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cRaig

Motronic 3.1 Running A Lambda

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cRaig

Im strongly considering running a lambda sensor when I convert to motronic 3.1, as it seems sensible to do it before the loom is in the car etc, I was wondering if anyone had any thoughts on a suitable lambda? Brian J has suggested doing it with a XM lambda (as he used on his setup) But they seem quite expensive/hard to come by.

 

I was wondering, as its a fairly old/simple management, would this bosch universal 4wire be suitable? It just needs a plug sorting, I imagine a JPT plug or similar would be fine, I understand from research that they shouldnt be soldered to the rest of the loom.

 

http://www.ebay.co.uk/itm/4-WIRE-UNIVERSAL-LAMBDA-SENSOR-GENUINE-BOSCH-/281165331880?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item4176c27da8

 

Another question, with regards to welding in a boss- is there a standard distance down the downpipe they should be? Presumably the same as the cat equiped 205s? Does anyone have a measurement or a pic of a 205 downpipe with a lambda?

 

Cheers,

 

Craig

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lapr

If your still about this way mate, ive still got my standard exhaust lying about if you wanted to come take some measurements...

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brian j

I don't think there's anything special about the xm lambda. I have it because I got it new and genuine for £15 on eBay. I suspect a decent 4 wire is fine. On position, you can't really go wrong. It has to be after the downpipe split, but before the pipe narrows just after the split. That gives a distance of about 50mm and the lambda is around 20mmso not much leeway. It can't be on the bottom half of the pipe or water can build up in it and cause damage. It can't face up or toward the gear linkage or it fouls, so you have a really small available space. I just put it in the middle of that space, just above the exhaust centreline.

 

I hope that helps.

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pug_ham

Any decent lambda will suffice, I'd say with an oe plug & not universal but, if you crimp the proper terminals & plug to suit it should be fine.

 

Wiring is dead easy, only one ecu pin needs moving iirc, a switched 12v to the sensor & join the earth from the sensor into the ecu pin & you're done.

 

I just got the boss fitted into my four branch when I was having the swivel joint changed to a flexi type, the place I got that done had the boss in stock & welded it in after the flexi joint, roughly in the same place as the location of the cat equipped cars lambda boss.

 

There are pics in a topic of mine somewhere, I'll dig out a link later if I can.

 

Best mod you can do imo.

 

g

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cybernck

Bumping and old topic but I haven't realised you could run lambda on MP3.1?

 

Does it need to be "enabled" in the ECU as well or does it simply work by itself?

 

I am confused as M1.3 uses/requires lambda as standard and wouldn't run well without one.

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pug_ham

No, simply re-pin the required wires in the ecu plug & it works straight away (at least on the ZX volcane ecu I have).

 

Add an ignition switched feed for the lambda & I spiced the earth into the ecu pin to keep things as neat & oe as possible.

 

g

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cRaig

Bit of a bump, but I've finally pulled my finger out to sort the Motronic 3.1 loom. (95% there now, all the bits moved to the right place, ign amp, relays moved to up by the ecu, have wired in the 205 brown plugs to connect to the dash loom etc)

 

With regards to the lambda and mixture pot- does someone have what-goes-to-what with wire/pin outs to hand? The lambda I have is a universal Bosch one, (2 white, 1 black, 1 grey, but no other markings) and the mixture pot is

Pin 1: M8 Earth

Pin 2: 24 White

Pin 3: 9A Blue

 

I'm assuming this the correct wiring for the lambda? Found on google..

 

4WireDiagram.png

 

Thanks,

Craig

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cRaig

Bump!

 

Have now tackled the last of the loom, putting new pins and plugs all round, so its just the lambda wiring to sort, if someone could give me a more exact heads up of what needs doing!? Then I can test fit the loom! :)

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brian j

Hi Craig.

 

I had to scratch my head about this because it has been a while, but:

 

The lambda sensor needs 4 wires:

Pin 8 ECU - Lambda Ground

Pin 24 ECU - Lambda Signal

Heater circuit.

 

The heater wires are white and interchangeable - one needs a switched 12v feed (The fuel pump relay is convenient and what I did) - it is probably wise to have the feed individually fused, because it is a lower power draw and therefore thinner wiring than the fuel pump). The other needs a good body earth. (NOT through the ECU)

 

The grey wire goes to ECU pin 8 - this is un-populated by default. so you will need a suitable connector and length of wire. (I stole one from another ECU Loom, but you could use the wire and connector which you remove from pin 9)

The black wire goes to ECU PIN 24. (Assuming your Bosch lambda diagram is correct. That is how the wires are coded on mine though, so it looks right)

ECU Pin 9 is no longer used in a lambda setup..

 

In addition, while making up the loom I would fit an inertia switch from a 306/406etc. into the fuel pump relay low power feed to provide a safety cut for the fuel pump in the event of an accident. The switch is mounted on the front of the drivers side suspension turret on some later 205s if you want a factory looking installation.

 

 

The information is all in the following two places:

 

http://www.euroscan.hu/files/mp31.pdf

http://forum.205gtidrivers.com/index.php?showtopic=137889

 

This one you probably know about, but was also helpful:

http://forum.205gtidrivers.com/index.php?showtopic=72242

 

I hope that helps.

 

Brian

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pug_ham

When I fitted a Lambda sensor to my MP3.1 install I used the ecu earth along with fitting the sensor pins to the new locations on the ecu plug & also used the fuel pump feed for the lambda 12v.

 

Basically using the same pins etc as the S1 106 rallye for the lamdba, maybe a fuse in the lambda power would be a good idea which I'll add shortly.

 

g

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cRaig

I was thinking of using the earth from the ignition amplifier for the lambda, which goes to the brown under dash multiplug, rather than the ECU pin- unless anyone can suggest that would be a bad idea? Ive ordered an additional inline fuse holder to go next to the fuse by the relays :)

 

So looking forward to Motronic-ness now! :)

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brian j

I think you need to use the ECU pin for the signal earth to be sure to avoid odd readingswith resistance in the earth connections.

 

The heater earth I just wired into a suitable earthing point on the body.

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cRaig

Hello again,

 

Finally got around to marking up the exhaust, interpreting Brian's guide to the location of the lambda- and I seem to have cocked it up, as Ive still hit the downpipe split!

 

Does anyone know how much futher back I should locate it? Brian said it should be before the narrowing of the pipe, but I poked a wire in the hole, and I think the divider continues until the ribbed narrowing part! Confused!

 

22055169954_939e371695_c.jpg

 

Cheers,

Craig

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pug_ham

I did mine (all be it in a four branch manifold) slightly further back than that, basically after where it has narrowed down at a similar point to an oe fit cat downpipe.

 

First go as above;

 

post-71-0-01248500-1446503512_thumb.jpg

 

This was too short to mate up with the standard cat middle box I planned to use so I modified it further;

 

post-71-0-72947400-1446503529_thumb.jpg

 

As fitted;

 

post-71-0-99168500-1446503543_thumb.jpg

 

As you can see, I fitted it quite a long way back so I had quite a lot of pipe to play with.

 

g

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cRaig

Thanks for the pics Graham :) I've offered the exhaust up again, and moved it quite a bit further back. Luckily only a small hole to weld up! :D

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welshpug

on the narrower part would be perfectly fine, I angled my boss for clearance, it was about an inch tall at least, so I cut it in half, as the thread on the lambda is only 1/4" tall or thereabouts.

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cRaig

Yeah, that brings me onto another question I was going to ask Mei, the boss is rather tall- is the lambda better closer to the exhuast flow, or doesn't it make any difference? I was thinking of chopping about 1cm off the boss, as you can see in the pic, it is quite tall. If it doesnt make any difference, and the clearance is ok, I may well leave it.

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welshpug

i just noticed it, that's about the same size as the one I cut in half.

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cRaig

Cool. Its threaded all the way, so I'll lop some off it :)

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