1998 V70 AWD Cat Delete with Photos

[deepsouth]

Hey all--
The cat on my 1998 V70 AWD was fiercely rattling and I (being perpetually poor) didn't have enough dough to replace it so a friend and I decided to delete it. (I had previously removed the propshaft so it wasn't an issue).

First we took off the airbox, and all airpipes and removed both O2 sensors completely. Next we removed the exhaust hangers and exhaust clamp (the one that couples the cat to the rear exhaust, and the hiden one up by the heat shield--breaking both frozen bolts). Then we removed the rear engine heat shield for easy access to the top exhaust bolts. Finally, we cut the exhaust just below the bellows and above the converter thinking that we could then unbolt the exhaust flange and maneuver the top end around the bevel gear front propshaft yoke/flange. Turns out this is very difficult to remove. We finally did get the top of the exhaust out by cutting off the upper mounting bracket (figuring we wouldn't need it because a straight pipe is much lighter than the cat). Once that bracket was cut off we then removed the heat shield and could finally wind the upper S exhaust around the prop flange and pull it out from the bottom. With everything finally off we lined up the old and (soon to be) new and took the appropriate measurements.

Next we cut off the old fitting and welded it into an 18" pipe (see photos) and pieced together the entire thing. We cut off the old O2 bung from the cat and welded in the appropriate place on the straight pipe. Finally we put the entire thing back together using an exhaust clamp up near the bellows. We also used a drilled out spark plug non-fouler as an O2 spacer to be sure the sensors didn't get the same reading and throw codes). Total time from start to finish was about six hours--with a dinner break. I do have to say that the cat on the AWD is serious PITA and not easy to remove without taking off the bevel gear.

Everything is back together and I have driven car about 1000 miles. It's a bit louder but everything is running smoothly with no problems. That said, I am not advocating that anyone violate any federal emission laws but deleting the cat can be done with a bit of patience and minimal welding ability.

Eric

[deepsouth]

Total cost was around $20 bucks. $15 for the exhaust parts (Autozone) and about $5 for the spark plug non-fouler.

[rmmagow]

How are you going to fake out the rear O2 sensor?

[rmmagow]

And as a ps, the fitting at the end of the bevel gear can be removed and greatly adds to getting the thing out.

[deepsouth]

The rear O2 sensor monitors cat efficiency--meaning that if the reading from the front sensor and the rear sensor are the same it throws a code (your cat is not doing its job). If you pull the rear sensor a bit out of the stream (with the drilled out non-fouler) the sensors have different readings and the computer thinks the cat is working.

[deepsouth]

rmmagow: That would have saved me about an hour. How do you remove it?

[sdube]

Can I ask what kind of welder you used? thanks

[deepsouth]

Basic MIG welder.

[rmmagow]

The cone thing has a nut in it. I didn't do the job, but watched the guy fixing it, he popped it out with an impact wrench and tapped the thing off, few minutes was all. Propshaft was already sitting on my garage floor.

[j-dawg]

hope you're enjoying the new smells.

how bad was the welding? was there any rust on the pipes you were welding up?

i have the downpipe and cat that came off my wagon when PO installed the test pipe and exhaust, but the "cat back" segment of the exhaust uses V-band clamps and the factory pipe uses a ball joint. i'd want to adapt the factory pipe to the catback so i didn't have to buy anything but adapters.

i have a pretty plain MIG welder as well but i don't know if the quality of my welds will be sufficient.

i would just take it to a muffler shop, but they are apparently forbidden by the EPA from installing used cats...