Everything you need to know about a MOT!

Apr 11, 2012
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So, for this non-mechanically minded caravanner, can you explain in simple terms what a DPF is, what it does and what is to be gained by removing it, please?
 
Jul 15, 2008
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.......removal of a DPF is not a simple procedure and will necessitate the engine being remapped.
Have a look at this firms website ......it has all the answers to any questions.
 
Aug 4, 2004
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Tractorbob3 said:
So, for this non-mechanically minded caravanner, can you explain in simple terms what a DPF is, what it does and what is to be gained by removing it, please?

DPF = Diesel Particulate Filter. Many people report that once the DPF has been removed and engine remapped, there have improvements all round including MPG. I am referring to a remap just to take into account removal of the DPF so the light doesn't come on.
 
Aug 11, 2010
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apology for the bluntness, but the emmision test for diesels has always been just a smoke test,always removed my cat on my diesels and as a DPF is a glorified cat when i have a car with one fitted when or if that plays up it too will be removed...

why would it invalidate VED. which is based on CO/km? A more efficient engine should give better mpg,as MPG and CO are directly linked the CO per KM would be improved.
 
Oct 28, 2006
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Because the VED is based on emmissions.The emmissions are calculated out on a dyno which is measured in grams per time.Can a cat regenerate its self?I thought not.Two entirely different things was my thoughts.A keen tester will spot its removal.Why not just fix the fault instead of removing it.
 
Aug 11, 2010
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seth said:
Because the VED is based on emmissions.The emmissions are calculated out on a dyno which is measured in grams per time.Can a cat regenerate its self?I thought not.Two entirely different things was my thoughts.A keen tester will spot its removal.Why not just fix the fault instead of removing it.
err the VED is based solely on CO/ per km and the average of and nothing else,so i repeat taking the dpf does not invalidate
your VED
,The MOT emmission test is a smoke test thats been around since the 1986 I seem to recall and it hasnt changed,so a car
will pass the smoke test with or without a DPF or cat as long as it could have passed with either or both in place.but i am sure you know that.. Now what a mot tester sees is irrelevent as neither is needed at the moment[ legally] becides which companies offer a service of taking out the DPF gubbings and doing a minor remap, so leaving the appearence of a DPF.and as i said the DPF is a glorified Cat, in laymen terms and yes a cat does regenerate itself just needs a rubber mallet and several hits and a airline to empty
years of build up alas a DPF needs a miricle to fix once it regenation system plays up..
Alas there seems no cheap fixes in most cases for DPFs and given there is no legal reqiurement for them at present taking them off is usually cheaper than fixing them..
 
Oct 28, 2006
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Ok im with you now.For a cat to regenerate you hit it with a hammer,so it doesnt do it on its own,or should i say as a built it function of the vehicle.A smoke test has nothing to do with the amount of VED paid on a vehicle as i said the emmissions are based on a wieght measurement that is carried out on an engine dynomometre.It consists of a filter that catches the deposites from the exhaust/engine over a set time scale and then wieghed at the end of the test.Its carried out in the early stages of development.Just for the record,took my car for MOT last week.Talking to the tester and he said removal of Cats,DPFs,exhaust brakes is an instant fail.I dont thing its the way to go,i know they can be a pain.My main worry would be removing it and then it still fails test on it being removed.
 
Aug 11, 2010
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Seth your MOT tester is wrong, It has never ever been illegal to remove a cat from a diesel engined car, it has always been illegal to remove a cat from a petrol engined car, i dont know how the law applies to say hgv's, but that is undisputed fact and i am suprised at your MOT testers lack of DOT/MOT rules. as for the DPF...as yet the same applies to that,afterall my bravo does not have a dfp but they are fitted [optional] as they were to many cars.how caoud you fail one 57 plate car for not having a dpf because some do? they will no doubt make it compulsary one day but they cannot go back dating to 57plates or 58 59plates as the same applies there some have them some do not.
you keep going on about the emmision standard test, yes i am fully aware of how it is done, they weight the CO,so they can get the co per km rating as i have repeatedly stated and the CO gas has nothing what so ever to do with Soot particles, ala the DPF, so again the DPF does not cannot and will not effect your VED rating, which incedentally is the stupidest rating test ever.....The cat remark ie hitting with a hammer was a quip, joke, although it does work and is common practice at reputable Diesel centres, although i can imagine that some would refute it being a good idea
So to summerise on a diesel car there is no legal reguirement or MOT test failure for the removal of, as the only test done on a diesel for emmisions is smoke and as i have said before the smoke test is ancient for diesels,[please go look it up for yourself] and a modern diesel should not fail it with or without a cat indeed it shouldnt fail it with a blanked off EGR valve either as long as the engine is in good condition and i know that is a sticky piont with some too. And lastly to re iterate the DPF has nothing and plays no part in the VED rating system, but with it looking likely as some piont to be a compulsary part and the Diesel emmision test surely needing updating because its so ancient ie the amount of soot you can actually have, still. then at some piont i would expect this all to change. Note the rules are far strickter for HGVs.
I would not suggest anybody take off their cat or dpf or indeed blank off there EGR valve, as when working properly they do a fine job.becides more moden cars its not as easy as less modern ones IE pre 2004/5, more electronic control means more hassle for a start.but given the costs of replacement or fixing of some parts then i wouldnt hesitate on blanking my egr valve or as i have done before taking off my cat, but note my cars are generally bought with plus 70k on them so build up of soot oil ect leading to build up of blockages and therefore replacement parts is somewhat different to people who have new or low mileage cars and therfore hopefully do not need to do these things.
 
Jun 20, 2005
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Hi Jonny
On the EGR valve thing mine played up four years ago . It wasn't opening fully and this lead to heavy black smoke at all times. The intercooler pipes and EGR were replaced and all has been fine ever since. In future if the same thing happens can I just remove or somehow blank off the EGR?
 
Aug 11, 2010
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Dustydog said:
Hi Jonny
On the EGR valve thing mine played up four years ago . It wasn't opening fully and this lead to heavy black smoke at all times. The intercooler pipes and EGR were replaced and all has been fine ever since. In future if the same thing happens can I just remove or somehow blank off the EGR?
i would say as you have already replaced it, you should be ok for a long time assuming the car is running well and regular serviced. i would guess yours is electronically controlled so on some models the Engine Management light would come on if a blanking plate was used,sometimes after a few days the light would go off and stay off. Some use a blanking blate with a little hole in it, just big enough to stop the EML coming on.so you would need to check what would work and i am sure some on the sorrento site would surey have done it
i am guessing here but as you mention the intercooler pipe was changed as well, there is a good chance the intercooler pipe was faulty and over time it meant you properbly had a rich mixture that sooted up the EGR valve quicker than normal and thats why it failed earlier as they can last 100k plus.also the electrical connector that plugs into a EGR valve can become defective again leading to EGR valve problems. mine on my mondeo is also nearing 4 years old and seems fine and mine had 2 replaced in months of each other under warranty mind you and the elcectrical connector was changed the second time around, so theres a good chance that that was the problem on my car all along.
personally i think cars that tow get to clean up the cars internals by working harder and blowing everything out of the exhaust,where as cars that tootal and drive arounf towns allthe time get gumbed up quicker..
 
Jul 15, 2008
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JonnyG said:
personally i think cars that tow get to clean up the cars internals by working harder and blowing everything out of the exhaust,where as cars that tootal and drive arounf towns allthe time get gumbed up quicker..

........I totally agree.

Diesel engines thrive on working hard and hate poodling around where they often fail to reach their optimum working temperature.
A hot hard working diesel engine tends to be self cleaning of sump oil pollutants and soot.
 
Aug 4, 2004
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Gafferbill said:
JonnyG said:
personally i think cars that tow get to clean up the cars internals by working harder and blowing everything out of the exhaust,where as cars that tootal and drive arounf towns allthe time get gumbed up quicker..

........I totally agree.

Diesel engines thrive on working hard and hate poodling around where they often fail to reach their optimum working temperature.
A hot hard working diesel engine tends to be self cleaning of sump oil pollutants and soot.

Buy some Carlune 2 stroke low ash oil from the supermarket and put about 200ml into your full tank. It helps lubricate moving parts that were previously lubricated by the sulphur in the diesel. Unfortunately the sulphur has been removed which then causes the sticking,
 
Aug 11, 2010
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1 part two stroke oil to 200 parts diesel fuel, low ash 2 stroke oil has a lower ash content than diesel so its ok even in a car with a cat
[before anyone asks] but a car with a DPF? i would double check on that one, i would have thought it would be OK, but as i dont know what chemical reaction could take place i would be careful of doing it on every tank fill.
I do it 5 or 6 times a year on my mondeo but she has a de cat and no DPF.
milllers ecomax fuel treatment is also a good option about £12 from halfords and is good for 500 litres of diesel.
 
Jul 15, 2008
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Surfer......the only additive I am prepared to use is a Redex diesel injector cleaner.

My old Terrano's engine has just shrugged off 111,000 miles and is just about run in now
smiley-wink.gif

I know the engine is considered low tech.......but to me that is an advantage!
It has already polished off 3000 towing miles this year on our winter trip down to the Spanish Mediterranean.
 
Oct 28, 2006
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Dusty Dog,dont you mean it wasnt shutting properly?Mental.Last year Daf BV spent 4 million pounds on research and development,they are not on their own.Car manufactures spend exactly the same amounts.We now see two bit companys who do actually think they know more than the makers.Brillant.I think i will continue to take advise of my VOSA tester and continue with 100% pass rate whether their right or wrong.September is the deadline for not testing for modifications after that it will fail.
 
Aug 11, 2010
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Hi seth. I didnt understand your last post and what you meant
By daf investment of 4 million pounds.ect ect. Into what surely not egr
Valves which wer being criticised back in 1998 by dieselcar
Mag. And others
Nor do I understand the bit about some think they know
Better that the car manufacturers, as many kbow better
I mean the MAF and piece of expensive junk or rather it was
For a decade clearly the car manufacturers didnt mind geting
That wrong due to replacement costs and why have one when
You could use a MAP sensor for a better reading ala
Decent racing cars. Then there is the Dmf what a wibber
That was on diesel cars; so good that manufacturers are
Looking at going back to single flywheels and Luk already
Make a range to replace Dmf s..Mmm manufacturer s know
Best do they! do I need to talk injectors Mercedes
VW FORD and many have had problems another
Expensive part.It seems everything these days are mega
Expensive but not necessarily quality as the R&D done
Seems to have been rushed.
Originally you questioned if removing a cat or Dpf
Effected your VED.on the grounds of the Co roadtax
Rating system being effected by such a deed hopwfully
You except that it does not from a scientific point of view
Not that anyone is saying you should be doing it.
 
Oct 28, 2006
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the truth is i live in the real world,im out in the field not reading it out of some magazine,which most of is pure crap.My post relates to other posts made by other users.The level of professionalism is a joke,for example how can an egr valve that doesnt open cause black smoke to which the poster got an in depth reply,not of myself of cause.We then hear how a VOSA tester is wrong. Maybe for now.This is what i was told-" An exhaust system that doesnt resemble what it originally looked like is an instant failure" Lets also not forget 2010 was the introduction of euro5 compliant vehicles with a reduction of 80% in exhaust emissions compared to euro4.As you will know the smoke limits are 2.00 for normally aspirated and 3.00 for turbo charged engines.My car was tested last week,the smoke read out was 1.77,my vehicle is well maintained, very low milage,never had a DPF problem in its life.Would this pass with the DPF removed?
 
Oct 28, 2006
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Hi Jonny ive just re read your post,i will try to answer two of your questions.

As regards to the maf(mass air flow sensor) its very reason for excistance on a diesel engines is actually to measure air flow across it,BUT more so to measure EGR opening times and also dictates when EGR opens.Not to be confused with map sensor(manifold air pressure)witch measures a positive pressure as agaist a negative pressure of the maf,chalk and cheese springs to mind.Yes a maf is not really required but why not,its another parametre to help.
 
Jun 20, 2005
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seth said:
Dusty Dog,dont you mean it wasnt shutting properly?Mental.Last year Daf BV spent 4 million pounds on research and development,they are not on their own.Car manufactures spend exactly the same amounts.We now see two bit companys who do actually think they know more than the makers.Brillant.I think i will continue to take advise of my VOSA tester and continue with 100% pass rate whether their right or wrong.September is the deadline for not testing for modifications after that it will fail.
Seth
I'm no diesel engineer and have to rely on what the professionals tell me. The EGR valve was not opening and closing properly. Apparently only 35% of its range. And believe me she was a real heavy smoker! Even I know what black smoke is and it wasn't comiong from the Vatican
smiley-laughing.gif
 
Oct 28, 2006
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I can well imagine Dusty,but sometimes on here the facts get forgotten and personal opinion takes over and it all gets a bit ammeture at times.One of my main worries concerning these issues is when all these emmission controls have been taken off and then the ECUs adjusted to suit and then the vehicles start failing annual test on these items,were do you stand then.Vehicles these days are not made to be messed about with,and its ok finding companys who are willing to delete the dpf parametre but i dont see any that are factory approved.Any body can have a posh web site as someone said to me, the web site is ever so good at hiding behind.
 
Aug 11, 2010
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seth said:
I can well imagine Dusty,but sometimes on here the facts get forgotten and personal opinion takes over and it all gets a bit ammeture at times.One of my main worries concerning these issues is when all these emmission controls have been taken off and then the ECUs adjusted to suit and then the vehicles start failing annual test on these items,were do you stand then.Vehicles these days are not made to be messed about with,and its ok finding companys who are willing to delete the dpf parametre but i dont see any that are factory approved.Any body can have a posh web site as someone said to me, the web site is ever so good at hiding behind.
Seth you of all people should know better. and scaremongering is piontless if you havent done the research yourself and frankly i feel
you know full well how do reason it out for yourself. I am talking about the original topic and your original post.which is similar to this last post of yours,and is as mis informed as one with your back ground could be...
Surfer,s original post was about CATs he was correct in assertion you were not,
Now you have moved this on to DPFs fine people should know what is what and then we have EGR valves thrown into the debate as well. which is quite crazy really as you keep forgetting one important thing over and over again with regards EMMISIONS..
Diesels have a smoke test,thats all nothing more exactly how will a DPF a CAT or a EGR valve play a part in that equation given and i say it again. the smoke test is sooo out of date for modern diesels? A sticky EGR valve will lead to higher smoke and a highly likely fail,as could a sooted up CAT or a faulty DPF. by blanking off a EGR valve or removing a CAT you will not fail a MOT your emmisions could actually be lower in older diesels as you have removed 2 Parts that do and can cause higher emmisions.with age and before thye fail totally so polluting far more than when new.
technically by removing said parts you end up with a ever so slightly more effiecent vehicle as a by product and Frankly With regards ECU ! please no adjustments are needed with regards the EGR valve or the CAT, only on the DPF is it needed and it seems
even those amatures! know this.
Now by doing this, sure you will be poluting more NOX and particles but not much and they have nothing to do with either VED or an MOT smoke/emmisions test.. REMEMBER THAT WAS THE TOPIC.. what surprises me most is you should know all this......and had you made a piont about polluting our beloved planet a tad more with particles and NOX rather than making claims of MOT failures i would have conceeded you had a piont,but i would still have countered with, in theory a more effecient engine produces less CO.which is also good for our beloved planet...
 
Oct 28, 2006
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Hello Jonny G,
Unless i cant read,surfers post referes to DPFs as well as cats.Gaffer Bills responce was to guess what DPFs.So was the post underneath that.My responce to EGR valves was to Dusty dogs post,i never raised it before that .
As i said my car got tested last week with a smoke test of 1.77 ish.A turbo charged engine is allowed 3.00 end off.My car is at the top of its game.dead low milage and well serviced.(fiat 2.4 multijet2. 210 hp)How would something go on with high miles,poorly serviced,and basically rough with the DPF removed.Fail the smoke test maybe?Please remember your taking a filter out of the exhaust.
As for harming the planet.i think my post speaks for its self.Although i think motor vehicles expell 5% of the harmfull gases to the planet,i understood nature to be alot worse.
Anyway i might think about it if you have an mot station and promise to mot my car for the rest of its life.
 
Aug 11, 2010
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1.77? assuming you are talking Fiat Croma Auto. rather than a Alfa 159..Mmm. and that is not a good reading as you are not getting a fast past rate,which is under 1.5 i/m. and if the car does get under that figure then the smoke test report will say so. I would assume this because you mention the Max of 3l/m and your reading is 1.77 L/m,.
My mondeo which has 120,000 plus miles on it, and no cat has the followering figures from last year
Limit applied.. 1.5.[the fast pass] absorption coefficient. .92 l/m zero drift 0.03 Abosorbtion coefficent after correction 0.89 l/m fast test..
My wifes fiat bravo was .48l/m... and walked under the fast test limit of 1.5l/m. my old Alfa 156 also passed under the 1.5 fast test limit with no cat and blanked up EGR valve..
Seth assuming it is a croma auto i dont know if being an auto makes any difference,ie blocking up the Cat or if its 5 or 6 years old the MAF not being at its best,but 1.77 isnt exactly that good.
err its not been remapped as it?
 

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