Decat on TDi - Fail MOT?

Aug 1, 2005
2,695
0
Cullompton . Devon
No the police cannot fine you as you have not broke any laws and it should pass an MOT as the exhaust is whole and in good condition. If anyone is that paranoid about it just get some flanges wielded onto to CAT when you have it removed and bolt it back in place at MOT time.
 

john_tdi

mmm 385lbft
Feb 21, 2007
687
0
s wales
No the police cannot fine you as you have not broke any laws and it should pass an MOT as the exhaust is whole and in good condition. If anyone is that paranoid about it just get some flanges wielded onto to CAT when you have it removed and bolt it back in place at MOT time.

agreed.

I've had two mots without it, performed by the chief MOT inspector within my local county. He sorts the MOTs for taxi's, buses, public transport , council, ambulance, and public vehicles.

Don't have to have a cat.
 
Feb 1, 2007
1,602
1
Nottingham
There is always the issue of noise particularly when you have a peformance exhaust fitted.
My magnex is very loud with the cat removed. Mot due Feb 2010.
Glynn
 

leontdi130

Active Member
Jan 20, 2008
277
0
Euxton (Chorley)
Just passed my 2nd MOT with no cat or EGR. He tested the CO2 and it was that clean it wouldn't read!! Thats proof driving it like you've stolen it is good for it!
 

Viking

Insurance co's are crap.
May 19, 2007
2,317
4
Near Richmond, North Yorks
Just passed my 2nd MOT with no cat or EGR. He tested the CO2 and it was that clean it wouldn't read!! Thats proof driving it like you've stolen it is good for it!

There's no doubt at all that he managed to get no reading for CO2.

1. Diesels are not tested for CO2 or any other emissions, only smoke value (or soot).

2. Petrols are not tested for CO2. They're tested for Carbon Monoxide (CO) Hydrocarbons (HC) Lambda and Oxygen (O2).

But mostly because...

3. The emissions test machine doesn't test for CO2, so even if he used the petrol engine test on a diesel, you'd get zero CO2 reading because there isn't a sensor to read for it.
 

trebormint

Active Member
Sep 17, 2008
333
0
Swindon
Right, got a interesting reply when I asked longlife exhausts about having a decat on a Tdi.

They told me it was illegal (!) for cars registered after august 2001 to have a decat.

Longlife would be fined if they were found out to do a decat to a car registered after August 2001
 
Last edited:

iain1970

I ♥ TDI
Apr 19, 2005
484
0
The Wrong side of the Pennines
This is like window tints. They are not tested at the MOT so a limo black tint on all side windows will pass, but they are in contravention of Construction & Use regulations, a whole different ball game.

I'd bet catalytic converters fall under C&U regs for diesels first registered after a certain date.
 
Oct 11, 2008
714
0
35
Bristol
here is something i picked up in Kwickfit

MOT1-1.jpg


mot2-1.jpg


:)
 

air121005

Active Member
Sep 28, 2006
1,609
6
Worcestershire
here is something i picked up in Kwickfit

MOT1-1.jpg


mot2-1.jpg


:)


:wtf: is this a :censored: wind up? :ban:

"the tester will accelrate until it hits the governor a maximum of 6 times"....:blink: boot it until the rev gauge bounces on the red-line:ban:
that can't be good for any car!!!!



"if your engine has been maintained this will not cause any damage to your engine"
so if it foooks it up, here's our disclaimer, you haven't looked after your car over the years!!! :ban:

is this generally what happens during a Diesel MOT test? :shrug:
 

Viking

Insurance co's are crap.
May 19, 2007
2,317
4
Near Richmond, North Yorks
Yes, this is usual. Diesel engines are different to petrol engines. Stronger built to cope with the extra compression, and top end rev range is limited more by the speed of the diesel burn rather than the physical capabilities of the engine. The engine is governed to stop you over revving it, simply because when you try to do that you end up losing power and throwing unburnt fuel out of the exhaust.
 

aaronbromley

TDISport.com Owner
Nov 25, 2004
338
0
Lincolnshire
www.TDISport.com
So basically it breaks down like this.
In order to pass the tests all cars are subject to, it will pass with flying colours all TDI's will.

HOWEVER

If your pulled over by a particuarly arsey police man he CAN fine you for it and take your car off the road.

or

If your MOT'er decides he wants to make some extra money he CAN say your car isnt road legal.


Basically, if you know someone whos pretty good and does MOT's or people who are lazy, Just do it.

The police PROBABLY wont notice, their inspections are normally of the tyres, washer jets etc.
and an MOT'er PROBABLY wont fail you for it.


The chances are always there however.

Pretty much covered it :D
+1
 

air121005

Active Member
Sep 28, 2006
1,609
6
Worcestershire
mines passed 2 MOT's without a cat and with a remap (mentioned that because of extra smoke:whistle:), but i didn't realise they did this as part of the test!

i never take mine to redline when accelerating, rarely past 4000rpm (because thats where the torque tails off;)) to be honest
 

brightsideteeem

I'm not like you guys...
Yes, this is usual. Diesel engines are different to petrol engines. Stronger built to cope with the extra compression, and top end rev range is limited more by the speed of the diesel burn rather than the physical capabilities of the engine. The engine is governed to stop you over revving it, simply because when you try to do that you end up losing power and throwing unburnt fuel out of the exhaust.

absolutely spot on.:)

hence: "smoke test"

I think this debate is going to go on forever, basicly its down to who tests your car, how you drive, NEVER USE RED DIESEL, and most coppers probably wouldnt be able to tell.

As long as your not bootin it round like a gonad everywhere, why whould they pull you anyway?
 
Chris Knott Insurance - Competitive quotes for forum members