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-   -   Cat delete & O2 sensors? (http://986forum.com/forums/boxster-general-discussions/44756-cat-delete-o2-sensors.html)

Timco 04-15-2013 05:33 AM

Cat delete & O2 sensors?
 
So besides a UD pulley, I am getting lots of peer pressure to do the cat delete as well. Gosh, this site takes me back sometimes! (Just do it, you'll like it....)

So....

1) is it legal to remove the cats?

2) if I tie-wrap the O2 sensor under the car, why does the false ambient air reading not cause the car to throw CEL codes? Why does the straight air not cause the car to mix or run different?

I just need all the facts before heading down yet ANOTHER fork on Boxster Road....

Thanks, Tim

shadrach74 04-15-2013 05:38 AM

Tie wrap will not work with your MY DME. You will need a row flash to properly eliminate the secondary O2. Running without cats is definitely not legal. Running with a single cat, configured differently than stock is a grey area that will depend on your state's laws...

jacabean 04-15-2013 05:45 AM

your secondary cats are not monitored. they are after your 02 sensors . you will not have any CEL .
Quote:

Originally Posted by Timco (Post 337509)
So besides a UD pulley, I am getting lots of peer pressure to do the cat delete as well. Gosh, this site takes me back sometimes! (Just do it, you'll like it....)

So....

1) is it legal to remove the cats?

2) if I tie-wrap the O2 sensor under the car, why does the false ambient air reading not cause the car to throw CEL codes? Why does the straight air not cause the car to mix or run different?

I just need all the facts before heading down yet ANOTHER fork on Boxster Road....

Thanks, Tim


stephen wilson 04-15-2013 07:22 AM

You can replace them with high flow cats. , though this is a more expensive option. Why would you feel pressured to do this? If you don't care about the few H.P. it MAY gain (especially without a "reflash"), just drive it as is and enjoy.

Timco 04-15-2013 07:57 AM

Quote:

Originally Posted by stephen wilson (Post 337562)
You can replace them with high flow cats. , though this is a more expensive option. Why would you feel pressured to do this? If you don't care about the few H.P. it MAY gain (especially without a "reflash"), just drive it as is and enjoy.

Oh, I kid. Every time I think heck, it's a Porsche, its fast enough, I see the same mods listed in sig lines. Then it turns out to be a quick, affordable mod that gives better sound, power, and access so it gets added to the short list. I'm not a track guy, but many of these simple upgrades like the pulley and these pipes are almost no-brainers.

cameronzero 04-15-2013 10:46 AM

i would suggest a highflow cat over a delete, only because there's a enough broke honda kids running around catless, making all the noise in the world and going nowhere fast.

Johnny Danger 04-15-2013 01:03 PM

Quote:

Originally Posted by Timco (Post 337509)
So besides a UD pulley, I am getting lots of peer pressure to do the cat delete as well. Gosh, this site takes me back sometimes! (Just do it, you'll like it....)

So....

1) is it legal to remove the cats?

2) if I tie-wrap the O2 sensor under the car, why does the false ambient air reading not cause the car to throw CEL codes? Why does the straight air not cause the car to mix or run different?

I just need all the facts before heading down yet ANOTHER fork on Boxster Road....

Thanks, Tim


The secondary cats are extraneous ! They can be deleted and bypassed without any concerns for CEL's or OBDII compliance. Get rid of them - and shed the equivalent of a couple of boat anchors !

jacabean 04-15-2013 04:49 PM

I do not think they quite get it Johnny D

Quote:

Originally Posted by Johnny Danger (Post 337670)
The secondary cats are extraneous ! They can be deleted and bypassed without any concerns for CEL's or OBDII compliance. Get rid of them - and shed the equivalent of a couple of boat anchors !


shadrach74 04-15-2013 06:20 PM

I assumed when you said cat delete and O2 sensors you were talking about headers. Secondary cats are breeze to remove with no CEL side effects. Don't expect much in the way of performance gains if that's all you do. If anything it's good for weight loss and perhaps improved throttle response...

Timco 04-15-2013 08:00 PM

Quote:

Originally Posted by jacabean (Post 337704)
I do not think they quite get it Johnny D

Oh, I do now, and really appreciate having things like this clarified.

Do I search for "secondary cat delete pipes" and is there a recommended brand name?

Thanks.

Homeboy981 04-16-2013 04:28 AM

Dump the secondary cats, they are worthless! Nothing is monitored on them (except in the older versions of the Box - you know who you are). The exhaust is stifled at that point too. So not only are you dumping weight, getting a much nicer exhaust note (barely noticeable but there), you are also doing it for virtually no cost! What's not to like? But...no pressure! Top Speed Pro1 makes good cat bypass pipes. If you sell the secondaries on fleabay you can recover most all the cost (about $150).

From what I have observed you may want to consider replacing the Thermostat with a low temp version PRIOR to installing an UD Pulley. Simply put, the devices on your system are running slower b/c of the UD Pulley. I noticed a SLIGHT INCREASE in engine temps as a result. It wasn't much of an increase...but it was not that hot yesterday and I was not running the A/C. With the addition of a low temp thermostat you can be sure your temps will not exceed specs IMHO. But don't let me pressure into that upgrade either.

When you are talking getting rid of the PRIMARY CATS and Headers...that is whole nother kettle of fish! (mine's running great BTW) ;) ...no back pressure!

Johnny Danger 04-16-2013 05:07 AM

Quote:

Originally Posted by Timco (Post 337739)
Oh, I do now, and really appreciate having things like this clarified.

Do I search for "secondary cat delete pipes" and is there a recommended brand name?

Thanks.

There's a member/vendor on the forum named Che who sometimes has them available. Otherwise, the only reliable source to purchase them from is FabSpeed.

Timco 04-16-2013 05:38 AM

Quote:

Originally Posted by Homeboy981 (Post 337781)
Dump the secondary cats, they are worthless! Nothing is monitored on them (except in the older versions of the Box - you know who you are). The exhaust is stifled at that point too. So not only are you dumping weight, getting a much nicer exhaust note (barely noticeable but there), you are also doing it for virtually no cost! What's not to like? But...no pressure! Top Speed Pro1 makes good cat bypass pipes. If you sell the secondaries on fleabay you can recover most all the cost (about $150).

From what I have observed you may want to consider replacing the Thermostat with a low temp version PRIOR to installing an UD Pulley. Simply put, the devices on your system are running slower b/c of the UD Pulley. I noticed a SLIGHT INCREASE in engine temps as a result. It wasn't much of an increase...but it was not that hot yesterday and I was not running the A/C. With the addition of a low temp thermostat you can be sure your temps will not exceed specs IMHO. But don't let me pressure into that upgrade either.

When you are talking getting rid of the PRIMARY CATS and Headers...that is whole nother kettle of fish! (mine's running great BTW) ;) ...no back pressure!

No pressure, but "everybody's doing it"...lol.....

I really enjoy these simple doable upgrades so pulley, stat, and pipes it is!

Thanks.

Homeboy981 04-17-2013 05:32 AM

As a newbie, the 2ndary cats were the easiest way for me to become familiar with my car, and not screw it up. Since then, I have done many upgrades. This mod is still one of the easiest with the highest probability of success.

BTW, if you have rusted bolts, soak 'em in PB Blaster and let em sit for a while. Also helps to "warm it up" first and let it cool down to work on it.

notech 01-15-2014 12:10 AM

Hello guys,
a quick one,
I own a 986S MY03 European, yesterday I've put straight pipes and car throw CEL, even with secondry O2 sensors connected (hanging around).
Did I miss any step?
Thanks,
Ser

BYprodriver 01-15-2014 07:05 AM

Quote:

Originally Posted by notech (Post 381039)
Hello guys,
a quick one,
I own a 986S MY03 European, yesterday I've put straight pipes and car throw CEL, even with secondry O2 sensors connected (hanging around).
Did I miss any step?
Thanks,
Ser

I think your car only has 2 O2 sensors. If that is correct then you need to have them installed in the pipes so they can read the air/fuel mixture & adjust as needed.

Steve Tinker 01-15-2014 01:29 PM

^^^^^ What BY says... ^^^^^
Ser,
If you are running ROW specs (which you are in GIB), you need to fit the O2 sensors into the pipes. I bought the Che cat delete pipes (Deluboz Parts) and had to weld in 2 x stub-ins for the sensors...

notech 01-16-2014 01:11 AM

Thanks a lot guys, the car is ROW ecu.
If I leave secondary sensors disconnected, will A/F mix work as normal, just showing CEL, no other side effects?

Timco 01-16-2014 04:06 AM

The Fab Speed pipes I bought has a front and rear bung for your O2 sensors. I had to plug both on my pipes since only the forward cats have sensors.

Timco 01-16-2014 04:09 AM

Quote:

Originally Posted by notech (Post 381240)
Thanks a lot guys, the car is ROW ecu.
If I leave secondary sensors disconnected, will A/F mix work as normal, just showing CEL, no other side effects?

The feedback from those sensors is not just FYI to the engine, it does change operating conditions.

jb92563 01-16-2014 10:14 AM

If your car has secondary cats with no sensors its a no-brainer as you will still pass emissions without them provided your main cats are hot when you do the test.

If you also replace the stock muffler with a more free flowing aftermarket unit like TopSpeed then what you get is faster throttle response and a nicer muffler tone without the drone.
Leaving the 2nd Cats in place with the TopSpeed mufflers only will result in an unacceptable drone.

It is still quiet when not punching the throttle and just cruising.

When you first go under a bridge and open your windows to hear the echos you will never want to leave that spot...it sounds incredible and will attract all the hotrodders attention immediately.

HP gains are unknown if any but the faster throttle will make your car leap off the line and potentially squawk rubber when you go into 2nd gear somewhat aggressively in an S model. You will be pushed back into the seat with some nice G's while accelerating hard in 2nd. :D

So do the mod and hang on to your Cajones (Edit Cojo's)!!!

It great to be "S'd"
http://goodlogo.com/images/logos/superman_logo_2940.gif

ppbon 01-16-2014 02:13 PM

Quote:

Originally Posted by jb92563 (Post 381284)
So do the mod and hang on to your Cajones!!!

Your cajones are your drawers (as in a dresser or a desk)
Your cojo... are what you want to hang on to and protect ;)
Happy Porscheing,
Pedro

notech 01-17-2014 12:15 PM

Quote:

Originally Posted by Timco (Post 381244)
The feedback from those sensors is not just FYI to the engine, it does change operating conditions.

I don't want to be mean, just curious,
with test pipes I feel sportier sound, car revs faster and generally feels quicker.
What changing conditions are altered without secondary O2 sensors in? Sure it doesn't feel worse than stock.

notech 02-17-2014 02:21 AM

Sorry guys, I didn't give a lot of attention till yesterday,
I saw my secondary CATs come with an 02 sensor at the begin of the CAT and then an 02 sensor at the end.
Is this normal for a 2003 year car? I thought these MY03 have one 02 sensor on primary CAT and one on secondary CAT.

Timco 02-17-2014 04:25 AM

Quote:

Originally Posted by notech (Post 387038)
Sorry guys, I didn't give a lot of attention till yesterday,
I saw my secondary CATs come with an 02 sensor at the begin of the CAT and then an 02 sensor at the end.
Is this normal for a 2003 year car? I thought these MY03 have one 02 sensor on primary CAT and one on secondary CAT.

I learned in another thread that Euro cars have O2 sensors in the rear cats. The Fabspeed pipes I bought have 2 bungs for sensors which I plugged but you will need.

notech 02-19-2014 02:02 AM

Quote:

Originally Posted by Timco (Post 387048)
I learned in another thread that Euro cars have O2 sensors in the rear cats. The Fabspeed pipes I bought have 2 bungs for sensors which I plugged but you will need.

Sorry, do I need to connect both of the sensors per pipe? cheers

Timco 02-19-2014 04:24 AM

Quote:

Originally Posted by notech (Post 387405)
Sorry, do I need to connect both of the sensors per pipe? cheers

If your car has them then you need them. It needs that feedback. Unplugging one will give CEL.

notech 02-26-2014 07:44 AM

Me again! :eek:
Yesterday I was changing spark plugs and found that manifolds don't have any cats!
My car is MY 03 and manifolds look pretty standard.
I am surprised, shoulnd't I have two cats on them?
Cheers

Ranfurly66 02-26-2014 10:49 AM

I have the same set up on my car - euro spec car, apparently EU4 emissions - has 2 cats at the rear just before the muffler box.

notech 02-26-2014 11:38 PM

Ok, that makes sense! so I am running with no cats then (the exhaust doesn't sound so loud as no cats at all, to me, still similar to stock at low rpm, then high ad 4K rpm of course).
I will try to put 2x O2 sensors on cat bypass and 2x O2 sensors out somewhere to pick clean air, that should fool ECU and remove CEL I believe.
Cheers,
Ser

edc 02-27-2014 01:13 AM

I don't know what your emissions test is like in Gibralter but no cats in UK would surely fail. As you have found out Euro cars only have 2 cats, what everybody else here calls secondary cats. I have just fitted 100 cell sports cats and had to space out the rear lambdas in an attempt to stop the CEL triggering. I guess you will need something similar.


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