MOT emissions test for diesel

[rapidyellow]

How are diesels usually tested at the MOT for emissions?

in the past, I am sure that the tester has held the car at near full RPM for a min or so, and check for smoke out the back.

can somebody clarify?


yesterday, the Mrs HDi Pug 308 failed its emission test, he revved it from idle to high just a couple of times and that was it, I think it had been idling for some time while it was on the ramp so maybe it was just clearing that.

car is running perfect, no engine light or depolution faults, pulls well and proper and is very good on fuel, no codes in ecu, nothing to suggest there is a problem and these HDis WILL chuck up a code if they arent happy.

am annoyed more than anything, mainly because the way it was tested yesterday, vs the way this and my own 207 HDi has been tested in the past. Held at constant high revs.

so, any info welcomed. thanks

[Rich]

A Minute? No, engine must reach max governed speed only very briefly. It's the acceleration part it monitors, holding the revs for any long period of time shouldn't affect the result as the soot is emitted during the rev-up period. Long and short of it, the car has been tested correctly by you account and you have something wrong, or at best it needs an Italian tune-up to clear out the exhaust,

Manual is here for all and sundry to read. I've linked the appropriate page for your query.
www.gov.uk/guidance/mot-inspection-manual-for-private-passenger-and-light-commercial-vehicles/8-nuisance#section-8-2-2

[mk2cossie]

At work anything diesel in for MOT gets a road test to make sure the engine is warm enough before the smoke opacity test.

Oil temp needs to be a minimum of 60°C, and the vehicle presenter is meant to say it is safe to rev.
The actual test is pressing the accelerator pedal fully (but not harsh or violently) in 1 second.


Most stuff that has been in use should sail through that, in 3 revs. Otherwise it is a more in depth test at 80°C oil temp, and a maximum of 6 revs.

Has the car only ever been trundled around in? As that is usually the main reason the diesel engines get smokey

[rapidyellow]

car was previously used a hell of a lot for the mrs travelling to work, but she now works at home 3 days per week, the commute she does in it now is less too but does include a few miles of motorway but the rest stop start traffic.

mot centre is about 6 miles away from us down regular roads, but I waited about half hour before they got it on the ramp, am not sure if it was running on the ramp or not but the exhaust test was at the last test they did.

not sure if the dpf has ever regenned, I was looking at the eolys additive level yesterday on my delphi and its at 61%, it was on 61% about 3 years ago as well!

car is serviced with proper oil and filters, we are taking it to north wales tomorrow and I am going to work in it sunday night and from work will take it on a motorway trip direct to the mot centre and get them to retest the emissions.

[jgtr]

Add some injector cleaner directly to the fuel filter, rest in the tank, the kick the ass off it for a good few miles. Then re-test it.

The test sounds as if it has been done properly.

[rapidyellow]

have just done nearly 200 miles in it, mixture of roads mainly motorway and quite a few full throttle accelerations. Also ran it at 60mph in 3rd for a few miles to clear it. I put some wynns dpf cleaning additive in the tank before we set off. Trip was set to 0 and the average MPG was 64, it just cant be faulted for how it runs.

I will take it for retest in the morning and will be able to give it more beans than today [its the mrs car, she don't like it driven rough!] so while I am in it on my own I can give it a good ragging [is that a tech term?] on the way. Might give the dpf and back box a clout with a hammer to dislodge any soot.

[welshpug]

don't go clouting the dpf!!

[rapidyellow]

May 15, 2022 17:23:16 GMT welshpug said:

don't go clouting the dpf!!

I wont! I realised why as soon as I pressed "create post"

[rapidyellow]

passed

a good ragging plus some additive in the fuel got it through.