Omen

Just going through the MOT today and its failed but i knew it would. I have a full decat magnex system and K&N induction kit but thought i would give it a shot just incase I was lucky!

In the end my readings were Fast Idle (.3% allowed) .63% 1st test and .53% 2nd test and natural idle (.5% allowed) .75%.

Fingers crossed the centre section will get me under the limit but what i would like to know is does the induction kit increase emissions - if so i might swap this too to make sure or its another 25 squid (only 1 free retest)!!

Anyone know?

TIA!
Omen

john banks

Cat should do the trick without the induction kit. If it doesn't can't see that changing the induction kit will help - more likely knackered or not hot cat.

Omen

Ok cheers! Thanks for the reply.

Dont suppose you know much about LAMBDA too? Just posted another thread in this forum about the reading being high!

john banks

How high was it? IIRC you have to be within 1 or 2% of lambda 1. You need this AND the cat to pass.

Omen

This is the other post:

2nd MOT failure post today! Done some searchin about but agai couldnt find an answer....

I've just noticed too that the LAMBDA reading on my emissions sheet is high:

1st test (1.03 limit) was 1.134
2nd test 1.209.

My questions are:

1. does the exhaust (cats) alter this reading?
2. Will a high LAMBDA reading fail the test (i assume so)
3. If the LAMBDA readng is high does it increase emissions?
4. Exactly where is the sensor?
5. What does LAMBDA mean?

TIA

john banks

1. does the exhaust (cats) alter this reading?
Not really, depends on how/where measured is my understanding. If you measure %CO in post cat gas then I think yes
2. Will a high LAMBDA reading fail the test (i assume so)
Yes, needs to be about 1 +- a tiny tolerance (ie closed loop ECU control required)
3. If the LAMBDA reading is high does it increase emissions?
Increases NOx mainly as the cat can't do its stuff unless lambda is 1. Not sure they do NOx on present MOTs though. However, you can get the HC and CO pretty low without a cat, but really need a cat to pass. For the cat to work you have to have lambda 1.
4. Exactly where is the sensor?
Downpipe on lates, headers in early
5. What does LAMBDA mean?
1 is the ratio for complete combustion of petrol. Needs air fuel ratio of 14.7:1 for the 3 way cats to work, 14.7:1 has high NOx, low HC and CO, the cat does the rest and cleans everything up.

You are probably the lean side of stoich because of your induction kit. Whatever, it would fail if the lambda sensor is not working - sounds like yours is not.

Potentially, failed MAF could be lean or rich depending on failure mode, and if >25% correction required, lambda may not get it back = open loop = MOT failure even with working lambda.

Most likely you have a failed lambda sensor though. This topic is not straightforward I am afraid!

[Edited by john banks - 2/26/2003 10:07:29 PM]

Omen

Voila!

Whacked the CS on last night and its flown through the test today.

Only just made the LAMBDA by 0.01 like but made it.

Thats a weight off my mind! :-)

bigsinky

we are lucky in NI. i have been told from a reliable source that there is no legal requirement for a cat and that your car just needs to pass emissions.

cheers

big sinky