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Help Me Get My Tacho Reading Correctly.

Simon-S14
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Simon-S14 Grand Master

Simon-S14

Posted
Posted

Neo R34 RB25 in a S14.

been running for a while and i wired in a 10K resisitor to the tacho line but that didnt seem to do much as tacho reads bigher then it should. never worried about it but i'd like to get it reading correctly now.

so..what should i do? change the resistor to a higher value? suggestions would be great.

cheers

BH_SLO32 Proficient

BH_SLO32

Posted
Posted

You can use the digital speedo corrector from Jaycar. I built one sometime ago and tested on my R32. You need to adjust the frequency of the pulse and you cant do that with a resistor. With the 6 cylinder motors there are 3 pulses per revolution, with the 4 cylinders there are 2 pulses per revolution. This applies for 4 stroke engines. Consequently the silvia tacho will be out by the ratio of 3/2 (it will read 1.5x higher than actual engine revs).

The resistor trick works with the R31 and VL as these factory tachos are looking for a pulsed feed however the RB20/25 ECU doesn't output a pulsed feed rather it simply earths a supplied power feed at the required frequency.

The digital speedo corrector costs about $50 but requires assembly. It is not overly difficult to assemble. Recalibration of the factory tacho may be your cheaper option :cool:

  • 3 weeks later...
Akshunhiro Rising Star

Akshunhiro

Posted
Posted

I recently went through this on my S13 trying to get the stock tacho working with the RB20 (had a monster tacho on the dash and I needed to get rid of it ASAP!).

You should be able to get a tacho module from a 32 (or any Skyline with a 6) and replace that with the one in the dash on the S14.

I was told to replace the whole tacho but, since it didn't match the dash (and the faces aren't the same size so you get light shining out around it at night), I only replaced the modules (so had to remove needles and carefully set the needle at idle once the 32 tacho module was fitted).

I took it for a drive prior to removal to see what rpm a certain gear sits at while at a particular speed and worked out it was 3rd, 60k's an hour @ 3000rpm. I also noted the idle rpm as this is easier to set the needle by (good luck trying to put the needle on while doing 60k's in 3rd trying to hold 3krpm) but went back to the 60k theory to test it. I did find it was slightly out but I think this could be due to the spacing between the numbers between the two different tacho faces.

Also, the monster tacho wasn't too accurate down low for idle rpm so I just set the stock one at around 850rpm. I am glad to get the stocko working though and have the monster off my dash even though the stocko could be slightly out, I'm not too concerned.

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