My car failed the NCT a month ago the main issues being emissions, discussed here and here and brake balance.
The Emissions results as follows:
Low idle pass
High idle
Lambda 0.825 Pass criteria 0.97 to 1.03
CO 6.6 vol% Pass criteria below 0.3%
HC 243ppm Pass criteria below 200ppm
Note the car was running on E5 at the time or at least 90% E5. So perhaps 3 to 4% ethanol in the tank.
The CO figure would appear to be the main offender
To remedy this the steps taken were as follows:
Fit replacement cat, and when tested at the garage without an air filter (I assume the logic is that it impedes airflow, and by removing it, the engine gets more oxygen leading to a more efficient burn), the CO figure came down to 0.4% (still outside the pass criteria of 0.3%). That said the engine would not have been running hot at the time.
For the test I also took the following precautions. Ran the car on an approximate 20% ethanol mix, along with a good slug of diepetane, removed the air filter, and took it for a spirited drive
Results at fast idle
CO =0.02%........quite a change form 6.6%
Lambda =1.000 (stoichiometric !)
HC=157ppm
The other issue was brake imbalance.
Pass criteria is below 30%.
Was 40% on the rear. due to worn caliper seals.
An 27% on the front (a pass), put the caliper had seized causing uneven pad and disc ware.
So I replaced the front pads, rear discs and pads, had all four calipers reconditioned and fitted steel braded brake hoses.
Result: 1% imbalance on the front. 4% on the rear.
I should at least be able to stop now. Unfortunatly the the front discs became warped as a result of the caliper seizing -all the more annoying as there was only~13k km on them. So will be fitting new uprated vented, grooved and cross drilled discs next week.
Now where did I put that decat pipe