Cats on Diesels

[The_Burg]

Currently running a 120k Passat. MPG has dropped off markedly in the last few months. Rarely getting over mid 40s MPG was getting mid 50s previusly.
No errors showing on diagnostic and MAF sensor was replaced less than a year ago.

DO cats clog up with age? I assume they must.
Does nayone make a CAT bypass for a Passat Diesel estate? If so will it make any difference anyway?

[tr7v8]

Probably needs an injector clean & service. Also these run VTG turbos so possibly getting coked up.

[Jack_and_MLE]

It might have nothing to do with your problems but...

I had a similar problem with my Audi A6 which is powred by the 2.5V6 tdi
I knew the battery was going and I have finaly replaced it on Tuesday. And the mpg was back up to about 39-40 @ motorway crued from about 36.

Jack

[The_Burg]

tr7v8 said:

Probably needs an injector clean & service. Also these run VTG turbos so possibly getting coked up.

Use injector cleaner every few tanks so hopefully should be alright.
Coked up turbo sounds expensive, never even though about anythihg like that.

Surely though the cat must get clogged with age and soot?

[BB-Q]

Very common problem on the VAG cars. Go take it down the motorway for 40 miles @ 4000rpm or so. If that doesn't cure it you'll need to replace the particulate filter (they no longer call them cats on diesels).

Basically, if you run a modern diesel round town constantly it will clog. Thrash the tits of it and it will un-clog. VAG systems are particularly prone to this.

[odyssey2200]

First rukle of Diesel tuning
Replace the fuel filter.

The performance of a diesel relies on the flow of fuel to the injectors and the atomisation of just the right amount of fuel.

A restriction in the filter will effect the performance and you will probably be using more throttle to compensate.

[Avocet]

Not sure about the VAG system but the Peugeot diesels have a cat and a particulate filter (not all have the particulate filter though). The cat does pretty much the same job as a petrol engine cat - cleaning up gaseous pollutants. The particulate filter does a completely separate job cleaning up the soot. I did once have one clock up because the regenration system wasn't working and it dramatically (20MPH up hills!) reduced performance.

[liner33]

Avocet said:

Not sure about the VAG system but the Peugeot diesels have a cat and a particulate filter (not all have the particulate filter though). The cat does pretty much the same job as a petrol engine cat - cleaning up gaseous pollutants. The particulate filter does a completely separate job cleaning up the soot. I did once have one clock up because the regenration system wasn't working and it dramatically (20MPH up hills!) reduced performance.

Skodas do as well they are totally different things .

I got rid of the cats on my diesel , helps the turbo spool up a little earlier and they arent needed for the mot (check with your tester first though)

[The_Burg]

liner33 said:

I got rid of the cats on my diesel , helps the turbo spool up a little earlier and they arent needed for the mot (check with your tester first though)

So anyonw know where i can get a bypass for a 2000 Passat 115 Sport?

[liner33]

Not a cheap option but i had a whole system made in stainless steel by longlife cost me £400 with a lifetime warranty

http://www.longlife.co.uk/

[S2AVANT]

I got a turbo back 2.5" Milltek system for our A3 TDi for £350. No cats.
It sailed through it's MOT today.

[ssray]

you dont need a cat on a diesel, the mot test looks for particulates(dust) not emissions,when i removed mine on my rover i could then go through 30mph zones in top.

the only thing is make sure the pipe work is as big as the rest of the exhaust,as ebay ones are for petrol cars and only come out at 2 inch not the 2.5 at least you need.
Ray