Monkeybutt2000

Deleting all the emissions on my GC because it will be off-road only. Does anyone know the thread pitch/size for the rear o2? TIA

tiwvr1

might as well keep it in there as a plug.

vadergator

just a guess. it takes a 13/16 wrench to loosen/tighten a sensor ( O2 ) and the threads are smaller by probably a quarter inch. i would guess between a 5/8 or 9/16. you could always call an auto parts store for exact specs.

vadergator

oh, and the O2's are the same size upstream and downstream. they just charge you more for the rear one.

5-90

M18-1.5. Bungs are standard, ask any exhaust shop.

Monkeybutt2000

This is correct. The converter is bad so I really needed to know what size bung to buy.

dave1123

I believe this is right. It just so happens that the check plugs from certain standard transmission Hondas fit also.

Monkeybutt2000

So I'm gona run no-cat into a turbo muffler. I know I'll throw a ce light with no cat but driveability shouldn't be an issue correct?

dave1123

The PCM controls fuel mixtures with feedback from the 02 sensors. I think you're going to have LOTS of problems. Maybe not as long as you maintain the front sensor.

Monkeybutt2000

The front sensor will be intact,I've always been told the rear isn't really that big of a deal.

vadergator

i have heard it from both ends of the tale and i imagine it varies from each vehicle. however, i have an inexpensive tip for you. look up any advance auto parts or auto zone etc. , and look up the muffler sections. you will see tape, pipes, bolts, etc. . because alot of people do what your about to do, a genius came up with an answer to avoid any and all problems. i cannot remember the exact name for it but, you can find it on the store sites. instead of installing the aluminum flex pipe, they have a exhaust piece extension with the O2 sensor hole in it. you cut out your catalytic converter and install this little piece in it's place with either a straightpipe or flex to your muffler. thing is, this way your computer never realizes the cat is gone because it is able to still get a downsream O2 reading. i want to say it costs between $18 - $ 25 dollars. better to be safe than sorry out in the middle of nowhere.

5-90

The upstream HEGO is there to handle fuel trim duties.

The downstream HEGO monitors catalyst efficiency, and has nothing to do wtih fuel trim.

You may want a simulator to make the ECU think that the DHEGO is still in place, check with speed shops for that.

(Since you said you're making it a dedicated trail rig, I'm not so worried about EPA regs for "vehicles operated on public roadways" - else I'd advise you to not modify the system.)

However, if you do remove the cat (which I don't suggest, we get enough flak from the Greenies...) make sure that some variety of spark arrestor is installed - since that's what the cat also does. Those EPA regs may not apply to off-highway vehicles, but the spark arrestor is required for any off-highway vehicle - both by feds, and most states (no sense in starting a wildfire, y'know?)