On 26/11/2013 16:20, Mike Barnes wrote:
"Dave Plowman (News)" :
In article , The Other Mike
wrote:
On Mon, 25 Nov 2013 19:09:31 +0000 (GMT), "Dave Plowman (News)"
wrote:

Notice you've missed out ordinary cars. Over 400g per mile.

If 'ordinary' means 'gross pollutor'

A Porsche 911 or a Land Rover Discovery only put out just over 300g per
mile

Try a Dacia Sandero 99g/km

To get any meaningful comparison, you'd need to test cars and aircraft in
the same sort of way. The government figures for cars are merely for
taxation purposes.

And for comparison *between* cars, presumably.

Can anyone answer me this? ISTM that the amount of carbon coming out of
an engine is exactly the same as the amount going in. If that were
precisely true there would be an exact reciprocal relationship between
measured fuel consumption and measured emissions for a given fuel. Yet
that doesn't seem to be the case. Is that to do with the form of carbon
emitted (elemental, monoxide, dioxide) or something else?


The figures for emissions are usually CO2 equivalent, which includes an
allowance for the effects of any methane or nitrous oxide present.
Methane is weighted at 21 times and nitrous oxide at 310 times, to give
the equivalent amount of CO2.

Colin Bignell

Nightjar :
On 26/11/2013 16:20, Mike Barnes wrote:
"Dave Plowman (News)" :
In article , The Other Mike
wrote:
On Mon, 25 Nov 2013 19:09:31 +0000 (GMT), "Dave Plowman (News)"
wrote:

Notice you've missed out ordinary cars. Over 400g per mile.

If 'ordinary' means 'gross pollutor'

A Porsche 911 or a Land Rover Discovery only put out just over 300g per
mile

Try a Dacia Sandero 99g/km

To get any meaningful comparison, you'd need to test cars and aircraft in
the same sort of way. The government figures for cars are merely for
taxation purposes.

And for comparison *between* cars, presumably.

Can anyone answer me this? ISTM that the amount of carbon coming out of
an engine is exactly the same as the amount going in. If that were
precisely true there would be an exact reciprocal relationship between
measured fuel consumption and measured emissions for a given fuel. Yet
that doesn't seem to be the case. Is that to do with the form of carbon
emitted (elemental, monoxide, dioxide) or something else?


The figures for emissions are usually CO2 equivalent, which includes an
allowance for the effects of any methane or nitrous oxide present.
Methane is weighted at 21 times and nitrous oxide at 310 times, to give
the equivalent amount of CO2.

Excellent, thanks. They're presumably "equivalent" in the greenhouse
effect sense.

--
Mike Barnes

On 26/11/2013 17:38, Mike Barnes wrote:
Nightjar :
....
The figures for emissions are usually CO2 equivalent, which includes an
allowance for the effects of any methane or nitrous oxide present.
Methane is weighted at 21 times and nitrous oxide at 310 times, to give
the equivalent amount of CO2.

Excellent, thanks. They're presumably "equivalent" in the greenhouse
effect sense.


Indeed. The ratios come from the IPCC, who believe in these things.

Colin Bignell