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Rob Turbo

Lc-1 Wideband Lambda Wiring

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Rob Turbo

My megasquirt loom is nearly done, just need to crimp a few more terminals onto the engine bay plug, solder all the wires to the ecu plug and wire in the lambda sensor, but I want to make sure it's right because once I get it in the car it will be a right ball ache to change!

 

Basically I know what everything is going to be doing, the 2 sensor wires will be going to the ecu and the afr gauge, the + wire will be going to the switched live which is quite simple, but the fitting instructions say to earth the 2 earth wires to to the same point on the block, yet it also told me to run all the wires into the car, so should I earth it to the sensor ground pin of the ecu (which provides an earth for all the sensors) or join the 2 wires together and run one wire back out of the car to the earth on the gearbox, or, extend both wires back out to the earth point on the gearbox?

 

Or, does it not matter as long as it's got an earth?

 

Thanks,

Rob

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perry318888

hi mate, im not sure where all your wiring is going but an earth is an earth! as long as you make sure the surface is clean (scratch the metal) it will earth fine. :D

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jackherer
hi mate, im not sure where all your wiring is going but an earth is an earth! as long as you make sure the surface is clean (scratch the metal) it will earth fine. :D

 

Actually a lot of sensors and specifically the one in question require an earth to be connected at the same point as other equipment they are interfacing with such as an ECU. If you use an earth in another place the tiny but nonetheless present voltage drop can confuse things.

 

Edit: http://www.innovatemotorsports.com/resources/grounding.php

Edited by jackherer

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Rob Turbo
Actually a lot of sensors and specifically the one in question require an earth to be connected at the same point as other equipment they are interfacing with such as an ECU. If you use an earth in another place the tiny but nonetheless present voltage drop can confuse things.

 

Edit: http://www.innovatemotorsports.com/resources/grounding.php

 

That's what I read, but in the instructions on the cd that came with it, it's just that with the megasquirt having a sensor earth output I wasn't sure if I should use that or run the earth wires back out to the earth point on the gearbox.

 

Thanks,

Rob

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pug_ham

On any wiring conversion's I've done I always use the same point for all management system earths, the gearbox earth stud.

 

Graham.

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Daz_C

I'm pretty sure that I read somewhere when I fitted mine (probably on the Innovate Forum) that they say to run 2 SEPERATE earth wires to the same earthing point. I ran mine directly to the battery earth.

Apparantly sensor earth on the Ecu will not be good enough for the LC-1.

 

This may help you understand why you need a good earth http://www.innovatemotorsports.com/forums/...read.php?t=3410

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Rob Turbo

So would it be better to trim the outer plastic cover right back to the engine bay and only run the power and signal wires into the car, leaving the earths in the engine bay to connect to the earth point along with all the other earths?

 

Thanks,

Rob

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DrSarty

I think the wording in the Innovate LC-1 instructions is dog s*it!

 

My interpretation of Innovate's 2 seemingly seperate suggestions is to join the blue & white (the instructions says 'silver'!) earth wires to a single lug (soldered) and then earth that as Graham says to a really good, clean earth stud on the gearbox, to which you are also earthing your ECU. This is the important bit I believe.

 

What you don't want - again, as I understand it - is the heater element of the LC-1 earthed seperately from the probe/sensor itself and the ECU earthed somewhere else again.

 

Simple terms: earth the ECU & LC-1 (both earths blue & white) on a nice fat, clean stud on the gearbox, that is also earthed with a chunky strap to the chassis.

 

As for the other wires: the red 12v switched LC-1 wire you can either power up inside the car or in the engine bay; the yellow you can tape-off (that's for narrow band IIRC) and take the brown to the MS O2 sensor signal input. The black wire: well I just put a bullet connector on it ready to take a short length of wire which incorporates the calibration LED and a little croc clip on the end.

 

REMEMBER: If you've followed the MS relay box instructions, your LC-1 will only fire up when the fuel pump relay is live, which on ignition switch position one is only for about half a second, and this isn't enough to do initial LC-1 calibration. So, for calibration, I have a second bullet connector teed off the 12v switched red wire, and have another short length of wire with another croc clip on. You attach the live croc clip to the batt positive when you want to calibrate, and when you add in the LED earth wire and ground that, you can do the calibration and set-up process. You can do all this with the ignition off. The just remove the croc clip wires once the LED has given all the flashing/steady patterns it should give you.

 

I hope that's not too confusing and helps you and anyone else tearing their hair out at Innovate's crappy, contradictory instructions.

Edited by DrSarty

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Rob Turbo

Thanks for that, I'll leave most of the wiring in the engine bay then and only run the 2 signal wires and the 2 serial plugs into the car (I'm using the narrow band signal for the afr gauge)

 

Now that's cleared up I'll get the soldering iron fired up and get cracking!!

 

Thanks,

Rob

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Rob Turbo

Just been thinking, what's the worst that will happen if I earthed the sensor in the wrong place? The earth wires for the sensor are different thicknesses and the earths to the ecu are different again so won't the "ground offset" be different anyway?

 

I'm still going to do it as best I can, just wondering what would happen if I didn't?

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DrSarty
Just been thinking, what's the worst that will happen if I earthed the sensor in the wrong place? The earth wires for the sensor are different thicknesses and the earths to the ecu are different again so won't the "ground offset" be different anyway?

 

I'm still going to do it as best I can, just wondering what would happen if I didn't?

 

I'm advising that you don't take the chance matey. It's your £100+, but why throw it away?

 

Just wire it up how we've suggested and you'll reduce/eliminate the risks of frying either your LC-1, your ECU or both.

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Rob Turbo

I intend on doing it right, I was just curious as to what would happen!

 

One more thing though, I take it it's ok to shorten the wires, or do I have to loop them about in the loom a bit?

 

Thanks,

Rob

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Daz_C
I intend on doing it right, I was just curious as to what would happen!

 

One more thing though, I take it it's ok to shorten the wires, or do I have to loop them about in the loom a bit?

 

Thanks,

Rob

 

You can shorten the wires, there's no problem doing that.

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