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Hooking up tacho to MoTeC M4 ecu

Robert_NZ

By Robert_NZ,
in Engines & Forced Induction

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Robert_NZ Newbie

Robert_NZ

Posted
Posted

I'm running a Motec M4 ecu on my RB26 in a S13 200sx and I'm trying to get the tacho to work. I'm using a R32 GTR tacho. I've set up the ECU so one of the AUX outputs is set to the tacho signal. I hooked up a multimeter to this wire and I get a RPM / 10000 signal (ie, 800rpm = 0.08 volts) which I've since found out from other theads that the tacho doesn't use this type of signal.

Is there anything I can do to change this signal so the tacho can read it? Or can I use another signal from the ECU that the tacho can use?

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https://www.sau.com.au/forums/topic/69143-hooking-up-tacho-to-motec-m4-ecu/
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MonstaS4 Collaborator

MonstaS4

Posted
Posted

Most tacho's use frequency to drive them. i.e a fixed duty cycle of 50% and the frequency increases proportionaly with revs. I don't know about the Motec, but my Haltech has a tacho aux. output. You set the "pull-up" value and duty cycle to 50% in the software, and your done. Maybe double check the Motec for this type of output?

MonstaS4 Collaborator

MonstaS4

Posted
Posted

RB30-POWER, the current switchover points are on at 1500 and off at 4250. 'Seat-of-pants' testing suggested a slightly lower switch off point than 4500, but i haven't backed this up with dyno testing. Also, the position of my cam belt tensioners didn't allow the cams to line up correctly, so from memory they are both advanced about 5-7 crank degrees. Me thinks some adjustable gears will be going in shortly.

Sorry bout the hijack Robert_NZ....

RB30-POWER Mentor

RB30-POWER

Posted
Posted

Cheers, yeah it makes sense that the switchoff point would be lower on the larger 3L motor. It would be taking the same air as the rb25det but much lower in the rpm range. With the stock cams anyway.

Also i think the VCT side cam gear could be adjusted by the four bolts on the rear of the gear. Might get that 5 or so degrees back to standard.

I have heard of people adjusting the VCT gear by this method with great results, but i don't know if the adjustment is for that purpose, or wether its to adjust the actual operation of the cam gear mechanism itself.

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