10 GT3

I've had a pair of cat bypass pipes sitting in a closet for a year and I am thinking about finally putting them on. I was curious if anyone is using them with O2 spacers to get rid fo the CEL and being successful in doing so. If so, what spacers are you using?

onefastviking

If you decide not to and would like to sell the pipes let me know. I need them for a racecar and don't care about the cel light.

himself

I tried to use them with my Cats, but the O2 sensor location is angled such that the spacer+O2 sensor will not fit in engine bay without hitting something on either side - either an engine part, or crossbar or something.

Hopefully your cat bypass has the angles right. I will go dig up the exact parts I used - the came from Autozone in a box of 2 for like $10. You probably need to use both to get it to work.

-td

Edit: here is the FVD part
Write up on using spark plug non-fouler (I tried this method) - but this part doesn't look like the one I have left over.

This second link shows the parts that I used (same part number)

ruey220

you have to use the L shaped O2 sensor spacers. i have them and they do the job.

67FJ45

Part number and source? Why do they have to be L-shaped? For the fitment?

10 GT3

Hmmm...strange discovery. I was looking underneath my car and did not see any secondary O2 sensors. I reached all around the cat pipes and no bungs or wires, except the 2 O2 sensors in front of the cats.

Do all US 996's have secondary O2 sensors? Parts catalog shows them only with M660 option. I looked up M660 and it shows to be OBDII. Looking at the option codes sticker under my trunk lid, 660 is not listed on the option codes. I also checked it with an OBDII scanner. There is no EGR (shows N/A), O2 shows "Ready" and Catalyst shows "Not Ready"...always.

Macster

One per side ahead of the converter and one immediately behind it. For 02 at least the Boxster Porsche started using pre-converters or warm-up converters that are part of the exhaust header. The larger converters further downstream do not have O2 sensors either just ahead or behind them. They are unmonitored. Porsche feels that if the warm up converters working properly the secondary converters working ok too.

Now if car not a USA or UK/Europe car... Or if car has had Ecu change. With a proper code reader you can query Ecu for what OBD support it has.

Sincerely,

Macster.

ruey220

yes for fitment. these are the ones I had welded on my pipe

http://www.procivic.com/pages-produc...032/index.html

smsarchitects

another option is to gut a set of old cats but not sure if that throws a CEL.

67FJ45

That's weird. I have same comments as Macster. One other thing you can do is look inside the engine compartment. As you face the car from the back, there should be two electrical connectors just to the left of the latch, behind the air intake runner (i.e., toward the back of the car). Those are for the bank 1 O2 sensors (see pic below). The O2 sensor electrical connectors for bank 2 are in front of the right taillight (and may be hidden from immediate view).

savannah996

i have a 2001 996 3.4L, no secondary sensors

dallasboats

you will not pass smog

10 GT3

WOW! Savannah revived my OLD post.

I did put the cat-bypass pipes on my car. Yes there are secondary O2 sesnsors, but you can't seen them until you loosen the cats. They are in the center of the cat on top. Surprisingly after I put the Cat Bypass pipes on, I never got a light. We even checked the computer and no codes. I had them on the car for about 2000 miles. Remember though, this is on an X51 with the latest factory DME. Yes, I could easily pass smog.

I talked to a few techs and a couple commented that dues to the different cams that the DME on the X51 is a little looser than regular 3.6ls. Don't know for sure if it is true or not. I just know I never used spacers and never got a light or code.

I did switch back to cats. I also got both cats replaced under warranty. I switched back for 2 reasons: sound and low end power/torque. With already having Fabspeed mufflers on the car and then adding the cat bypass pipes, I lost a lot of torque down low. Below 2000 rpms, the car felt like a 2.5l Boxster and laggy below 2500 rpms. I didn't notice any significant power difference. Keep in mind again that this is on an X51 that has different heads, cams, intake and exhaust manifolds. Regular 3.6ls may not be as sensitive to the lack of back pressure. After putting the cats back on, the car was simply a lot happier all the time. Sound wise, I didn't like them. First they are loud with the X51 engine and Fabspeed mufflers. I started getting resonation from the mufflers in the mid range. As I revved above 4000 rpms, the exhaust pitch got noticeably higher. I didn't like the tone. Putting the cats back on made it a lot quieter, took the resonation away and brought back the low growl I like.

When I sold the car, I sold it with the cats on. I am going to put the cat bypass up for sale as I have no use for them as they won't work on a 997 GT3.