Diesels and MOTs

[graham2306]

Just had my 90 MOTd, it passed eventually. Evidently new EU regulations say that the emissions test needs the engine to rev to 4000 rpm and my normally aspirated 2.5 diesel only reved to just over 3800. The testers umed and ahed a bit but eventually issued a pass. Anyone else had problems or know anything about it????

Graham

[Paul]

Hello Graham,

Refering to section 7.4 of the tester manual:

Vehicles first used on or after 1 August 1979

If appropriate, remove oil temperature probe. Raise the engine
speed to around 2500rpm, or half the maximum engine speed if
this is lower and hold for 30 seconds to fully purge the inlet and
exhaust system.

Raise the engine speed slowly to maximum to check the operation
of the governor. Once the engine speed has stabilised or if it becomes
clear that the governor is not working, release the pedal, return to idle
and stop the engine.

Prompt the meter to carry out a zero check

Check that the smoke meter probe can be inserted into the tailpipe
1. Insert the probe fully and securely, in line with the gas flow. Restart
the engine

Test
Following the meter prompts, depress the accelerator pedal quickly and
continuously but not violently, to reach full fuel position in less than 1
second, hold it there until a release prompt is given, then immediately
release the pedal. Allow the engine, and any turbocharger fitted, to
return to idle speed.

At the end of the 1 st acceleration read the smoke level displayed on the
meter. If it is at or below 1.50m-1 the vehicle has passed this part of the
test and a pass result will be displayed on the meter. Go to Method of
Inspection 3

2. If the 1st acceleration smoke level is greater than 1.50m-1 carry out
two further accelerations following the meter prompts.

At the end of the 3rd acceleration, read the mean smoke level displayed
on the meter. If it is at or below the appropriate limit, the vehicle has
passed this part of the test and a pass result will be displayed on the
meter. Go to Method of Inspection 3

If the mean smoke level is too high, carry out further accelerations up
to a maximum of 6 in total

After each acceleration, check the mean reading. This part of the test
is complete when either:

The mean of any 3 consecutive smoke readings is at or below the
appropriate limit, or six accelerations have been performed

3. Assess whether the smoke emitted from the exhaust, regardless of
measured density, is likely to obscure the vision of other road users


HTH

[karloss]

At risk of sounding a bit dim....again.
Why do they have to rev the pants of a diesel when a petrol gets away with relaxing at tickover? Apart from the visible smoke aspect of course.

[Paul]

Why do they have to rev the pants of a diesel

It's only done once to test the governor is working.

[karloss]

AAaahhh, penny drops.

[graham2306]

Thanks for that Paul, and for posting it on the GLASS forum, it's such a small world this off road one :D .

I'm a bit confused by your comment about they only thrash the diesels once.

Following the meter prompts, depress the accelerator pedal quickly and
continuously but not violently, to reach full fuel position in less than 1
second, hold it there until a release prompt is given, then immediately
release the pedal. Allow the engine, and any turbocharger fitted, to
return to idle speed.

Surely that paragraph and the following ones suggest they can thrash the balls off it up to six times.

Anyway, no mention of a 4000 rpm requirement so I wonder where the testers got that from?

Ho Hum.

Graham

[Paul]

Surely that paragraph and the following ones suggest they can thrash the balls off it up to six times.

You only go to full fuel position on the first test and that is only done the once.

If it passes after the first opperation you then move onto "Method of Inspection 3" a visual check.

Anyway, no mention of a 4000 rpm requirement so I wonder where the testers got that from?

Don't know, Sounds like he needs to read his testers manual. :lol:

[hobbit]

A lot of testers dont agree with the revving of a diesel and looking for bits underneath afterwards, but they have to follow the rules set, sometime in the future I imagine the tests will change, but god knows when, until them, all you can do is stick your fingers in your ears and pray

[Manicminer]

Is a reading of 0.92 K(1/m) good for a diesel engine?

[Paul]

Is a reading of 0.92 K(1/m) good for a diesel engine?

Yes.. That's fine.

[cstokes]

On the new test system, you only need to rev the engine to the govenor speed once, if the vehicle is below the recommended limit of smoke emission then the machine won't ask for another reading and automaticlly stops the test and issues a pass print out.  It is called fast pass.  As is for the BET test on petrol engines.