[cstavaru]

Hi,

I was just thinking, how hard would it be to relocate the O2 sensors after the secondary cats and run a catless downpipe setup without getting O2-related engine codes ? Are there special wires used ? Could this relocation guarantee a CEL-free operation ? I find an O2 simulator in the ECU bay to be a less than elegant solution, especially with a flash...why flashing if still needed to mess with the ECU wiring...

[blisstik]

Interesting idea. I don't think the sensors are long enough. In a car like the 350Z, they use thick washers (spacers) so the sensors aren't all the way in the pipe. That solution works for the 350Z but I'm not sure why it wouldn't for the E92. I'm sure if it does, it would've been done already.

[s.myrr]

I know it was discussed in a thread a while back... don't think it worked out! (spacers for sensors)

[vasillalov]

Originally Posted by s.myrr

I know it was discussed in a thread a while back... don't think it worked out! (spacers for sensors)

Spacers will definitely work. It is a matter of finding the correct length of a spacer.

In the VW/AUDI world it is very common to run full catless exhaust and downpipes and not throw a catalytic converter code. Most of the aftermarket downpipes for those engines come with longer O2 bungs pre-welded....

What I do not understand is why not run the BMS O2 simulator?... It works fantastic...

[s.myrr]

Agreed. Seems to me that warranty issues from DPs would be a bigger issue than having to use a sim or deal with a CEL. I'm guessing most people on this forum don't know too many details about the installation and usage of the O2 sim.

[bryans2k]

The readings would be too off because the exhaust gas would've cooled too much.

[cstavaru]

Originally Posted by blisstik

Interesting idea. I don't think the sensors are long enough. In a car like the 350Z, they use thick washers (spacers) so the sensors aren't all the way in the pipe. That solution works for the 350Z but I'm not sure why it wouldn't for the E92. I'm sure if it does, it would've been done already.

I think it works, Supersprint advertises this solution. They sell catless downpipes and catted midpipes with O2 sensor bungs made especially to relocate the O2 sensors.

Also, I read this magazine did the relocation on their 335i:

http://www.europeancarweb.com/tech/e...own_pipes.html

"Supersprint downpipes can be used with the stock exhaust, but the problem is the elimination of the primary catalytic converters, which sets off the 'check engine' light. This is why we opted to install the front connecting pipes with the 100-cell HJS converters, since they have a provision for the re-location of the rear O2 sensor. With the complete set-up installed, it's like removing a cork from a bottle; you can just feel the turbos spool. This set-up would definitely support higher boost levels. Eliminating the catalytic converters in the engine bay helps to lower underhood temperatures. The overall sound level increases, but not enough to cause any annoyance."

I think I will contact Supersprint on this...maybe they have a relocation harness available (I'm sure it will be expensive as hell).

[marconi118]

in this magazine they state:
"No extender harness for O2 sensors"

the rear O2 sensors are normal narrow band, you can use simple wire to lengthen the connection to the DME, the only difficult thing is to find the connectors.

Maybe grab them from an old car...

[chiaobaby]

Originally Posted by cstavaru

I think it works, Supersprint advertises this solution. They sell catless downpipes and catted midpipes with O2 sensor bungs made especially to relocate the O2 sensors.

Also, I read this magazine did the relocation on their 335i:

http://www.europeancarweb.com/tech/e...own_pipes.html

"Supersprint downpipes can be used with the stock exhaust, but the problem is the elimination of the primary catalytic converters, which sets off the 'check engine' light. This is why we opted to install the front connecting pipes with the 100-cell HJS converters, since they have a provision for the re-location of the rear O2 sensor. With the complete set-up installed, it's like removing a cork from a bottle; you can just feel the turbos spool. This set-up would definitely support higher boost levels. Eliminating the catalytic converters in the engine bay helps to lower underhood temperatures. The overall sound level increases, but not enough to cause any annoyance."

I think I will contact Supersprint on this...maybe they have a relocation harness available (I'm sure it will be expensive as hell).

There is someone selling supersprint downpipe and catted midpipe for $2000.00 in for sale section

[cstavaru]

Does anyone know if the rear O2 sensor socket looks like this ?

http://www.densoaftermarket.com/cata...4876&part=o2sn

http://www.partstrain.com/store/deta...?location=Rear

In this case, I see those are just regular wires...I suppose they can be extended by soldering longer wires ?

[ES BMW]

This was common with the Audi B5 S4s but the factory cable for the second O2 sensor was long enough to be relocated after the second cat. However, they were a lot closer together than the N54 setup.

[E92Fan]

I originally did this over three years ago!! I bought one of the first sets of AR Design downpipes, but asked Andrew not to install the lower O2 sensor ports. Hence the downpipes only came with the top ports for the front lambda probes.

I then extended the wires of the secondary probes literally by cutting the existing loom and splicing a longer length of wire into it. The exhaust shop cut new O2 ports behind the secondary cats, the lambda probes were screwed into there and job done.

Never had a CEL light, never had any reliability issues whatsoever regarding O2 sensor regulation.

About a year later however I did change the secondary cats to 100 cell HJS race versions and then sometimes I would get a CEL light, sometimes not. This is purely down to the fact the 100 cell cats aren't doing as much as the normal 600 or 750 cell cats that are OEM on the car.

I had my remapper program out the O2 CEL light and the situation with the lambda probes has never crossed my mind since then.

I've done several of these lambda probe extensions for other people, all using the OEM secondary cat, and not one have had any CEL issues.

[cstavaru]

Originally Posted by E92Fan

I originally did this over three years ago!! I bought one of the first sets of AR Design downpipes, but asked Andrew not to install the lower O2 sensor ports. Hence the downpipes only came with the top ports for the front lambda probes.

I then extended the wires of the secondary probes literally by cutting the existing loom and splicing a longer length of wire into it. The exhaust shop cut new O2 ports behind the secondary cats, the lambda probes were screwed into there and job done.

Never had a CEL light, never had any reliability issues whatsoever regarding O2 sensor regulation.

About a year later however I did change the secondary cats to 100 cell HJS race versions and then sometimes I would get a CEL light, sometimes not. This is purely down to the fact the 100 cell cats aren't doing as much as the normal 600 or 750 cell cats that are OEM on the car.

I had my remapper program out the O2 CEL light and the situation with the lambda probes has never crossed my mind since then.

I've done several of these lambda probe extensions for other people, all using the OEM secondary cat, and not one have had any CEL issues.

This is great news, thanks ! I am planning to use catless downpipes with 200-cell HJS cats on the midpipes.

I think that this should be a very popular mod on this forum...it would cost maybe less than $80 which is the cost of the BMS downpipe fix and it would be a more elegant solution.