Installing AFR gauge while keeping Lambda

[RDM]

Good afternoon!

I was fortunate enough to buy a custom quad gauge from John Bell for my '80SC. It's all conceptually straightforward, but the difficulty is in the details, particularly the oxygen sensor wiring. Help me out here.

So here is the wiring diagram for the Lambda system



At Rob's suggestion, I have an Innovate LC-2 interface box. with the following wires to be connected.
- Red to +12V, proposed terminal 30 on the frequency valve relay
- Black to ground, proposed FRV relay terminal 85, (also to gauge?) (also to Lambda box terminal 2 or 4?)
- Yellow (0-5 V) to gauge
- Brown (0-1 V)to lambda box terminal 2 or 4....

This is where I am stuck. The wiring diagram shows the oxygen sensor connecting to the Lambda box terminals 2 and 4 through what looks to me like a coax cable. The LC-2 has a single wire for the low voltage output.
- which pin should the yellow wire connect to, 2 or 4?
- should something else be connected to the other, unused 2 or 4 pin, like a ground?
- where is the best place to connect these wires? In the engine bay connector, or open the Lambda box connector somehow?

You might get the impression I'm over my head, and your impression would be right. But I'm still having fun and learning stuff so I'll press on.

[76FJ55]

For the O2 sensor Pin 2 is the signal to the control unit.

pin 4 is the shielding around the signal wire to cut down on interference in the signal. Pin 4 is essentially the ground connection for that shield.

the Lambda control unit is expecting a 0-1 V signal (oscillating around 0.5). this would be the brown wire out of the Innovate LC-2.

the yellow wire would go to the wideband display at the bottom of you new gauge.

I don't know your layout, so can't say where the most convenient location to connect the wires would be, but you can connect the LC-2 brown wire in the engine bay at the original O2 sensor plug. if you do this the shielding would still be in place around the original signal wire, so you wouldn't mess with pins 2 or 4 at the control unit.

[AndrewCologne]

In the innovate setup software you maybe have to change from "0.00 Volt" to "high impendance" output in the input field "Warmup output" – as the original ECU expects that from a cold state of an original non heated OX sensor.

[RDM]

Originally Posted by 76FJ55

I don't know your layout, so can't say where the most convenient location to connect the wires would be, but you can connect the LC-2 brown wire in the engine bay at the original O2 sensor plug. if you do this the shielding would still be in place around the original signal wire, so you wouldn't mess with pins 2 or 4 at the control unit.

Layout is pretty much stock SC, especially in the engine bay.

Given the easy access to three of the four needed LC-2 connections on the left side of the engine bay, I am sorely tempted to put the LC-2 there, behind the plastic cover. Then, the only wire to run forward would be to the gauge. Or are conditions there too harsh for the LC-2?

So under this plan,
- Red to +12V, proposed to rear fuse box. I don't have a rear blower, so that's easy
- Black to ground, proposed just behind the rear fuse box. I'm not clear if I also need to run this ground to the gauge, and / or also to the OXS coax shielding.
- Yellow (0-5 V) to gauge
- Brown (0-1 V)to lambda box. Does this particular connector have a name or known source? It's a one-wire connection as far as I can see, and I'd rather not cut the connector off of a perfectly good oxygen sensor.

Originally Posted by AndrewCologne

In the innovate setup software you maybe have to change from "0.00 Volt" to "high impendance" output in the input field "Warmup output" – as the original ECU expects that from a cold state of an original non heated OX sensor.

Andrew,

I dread this as I don't own a Windows computer with a serial port, and I think that's what is required to change settings. The oxygen sensor input is ignored until the motor warms up- how does the oxs warm-up time compare to engine warm up time? Or is this a warm start problem?

[76FJ55]

the brown wire is an Analog Output. in this case you will be using it as a simulated narrowband O2 signal.

as for the ground locations, ideally you would add/extend the ground to all the affected locations, so one to the wideband mixture display gauge, and a second location at the Lambda control unit.

Sorry don't know a source for the O2 connector.

[AndrewCologne]

Originally Posted by RDM

- Brown (0-1 V) to lambda box. Does this particular connector have a name or known source? It's a one-wire connection as far as I can see, and I'd rather not cut the connector off of a perfectly good oxygen sensor.

It's port 2 of the ECU which also leads to the original OXS sensor. You can open the Sheathing of the wire loom which comes from the big connector which will be fastened to the ECU, there the inner wire of the big green shielded wire is the one where you can connect the brown wire of the Innovate controller to.
https://www.sip-scootershop.com/en/product/wire-brakeout-plug-1-0-2-5mm-cable-600v-105-c_10156400

I dread this as I don't own a Windows computer with a serial port,

Im on Mac OS and "Parallels" Wirth a USB2Serial adapter is the ticket here.

and I think that's what is required to change settings.

The controller needs a time to initialize where in that time no signal is provided via the brown wire. IF the controller in that time provides a simple 0v signal then the ECU does behave as if the engines leans out and a huge enrichment will be the result, so a "high impendance" in the software set up, means a simple line cut off by the controller, will make behave the ECU as if the sensor has been disconnected and during that time the enrichment will be static at 50% – means open loop mode until the controller is initialized where then the correct voltage 0-1v will be provided and the ECU switches to closed loop mode.

The oxygen sensor input is ignored until the motor warms up- how does the oxs warm-up time compare to engine warm up time? Or is this a warm start problem?

It depends on the environment temperature and therefore how long the engine oil will need to exceed 15°C to make the ECU switch to closed loop. The initializing time of the Innovate sensor is static and takes about 30 sec IIRC.

[porschedude996]

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