No diesel emissions tests for MOT in NIRL for last 12 years

Atlantic Dawn

This is on BBC Spotlight tonight at 10.40 on BBC1 NIRL, am I correct in saying that the NCT similarly does zero tests for measuring diesel emissions?

Emissions tests on diesel cars have not been carried out during MOTs in Northern Ireland for 12 years, despite being legally required.
The tests were crucial, an air pollution expert told BBC Spotlight, and not to do them was "virtually criminal".

The government is legally required to do an emissions test on diesels.

The Driver & Vehicle Agency (DVA) said its staff do a "visual test" and make a "personal judgement" about emissions.

Both EU and Northern Ireland domestic law requires the government to do an emissions test on diesels at MOT using a machine called a smoke meter.

https://www.bbc.co.uk/news/uk-northern-ireland-45643031

Interslice

Smoke meter isnt far off a visual assessment to be fair.

Renegade Mechanic

Interslice wrote: »

Smoke meter isnt far off a visual assessment to be fair.

Exactly, and things like EGR and less than perfect DPF filters can actually bring smoke above a lever that'll fail an NCT. Remove everything, DPF, cat, egr (and fiddle ECU if necessary) and maintain the usual service items and the vehicle can pass the smoke test with pretty much zero smoke.

Mad, really. Once they start properly testing diesels I'll probably just stick a small petrol into my yoke (easily done with my model) and carry on. It'll even cost a couple hundred less to tax

CiniO

Out of curiosity, why are diesel exhaust fumes not tested the same throughly as petrol ones. That's the case all over EU.

Is it because of technical limitations, or some other reasons?

Leonard Hofstadter

I'd be interested in this as well. I've never understood why CO and HC emissions are not assessed in a diesel like they are in a petrol.

zilog_jones

Renegade Mechanic wrote: »

Exactly, and things like EGR and less than perfect DPF filters can actually bring smoke above a lever that'll fail an NCT. Remove everything, DPF, cat, egr (and fiddle ECU if necessary) and maintain the usual service items and the vehicle can pass the smoke test with pretty much zero smoke.

I believe a properly functioning EGR valve in a diesel actually increases the amount of soot generated (its main purpose is to reduce NOx, which isn't tested at all in the NCT or MOT), though this should be mitigated by the DPF where fitted.

I must admit I disconnected and blanked the EGR valve in my previous diesel, as I knew it would not cause any trouble with the NCT. It was hard to justify the cost of replacing it on a car where the annual motor tax cost more than the value of the car, and was at least better (for me) than the previous situation of the broken EGR valve leaking exhaust into the cabin

Now I have a hybrid :rolleyes::rolleyes::rolleyes:

Sabre Man

CiniO wrote: »

Out of curiosity, why are diesel exhaust fumes not tested the same throughly as petrol ones. That's the case all over EU.

Is it because of technical limitations, or some other reasons?

The tests were introduced at MOT in Northern Ireland in 2006 but were suspended 12 weeks later due to concerns about health and safety in the testing halls.

fancy pigeon

CJhaughey

Sounds like a workplace issue where the employees were exposed to lots of continuous smoke and complained or asked for better fume extraction and management decided that it was easier not to do them.
With no government in Stormont its not a surprise that stuff like this is going on, but I bet if you went to some other EU countries you would find the same thing as well.

Renegade Mechanic

zilog_jones wrote: »

I believe a properly functioning EGR valve in a diesel actually increases the amount of soot generated (its main purpose is to reduce NOx, which isn't tested at all in the NCT or MOT), though this should be mitigated by the DPF where fitted.

I must admit I disconnected and blanked the EGR valve in my previous diesel, as I knew it would not cause any trouble with the NCT. It was hard to justify the cost of replacing it on a car where the annual motor tax cost more than the value of the car, and was at least better (for me) than the previous situation of the broken EGR valve leaking exhaust into the cabin

Now I have a hybrid :rolleyes::rolleyes::rolleyes:

It increases the soot alright, be continuously recirculating exhaust gasses. That loop of inert gas doesn't burn, taking up space that would otherwise be occupied by a burning air/fuel mixture.
Now, this does reduce NOX emissions because it brings cruising combustion temperatures below that magic number of... erm... around 1,200 degrees if memory serves
Above that number and NOX emissions really pile out and with modern diesel engines running as lean as 60:1 at times that happens quite a lot.

Blocking the egr doesn't damage the engine - it easily withstands the temperature increase, however the increased NOX does put any traps in more modern yokes under pressure, and a lot of it does make it through. A fair few gut the exhaust entirely, keeping the external shape (as they do fail it they're obviously missing). If, like me, you look at the likes of Emma Maersk throwing more sulfur and NOX into the air than entire countries, you care a little less, pay yer green taxes for exactly what they are and carry on

CJhaughey

EGR also contaminates the oil with carbon a lot more than if the engine was pumping fresh air.

demanufactured

Getting mine blanked on a mk4 mondeo it's leaking....And will be cheaper to blank than to replace.

Leonard Hofstadter

Leonard Hofstadter wrote: »

I'd be interested in this as well. I've never understood why CO and HC emissions are not assessed in a diesel like they are in a petrol.

Because diesel fuel is oil and exhaust won't have unburnt hydrocarbons or carbon monoxide in gas form in any sort of meaningful quantities.

In diesel exhaust the CO and HC are in the unburned fuel (=soot). These particles and NOx are the main pollutants in the diesel exhaust and only soot can be somewhat tested and seem to work fine in practise to weed out the properly dirrrty diesels. Of course CO2 also exists in exhaust but again, and like during petrol emissions testing, the volumetric reading with the car stationary doesn't have any meaning.