Oxygen sensor & cat retrofit

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tlake
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Oxygen sensor & cat retrofit

Post by tlake »

If you have a Euro car with L-jet, I am wondering if the aftermarket has a piggyback device (corrective signal back to the ECU) to allow you to fit a 3 way cat and oxygen sensor :?: Basically doing what the factory US spec 1979-81 e12 528i did. I know Euro L-jet ECUs had no provision for the oxygen sensor, and no engine harness wire to the sensor.
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Mike W.
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Re: Oxygen sensor & cat retrofit

Post by Mike W. »

tlake wrote: Mon Jan 04, 2021 2:33 pm If you have a Euro car with L-jet, I am wondering if the aftermarket has a piggyback device (corrective signal back to the ECU) to allow you to fit a 3 way cat and oxygen sensor :?: Basically doing what the factory US spec 1979-81 e12 528i did. I know Euro L-jet ECUs had no provision for the oxygen sensor, and no engine harness wire to the sensor.
Yes, but...

At the time they did that with what was generically called a "Johnson Box" after one of several manufacturers who made them was Johnson. They used the O2 input and intercepted the coolant temp circuit to provide a correction factor on it. It was a common "conversion" for euro cars brought into the US. Now for the but part. They did not have a good reputation for reliability or drivability and while I'm sure there's some left, most have been discarded. There are also stories about how much better and cleaner the car ran after the were removed. They may have been fine when new, but I'm not even sure about that. Other than "Johnson" I don't know who manufactured them, or if they are still in business.
Mike W.



1980 528i, 3.5 euro, 5 speed conversion
1981 528i, 3.6, Recaros and more. Project
1998 328is, quick and efficient, but not satisfying
2000 528iit, Vacation mobile/wife's grocery getter
PatinaBeforePolish
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Re: Oxygen sensor & cat retrofit

Post by PatinaBeforePolish »

Mike - here's a 10 year old post in the e28 forum with some comments from you that may help:

https://www.mye28.com/viewtopic.php?t=98476

It's interesting to compare electronics failures in early BMWs that are starting to pop up to the same thing happening in the Porsche world. After years of use and jiggling around, the sometimes delicate solder joints start to fail. There're enough 944s and 911s around that ECUs and relays are being rebuilt (very affordably) with solid state electronics. Maybe someone's doing this in the BMW world but I haven't heard of it.
79 528i
tlake
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Re: Oxygen sensor & cat retrofit

Post by tlake »

Thanks guys, that's very interesting. I suppose you can't beat factory (i.e. the 1979 528i with lambda sond)

I suppose using a modern aftermarket injection system like Megasquirt would be a way to incorporate a 3 way cat, and get rid of the distributor and AFM at the same time, but that's not inexpensive. :)

I guess if there weren't any pollution laws we would be running triple carbs. :!: :mrgreen:
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Mike W.
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Re: Oxygen sensor & cat retrofit

Post by Mike W. »

I'd say the best, easiest way would be to go to Motronic 1.3. That's what they used on E34s. You would still need to (in an easy installation) retain the distributor, although once reasonably close you could just literally have it distribute the spark, not generate it. No need for a different flywheel, although you would need a different harmonic balancer. Lots of data on it at Mye28, although a bit different since they were already motronic.
Mike W.



1980 528i, 3.5 euro, 5 speed conversion
1981 528i, 3.6, Recaros and more. Project
1998 328is, quick and efficient, but not satisfying
2000 528iit, Vacation mobile/wife's grocery getter
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Lock
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Re: Oxygen sensor & cat retrofit

Post by Lock »

Mike W. wrote: Wed Jan 06, 2021 1:25 pm I'd say the best, easiest way would be to go to Motronic 1.3. That's what they used on E34s. You would still need to (in an easy installation) retain the distributor, although once reasonably close you could just literally have it distribute the spark, not generate it. No need for a different flywheel, although you would need a different harmonic balancer. Lots of data on it at Mye28, although a bit different since they were already motronic.
Agree with this, I was going to say the easiest fix would be to get a US 528i lambda ECU and wire up the o2 sensor and tap an o2 sensor into the exhaust. But upgrading to Motronic 1.3, while it took some time, it wasn't that difficult and has a number of other improvements. I use the e12 distributor and at any speeds and loads it doesn't misfire, so it's clearly 'near enough'. All the other parts swap in like Lego.
1979 528i 5-speed conversion G260/6, Motronic 1.3 179
1980 Honda CX-500
tlake
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Re: Oxygen sensor & cat retrofit

Post by tlake »

Lock wrote: Sat Jan 16, 2021 1:29 pm
Mike W. wrote: Wed Jan 06, 2021 1:25 pm I'd say the best, easiest way would be to go to Motronic 1.3. That's what they used on E34s. You would still need to (in an easy installation) retain the distributor, although once reasonably close you could just literally have it distribute the spark, not generate it. No need for a different flywheel, although you would need a different harmonic balancer. Lots of data on it at Mye28, although a bit different since they were already motronic.
Agree with this, I was going to say the easiest fix would be to get a US 528i lambda ECU and wire up the o2 sensor and tap an o2 sensor into the exhaust. But upgrading to Motronic 1.3, while it took some time, it wasn't that difficult and has a number of other improvements. I use the e12 distributor and at any speeds and loads it doesn't misfire, so it's clearly 'near enough'. All the other parts swap in like Lego.
I was thinking that too concerning using the US 528i ECU :!: Thanks Lock. :)
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