NEED HELP: Failed emissions test

[AudiB720TS]

Today I was going to pass MOT and use it as the start for my turbo project.
Instead the car failed testing. Overall they said the car was in perfect condition, but they fail it because of the emissions tests. I now have 30 days to pass a retest or I am not allowed to drive the car. Needless to say, I won't be buying parts for my new project until the car is road worthy again.

You guys have similar tests and thresholds, referring to "EU 82.1.2" standards.

• CO value at idle speed: 0,4 (0,3 is highest permitted value)
• CO value at fast idle speed (2.500 RPM): 0,5 (0,2 is highest permitted value)

NOTE: other exhaust emissions values were within range: Lambda 1.0 (0.97 - 1,03), HC 68 (200).

My thinking is that 02 sensor(s) is OK because other values are good, and car runs really well. I am running a 034 Motorsports high flow cat, could that be the issue? Has anybody passed MOT with this cat before? On the other hand, my old WRX STI passed with a 100 cell cat without a problem. The cat was warm prior to test - I had driven aggressively for almost an hour just before the test so it was absolutely at good working temperature.

More info:
- Oil change and engine flush, late 2017
- New spark plugs (June 2018)
- Runs on Shell V-Power
- HFC at working temperature during test

Any and all help welcomed!


EDIT: My lambda is 1.0 which is a perfect 14.7:1 air to fuel ratio. That should mean that my mixture is OK (good actually), right!? Meaning its an issue with the HFC not reducing the CO's.

 

[DieselJake]

Was the car warm when they tested it? Best to get it up to tempreture and give it an "Italian style tune up" before an MOT, failing that get it tested somewhere more friendly.

 

[Metalsmurf]

I failed mine about a month ago, exactly the same. But standard Cat. Took it for a thrashing and passed no problem afterwards. Bit worried now as I'm going to put my 034 cat on next week.

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[AudiB720TS]

Was the car warm when they tested it?

It was VERY warm. Had been driving fast on lower gears.

I failed mine about a month ago, exactly the same. But standard Cat. Took it for a thrashing and passed no problem afterwards. Bit worried now as I'm going to put my 034 cat on next week.

Might not be the cat. Could be the JHM stage 2 tune. I found this explanation on CO (google translated):

"CO is formed when oxygen is insufficient during combustion. High carbon monoxide levels (measured as a percentage of exhaust gases) may be caused by excessive mixing, low idle speed, incorrect float level, clogged air filter, poor operating PCV valve, or incorrectly set gasification or injection. Low oxygen levels indicate that there is more fuel than can be consumed with the oxygen available. This may be called acid deficiency. The solution is to reduce the amount of fuel"
​

Going by that: my air filter and is fine (its new). Idle speed is good. PCV does have a catch can but that should improve values IMHO.
So I would guess that the tune I am on is too "fat". I can't change program on the ECU though.

Would adding E85 help?



EDIT: My lambda is 1.0 which is a perfect 14.7:1 air to fuel ratio. That should mean that my mixture is OK (good actually), right!? Meaning its an issue with the HFC not reducing the CO's.

 

[Metalsmurf]

Best bet is to put the standard Cat back on for the test, however if I had to do that every time I would get rid of the hfc and just straight pipe it.

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[Dan_Avant]

Check your MAF and MAP sensors are working properly.

I had the same issue. Changed my MAP sensor and cleaned the MAF and it got me through MOT

 

[AudiB720TS]

Check your MAF and MAP sensors are working properly.
I had the same issue. Changed my MAP sensor and cleaned the MAF and it got me through MOT

Hi Dan,
When you say you had the same issue, can you confirm you had good lambda value but poor CO?
How did you conclude you had an issue with MAP/MAF?

 

[Jon13s]

Mine has a 034 cat in and fails unless its really hot. Interested to see if there's something that has an effect on it.

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[Charlie Farley]

just a bit from me, I fitted a 034 to my old bus and it passed no problem , well within specs but it is with the standard oem system just a larger dia down pipe, maybe it is more an issue with after market systems connected to the sports cat, just a thought.

 

[AudiB720TS]

I talked to my mechanic last night. He will test my emissions again next week.
Prior to that I will do some maintenance on the car. If it fails his test, I'll have him install the OEM cat, take it to MOT and then reinstall the HFC.
Talked to JHM as well: they said it would be OK to run the Stage 2 program with stock cat provided I'm not racing the car.

 

[AudiB720TS]

This is now resolved!

Car passed emissions tests having reinstalled the stock cat converter.

Question now is: is there any Audi HFC out there that will actually pass EU emissions?

 

[Charlie Farley]

My 034 HFC passed with no problems whatsoever and they didn't need to thrash the engine to get it super hot either.

maybe in Sweden the test requirments are much stricter....

 

[Jon13s]

Mine doesn't pass first time and needs to be hot. However it now does much longer journeys so fingers crossed for the next MOT.

I suppose it could be the map?!

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