Xantia TD De-cat

Kowalski · Post by **Kowalski** » 07 Jul 2004, 14:52

I de-catted my Xantia a couple of months back, the immediate effect was improved performance i.e. less turbo lag and more torque below 2000 rpm.
After a few tanks of fuel, the economy figures are in. I seem to have gained about 4 to 5 mpg. At 70 mph I get about 48 mpg now, where as typically I would be getting 44 mpg previously. If I limit my top speed to 60 mph I get 53 mpg, where as previously I had got 48 mpg. This is over the same drive into work and home each day and not a lot else, over 4 tanks of fuel.
The difference is suprising, just goes to show what harm a restrictive exhaust could be doing to everybodys cars fuel economy.

wotsupnow · Post by **wotsupnow** » 07 Jul 2004, 18:21

Perhaps we should all do that as a matter of course, I assume they where only fitted by the fuel industry to sell more fuel

cough, cough, pass the oxygen.............
Pete

mark_sp · Post by **mark_sp** » 07 Jul 2004, 20:38

I think it's likely that the Cat was partly blocked due to age and or accidental damage.
Having said that If I keep my car long enough for it to need a new exhaust system I'll also probably remove the cat and maybe the EGR as well.
Mark

Post by **philhoward** » 07 Jul 2004, 23:44

Which one did you remove it from; the 95 or the 97? Has the '97 one got the ECU on it or not?
Wondering if its worth removing the one off mine if its that good...

John F · Post by **John F** » 08 Jul 2004, 00:04

How do you all you de-catters cope with the MOT? Millers Diesel additive is good but is it that good?

nick · Post by **nick** » 08 Jul 2004, 00:32

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by philhoward

Which one did you remove it from; the 95 or the 97? Has the '97 one got the ECU on it or not?
Wondering if its worth removing the one off mine if its that good...
<hr height="1" noshade id="quote"></blockquote id="quote">
Your '94 TD shouldn't have a cat in the first place. I think it was only late '96 onwards models with ECU that were fitted with cats.
Nick

Post by **philhoward** » 08 Jul 2004, 00:34

I thought ALL Xantias were fitted with Cats, or am I thinking of Petrols only? I'd have a scrabble underneath, but its p!ssing down here...

nick · Post by **nick** » 08 Jul 2004, 00:37

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by philhoward

I thought ALL Xantias were fitted with Cats, or am I thinking of Petrols only?
<hr height="1" noshade id="quote"></blockquote id="quote">
Yes all the petrols had them, but the diesels didn't get them til about P reg.

Richard Gallagher · Post by **Richard Gallagher** » 08 Jul 2004, 01:00

The MOT test for diesels only tests for smoke (particulates). The catalyst however only reduces the output of a gas which I believe is called Nitrates of Oxygen (Nox). Therefore the test is not influenced by the removal of the cat.
I took the cat off and disconnected the EGR my 97 Xantia when it was new, after having owned a 95 version the 97 felt sluggish. I've never had a problem at MOT time.
If anyone wants an almost new cat then give me a shout, its been laying in the roof of my garage since 97, one day I dare say it will fall down and dent the roof of its donor.

RichG · Post by **RichG** » 08 Jul 2004, 01:28

How easy is it to de-cat a diesel Xantia? My cat is welded into the front pipe so I would think that a similar length of pipe needs to be welded in after the cat has been cut out. How do you keep the correct alignment?
Richard

Post by **philhoward** » 08 Jul 2004, 01:50

There was a de-cat Xantia TD pipe on Ebay recently...are they just a pre-97 one?

Kowalski · Post by **Kowalski** » 08 Jul 2004, 14:36

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by philhoward

Which one did you remove it from; the 95 or the 97? Has the '97 one got the ECU on it or not?
Wondering if its worth removing the one off mine if its that good...
<hr height="1" noshade id="quote"></blockquote id="quote">
The '95 never had a CAT or an ECU, the 97 had both. The only reason I decatted was because the exhaust rusted through and dropped off, and there was a £100 + VAT difference in price between the CAT and non CAT pipes.
Diesel CATs are oxidation catalysts, they oxidise carbon monoxide down to carbon dioxide, converting some nitrogen oxides back to nitrogen, they don't have any noticable effect on particulates. If your diesel is smokey the catalyst gets coated with tarry particulate residue and stops working completely...

John F · Post by **John F** » 08 Jul 2004, 16:58

Then an HDi should solve most of the problems associated with unburned diesel particulates, leaving the cat to process the gasses. However, I understood that the exhaust gas analyser could differentiate between monoxide & dioxide.

Kowalski · Post by **Kowalski** » 08 Jul 2004, 19:27

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by John F

Then an HDi should solve most of the problems associated with unburned diesel particulates, leaving the cat to process the gasses. However, I understood that the exhaust gas analyser could differentiate between monoxide & dioxide.
<hr height="1" noshade id="quote"></blockquote id="quote">
It probably can, but the only emissions requirements on a diesel is for particulates, and these are measured using a lightsource/sensor, i.e. only the opacity of the exhaust gasses are checked.
An HDI is no different to a XUD TD, once the injectors get worn and dirty they put out just as much smoke as a XUD TD. I've yet to see a diesel that doesn't smoke even the newest common rail or PD engines smoke. Some engines are very clean but they all smoke at some point or other, usually it seems to be where the driver puts his foot down and the turbo takes a while to catch up with the fueling.

drpau · Post by **drpau** » 28 Oct 2004, 16:32

My exhaust has just gone on my xsara hdi- just on the weld where the CAT is,, new front pipe and cat is all one piece and was quoted £150 plus VAT (a dear do!),Ive had it welded by the exhaust place for the time being but they said it was very thin. Could I get someone to make up a front section for me do you think, and do away with the cat? Does anyone know of anywhere in North West area where I could get this done?
CHeers
Paul