K Series & MOT lambda limit

[john milner]

The car has just passed the MOT but I noticed something a little odd. Using my car reg the lambda max limit on the test equipment was 1.03 but the official DVSA limit is 1.09. The engine was coming in at around 1.05 so was failing. I had a copy of what it should be so the tester entered all the specific engine details (1.8 VVC engine type RC) and it passed easily. I had the details with me because every year it struggles with lambda and thought it would be a good idea to arm myself with the correct numbers.

https://www.gov.uk/government/publications/in-service-exhaust-emission-standards-for-road-vehicles

[Wrightpayne]

Mine is a '98 K self build (pre SVA) and only needs a visual check.

[StevehS3]

My 2012 K MOT cert. says a limits of 0.97 and 1.03. I can't see the reference to 1.09. My actual was 1.017. The previous year it only just passed but that as due to a faulty heater in the lambda sensor. 

[John Vine]

I can't see the reference to 1.09.

The Caterham list is on pages 23-24 in the DVSA PDF referenced in #1.

Interestingly, all the models listed have 0.95-1.09 except for the VX 2-litre.

At my last MOT, I took along this list for my R400D.  I was glad I did because the tester (or, more accurately, his gas analyzer) insisted on applying an upper limit of 1.03. (I was coming in slightly higher.)  With the help of the list, he was able to select an engine type with the 1.09 limit.

What puzzled me was that, although the tester had input the VIN, the machine was applying an incorrect lambda range.  I'd assumed that it would have been programmed to implement the DVSA values.

JV

[john milner]

Exactly my point. Those numbers should be 0.95 and 1.09. Check the link.

[john milner]

Same as me the VIN was not pulling up the correct parameters.

[John Vine]

Re #6:

Ah, so it's not just me. I think I'll ask DVSA. I'll report back.

JV

[Tazio]

The references to the VX, one shows 2.0 efi, the other 2.0i, so what about those on carbs?

[StevehS3]

I see now. I also notice that the CO limit should be 0.30 whereas the MOT test report says 0.20 for my K series, so that is wrong too. I wonder which is wrong, the list or the analyser

[John Vine]

...what about those on carbs?

Good question. It's not clear to me but I guess it would depend primarily on year of manufacture?  What age would a typical one be?

I wonder which is wrong, the list or the analyser

Another good question.  My money's on the latter, given that DVSA themselves publish the list.

JV

[John Vine]

Re #10:

I wonder which is wrong, the list or the analyser

Looking at the relevant pages of the MOT Manual (Section 8: Nuisance), I don't think either is actually "wrong".  It looks as though the 0.2% CO figure is part of the Basic Emissions Test.  If the car fails that, the tester moves on to a more specific test.  There's a very informative flowchart in that section, too.

JV

[pgm]

It isn't just our type of cars that have wider limits for the lambda readings. Quite a few of the newer BMW's have a much higher limit due to their design. Watched my local tester selecting various menus to allow a Late 3 series to be tested.

 

[john milner]

The DVSA document that has information that sort of explains the reasons on pages  4- 6. To me it seems a bit daft but my reading of it is that the lambda result should be between 0.97 & 1.03 but if it fails then check the list and if the vehicle/engine is listed then do another test that has a wider tolerance. It sort of means that 0.97-1.03 is a default pass but there are exceptions (possibly all K Series Caterhams). The test kit must use the default rather than automatically look up the the wider band based on the VIN. 

 

 

"The emissions limits to be met are specified for both the fast and normal idle tests.
At fast idle, CO must be at or less than 0.2%, HC at or less than 200 parts per million
(ppm), and the lambda value(1) must be between 0.97 and 1.03. At normal idle, CO
must be at or less than 0.3%.
Where these limits are not met, a check will be made to identify vehicles (e.g. those
without a catalyst) which should only be required to meet the non-catalyst emissions
check requirements. If the vehicle does not fall into this category then the analyser
will automatically schedule an extended emissions test using the values quoted in
Table 1 or Table 2 and the listings in the Annex in this booklet.

Extended emissions test
As indicated above, an extended emissions test will be applied where the limits are
not met under the basic emissions test and where the vehicle has been identified as
needing to meet the “catalyst” test requirements. These will include petrol-fuelled
cars fitted with advanced emissions control systems (e.g. vehicles with catalytic
converters) first used on or after 1 August 1995, (2) petrol fuelled cars first used on or
after 1 August 1992 which are listed in the Annex to this booklet and large passenger
cars and light goods vehicles first used on or after 1 August 1994 and listed in the
Annex to this booklet.
As in the basic test procedure, emissions are assessed during two separate tests.
The “fast-idle” test in this case involves running the engine at the speed specified in
the Annex to this publication (typically 2500 - 3000 rpm), and the emissions of CO,
HC and Lambda values are checked. A check of CO emissions at ‘normal idle’ speed
is also carried out.
The analyser will require the tester to complete each stage of the test before
proceeding to the next. In addition, where a failure is recorded during the fast idle
test, the analyser will automatically schedule a repeat test.
(2) Passenger cars first used before 1 August 1995 and not mentioned in the Annex to this publication are tested
to non-catalyst standards.

6
This is to ensure, as far as practicable, that the catalytic converter has reached its
normal operating temperature.
Before starting the emissions test, the Tester will check the engine oil temperature to
ensure that the engine is at the manufacturer’s stated operating temperature. This
will require an oil temperature probe to be inserted into the dipstick tube.
Once the preliminary checks have been carried out and the Tester has identified the
vehicle model in the Annex to this booklet (stored on the emissions analyser
database) the Tester will begin the fast idle emissions test.
This test requires the engine speed to be increased to that specified in the Annex.
Once the engine speed has stabilised between the upper and lower limits, the
emissions will be measured for a continuous 30-second period. At the end of this
period, the analyser will automatically compare the results of the test with those
specified in this booklet. Provided the results are equal to or below the specified
limits, the vehicle will have passed this section of the test and the analyser will
automatically proceed to the normal idle test. As indicated above where a failure is
recorded during the fast idle test, the analyser will automatically schedule a repeat
test.
The “normal idle” test is the same as that described above for the basic emissions
test.
The vehicle must pass both the fast and the normal idle emissions tests to secure a
pass result."

[John Vine]

The test kit must use the default rather than automatically look up the the wider band based on the VIN. 

Yes, I suspect that's exactly what happens.  I've asked DVSA to clarify.  I'll post up their reply.

Maybe it's set up that way because the basic test is simpler (and cheaper?) to apply than the extended test? 

JV

[john milner]

It could be done that way to encourage people to get their cars as clean as possible. For example I think my lambda reading is on the high side so I may have a pinhole leak in the system. My 2019 reading was 1.001 but that was with a plastering of Gun Gum in several places after a noticed a cracked weld at the exit of the cat a couple of days before the test. I had it re-welded shortly after the test. This year with no Gun Gum the reading is 1.050.

[Geoff Brown]

Or to avoid confusion find an MoT tester who applies common sense..........nudge, nudge, wink, wink.

[John Vine]

Re #14:

Well, I asked DVSA, and this is what they said:

On all petrol engine vehicles first used on or after 1 August 1992, the exhaust gas analyser will conduct a basic emissions test (BET). The BET applies default limits of 0.2% CO, 200ppm HC and a lambda of 0.97 – 1.03. The majority of vehicles will pass the BET and that provides a speedy and efficient emissions test process.
 
If a vehicle fails to meet the BET requirements, it goes on to have an emissions test specific to the engine age and type, which commonly means testing to vehicle specific limits, which in this case meant testing to broader Lambda limits.

Whilst this emissions test process requires two emissions tests to be carried out on a small number of vehicles, it provides a quicker process for the vast majority.

This is what we'd assumed, I think.  The moral of the tale is to be sure to take the relevant page of the DVSA Emissions Standards with you, just in case!

JV

[MADMALC]

Hi Tazio,

We have a 1992 Rover Mini that has a 'cat' but is on an SU carb. There is a list of anomalies in the MOT testers appendix for this type of vehicle. The Mini is on this list and requires to pass the 'pre cat' emission test.

My MOT tester states 'if it has a choke then it is pre cat limits'.

Sorry I do not have the location of this appendix to hand but hope this helps a little in understanding the complexities of this legislation.

[john milner]

Good to to know the reasons. I had a tester a few years ago say I was just failing but he had another bigger test he would try and it passed with ease. It made little sense at the time but it is now clear. The tester this year seemed a bit stumped until I showed him the full limits and then he offered a very weak explanation of why there is a softer set of limits so it is definitely worth having the paperwork and knowing why. It's probably something the testers have to learn but might not remember the reasons as older engines become rarer.

[John Vine]

It would also be worth taking along the two flowcharts (Charts 1 and 2) from Section 8.2.1 of the MOT inspection manual.  As you'd expect, they match exactly what the DVSA person said to me (#17).

JV

 

[StevehS3]

Just reviving this thread on emissions limits. My Sigma 310R had its MOT today which it passed using the analyser limits of 0.970 and 1.030. However, the  DVSA states 0.95 to 1.09 for a Sigma car. I haven't noticed before but the V5C special notes section under SVA/IVA emissions limits states the tighter limits of 0.97 and 1.030. I wonder which are correct? Because the analyser and V5C agree on the tighter limits I am tending to think that is correct.

[Jonathan Kay]

Two sets of limits... see also https://www.caterhamlotus7.club/comment/2406731#comment-2406731.

Jonathan