better off trying to set it up as oddfire?

I know that Im close but I still need to fudge with it a bit more to get it to read 100% right..any guesses as to what path to take?
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Old 02-20-08, 10:24 AM
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The output on the trailing coil is simply a turn out from the stock circuit that feeds the tach and the same circuit you tapped into on the cluster. Just an FYI for anyone that might be looking to go down the same path. It's a low side output so it's not seeing a huge amount of voltage like you would on the high side of the coil.

The stock tachs in 1st and 2nd gens read quite high. I just finished up tuning a 2nd gen that was idling at 1000 rpm according to the Haltech data but was at 1500 on the tach in the dash. Trust the G2x. I figure Mazda probably fudged tach settings to try to keep people from really revving the **** out of the engine or to make people think they were getting a lot more revs than they really were.
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Old 02-20-08, 10:11 PM
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Yeah, thats what the techs at racetach said...I guess Ill just keep it as is, and not worry!

Thanks again Ludwig...Guess I probably could have saved myself some time and picked out the signal directly from the coil then :\
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