CO2 values and where they come from

peasant

To my limited understanding the output of CO2 of any engine stands in more or less direct relation to the amount of fuel used. Some tricky engine management setup may change the ratio by a few small percent, but the general rule (according to wikipedia) is this:

1 l Diesel ≈ 2,62 kg CO2[1]
1 l Petrol ≈ 2,32 kg CO2[1]

So, in order to get the grams of CO2 per kilometer, you take the fuel consumption in Liter/100km, divide by 100 and multiply by 2620 g for a diesel and 2320 g for a petrol engine.

10l/100 km = 262g for a diesel; 232 g for a petrol
7.5l/100 km = 196.5 g for a diesel; 174 g for a petrol
5l/100 km = 131g for a diesel; 116 g for a petrol


Now ...there are (BMW) people out there that claim that you can drive a 200bhp+, 2 liter twin turbo diesel, capable of 0-100 km/h in 7 seconds around the 5 liter / 100 km mark (or 56 mpg in old money)

This cannot be true ...certainly not if you drive that car according to its capabilities.


AFAIK the CO2 values for new cars are measured on the standardised EU test run ...on a simulator, at certain fixed speeds.
The BMW from the example above would do that at idle, producing such low figures ....but as soon as you drive it as its meant to be driven, I reckon it will easily double its values.


Anybody who has ever compared their actual consumption figures for their car with what's stated in the glossy brochures will relaise that this whole CO2 malarchy is just arbitrary and once again ...smokes and mirrors

E92

Why mention BMW? Same rules for all cars. No one said it was accurate, all it is is a comparison. And if you drive any car with vigour you will get rubbish fuel economy. Example: the BMW 535d apparantly did 12 yes 12 mpg around the Top Gear test track(thats what TG said anyway). That said the Mitsubishio Evo IX I think it was did 4 mpg:eek:. And the BMW is kinda like a Hybrid, the engine doesn't run when it's stopped, has brake energy regeneration, alternator that only charges only when needed, optimum gear indicator(manual box). No mystery really....the EU tests are overly simplistic, not just for the Bee-Em, but for all cars.

JHMEG

The 123d uses all the goodies found in hybrids (in a nutshell).

peasant

E92 wrote: »

Why mention BMW?

Because it's the one marque that gets mentioned in all the other CO2 related posts ...


... and to get you personally annoyed :D:D

mvpr

Now ...there are (BMW) people out there that claim that you can drive a 200bhp+, 2 liter twin turbo diesel, capable of 0-100 km/h in 7 seconds around the 5 liter / 100 km mark (or 56 mpg in old money)



I was getting those figures from the internet. It does sound a bit too good to be true alright.

However, if you were driving the 123d (or indeed any car) and getting 55mpg, surely your Co2 emissions will be way less than someone driving a 2.0turbo petrol engine, capable of 40mpg max...?

[I'm not trying to start an argument here - genuinely want to know whats going on...]

JHMEG

peasant wrote: »

you take the fuel consumption in Liter/100km

At what speed?

Are you taking idle into consideration, which is part of the EU test?

At idle the 123d, Prius, Civic Hybrid etc will release 0g (yes, ZERO) of CO2, which gives them a great advantage over conventional cars in the tests.

peasant

JHMEG ..AVERAGE fuel consumption according to EU DIN ISO goodknowshich

E92

What they do is conduct the whatever it is cycle, measure the car's CO2 emissions and then convert this to litres/100 km(the total CO2 produced in the Urban cycle for instance divided by 4 as the distance travelled is 4 km).

testicle

peasant wrote: »

Anybody who has ever compared their actual consumption figures for their car with what's stated in the glossy brochures will relaise that this whole CO2 malarchy is just arbitrary and once again ...smokes and mirrors

Don't you mean smoke and daggers? :rolleyes:

peasant

smoke and mirrors ...one "S" too many

JHMEG

peasant wrote: »

JHMEG ..AVERAGE fuel consumption according to EU DIN ISO goodknowshich

I'm not a MINDREADER!

testicle

peasant wrote: »

smoke and mirrors ...one "S" too many

Bertie changed it. You're not allowed say that anymore...