Everything you need to know about a MOT!

[seth1]

I know its not,and thats what im trying to get at.It is a Croma auto with factory upgrade.(238hp)Its now done a massive 40k.The engine is perfect and i have a genuine Fiat examiner which i use to do a forced regen before every oil change as the oil degradabilty is monitored as one of the parametres.I dont think ive ever seen the DPF past 50% full.The kind of stuff we repair runs at nearly always 0.01 and requires a stethascope to register the engine is running.I dont think there is a common path in all this.I would be cautious.

 

[JonnyG]

I know its not,and thats what im trying to get at.It is a Croma auto with factory upgrade.(238hp)Its now done a massive 40k.The engine is perfect and i have a genuine Fiat examiner which i use to do a forced regen before every oil change as the oil degradabilty is monitored as one of the parametres.I dont think ive ever seen the DPF past 50% full.The kind of stuff we repair runs at nearly always 0.01 and requires a stethascope to register the engine is running.I dont think there is a common path in all this.I would be cautious.

Wow dont know much if anything about factory upgrades but i do know the 5 cyl Fiat/Alfa is a gem of a diesel engine, dont know how it works in Auto form but assume it works pretty well.

 

[seth1]

Yeah thanks Jonny it aint bad apart from one snagg very difficult to work on with the extra cylinder.Engine out to do most things,timing belt,even alternator last year.Thankfully as you say the 5 cylinder is quite robust.

 

[ProfJohnL]

I know this may seem petty, but the VED on a vehicle type is calculated on the emission mass of Carbon Dioxide CO2 produced over 1kM, not Carbon Monoxide CO. CO2 is a gas not a solid.

The VED grammes/CO2/kM rating is produced as part of the vehicles type approval process, and does not change over the life of the approved vehicle.

As Jonny has been stating, the DPF (Diesel Particulate Filter)does what its name implies, it collects particles, such as soot. Soot is fundamentally just Carbon which is a solid. Gasses such as CO2 will pass straight through.

The MOT test looks for the particulates that are emitted from the vehicle, not the gasses. So a DPF should reduce the emission of particulates but again as Jonny has suggested, the limits for the MOT test are set for rather older technologies and any correctly set up modern engine should be well inside the limit even without a DPF present.

The new MOT standard looks to see if a car has been modified. It is unclear to me how that will be applied, and if it would also pick up the removal of a DPF as a modification even if the vehicle still passes the emission tests.

I shall check with my BIL who runs a garage with MOT test station.

If a vehicle has failed an MOT on the basis of a modification then there will be two course of action. The first is to restore the vehicle to manufacturers specification, or the second is to get the modified vehicle reassessed by VOSA/VCA on a single vehicle assessment procedure (like kit cars and single build cars)

 

[JonnyG]

With regards the DPF and the soon to change MOT test with regards changing from stock. Now not that i know for sure but it wil surelyyl have to be applied to say EURO 4 or EURO 5 type vehicles? maybe even Euro 5 only although i would be glad to know eitherway, as the problem with this is cars, well Fiat for starters as late as 08 plates for sure had the policy of "do you want a DPF on or not so to speak, so one would assume it difficult to base this new test on say 2007 or 2008 cars for starters and maybe even later.
Now i am not advocating doing this but as i said earlier if certain parts become probmatic ie cat EGR vavle, i will remove them or blank them off, for now, DPF i dont have one but it seems the aftermarket is on it toes with regards these things and future changes to the law. As some specialist are knocking the DPF out, they dont actually take them off, they merely remove the innards and remap the ECU.so leaving the appearence of a DPF.. and as long as we have the smoke test for emmisions CO2 [thanks prof] set so high then there should not be any problems passing the MOT smoke test..Again not avocating anyone to do this but i believe its nice to know all your options given the costs these days of motoring and certain parts.....

 

[seth1]

No it does not.It tests for carbon monoxide not soot which is very vague and what you actually mean is NOx or nit oxides which is high in risk to cancer.By takeing a dpf of your actually turning a euro 4 or 5 spec engine back to euro 2.

 

[JonnyG]

No it does not.It tests for carbon monoxide not soot which is very vague and what you actually mean is NOx or nit oxides which is high in risk to cancer.By takeing a dpf of your actually turning a euro 4 or 5 spec engine back to euro 2.

hey you two sort yourselfs out heh heh heh, and as for me,i should not doubt myself.. heh heh heh...yep Co the Egr valve is used to lower the NOx gases by lowering combustion temp, so goes the theory which i am sure you know except it only lowers the temp under low throttle openings ie when the engine is not working too hard, thing about that one for a start it only works when the engine is being quite efficient in terms of burning less fuel! which means less pollutants! which kinda defeats the object in my mind. Also bear in mind that it is quite possible the EGR valve if faulty and they do start to stick slightly open with age without giving obvious sighs at first will actually then cause problems for CAT and DPF ie more soot than there should be.and indeed this in itself
leads to a less efficient engine from more crap to more back pressure so on the whole a car that performs slighly worse generally than it should! who measures the differences? no one that who.
never the less over time it will add alot of soot and sludge back into the engine regasrdless of if it is working properly.
If you ever feel the need to see just how stupid the system is take your air inlet pipe off the one that goes to the engine air intake and please wear glove, with age and mileage the intake track because slugged up this was being reported back in 2000 how that can be a good idea is beyound me as this unmetered sludge will in small parts find its way back into the engine meaning greater qualities of NOx coming out than the normal prescribed amounts and of course wear on the engine interanls which make it even more of a pollutant..Now that defeats the total idea of having a egr valve in the first place and like most poisons a little is indeed bad but greater qualities all at once more so... and they have the check to claim a only petrol engines get more NOx pollutant with age due to build up! just a thought

 

[Surfer]

Please don't forget to write to the EU to thank them for imposing all these new regulations on us!

 

[seth1]

Very well put Jonny,and the only thing i can add is EGR recycles 70% of the exhaust gases only on the over run though and does indeed lower the combustion temp as there is no oxygen to burn which goes agaist what most misinformed people think as exhaust gas is hot.BUT there is another option- Urea as an SCR treatment but at 40pence per litre extra on top of the cost of fuel i,ll stick with EGR.

 

[airsiggy]

I don't know if this is relevent so if its not don't give me a hard time.
So, my 20 year old Renault Clio with an old fashioned 1.9 diesel, nothing electronic or filters of EGR, etc, etc.has always passed the MOT emissions on a "Fast Pass", first time (i.e. its in first class condition on the exhaust gases) It does get trashed a bit and could get me in trouble on the m'way speed limits and has the odd drop of Millers. Only maintenance it gets is a cam belt change and an oil change once a year.

 

[JonnyG]

I don't know if this is relevent so if its not don't give me a hard time.
So, my 20 year old Renault Clio with an old fashioned 1.9 diesel, nothing electronic or filters of EGR, etc, etc.has always passed the MOT emissions on a "Fast Pass", first time (i.e. its in first class condition on the exhaust gases) It does get trashed a bit and could get me in trouble on the m'way speed limits and has the odd drop of Millers. Only maintenance it gets is a cam belt change and an oil change once a year.

there is something to be said for older cars and with diesels in particular newer ones simply dont cannot be rev'd properly and often enough to clear them out.. err 1993 clio? you maywell have a manual EGR valve but again being able to rev them clears them..