[Closed] DPF removal and the MOT.

If you are doing shorts journeys like that you don't want a diesel. Deleting the DPF might cure that problem but the engine won't be at full efficiency/temperature in that time unless its very small and useless for towing. Looking after a turbo diesel is not hard. You just have to make sure it gets warm every trip, once the engine is fully warm (AND THE OIL) rag the shit out of it pulling onto a motorway every now and then and also make sure you don't park it then switch the car off straight away. Needs 20-30 seconds to let the turbo spool down and cool down.

Also DPFs are good for the environment. Atleast keep it in until it dies then get rid of it. Think of the children.

any interference with the emissions is an MOT failure (think removing the cat on a petrol car).

Whether the MOT spot it's been removed on an encapsulated engine is another thing, of course.

This was done on here recently, best search. IIRC, it was suggested, technically this could be a potential MOT failure as the exhaust system wouldn't reach manufacturers original spec after DPF removal. Not sure how much of a barrier that would be mind...

defo failure if removed. read recently manufacturers are looking at ways to not have DPF due to there failure rates on short journeys etc. could by an older car without?

It's only a cursory visual inspection, they can't look any further than that, as long as it passes the emissions test, it'll be fine

Looking after a turbo diesel is not hard. You just have to make sure it gets warm every trip, once the engine is fully warm (AND THE OIL) rag the shit out of it pulling onto a motorway every now and then and also make sure you don't park it then switch the car off straight away. Needs 20-30 seconds to let the turbo spool down and cool down.

People always say this about diesels but I tend to disagree. We've got a fleet of diesel ambulances and response cars at work that are driven with absolutely no mechanical sympathy whatsoever. They're fired up and thrashed mercilessly from cold regularly, they will be thrashed to a call where they'll be switched off without letting the turbo spool down or anything else like that and the majority of them have covered 150,000+ miles with no more problems than any other diesel car or van I've worked with.

Personally, I don't like the idea if a car with a DPF as its gonna be expensive when it goes wrong. No other reason.
I'm also not a fan of dual mass flywheels fitted to modem diesels as again, they are big money when they fail!

dunno about DPf but i can confirm my diesel van recently went through an mot without a CAT - the old one rotted through and i replaced it with a straight through pipe..... not even an advisory saying it was missing ......

dunno about DPf but i can confirm my diesel van recently went through an mot without a CAT - the old one rotted through and i replaced it with a straight through pipe..... not even an advisory saying it was missing ......

The cat isn't a requirement on the MOT for a diesel, at least it never used to be because my Peugeot 306 cat rotted through so it was replaced with a bypass pipe and still passed MOT's no problem.

correct me if im wrong but isnt the mot requirement for a vans emissions not just a smoke opacity test ? IE when you boot it and let off you dont smoke out the cars behind ?

although this knowledge is based on what the garage said to me when i took my 27 year old land rover in for a ticket !

correct me if im wrong but isnt the mot requirement for a vans emissions not just a smoke opacity test ? IE when you boot it and let off you dont smoke out the cars behind ?

You're right, it's a smoke test rather than an emissions test.

I've got an '08 VW Transporter that has had a DPF delete and remap. It's been through 2 MOTs now and passed 1st time.

I had the work done because the engine management light kept coming on occasionally and putting engine into limp home mode as the DPF was getting blocked. The DPF is still there just that the internals are missing and the sensors have been turned off. It was done by Pendal Performance at the back of the Hope factory in Barnoldswick, Lancs.

The delete fixed the problem instantly and the light hasn't been on since.

They're fired up and thrashed mercilessly from cold regularly

That's the point.

Diesels need to be ragged occasionally, that's all. And as with all engines, ragging from stone cold is not a good idea, but you only need like 30s or so to get the oil circulating. If you ONLY do short trips and NEVER rag it, then you might get problems.

Doing 6 mile trips is not an issue in itself as long as you ALSO have long ones, and make sure you do thrash its nuts off once a month or so.

DPFs can't go wrong as such, they are just a filter matrix. If it gets blocked through lots of trips, a light comes on and there are specific instructions on what to do - at least on VAG cars and I think Peugot/Citroen cars too.

SOME DPFs (ie Ford and Mazda) need you to add a fluid to a tank in the engine, otherwise it blocks. From what I hear, many dealers don't tell you this, so people are unaware, don't re-fill it and then get problems.

if you ask me the whole diesels and short journeys are bad is an urban myth.

i have a diesel fiesta and the wife which both do 90% short journeys and they are fine.

mind you neither have DPF

so much conflicting information in one thread, yet every piece presented as fact.

losing the DPF on a diesel car is entirely beneficial for the engine and running gear in the same way that shedding weight has a knock on positive effect on every aspect of driving.

there is no MOT emissions test for diesels it's a visual check for excessive particulates. if you have a particularly keen MOT tester they might do a visual check but there's no way to tell if your DPF pipe has been emptied of its restrictive contents.

don't be fooled into thinking you're saving the environment by having a DPF as all the crap they accumulate is simply blown out all in one go during an 'italian tune up' i.e. giving it the beans. which is where the short journey warnings come from. an unstressed DPF will simply block up increasing exhaust back pressure, strain on the injection system and turbo and increase the chance of a very expensive failure. removing it lets everything run more freely increasing power, economy and reliability.

the DPF has been forced onto car manufacturers by environmental legislation and they have to do it to get cars to market, passing the grief onto the consumer. just like the utterly hateful concept of EGR (exhaust gas recirculation).

sharkattach
don't be fooled into thinking you're saving the environment by having a DPF as all the crap they accumulate is simply blown out all in one go during an 'italian tune up'

and

the DPF has been forced onto car manufacturers by environmental legislation ...

Usual overuse of the word 'environmental' to cover anything vaguely atmospheric! But that point aside, the purpose of the DPF is to capture diesel particulate emissions and particularly sulphates and soot (or black carbon) which have such small size they affect human lungs - the legislation comes under the banner of air quality but the beneficiary is the general population through improved health (asthma, cancer etc.).

And most DPF systems are designed with a "filter regeneration" cycle where the soot and particulate build up is removed by 'safer' means, for example by combusting the carbobn or from a burst of NOx through the DPF at an optimum temp and pressure to oxidise the carbon and hence, what comes out of the exhaust is chemically NOT the same and certainly nowhere near as detrimental to human health.

Edited typos! and for clarity

don't be fooled into thinking you're saving the environment by having a DPF as all the crap they accumulate is simply blown out all in one go during an 'italian tune up'

It's not blown out, it's burned or reacted out. Converted from tiny bad particles into less bad gaseous CO2. At least that's how it should work.

Usual overuse of the word 'environmental' to cover anything vaguely atmospheric!

Er, what's the atmosphere if it's not our environment? Environmental can mean climate change or local air quality.

Basically wot konagirl says. I wish I had a DPF.

Quick off topic... Moly did you get your subaqua ECU fixed in the end?

Well yeah, I got a new ECU. Car's not fixed tho still, in fact it's basically the same. I'm now wondering if they fibbed about the old unit being damaged... Feeling like I might've been taken for a ride.

Not all diesels come with DPF, with VAGs it tends to be the 'sportier' models. The GTTDI and S-Line models (170bhp versions), most of the 140bhp standard 2.0 tdi's won't have a DPF.

I wish i didn't have a DPF tbh, just more money when it goes wrong. Im looking into getting a DPF and EGR delete on my S-line with a remap in the near future.

Also, the bluemotions and 'eco' friendly models may have them. Im not sure about other cars.

Had a DPF diesel for 5 years now, its spend most of its time doing a 6 mile, town commute with multiple traffic lights and stops. Never had a problem in 70,000. Sometimes it feels a bit lumpy when idling and pulls unevenly so I either go the long way home with some NSL lanes or bung it up the motorway at the weekend.

Managed to clog my DPF and I don't drive like a granny - and my shortest trip is about 20 miles, more usually 50 or 60 (several of a day). The engine stalled, on restart the light came on and the clearing technique in the manual proved fruitless.

Fortunately still under warranty so Mitsubishi sorted it for me without a massive bill being involved. They told me how much it cost Mitsu, and frankly the cost scared me!

Sounds like a fault if the filter got clogged. Let me re-iterate.

Short trips do clog the filter BUT the car is designed to clear this out. If it can't, it gives you instructions on how to clean it out by driving a certain way.

EVEN IF you do short trips, the DPF should be ok (failures of systems notwithstanding) provided you follow the instructions.

However short trips can cause other issues that require longer trips to clear up.

Anyway DPFs themselves can't 'go wrong' any more than a collander can go wrong. The regenerating systems can though.