Oxygen sensor placement upon M117 dual conversion?

[Hit Man X]

Okay gang, Euro true dual logs with downpipes are now installed on the '91 560. Sure, not as good as the four piece setup found on the 10:1 cars, but this really flows a pile better for cheap. I paid around $120 for my manifolds and downpipes. Welded the stuff up myself with the help of my brother.

I will post pictures if anyone is interested, not much to see really, just no more precat and no more 1-5/8" crossover pipe from the driver's bank to the passenger bank.

Anyway, the OE setup had all eight cylinders mixing into the passenger side collector with one oxygen sensor beside the precat. I am still using the OE cat in the OE position.



So this is the question:

Is there an ideal place to mount the sensor given the lack of space? I would like the sensor to act similar to stock if possible (drill and weld my O2 bung to the cat body to read mixture from both banks?)

If this is not possible, which bank is preferred for the single sensor input... driver or passenger?



Thanks

[Hit Man X]

Here are a few lame cellular phone pics of the conversion, first the crossover pipe with the heat shield removed... how in the world that motor breathed through that is beyond me. Second shows that I am still using the OE MB cat. I just flipped one of the OE pipes that was to the precat, chopped it down with my saw. Maybe I will run a high flow cat in the future, maybe not. I do not expect a huge gain going from the OE cat to a high flow, so I just left that factory unit in place.

The manifolds/downpipes are off a grey market 500SEL. Nothing special, just true dual euro logs. I had to use new exhaust port studs for the install on and new copper nuts. I also opted to install new gaskets. EGR is blocked off, heat shields reinstalled.

Driver side installs from the top, with the cam cover removed. Passenger side installs from the bottom, with the cam cover removed. It is very tight in there.

Pretty simple swap.

[alabbasi]

Eric, how is this project going? On my Euro 560 with logs, the O2 sensor was in front of the secondary cat where they joined. I removed the cat after some running issues and welded a bung to one of the pipes, no problems.

[Hit Man X]

Oh, I should have updated!

O2 is placed on the driver side of the cat, just behind the downpipe. I used a stepped drill bit, welded in the bung. Does not seem to have any issues for the last few years.

Worthwhile mod for sure. The US Cat assembly is comical at best. The car is now exempt, so if I had "a do over" I would probably dump the main cat too.