Does the stock exhaust have a crossover/balance pipe in the centre muffler so gases can mix ?

 

I could be wrong on this, but...I believe the center muffler IS the "crossover/balance pipe", so to speak. From what I've read here, when removing the center muffler, people either go with two straight pipes and no crossover, an "X" crossover, or an "H" configuration.

 

Thanks.
I am doing some remote diagnostics with only the MOT (UK) emissions fail sheet to go by until I get the car. One bank seems to be running very rich and the other only just out of acceptable range so I am thinking if there is gas mixing in that centre muffler then that would account for the other bank readings - or it might be a separate issue affecting both banks.

 

Wight,

Firstly I think we need a few more details on what the problem is. Post the MOT results here for us to look at.

AFAIK, the O2 sensors are on the CATs which are between the engine and the large central silencer/muffler under the car. Are these O2 results showing the problem? Probably unrelated to the exhaust system.

You say the car is running rich - ie over fueling and it seems to be a problem on both banks. What are your STFT and LTFT? This data is available over the OBD2 port. Any semi decent garage will read DTCs too which will point towards the problem.

Is the car running ok or stalling at low speeds?

I would first suspect the MAF sensor behind the air box, and it is easily removed and thoroughly cleaned using dedicated MAF cleaner spray. Cheap and easy thing to try first.

 

Thanks David.
Sorry I should have said I have a theory based on the emissions that I am seeing, not really looking for help right now. Just needed to know about possible exhaust gas mixing. The garage's opinion was (apparently) that it needed two new cats.
I am not yet of the same opinion looking at the emissions.
- I will post up a thread for diagnostic entertainment when I have the car in my possession, then I can get the fuel trims and get the oscilloscope on it.