NCT Emissions

I put the car through the NCT and it failed on Lambda emissions, it seems that emissions are not far off and one of the lads who is a mechanic reckons that putting diptane for the test should bring it down and pass. Since it seems that lambda is off I was thinking of getting new lambda.

Any advice regarding this? (attached nct fail sheet)

Dipetane will have no effect on lambda reading it helps the fuel burn cleaner.
Lambda is your air fuel mixture your reading indicates high oxygen content which is either very lean mixture which could be caused by a host of different things faulty sensors etc. or an exhaust leak after your O2 sensor.
I'd check your exhaust for leaks first, i dont think your Hydrocarbon reading would be that low if you were running that lean but i may be wrong.

tester mentioned it could be the exhaust leak

i had bits and pieces of the exhaust welded before the nct but the mechanic must have missed a spot somewhere id imagine? unless its one of the flanges is leaking and needs bit of sealant?

ill need to get it checked out anyways

thanks

Lambda 1.18 would indicate running well lean...

Seeing your other values like CO and HC are well within margin it most likely causes are:
1) Exhaust hole leaking air (oxygen) into the exhaust system giving a false lean reading
2) lambda sensor on way out giving a false lean reading.

Diptane is not going to really help you pass the lean Lambda reading as the issue is lean/rich and Diptane more helpful with CO and HC (optimises combustion).

Other cause could be modifications or mapping... did you fit any mods like sports cat / open back box / free-flow airfilter without mapping for those mods?

[quote author=Keadeen link=topic=38630.msg441473#msg441473 date=1374577501]
Lambda 1.18 would indicate running well lean...

Seeing your other values like CO and HC are well within margin it most likely causes are:
1) Exhaust hole leaking air (oxygen) into the exhaust system giving a false lean reading
2) lambda sensor on way out giving a false lean reading.

Diptane is not going to really help you pass the lean Lambda reading as the issue is lean/rich and Diptane more helpful with CO and HC (optimises combustion).

Other cause could be modifications or mapping... did you fit any mods like sports cat / open back box / free-flow airfilter without mapping for those mods?
[/quote]

Car is pretty much standard except apexi induction kit and Fujitsubo Gaiken muffler which i think is standard on the RS-B leggys?

I doubt any of those mods would make an effect as in the past I have put cars thru nct that had full catbacks and induction kits??