How can you determine your cars CO2 emissions per Km?

atlantean

I was just wondering how one could determine their cars actual CO2 emissions. I have just had my car NCT'd and it had no problem with the emissions test but it does not give a g/Km result.

All new cars have a g/km figure on which their VRT and road tax is calculated from. I was wondering how my old car would compare with these.

Is there a simple formula that can be used?

Anan1

I'd imagine CO2 emissions are directly related to fuel used?

atlantean

True, and how well it is actually burned!

BlackWizard

entire rain forests are disappearing because the rely on the CO2 that our cars produce. You are killing off the trees :mad:

Edit: I.e stop worry about CO2.. just keep producing it to keep the trees happy

Anan1

BlackWizard wrote: »

entire rain forests are disappearing because the rely on the CO2 that our cars produce. You are killing off the trees :mad:

?? Rain forests absorb CO2, producing oxygen and storing the carbon in the wood, no?

alias no.9

atlantean wrote: »

I was just wondering how one could determine their cars actual CO2 emissions. I have just had my car NCT'd and it had no problem with the emissions test but it does not give a g/Km result.

All new cars have a g/km figure on which their VRT and road tax is calculated from. I was wondering how my old car would compare with these.

Is there a simple formula that can be used?

The NCT emissions test has nothing to do with CO2. It checks CO and unburned hydrocarbons, essentially checking that your engine is in tune and your catalytic converter is working. To find the official figures for your car, try www.smmt.co.uk and to do the real calculations for yourself, for every litre petrol consumed, approximately 2.38kg of CO2 is produced, the figure for diesel is 2.65kg.

BlackWizard

alias no.9 wrote: »

for every litre petrol consumed, approximately 2.38kg of CO2 is produced, the figure for diesel is 2.65kg.

Is this really true? Seems like a lot of CO2

Mr Benevolent

Is this really true? Seems like a lot of CO2

Let's see:

Assume a 1.9TDI engined VAG producing 147g/km

Fuel efficiency would be @ 50mpg or 17.8 km/litre

Diesel weighs about 900g per litre (specific density)

So 1kg of diesel = 1.10 litres

17.8 * 1.10 = 19.6km

19.6 * 147 = 2.878kg

Close enough...

galwaytt

atlantean wrote: »

I was just wondering how one could determine their cars actual CO2 emissions. I have just had my car NCT'd and it had no problem with the emissions test but it does not give a g/Km result.

All new cars have a g/km figure on which their VRT and road tax is calculated from. I was wondering how my old car would compare with these.

Is there a simple formula that can be used?

Short answer, no.

The CO2 g/km figure you're referring to is calculated according to a particular ISO standard, which involves certain speeds etc etc.. You can't work back to that, for a car that was never tested to that standard.

The problem with using fuel actually used and the CO2 produced during it's combustion is, that if you used that formula, the new 'green cars' wouldn't be half as green as they're made out to be.........and that wouldn't suit a bunch of people......

Rest assured, that if you have an older car, that is clean on CO2 on idle, doesn't burn oil, and is running well, that, by keeping it on the road for as long as possible, you are de facto making a bigger contribution to NOT producing CO2 compared to ANY new car, due to you not incurring any CO2 in manufacture of a replacement vehicle.

Anan1

Confab wrote: »

Aren't the two of you saying the same thing?

No - BlackWizard is saying the CO2 is killing the trees, i'm saying they're using it to grow.

alias no.9

BlackWizard wrote: »

Is this really true? Seems like a lot of CO2

Example: Fiat 500 1.2 petrol 55.4mpg / 119g CO2/km
55.4mpg / 0.62 = 89.35 km/gallon
89.35 km/gallon / 4.55 = 19.64km/l
19.64km/l * 119g CO2/km = 2337.16g CO2/l = 2.34kg CO2/l

The figure I quoted above is averaged over a range of cars.

siralfalot

Just buy a V8 and forget about silly and irrelavent things like CO2

unkel

BlackWizard wrote: »

Is this really true? Seems like a lot of CO2

Yep. You can work it out the other way around. Say an average petrol car emits 160g of CO2 per km. With a fuel consumption of 15km/l (40MPG) this amounts to 15*160 = 2.4kg for the one kilometre

Anan1

BlackWizard wrote: »

Is this really true? Seems like a lot of CO2

I'm no chemist, but if every carbon molecule bonds to two oxygen molecules to make CO2 then the weight sounds about right.

sparklepants

A lot easier than all of the above.

Petrol emits 2.33 kg CO2 per litre consumed
Diesel emits 2.68 kg CO2 per litre consumed

Just track the amount of fuel you use and the CO2 calculation is easy.

sparklepants

unkel wrote: »

Yep. You can work it out the other way around. Say an average petrol car emits 160g of CO2 per km. With a fuel consumption of 15km/l (40MPG) this amounts to 15*160 = 2.4kg for the one litre

Corrected that for you!

Dartz

Who cares?

Really, truly. The green party? They're a bunch of blithering idiots who I wouldn't deign to waste a bullet on. I don't believe Co2 harms the planet or causes climate change. It'll bloody well do that on it's own, no matter what we do here.

Mr Benevolent

I'm confused now. Is it per kg or per litre? There can be big differences because of different specific gravities.

Anan1

Dartz wrote: »

Who cares?

Really, truly. The green party? They're a bunch of blithering idiots who I wouldn't deign to waste a bullet on. I don't believe Co2 harms the planet or causes climate change. It'll bloody well do that on it's own, no matter what we do here.

I can't imagine climate change much cares what you think either, TBH.

sparklepants

Confab wrote: »

I'm confused now. Is it per kg or per litre? There can be big differences because of different specific gravities.

...

sparklepants wrote: »

A lot easier than all of the above.

Petrol emits 2.33 kg CO2 per litre consumed
Diesel emits 2.68 kg CO2 per litre consumed

Just track the amount of fuel you use and the CO2 calculation is easy.

Mr Benevolent

ahaaaaaa... light dawns