Tacho Output - LS7 Please help...

[V8 Vum]

Does anyone know what type of signal output come from the LS7 GM ECU (white wire) - Labelled Tacho ????

As far as I can tell it is standard. in the same bunch of wires is a speedo output (????) dark green.

If no-one knows, how do I, or where can I find out?

cheers

keith

[Watto GTR]

my ecu is the e67 the signal is a 2 pulse/rev output if thats any help

[V8 Vum]

Watto GTR said:

my ecu is the e67 the signal is a 2 pulse/rev output if thats any help

Thanks

so I have found out that the tacho feed for the SPA dash only requires a resistor if a magneto type ignition system, but will easily take short CDI type pulses up to 500v...So since the engine is not running yet, I need to get confirmation that the output is suitable, and thus complete the wiring and I don't blow up the Dash when I do start the engine .

BTW - what the heck is the speedo wire for? I see no source? Is this redundant?

cheers

Keith

[Watto GTR]

i did not use speedo wire used factory setup as i have factory gauges

[GTR One]

V8 Vum said:

.

BTW - what the heck is the speedo wire for? I see no source? Is this redundant?

Should be a toothed wheel and pickup on one of the driveshafts (so that ECU knows the vehicle speed), that also gets repeated as an output on the wire to the dash. I have aftermarket gauges with a high (ie from ignition coil) and low level (for ECU style output)..though at the end of the day I actually wired the speedo to a front wheel pickup.

[V8 Vum]

GTR One said:

V8 Vum said:

.

BTW - what the heck is the speedo wire for? I see no source? Is this redundant?

Should be a toothed wheel and pickup on one of the driveshafts (so that ECU knows the vehicle speed), that also gets repeated as an output on the wire to the dash. I have aftermarket gauges with a high (ie from ignition coil) and low level (for ECU style output)..though at the end of the day I actually wired the speedo to a front wheel pickup.

I do have an aftermarket cog and pickup sensor - in fact I am flooded with them!

The spa dash has a hall effect unit with magnet, the RaceLogic ones have a pickup (cog type) for each wheel, and for some reason I have another one (cog type)that might have come with the engine originally now I come to think of it.

I would love to double-up where I can otherwise there will be sensors everywhere which is rediculous, but not sure any are compatible with each other! Any electrisical experts out there that can tell me?

So if indeed the latter of the pickups is for the engine, I suppose I need to know where it feeds the LS7 loom! I have gone through all the leads and the only one I can find is this green single wire labelled speedo, which originally I assumed to be an output - so is this the input from sensor to the ECU (only one wire though??), or output from ECU to dash (in which case where is the corresponding input???).

Any help to unravel the above mysteries would be very, very helpful!

cheers

Keith

[GTR One]

V8 Vum said:

GTR One said:

V8 Vum said:

.

BTW - what the heck is the speedo wire for? I see no source? Is this redundant?

I have gone through all the leads and the only one I can find is this green single wire labelled speedo, which originally I assumed to be an output - so is this the input from sensor to the ECU (only one wire though??), or output from ECU to dash (in which case where is the corresponding input???).

Any help to unravel the above mysteries would be very, very helpful!

cheers

Keith

That sounds like the output to the ECU. I seem to remember your ECU and engine being JS supplied? The speed pickup has 3 connections +/-/rtn. PM me and I'll explain..

Edited by GTR One on Thursday 3rd June 02:55

[V8 Vum]

PMd you Liam!

This LS7 Loom is doing my head in!

cheers

Keith