1.6k Series MOT Failure on emissions

[grumpy the 7th]

There are also TWO different criteria for MOT emissions test on K series cars. Both have the same software release 11.2 and both are dated May 2018. See my last 2 MOT emission test results 2021 shows "vehicle model" as ALL TYPES with fast idle CO at 0.30% and Lamda at 0.95 - 1.09 and Natural idle CO at 0.50% This years 2022 doesn't specify what model and shows different CO & Lamda values.

Since 2004 the MOT certificates I have show there have only been 'ALL TYPES' entered 3 times (2008, 2020 & 2021)  

I can only assume the tester has a choice of entering "vehicle model" ??? see attached picture

 

[Jonathan Kay]

Two sets of limits... see also https://www.caterhamlotus7.club/comment/2406733#comment-2406733.

Jonathan

[John Vine]

#51:  I can only assume the tester has a choice of entering "vehicle model" 

I'm not sure he has a "choice" as such.  I believe the testing procedure works like this:

The MOT chap carries out a Basic Emissions test first (including lambda 0.97-1.03).  If the vehicle passes, the test is complete.  But if it fails, he then conducts a vehicle-specific test using limits set out in the In-service Emissions Standards book. 

Note that, according to that book, the wider lambda range of the specific test applies to all Caterhams except the VX 2-litre models with engine Code VJ.

It looks as though, in 2022, your car passed the basic test, but in 2021 needed the vehicle-specific test.

JV

 

[Andrew 21 Edney]

Interesting list, wondering how engine code Z3 for the 160 would be handled...

Limited Volume Type Approved Fully Built Vx HPC seem to be subject to tighter emissions (code F) rather than it being the engine code per se.

[John Vine]

Except that "Seven Vauxhall 2.0i HPC 16v VIN Code S or K Engine Code VJ" has the same limits.  Were there in fact any type-approved UK Vx cars?

All very confusing.  I don't understand why a 2L Vx injection engine should be tested more strictly than a K, Sigma or Duratec.  No doubt DVSA has a reason.

Also, I take it the "1020" max rpm for normal idle should read "1200"?

JV

[Andrew 21 Edney]

Hmm, not sure what happened to my reading skills this morning, you're correct that kit and factory built cars have the same limits...

[StevehS3]

Just an observation, having seen a few MOT emissions results it is often the case that the mixture shows lean not rich. Any thoughts on why this is? 

[John Vine]

#57: When my R400D kept failing the basic test on high lambda, the MOT chap felt it was due to exhaust leaks at the cat collector - quite a common problem with 7s  perhaps? I don't use sealant there so he may well have been right. The car did pass the vehicle-specific test though.

JV

[StevehS3]

#58 I was wondering about that but as those joints are before the car's lambda sensor I had it in my head that the lambda would measure lean and in-turn richen the mixture. Perhaps it can't richen enough to compensate? Either way it could result in the engine running richer than needed when in closed loop (which obviously wouldn't be a good thing). 
The collector joints rattle a bit on my car so I don't think there is a good seal. I have thought about using a sealant on the joints but didn't want to make them difficult to separate in the future.

[simon_h]

Seal them with O2 sensor safe silicone gasket maker, not bathroom sealant. It'll hold and seal enough while assembled but come away when you pull it apart 

[John Vine]

I have a tube of Permatex 81878 ready to go, but haven't got round to using it yet.

JV

[grumpy the 7th]

Hi, John. It would seem like that but that's not the case. It's a VERY Caterham friendly garage  

I actually sit in the car whilst it's tested and go up on the 4 post lift to operate the switches & pedals etc, so I know what they're doing. It wasn't until this OP thread that I looked at my test results and realised my past history has different test criteria.

 

[StevehS3]

Ordered a tube of Permatex 81878. Leaks just upstream of the lambda sensor can't be a good thing. 

[john milner]

My understanding (which is often wrong) is that Lambda sensors check for oxygen. if an MOT reading is high either the mixture is either low on petrol or more likely the exhaust is leaking and sucking in air which dilutes the exhaust fumes.

The sensor fitted to the car tells the ECU the oxygen content of the exhaust fumes as they leave the manifold. The ECU then tweaks the mix, ignition etc.

The probe used by the MOT examiner checks the oxygen content at the tail pipe. I think the main reason for this test is to avoid the occupants of a car being gassed by a leaky exhaust system.

As most of our exhaust systems are fitted on the side of the car the risk of being gassed is much less than with a more conventional car.

[C7 Owl]

Thanks for all input on this.  Really appreciated.  So had another crack at finding an exhaust leak over the weekend.  After fair bit of searching decided not leaking in the exhaust system.  So I replaced the lambda sensor.  Took a fair bit wd40 and running the car to get it hot.  But got it off.  Was a bit disconcerting after refitted the new bosch part that when the engine was running there was some fumes emanating from near the sensor .  Didnt have MOT so couldnt take it for a run.  So I crossed my fingers that it was the preapplied grease and some residual WD40 burning off.  Took it for a decent run this afternoon on way to test centre.  After the run there were no fumes coming out so decided I had tightened sufficiently and was not exhaust gasses.  

Passed the retest with Lambda of 1.030 so well below the max 1.090.  Very relieved because it didn't sound like many more things to try other than getting more experienced mechanic to find an exhaust leak.  

 

 

[John Vine]

Excellent!  Thanks for posting the fix. 

Out of interest, which testing station did you use this time?

JV

[C7 Owl]

Took it to Morleys Auto Services in Redhill who did the 2nd test that failed.  This was the free retest.  They are who I took it to for the previous 2 years.  

 

 

[John Vine]

Thanks.  Glad you got a free re-rest. 

Presumably, they've now withdrawn their accusation that you'd removed the cat.

JV

[Jonathan Kay]

Well done. Thanks for adding the solution.

Jonathan

PS: I recommend using penetrating fluid (such as PlusGas) rather than ordinary WD-40.