Probably every downpipe brand is a little different, but ours comes so close to the exhaust manifold that you can't get a socket over the Oxygen sensor. Borrowed the special one with the slot but the thickness is more than the clearance from the manifold.

So, I'm guessing a stubby open ended 7/8.

Any thoughts on whether it's easier from the top or bottom?

Thanks.

 

Very hard to say, downpipes put the O2 sensor in all kinds of crazy spots. But, in general, I'd think from the top. If you removed the intake plumbing for the secondary turbo you'd probably have really good access.

Generally, O2 sensors aren't torqued that tight. It's just supposed to be enough to crush the crush washer. Also, they come with antisieze on the threads from the manufacturer.

Or get a PowerFC and turn it off .

Dale

 

most downpipes place it in the middle of the pipe facing the engine slightly.

having tuned many 7's it's just easier to get at those from underneath. unless the car has no ABS, but most do.

i also use a full length 7/8" open wrench because you will most likely need the torque to get it loose.

 

May collect moisture and rust if under the downpipe

 

The ABS is still there, so it's probably a toss up.

My full size 7/8 is just too long to work, so I'm going to try a shorter
version and hope there's enough torque.

Thanks