Emissions - high or low which is best?

[g717xnm]

Hi All.

I have just put my MK1 G plate 2.0i though its mot with out a problem. For the second year the co and the hc has been very low. (co 0.618 and hc 94 allowed 3.5 and 1200) so the question is what level should these be at for the engine to run at its best?

Thanks
Chris

[Sharo]

Hi, this is the graph of lambda/emissions.




I don't know the exact numbers for XM for brand new 2.0 engine (and i doubt that there is any) at lambda=1. But the numbers you specify are low enough so your oxygen sensor is OK

However, the best power is obtained at lambda=0.85-0.9. Note that in high power regimes, the ECU ignores oxygen sensor readings, and use table only for fuel, where it is assumed to run slightly rich.