NCT - comparing reports

PauloMN

Got my other half's car NCT'd yesterday, it passed, so ok on that front. Like I usually do, I compared the new report with the previous one from 2 years ago, just to see if there's any major disimprovement from before.

Nothing stands out in the suspension/brakes etc. tests, but the "Smoke" test worries me a bit.

2010 reading: 0.06 /m
2012 reading: 2.910 /m
Limit is 3.00 /m

so it looks like I passed the smoke test by a hair's breadth.

Question is, am I looking at a failing cat/DPF? If so, I guess it's lucky I have 2 years to save for a new one anyway! Not even sure if the car has a DPF - how do I check?

TestTransmission

Make, year and model of car will deffo help with answering the question

PauloMN

TestTransmission wrote: »

Make, year and model of car will deffo help with answering the question

Sorry. A4 Avant 2.0 TDi, 2006. Imported from NI if that makes any difference - it's an SE spec. 83k miles on it now.

dr.fuzzenstein

It would depend on the type of driving done since last NCT.
If there was a lot of short trips and if the car was not properly up to temperature when the NCT tested it, this may cause more smoke.
Also, how's your air filter? If it's manky, it doesn't help.
When I put my car through the NCT (1.8 TDCI Focus, 200000 km on it), the garage, who where fixing an electrical fault, put some hydraulic oil into the tank, along with some fuel treatment.
This was about two/three weeks prior to the NCT, I gave it the beans on the motorway and my smoke test was 0.something low anyway.
Since your NCT has been and gone, it is of course hard to test without going the fuel treatment/motorway route and re-testing it.

PauloMN

Actually the car is used for longish journeys and commutes mainly, 50ish miles per day, cruising at 80k/100k. Not many short journeys at all.

Satanta

continuous low rev driving can cause particles to build up in the dpf too. I found this to be the case in mine. even though driving 70 mile trips the particle filter didn't regen because the exhaust temp was too low. Do 20 mins in third gear at 100 kmph and you might force a regen.

Atlantic Dawn

If the car was sitting idling at the NCT centre or was stuck in traffic beforehand this could increase the results.

PauloMN

Atlantic Dawn wrote: »

If the car was sitting idling at the NCT centre or was stuck in traffic beforehand this could increase the results.

I'd say it was, cause I was waiting for ages before they started with the test. My economy reading was unusually low also when I started driving away from the NCT centre.

PauloMN

Satanta wrote: »

continuous low rev driving can cause particles to build up in the dpf too. I found this to be the case in mine. even though driving 70 mile trips the particle filter didn't regen because the exhaust temp was too low. Do 20 mins in third gear at 100 kmph and you might force a regen.

'Scuse my ignorance, what's a regen?

MarkR

I think when the particle filter heats up to a sufficient temperature, it burns off the carbon buildup?

swhyte027

It might not be the cat it could be because the car might need a service there could be vacuum pipes leaking anything could cause that not always the cat or dpf so don't jump the gun.theres a lot of pipes on that engine which crack and leak and u might not even notice it yet.i wouldn't worry about it yet, maybe when it's next service u could find u might need to change something and that could have ur emissions back to normal again.

Satanta

its when the dpf regenerates or simply burns off the soot/particle buildup. As suggested the exhaust temp needs to be high enough for this to happen. It may not reach the right temp at low rev driving.