Headers and o2 sensors

[snapfrank]

i have headers for my 2001 boxster but there are no holes for the o2 sensors so what do i do with the sensors and will the car run if there not pluged in. there are 2 o2 sensors on each side 1 and 2 which can i cancell.

[root_werks]

All 4 must be plugged in to run properly.

On the 2001 the first two must be screwed into the exhaust. The second two you might be able to get away with not having them in the exhaust and simply plugged in, but you'll throw a CEL420 and 430.

Sounds like you got the early 986 2.5 headers. Are the flanges (Triangle ones) flat edges or kinda rounded? Can you post a picture of them?

[snapfrank]

headers that i want to fit on my 986 2001 all 02 are on the manifold

[Orient Red]

On each bank, one of the O2 sensors is supposed to be upstream of the catalytic converter, and one is supposed to be downstream. Many people who put aftermarket headers end up putting the downstream O2 in a new "bung" which is welded into the rear of the catalytic converter (this also requires lengthening the O2 sensor wires. If neither the headers or catalytic converter pipes has an upstream O2 sensor bung, then that will need to be added as well (either to the collector of the header or the first section of catalytic converter pipe).

[snapfrank]

Where should they go ( Remove Manifold) replace with headers

part 26 and 27 we move The o2 sensors


986 2001

[Orient Red]

Where you see the other O2 sensors (item 25, although they only show two in your picture, there are 4, one before each catalytic converter, and one after). Unfortunately, at least on my '01S, they eliminated the O2 sensor mounting points ("bungs", which are essentially threaded holes), so I had to have a muffler shop weld some on...

[Daniel R]

Just a thought, and I welcome anyone who knows more about this sort of thing to correct me, but there may be a way to delete 2 of the oxygen sensors.

Here in Australia, our cars are delivered new with only 1 oxygen sensor per bank, as we do not have 2 sets of cats (the ones on the headers are not there).

Would it be possible to reflash the car computer with the "Australian version" which is programmed only to process readings from one set of sensors and hence no CEL?

What do you guys think?

[snapfrank]

this is what i got from a local shop as of where they should go. place on headers with bungs. how to exstend the o2 wire now.

[JFP in PA]

Originally Posted by Daniel R

Just a thought, and I welcome anyone who knows more about this sort of thing to correct me, but there may be a way to delete 2 of the oxygen sensors.

Here in Australia, our cars are delivered new with only 1 oxygen sensor per bank, as we do not have 2 sets of cats (the ones on the headers are not there).

Would it be possible to reflash the car computer with the "Australian version" which is programmed only to process readings from one set of sensors and hence no CEL?

What do you guys think?

You are actually on to the correct solution. Only the US cars run four O2 sensors; if you install headers without the second set of O2 sensor bungs, you need to have a PST II/PIWIS reflash your DME to the RoW (Rest of World) profile, and the system will be happy with only two sensors..............

[root_werks]

Before we have him start drilling holes in those headers and having bungs welded in, look closely at the 3-bolt flanges. Do those look rounded to you? They kinda do to me.

I believe those are 2.5 headers and will NOT bolt up to your secondary cat-pipes. The flanges are DIFFERENT.

I could be wrong, but double check it. Take a striaght on picture of your collector flange, post it here. Those may not work on your Boxster.

-Dan

[root_werks]

97-99 flange gasket:
996-111-113-02
2000-up flange gasket:
996-113-113-00

Different and from what I have read, not interchangible.

[snapfrank]

what iv seen of the headers on my 2001 is that will bolt on i need two bungs as the pic in lower case. headers sold for my car with the 2 o2 sensors are at the same place that i have should in the pic. i will try it and let you know. now is it a 18-1.25 or 18-1.5 bungs i need 986 2001 us model.

[manolo]

Its M18x1.5 for the sensors.

[Lightning]

You can use one of those locations on the header to install the leading O2 sensors.

If you don't put the trailing O2 sensors behind the remaining catalytic converter, you WILL get a Check Engine Light (because the ECU checks to see a difference in O2 readings between the leading and trailing sensors) and it won't go away.

As far as re-flashing the ECU, it depends upon your country's emissions testing laws...

[snapfrank]

so do i move them like in the pics or back all of them 1 space

[snapfrank]

there are two o2 holes so it should work if i add 2 bungs on my headers, what do you think.

[Lightning]

Originally Posted by snapfrank

so do i move them like in the pics or back all of them 1 space

Yes, attach one to a bung on the collector of the header and one to a bung on the rear of the catalytic converter they way you have it shown in the diagram.

[Johnny Danger]

Snap Frank,

If you don't mind me asking, what do you hope to gain after all of this ? Once you decide to eliminate the oem headers and pre-cats, and your done running new O2 sensors, creating bungs and likely chasing cel's until you're cross-eyed, you'll still be left with a set of very restrictive 400 cell secondary cats. Unless you plan to go "catless", and that would not be advisable for both emissions, as well as performance concerns, in my opinion I think that you are heading in the wrong direction. Unless you have planned out a "system" that involves high quality headers of a proven design along with lower cell cats (expensive !!!!!) of equal attributes, quite frankly, I don't think you stand to gain anything with what you are attempting to do. Perhaps, a better decision would be to leave the existing headers and pre-cats alone, and simply delete and by-pass the secondary cats. In my experience, by doing so you'll stand to free up the exhaust flow a little bit more, shed some unnecessary weight, and perhaps most importantly keep the vehicle OBDII compliant.

[snapfrank]

like this


Johnny Danger, nice reflection, i just want to use that headers, but it that does not work i will but back the old manifold on and that all. it's just to passtime that i want to put it on my car, but i will think about what u said.

Originally Posted by Lightning

Yes, attach one to a bung on the collector of the header and one to a bung on the rear of the catalytic converter they way you have it shown in the diagram.