MOT emission readings ?

[Schakal]

these are the readings i have been given at the mot test a few days back .
just wondering what actually they mean in plain english .
can anyone shed some light to this pls ?

CO %VOL ----- MAX LIMIT = 3.500 ----- ACTUAL VALUE = 0.607
HC ppm vol ----MAX LIMIT = 1200 ------ ACTUAL VALUE = 143

[dave j gtt]

these are the readings i have been given at the mot test a few days back .
just wondering what actually they mean in plain english .
can anyone shed some light to this pls ?

CO %VOL ----- MAX LIMIT = 3.500 ----- ACTUAL VALUE = 0.607
HC ppm vol ----MAX LIMIT = 1200 ------ ACTUAL VALUE = 143

in plain english it passed with ease

[RichR]

What don't you understand about the figures? What they represent, or why they are the values they are?

In simple terms, the percentage of carbon monoxide in the exhaust gas was measured at 0.607%. You're allowed up to 3.5%. Also there are 143 parts per million of unburnt hydrocarbons in the exhaust (and you're allowed up to 1200).

This implies that the combustion is pretty close to being perfect in terms of reacting the hydrocarbons in the fuel with oxygen to get the maximum energy out with nothing left over. On the other hand, it could indicate that it's running with an excess of oxygen - ie lean - at some point. Only a wideband lambda sensor (which measures oxygen in the exhaust) will tell you that. On fuel injected cars, you tend to get the Oxygen figure on your MOT emissions test too.

[Schakal]

What don't you understand about the figures? What they represent, or why they are the values they are?

In simple terms, the percentage of carbon monoxide in the exhaust gas was measured at 0.607%. You're allowed up to 3.5%. Also there are 143 parts per million of unburnt hydrocarbons in the exhaust (and you're allowed up to 1200).

This implies that the combustion is pretty close to being perfect in terms of reacting the hydrocarbons in the fuel with oxygen to get the maximum energy out with nothing left over. On the other hand, it could indicate that it's running with an excess of oxygen - ie lean - at some point. Only a wideband lambda sensor (which measures oxygen in the exhaust) will tell you that. On fuel injected cars, you tend to get the Oxygen figure on your MOT emissions test too.

thats what i was after , thanks muchly