Dual Cat Removal

[Ron220]

Hi guys, just wondering if it's possible to remove the cat from the exhaust on a 08 is 220d to improve flow, and if so does it throw up any alarms/warnings on the dash?

[ChumpusRex]

The oxidation catalyst on the exhaust is not monitored electronically, and it is not tested or inspected at MOT time.

[is200 Newbie]

Doesn't a car with a cat at the time of manufacture after 2003 need to keep it installed?

Is this a different ruling for petrol engines?

[ChumpusRex]

Yes. A catalyst is required to meet MOT standards on a petrol car, if one was originally fitted.

On a diesel, a catalyst is not required. Instead, the car must meet emissions standards at the time of design. There are many ways of meeting emissions standards, of which one way is a DOC. VOSA did consider making a tampering with diesel emissions a fail, but because there are so many possible options, they considered it would be impractical for testers to be able to check these complex systems which differ from model to model.

So, for a diesel, yes - there is a loophole, and you can remove an oxidation catalyst.

[Ron220]

Thanks Campusrex, so I'm going to give this a try with a high flow silencer to see if it gets the turbo spooling a bit quicker in the lower revs.

[Ron220]

1. Just wanted to say...I bypassed the EGR valve and removed the DPF filter about 2 years ago and installed a high flow K&N air filter, so I'm hoping all this will make the 220d go like it should...fingers crossed.