best way to remove cats? - 986 Forum - The Community for Porsche Boxster & Cayman Owners

djomlas · 10-13-2008, 05:16 PM

my car is a 98, so only has one set.
if i remove these, will the CEL come on?
and if it does (i don't care for it being there, nor does it bother me), will that hurt the engine performance now that the O2 sensors are not there?

whats the best way to tackle this?

chaudanova · 10-13-2008, 06:09 PM

You can go with some cat-bypass pipes. The CEL that comes on due to the O2 sensors won't affect your car's performance... It will just simply be on to alert you... Some people that get them on due to the bypass pipes or headers that remove cats just take the bulb out of the instrument cluster that goes to the CEL

P.S. I have a brand new set of Stebro racing cat bypass pipes if you're interested...

djomlas · 10-13-2008, 06:49 PM

awesome, just the answer i was looking for...i dont really care for the light so thats not a problem.
i may just do this mod this weekend, might give the new exhaust a better note.

just curious, how much do bypass pipes go for these days?

chaudanova · 10-13-2008, 07:49 PM

Quote:

Originally Posted by djomlas

awesome, just the answer i was looking for...i dont really care for the light so thats not a problem.
i may just do this mod this weekend, might give the new exhaust a better note.

just curious, how much do bypass pipes go for these days?

The Fabspeed bypass pipes go for $495/set http://www.fabspeed.com/Boxster.html

The Maxspeed/NHP are on sale for $499.99/set
http://www.maxspeed-motorsports.com/986nhpmidpipes.html

I'll PM you on the set that I have...

Cloudsurfer · 10-13-2008, 09:04 PM

There will be zero gain to be had by removing the cats unless you are also upgrading the headers to some that flow well. The rear muffler isn't actually that restrictive, but the factory headers are horrible.

As to CELs, you will get a catalyst inefficiency error due to the lack of difference in pre and post cat O2 readings. You can either flash your DME to RoW program with a PST2 (which ignores the secondary O2s), or you can try locating the secondary O2s after a spark plug defouler, which may work.

Patrick

Boxtaboy · 10-14-2008, 03:04 AM

This may not matter in your state, but if Illinois does require state inspections, wouldn't the CEL trigger prevent you from passing any inspections? Here in NY/NJ, if you have a CEL light, and then try to mask it by disconnecting your battery and resetting the light, you still won't pass the inspection because your readiness codes will not have reset until you drive a certain amount of drive cycles, and by then, your CEL would reappear. Just curious.

djomlas · 10-14-2008, 03:47 AM

i just passed the inspection, i had a CEL few days prior, and just turned it off with OBD reader...they dont really care here.
i passed inspection with straight pipes on my other car 3 yrs ago as well , pretty neat

Brucelee · 10-14-2008, 05:32 AM

The issue I see is that if you CEL is always on and you develop an additional code, you won't know it.

It seems to me that this could be an issue, no?

djomlas · 10-14-2008, 06:47 AM

you make a good point,
i have my OBD reader plugged in at all times, so pushing the "read" button every now and then should not be that hard.

also, if i do put the test pipes on there, can i just plug the O2 sensor in there? or does that not even matter now that the cats are gone and that the reading off of them will be wrong?
just triyng to understand all this...

DJ

chaudanova · 10-14-2008, 10:56 AM

Hey DJ, check out this thread that MTS just made:

http://986forum.com/forums/showthread.php?t=18467

The notable part was:

"I did with and without dyno runs with the Fabspeed 2nd cat bypass pipes. The car is a 2004 Boxster S Special Edition with 17k miles (de-snorkled). The baseline runs showed 228 whp. With the bypass pipes installed, the dyno showed 237 whp with a negligible/no change in hp curve. Given all the slight variations run to run, etc, I'd say the Fabspeed claim of 8 hp for using the pipes appears to be accurate, at least on my car."

He gained 9whp on the dyno... not too shabby!

Allen K. Littlefield · 10-22-2008, 09:27 AM

Do you know if the Fabspeed bypass pipes have a bung for the second oxy sensor?

AKL

boxster_s_boy_34 · 10-28-2008, 11:49 PM

From everything that I can remember both bungs are in the header, so swapping mid pipes is no biggie. The only issues are going to high flow cats in the header with no cats in the mid-pipe ( for analy retentive smog states) and/or no cats at all.

Allen K. Littlefield · 10-29-2008, 05:28 PM

Quote:

Originally Posted by boxster_s_boy_34

From everything that I can remember both bungs are in the header, so swapping mid pipes is no biggie. The only issues are going to high flow cats in the header with no cats in the mid-pipe ( for analy retentive smog states) and/or no cats at all.

You are right, I checked it out with Fabspeed and since all the OBD readings are done off the primary cat (fore & aft), you will get no CEL with the bypass, lose about 25 lbs in the right place and sound a bit louder. Claim is anywhere from 7 to 9hp increase. At what speed I don't know but a bit more sound and less weight would do it for me.

How many other mfgs. are making these bypass pipes and at what price?

AKL

chaudanova · 10-30-2008, 12:01 AM

Anyone want to grab a set of Stebro bypass pipes? PM me...

boxster_s_boy_34 · 11-01-2008, 04:57 PM

Another thing that you can also do is put a spark plug defouler in around your second O2 sensor and then you may be able to go completely catless w/o a CEL

ekam · 11-01-2008, 05:42 PM

djomlas · 11-01-2008, 08:54 PM

Quote:

Originally Posted by boxster_s_boy_34

Another thing that you can also do is put a spark plug defouler in around your second O2 sensor and then you may be able to go completely catless w/o a CEL

where do i get that from?

boxster_s_boy_34 · 11-02-2008, 01:13 AM

Quote:

Originally Posted by djomlas

where do i get that from?

It's usually a mod that's found on a lot of gutless wonder japanese cars, but you should be able to find one to fit your bung. All it really does is pull the O2 sensor out a little ways so that it doesn't get as much of a reading as it would normally installed and it fools the computer into thinking that there is still a CAT installed.

Cloudsurfer · 11-02-2008, 07:00 AM

Quote:

Originally Posted by ekam

Am I the only one who found this hilarious?

Patrick

Tool Pants · 11-02-2008, 09:24 AM

I have a 1997. There is a sensor before and after the cat. You need the one before. You do not need the one after. The one after talks to the one before to see if the cat is working. It was forced by the EPA to monitor cat efficiency.

If you disconnect the rear sensors the car runs fine, but you get a check engine light and you will not set all the rediness codes. This is important only for a smog inspection. I have had 5 inspections, every 2 years in smog-nazi California. Now they are going to put video cameras in to make sure the visual inspection is done. Here you would fail visual with bypass pipes, and not even go on the dyno. Some shops even have a floor mirror to see if the cats are there.

I have replaced the bank 2 after the cat sensor 5 times when I get ready for smog. I probably have a bad bank 2 cat and it is not the sensor.

Inspection #6 is due in a few months. What I am going to try is to reprogram the DME for a ROW car. ROW cars do not have the sensors after the cat. I have PST2 and the DME programming code. Then I will find out if the smog machine can detect the change.