Emissions test parameters and engine size...

[cornishsteve]

Hello... 
Yesterday my car has it's MOT test and failed on emissions, specifically too high a Lambda reading on fast idle (most likely due to a small leak in the forward flexi-pipe section of the pipe, which was noted as an advisory item).  I thought it would probably fail because of that leak, but my query is not about that as such, it's about the parameters of the test.
When I got home and read the emission test results printout more carefully, I noted that the engine size was listed as 1600, whereas my car has a 2.0 litre engine. I'm hazarding a guess that the pass/fail parameters vary according to engine size. Is this correct, and could it explain the Lambda reading failure?
I don't want to have to shell out for a repair of an advisory item if it's not absolutely necessary right now. Can I ask the test station to retest the emissions with the correct engine size criteria?

[chronic]

Hello,

The emissions analyser should have been set up using the exact engine code from the vehicle once it had failed the first part of the test (BET). Very often these engine codes are not available, so a tester may just take a best guess.

The pass/fail criteria DO NOT vary according to engine size. 99% of petrol emissions tests lambda limits are the same ( 0.97 - 1.03 ). So it is unlikely that retesting with the correct engine size/code will make any difference.

There are a few exceptions, I'm thinking of some BMW's (lean burn engines) and Rover's do have a wider range of lambda limits.

What vehicle do you have?

You are correct in assuming that the exhaust leak will cause a high lambda reading.


Regards.

[ht]

Mar 8, 2018 7:13:07 GMT 1 cornishsteve said:

Hello... 
Yesterday my car has it's MOT test and failed on emissions, specifically too high a Lambda reading on fast idle (most likely due to a small leak in the forward flexi-pipe section of the pipe, which was noted as an advisory item).  I thought it would probably fail because of that leak, but my query is not about that as such, it's about the parameters of the test.
When I got home and read the emission test results printout more carefully, I noted that the engine size was listed as 1600, whereas my car has a 2.0 litre engine. I'm hazarding a guess that the pass/fail parameters vary according to engine size. Is this correct, and could it explain the Lambda reading failure?
I don't want to have to shell out for a repair of an advisory item if it's not absolutely necessary right now. Can I ask the test station to retest the emissions with the correct engine size criteria?

Regarding emissions the manual says,
Exact Match: To find an exact match in the current emissions data book, you will need the make, model and other data such as engine size, model code, engine code, VIN code or serial number. If after normal cleaning and/or scraping processes a particular code is unreadable or inaccessible, carry on as if no exact match can be found. Test to default limits, carry out that test, but use the less demanding of either the default limits or the specific limits for any vehicle which is an exact match in everything but an unreadable code.

The emissions standards for any specific vehicle should be found in this book
www.gov.uk/government/uploads/system/uploads/attachment_data/file/676700/in-service-exhaust-emission-standards-for-road-vehicles-19th-edition.pdf

As mentioned in the previous post the lambda reading is the same across the range except for a few engines, Hope this helps 

[bikenut]

Lots of variations from the base 0.97 to 1.03 for a fair few makes and models if you look. Surprising and makes interesting reading if you like keeping up to date    

[castrolrob]

please also keep in mind that some makes/models have identical emissions rqmnts across the range and as such even with correct info entered will not neccesarilay provide an engine size when logged in.some analysers don't allow you to proceed without entering something in the box so best guess would do,i persomally enter . or similar to avoid precisely this sorta argument.as a general rule if its a motor after 2002 with a very few exceptions lambda shud be 1.030-.970 whatever youre driving.the reason hes advised the flexi is cos its gotta be bolloxed to fail,on its last legs aint quite enuff,not the first time ive seen summat that's a borderline pass but would need fixing to rectify a different fail.imbalance on brakes with an advise on rotten discs would be another common one