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Decat on TDi - Fail MOT?
- Thread starter trebormint
- Start date
WHAT THE HELL was you doing in KWIK-FIT!? 
well it was manor tyres lol (owned by kwickfit)
was there today aswell they aligned my hids for free and also confirmed (currently) hids are NOT a failable item on an mot
was there today aswell they aligned my hids for free and also confirmed (currently) hids are NOT a failable item on an mot
"the tester will accelrate until it hits the governor a maximum of 6 times"....boot it until the rev gauge bounces on the red-line
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!!!
is this generally what happens during a Diesel MOT test?
My MOT tester employs some common sense...takes it to a reasonable RPM first and looks to see if there's much smoke, if not then he doesn't go any further. Only if it's belching out clouds of smoke and likely to be borderline or fail would he follow the test to the letter. He doesn't want to risk damage to anyone's car unless he has to.
Remember that the smoke test is not done under any load.
So while we might think some remapped/big-turbo'd TDIs are smokey - that's only when they are accelerating hard under load. If you just rev them at standstill there'd have to be something seriously wrong to belch out enough smoke to fail the smoke test.
Just to let everybody know that a cat test is not carried out on diesal cars as for the one main reason there is no cat on diesal engines they are not made with cats they just have a smoke box where you would usually find a cat. This is why they carry out a smoke test on diesals and an emissions test on petrol engines.
Most modern diesels DO have a cat, they are not testable though, only the smoke content is testable
It's a passive cat not an active one and as such, has no input on engine management unlike a petrol car which has an active cat with a sensor which does have an input on engine management.
Your diesel either smokes or it does not and its emissions are either correct or they are not - the presence of the cat makes not one bit of difference to this
In England, if you decat a petrol car but still passes the emissions test it will pass the mot. As for its legality on the road, you would need to ask a copper.
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It's a passive cat not an active one and as such, has no input on engine management unlike a petrol car which has an active cat with a sensor which does have an input on engine management.
Your diesel either smokes or it does not and its emissions are either correct or they are not - the presence of the cat makes not one bit of difference to this
A+, But they still have a cat lol
I think its there for other countries similar to why the EGR valve is there, some countries actually test them and over here we dont?
You dont need a silncer on a diesel either, as they only test it by, and im quoting my MOT tester, "How loud it was last time" Lol, so basicly it dosnt matter then.
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i've always thought a petrol has to have a CAT on for it to pass an MOT and even come close to passing an emissions test?
as for deseils.....mine has passed 2 MOT's with no CAT
Ive heard that aswell on petrol's, but i think its few and far between that one passes without a cat...
i've always thought a petrol has to have a CAT on for it to pass an MOT and even come close to passing an emissions test?
as for deseils.....mine has passed 2 MOT's with no CAT
The cat itself isnt the testable item, its just the gases that come through it. As i have said earlier, some cars that running correctly are efficient enough to pass a BET test without a cat in the exhaust system.
We had a car sales pitch near to were i work that where a bit dodgy, they some times presented a sales car for Test that would only just scrape through the emissions test and when told about it, we have on occasion been told that they have emptied the cat of its contents as it was rattling. They still got a pass certificate.
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A+, But they still have a cat lol
I think its there for other countries similar to why the EGR valve is there, some countries actually test them and over here we dont?
You dont need a silncer on a diesel either, as they only test it by, and im quoting my MOT tester, "How loud it was last time" Lol, so basicly it dosnt matter then.
It's a visual smoke test / leak test only - noise is subjective and not usually measured not least because there is no load testing done.
I've taken the contents out of a cat on a petrol 106 because it was rattleing and that kept passing mot's. But it did only have a lawn mower engine. I never have a problem with my leon having no cat and the place i take my cars are that strict you even have to have the BS number on your number plates,
bs numbers are more visible to coppers on the road to cats if you get stopped by the old bill with a recent mot , and have illigal plates he knows your cars been dodgily done , where as a cat unless its exessivly loud hes not gona know the difference to that or a cherry bomb back box
Not true. We MOT taxi's mainly and they all come in with perfectly legal plates. When they pass, they simply pull over a mile down the road and swap the plates back to their personal/illegal plates. Its known, but nout can be done about it!
Lol yeah, its like decat pipes on petrols anyway, if they bolt on and off, you can put the cat on, take for MOT, take it home and put ya decat pipe back on. MOTs arnt worth the paper theyre written on really...
Unless your cars rotten or the brakes are shot! A copper would have to have bloody good eye sight to see the BS number on a plate wouldn't he? We have a lot of trouble with VOSA round us because of the amount of chavs and their sheds which have all the stick on bits from Halfords. They have a field day going through all their cars which is why the MOT stations are on the ball with everything and both my leon and my discovery pass their tests with no cat.
If they don't test for emissions a diesel why has the guy at our garage put both of my cars on the emissions? I thought it was only a smoke test or have they changed the goal posts recently.
If they don't test for emissions a diesel why has the guy at our garage put both of my cars on the emissions? I thought it was only a smoke test or have they changed the goal posts recently.
My car failed its MOT for...
Not having a backbox
Being louder than the standard vehicle.
Took it for a test at another place... it passed straight through. Go figure... Soon to have a full straight through system haha!
Its 100% subjective to how cu*tish the tester wants to be.
See my thread on In n Out for more info.
As for the CAT's as far as i was always aware... Dervs dont require, but petrols will. Though my friend gutted his cat on a mr2... and it still passed MOT's.
Not having a backbox
Being louder than the standard vehicle.
Took it for a test at another place... it passed straight through. Go figure... Soon to have a full straight through system haha!
Its 100% subjective to how cu*tish the tester wants to be.
See my thread on In n Out for more info.
As for the CAT's as far as i was always aware... Dervs dont require, but petrols will. Though my friend gutted his cat on a mr2... and it still passed MOT's.
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