Peaty

If you install a downpipe and or a hi flow catalytic converter you may get a CEL code P0420 - Catalyst System Efficiency Below Threshold. There are two fixes for this one is electronic and involves cutting wires and installing a resistor, you can get one of those here:

http://ponyexpressperformance.com/ (website 404 seem to be out of business. Check the bottom of the page on how to make one.

But another solution is a mechanical fix. The following information and pics are supplied by screen name STiLL WILL on the NASIOC board:

--------------------

1.Go to your local auto parts store and buy this:

See pic 1

or you can also use the #42002 version, all your preference:

See pic 2

2. With a 1/2" drill bit, bore out only ONE of the anti-foulers in order to accommodate the size of the o2 sensor head. Screw in your o2 sensor into the bored out anti-fouler then screw that into the other untouched anti-fouler and voila! Here is a pic of my STi with this setup:


See pic 3

Attached Thumbnails

     

__________________
Peaty

cheeze@sunflower.com

2004 Forester XT - MT Cobb Stage 2

2006 B9 Tribeca - 7 pass Ltd (wifes ride)

1999 Miata - Daily Runabout

 

bofh

Some additional details... It works by pulling the sensor out of the stream, so it will not detect as much unburned fuel. However, if you pull it out too far, (Or if you have a lot of exhaust leaks) you will get P0139 Rear oxygen sensor circuit slow response. The range of acceptable seems wider on 02-03 than it is on 04+ and it may require a bit of tunning. If you get the P0139, first check to make sure there are no exhaust leaks between the engine and the rear o2 sensor. If there are none, you may need to widen the hole in the second spacer as well. I have seen some which required only one spacer.
On the other hand, if you are still getting the P0420 with the system above, you may be running unusually rich. Do some datalogging, and check your tune.

Peaty

Info on the right tool to remove the sensor:

http://www.scoobymods.com/forums/showthread.php?t=5464

__________________
Peaty

cheeze@sunflower.com

2004 Forester XT - MT Cobb Stage 2

2006 B9 Tribeca - 7 pass Ltd (wifes ride)

1999 Miata - Daily Runabout

Peaty

http://www.scoobymods.com/forums/showthread.php?t=3768

or you can make the above.

__________________
Peaty

cheeze@sunflower.com

2004 Forester XT - MT Cobb Stage 2

2006 B9 Tribeca - 7 pass Ltd (wifes ride)

1999 Miata - Daily Runabout