Tacho Signal

[Rancher]

Hello all

I drive an RB20DE powered Silvia, the guy the owned the car before me did the conversion from the CA18DE. The tacho doesnt work, I know its a 4cyl tacho, and it's a 6cyl enginge, but there is no Signal. No signal from the ecu either.

Ive bought a tacho (Sparco 4 1/2") set it to 6cyl, and no Singal from either the ecu and the CAS. I know I am plugging it into the tacho signal wire from the ecu, I'm not silly.

Can someone please help, Its rather annoying not having a tacho, and I cant figure this out. If you can fix it, I'll be forever in your debt.

I'm sorry for posting something like this on my first post, But I'll post more, I havnt had the car for long ^^;

[BH_SLO32]

I assume you are looking for a DC voltage at pin 7? As the output is a low voltage supply I would expect that the ECU uses a built-in circuit which uses the ignition timing as an input to generate the tacho output signal. If you are not getting an output from pin 7 then it maybe an internal fault in the ECU.

The fault may have occurred if the circuit was overloaded due to incorrect wiring or possible shorting when the conversion was undertaken. If you have access to another ECU you could try it but if the wire from pin 7 is currently connected to the Silvia body loom then it would pay to disconnect this before plugging in the other ECU to prevent possible shorting in the event the conversion wiring is incorrect.

Incidentally I recently purchased a digital speed correcting kit from Jaycar for about $45 which I tested on my R32 with RB25det and an adjustable digital tacho (4 or 6 cylinder selection). I was able to adjust the 6 cylinder tacho signal to give a 4 cylinder signal for driving a 4 cylinder tacho (the digital tacho in this case). Some food for thought.

As with my digital tacho I would expect the Sparco tacho has provision for both a low and high voltage input? If so, make sure you have not hooked up the wire from pin 7 to the high voltage input.

Hope this helps.

Cheers

Edited May 12, 2006 by BH_SLO32

[Rancher]

I didnt know that there was a high and low voltage signal actually, So I'm looking into that. But my tacho doesnt have the high/low switch, just 4/6/8. When its on 6cyl mode from the CAS it goes up to about 2500RPM and wont go any higher, even if I'm revving the tits off it >.<

If anyone in the brisbane has an RB20DE ECU they wouldnt mind me using to test the tacho, it would be grealy appreciated.

[BH_SLO32]

I didnt know that there was a high and low voltage signal actually,

I wasn't aware either until I read it in the instructions for the digital tacho which has provision for both low and high voltage inputs. Traditionally tachos are driven off the negative side of the coil and the instructions refer to this input as a "high voltage" input. I can't see how as the tacho wire should be connected to the switched side of the primary coil which typically operates between 8-12V DC. In any instance the instructions recommended using 250VAC rated wire if the coil input was used, go figure???

Anyway, if you have managed to get the tacho to work already I would suggest the signal strenght is ok. Can you please explain where you got the signal feed from the CAS? I assume you are refering to the Crank Angle Sensor (CAS).

The output signal from the ECU at idle is about 1V if measuring DC voltage. The signal is actually a pulsed DC wave with a voltage of about 6V which you would see with an oscilloscope.

Sorry this probably doesn't really help.

Cheers,

Edited May 13, 2006 by BH_SLO32

[Rancher]

Well, on the CAS there are 4 wires,

Green with black follow,

Green with yellow follow,

Black with yellow follow, and

Black

The one the gives the Signal (only worked with my dash tacho, and went way to high to be used) is the Green with black follow.

I stll havnt gotten it to work, though. Your idea's have really helped, I actualy went to Jcar to find the Digital tacho, but it was about $50 more then I could afford, and in doubt that it would work stopped me from using other funds.

[Rancher]

Still havnt fixed the problem. Unable to get an ECU or another tacho to try. Would love to hear if anyone else has had a similer problem and how they fixed it.

Or if its just a simple as replacing the ECU (Which I cant afford, fuel is bad enough getting to work).

[BH_SLO32]

The one the gives the Signal (only worked with my dash tacho, and went way to high to be used) is the Green with black follow.

I stll havnt gotten it to work, though. Your idea's have really helped, I actualy went to Jcar to find the Digital tacho, but it was about $50 more then I could afford, and in doubt that it would work stopped me from using other funds.

I have an idea. You may be able to use the signal from the CAS (presumably its the 120 deg signal) and modify it with the Jaycar digital speedo corrector unit. I have built the circuit and would be happy to donate for trial. I'm on Brisbanes Southside as well.

Cheers,

Ben

[HR32_GTS-T]

rancher u still having problems with that bloddy thing buy a skyline an u'll have no worries...Joel