End all question to Sensors & Cats!!!!

[porsche986spyder]

Okay, I've asked this question before and am still confused to this day as to the proper number of cats on each year and model. So lets hope this thread will put an end to it and clear up some confusion. I want to see some pictures to explain what people are talking about. Because when people say a set or a pair of cats I want to know which area they are talking about. The headers with cats or the down pipes with cats just before the muffler? Depending on the year, I know it varies. So let me start by showing what I have found and hopefully some one can post another picture of the 2000-2004 diagram from a repair manual and circle the O2 sensors as I have, to show them on the cats. Here is the image from a European repair manual I found for the older Boxster(97-99) showing the set up with only 1 set(pair) of cats on the down pipes just before the muffler. No cats at all on the headers as you can see. Now can someone please show me, and circle the ones for the 00-04 models? I've heard everything form 2 to 4 sensors all located on the later models years 00-04 in the headers only. If that's true, then are there still another set of sensors on the ones located on the cats connected to the down pipes for the 00-04 models?

[porsche986spyder]

Here is the 00-04 diagram. It shows 8! bung wholes but only 6 sensors being used. I am assuming that the sensors that are shown on one side of the diagram are not shown again on the other side. Why I do not know, but the you can clearly see the wholes for them. I circled all of them in red.

[tholyoak]

If you are talking about north american cars, the early cars have 2 cats and 4 O2 sensors,with the cats in the midpipes. The later cars put the primary cats in the headers and a second set of cats where the primaries used to be. These still have 4 sensors, up and downstream of the primary cat. There are no O2 sensors after the second set of cats in the midpipe of the later cars. That is why you can eliminate the cats in the midpipes of these cars without CEL issues as the levels are not measured after the secondary cats.

todd

[porsche986spyder]

Originally Posted by tholyoak

There are no O2 sensors after the second set of cats in the midpipe of the later cars.

todd

That makes sense, but please be specific about the year model(later cars) you are referring to. I have an 01. Are you referring to 02-04??? If you look at the diagram of the 01 Boxster I have posted you can see there are sensors there. I even circled them in red.

[porsche986spyder]

If you look at this set of downpipes with cat deletes you can see they left the bung holes for the sensors close to the top where you would bolt them up to the headers. But there are no holes for the ones the were deleted from the cats themselves. What do you do with the wiring after you remove the cats and install the by-pasd pipes? You would still be left with the wiring hanging.

[tholyoak]

All cars use only 4 o2 sensors. 2 pre cat and 2 post cat, the precat sensors are used to determine the mixture under closed loop and the post cat are for emissions. The ROW cars have no post cat sensor.

If you have cats in the headers, you have a sensor pre and post this cat. There is no O2 sensor post the midpipe cat on these cars. These cars have a total of 4 cats

if you have no cats on the headers you have one cat in the midpipe, and the o2 sensors are pre and post this cat.

The 5.2.2 DME, the 7.2 DME and the 7.8 DME only have input for 2 o2 sensors per bank.
In your illustration there is no o2 sensor post that cat on the later cars that can use those bypass pipes, as the cat is in the header, thus no wire to leave hanging.
Todd

[porsche986spyder]

Originally Posted by tholyoak

In your illustration there is no o2 sensor post that cat on the later cars that can use those bypass pipes, as the cat is in the header, thus no wire to leave hanging.
Todd

Which illustration are you talking about? As you can see, there are several. Both diagrams weather they are for the 2.5 or the 2.7 & 3.2Ltr. clearly show 2 sets of O2 bung wholes post cats.

[porsche986spyder]

Originally Posted by tholyoak

In your illustration there is no o2 sensor post that cat on the later cars that can use those bypass pipes, as the cat is in the header, thus no wire to leave hanging.
Todd

Which illustration are you talking about? As you can see, there are several. Both diagrams weather they are for the 2.5 or the 2.7 & 3.2Ltr. clearly show 2 sets of O2 bung wholes post cats. Look at this diagram, there are 6 sensors being used for models 00-04.

[rule1]

I have a 2000 986 with maxspeed headers, 2 o2 sensors per header. There are no o2 sensors on the second set of cats. I know because I installed my headers and i'm getting ready to install 200 cell sport cats and there are no o2 sensors on these or the stock secondary cats.

[Tool Pants]

Todd has it right. The parts diagram is just going to confuse you.

A 1997-1999 2.5 is different than a 2000-2004 2.7/3.2. Then you have ROW cars which are different then our cars. The parts diagram jumbles everything together in one diagram.

This picture is a North American 2.7/3.2. There are 2 cats on each side, for a total of 4.

The first or starter cat is part of the exhaust header. There are 2 sensors on the first cat. There is another cat before the muffler but it has no sensors. This is for one side.

Then you repeat for the other side of the car.

[porsche986spyder]

I finally jacked my car up last night and crawled up under it. Sure enough, that diagram I had was all wrong for my year and model. Well, sort of. That image/diagram shows ALL YEARS/MAKES on one sheet. That why it's so confusing. My 01 only has the 4 sensors on the cats located in the headers just as you guys told me. Thanks again. Guess I just had to see it for myself to understand.

[dcporsche99]

Wow, I defintely like how your sensors are more accessible as compared to my '99...there's so much more room to work with.