Drill the Cat

[geoffreytro]

Having just replaced the turbo on my 2.5 tdi - I have been advised to put a 20mm hole in the filter in the catalyst. Is this wise? :confused:

[Alan02]

Is this because it dumped oil down the exhaust if turbo failed? If so, personally, i would replace it as you will be putting out plumes of smoke for a long time.

[abyrne153]

Some turbo repairers suggest this if the turbo was damaged by a blockage in the cat causing back pressure in the exhaust. If you drill the cat you will weaken the delicate honeycomb structure and it could collapse altogether blocking the system once again. Knock the entire cat out altogether or replace it but I tried drilling them before and invariably they always disintegrate later and block everything up.

[geoffreytro]

Litle evidence of oil in the CAT which is quite sooty. I think the advice receved was on the basis a cat isn't required. Begining to think that destroying an expensive part - albeit one with dubious advantages - is not good value for a small increase in performance.

[green A8]

I phoned VOSA a couple of years ago and asked if I was allowed to delete the cats on a 1999 2.5 TDi A6. To my surprise they stated that I could fully remove the cats and it would have no impact on current or future MOT's. I'm not 100% certain that this info is valid today, bearing in mind the ammended DPF rules. A quick phone call to VOSA's helpline should settle this matter.

The only reason I asked was that the car had been recently bought by a friend and the cats had already been removed by the previous owner, who had installed a full stainless steel exhaust from the manifolds back.