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Tach Issue after swap


~KnuckleDuster~

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Need a bit of help here gents. I wanto keep my stock tach but were unsure on how exactly to hook it up. Theres an MSD Dis-Tach Driver installed but not currently wired to anything. I did a bit of searching and found this http://wiki.r31skylineclub.com/index.php?title=Wiring_a_Silvertop_RB20DET_into_an_R31

 

..but not sure since its an rb20. Any help would be greatly appreciated! -Adam

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Adam,

 

Is there any particular reason why you want to keep the stock tach?

As far as I know there isnt any stock tachs compatable with the RB.

 

Autometer makes tachs that fit almost perfect in the stock tach hole on the dash.

 

I just wanted to leave the interior somewhat original.. Guess Ill have to upgrade.

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Anybody care to explain how to get the auto meter tach to work off the engine harness. I'm using the HKS vpro and it doesn't have a direct tach output. i have to use the coil harness. i wired in a tach adapter according to the instructions but it didnt work

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Anybody care to explain how to get the auto meter tach to work off the engine harness. I'm using the HKS vpro and it doesn't have a direct tach output. i have to use the coil harness. i wired in a tach adapter according to the instructions but it didnt work <

 

I always thought the only way was to use the tach adaptor. I know there is a cheap one from summit for 30 bucks.

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  • 1 month later...
  • 2 weeks later...
I always thought the only way was to use the tach adaptor. I know there is a cheap one from summit for 30 bucks.

 

Yea im pretty sure also... Just wondering if anyone had done it and maybe have a diagram with wire colors and all.

 

Again i have to pull my tach signal from the engine harness. There is no tach out (that i know of) as the HKS computer was designed so you could maintain the stock computer for all the gages and crap.

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  • 2 weeks later...

Most Tachs old or new use a 12v signal from the coil. If you can find a 5v signal then do what china elephants suggested. It is called a pull up resistor. It pulls the 5v signal up to 12v so the tach can trigger off that voltage level.

I have the autometer tach and this is what I did. works great.

 

Tachsetup.jpg

 

Should be able to do the same thing with the stock tach.

Might want to use a 10k resistor to be safe.

icon12.gif

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Most Tachs old or new use a 12v signal from the coil. If you can find a 5v signal then do what china elephants suggested. It is called a pull up resistor. It pulls the 5v signal up to 12v so the tach can trigger off that voltage level.

I have the autometer tach and this is what I did. works great.

 

Tachsetup.jpg

 

Should be able to do the same thing with the stock tach.

Might want to use a 10k resistor to be safe.

icon12.gif

 

 

O yeah I got my RB25det to work with the autometer tach. Works great. Thanks for the diagram

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Anybody care to explain how to get the auto meter tach to work off the engine harness. I'm using the HKS vpro and it doesn't have a direct tach output. i have to use the coil harness. i wired in a tach adapter according to the instructions but it didnt work <

 

 

It's actually quite simple.

 

Theres a 12V power source coming from the ignitor chip that powers all six coils. Cut the power source wire after the ignitor chip, before the six coils and splice in the tach adaper. I Know MSD and Autometer make one and share the same wire colors. The red wire connects to the power source wire towards the ignitor chip/ignition relay direction, the red/green wire connects to the other power source wire in the direction of the six coils. The other two wires are ground and tach signal.

 

It basically works by splicing into the coil power source wire and "sences" when a coil draws current and transmits that into a tach signal.

 

Just makes sure you have a tach adapter for a distributorless ignition system. That's MSD # 8913.

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