Closed Loop with 1 O2 Sensor Possible? - Single Turbo

So I've got a single turbo setup with a narrow band in the RHS bank and a narrow band in the dump pipe. Been trying to get it to work in closed loop but one side just thinks it is rich and tries to lean out to compensate but it's already lean.

I was thinking to try and get the E38 to run the injectors in closed loop with only the narrow band in the dump pipe, just like the engines of the 1980-90's used to. I've tried disconnecting the narrow band on the RHS and then setting the DTC to No Mil Light so it stayts in fault but the ECM then only wants to trim one side. My only other thought is to put the RHS narrow band into the dump pipe as well.

Any ideas or is there a way to tune this properly in my current setup?

Just a wild guess here but it might be worth trying connecting both O2 sensor ECU signal inputs to the one sensor. I believe the ECU has separate closed loops for each bank but it might not confuse it to see both banks synchronized. On my logs I see that happen sometimes by coincidence. If the STFTs go crazy after trying this then I'd say it's a failed experiment.

It needs two o2 sensors for closed loop.

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Originally Posted by 5FDP

It needs two o2 sensors for closed loop.

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Can they be in the same pipe?
Or do they expect to see some differences based off bank commands/pulse widths?

I have no personal experience, but I'm going to assume they need to be before your exhaust is merged. Otherwise it won't know which side needs adjusting to correct the fueling.

In an extreme example, if it's aiming for 1.0 Lamda, you could have one bank running at .7 and one running at 1.3 and it would average to 1 and the o2s be happy.

your examples of 80/90s cars probably had throttle body injection, rather than port injection so bank to bank fueling wouldn't be individually ajustable.

is it a weekender or drag use ? u could just go full time OL if its easier just keep a WB working in the car all all times just encase, i was driving around for years OL and once u get it dialed in over the year for the seasons it works quite well, or ur prob best to weld a bung on the other bank also so u can use both for CL

Works in dodges but not GM! Best bet is to run OL

it can be done...

Awesome!!! Could you please share the details of how it can be done?

parameter is not available in hpt.

A quick search turned up this video of a gen 3.

https://m.youtube.com/watch?v=sZpYKgrDP5k

My gen 4 e67 has injector bank select which he used. Won't hurt to try.

Disclaimer I have no idea if it'll work. Just trying to be helpful.

i would run the car in open loop for sure, you dont want 1 bank over or run less fuel

open loop all day.. don’t do any hacks with one bank….

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Originally Posted by SultanHassanMasTuning

i would run the car in open loop for sure, you dont want 1 bank over or run less fuel

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If you have split BLMs you have other issues. The motor shouldn't have any issues at all between banks. If you have an exhaust leak in one bank it will overfuel in one bank anyways. So running one O2 sensor is not really a problem nor a disadvantage. Just lack of information for diagnosis purposes.