Page 1 of 1

### g/km to ppm

Posted: Mon Nov 06, 2006 9:34 pm
hi,

i need to convert g/km to a ppm reading

im really not sure how to go about this however im preety sure i will need the speed of the vehicle and exhaust gas flow
all i want is an average so if i take speed as 40k/hr however i cannot find an average exhaust flow for a vehicle

any help would be greatly appreciated

Posted: Tue Nov 07, 2006 12:04 am
You would have to know the average fuel economy.

Then you could:
*Convert the fuel volume to mass
*Write the stoichiometry equation (assume isoctane)
*Determines moles of fuel burned, and moles of O2 to burn it
*Air is 21% O2, so you could compute moles of air
*Convert moles of air to mass
Now you mass of pollutant/mass of air and can do ppm.

Far from trivial. And pointless, as US emissions are stated grams per mile. Big engines need better controls as they burn more fuel (and air) yet have to meet same emissions (cars and light trucks). Heavy truck emissions are per horsepower-hour.