On Sat, 15 Oct 2011 11:26:12 +0100
"Recliner" wrote:
It depends what you mean by 'cleaner' -- catalytic converters make
engines less, not more, efficient in terms of CO2 emissions. What has
made a positive difference is fuel injection. High bypass turbofan aero
engines are more efficient in every way than their low bypass or
turbojet predecessors.

The latest turbine engines are actually little more efficient in the amount of
work done per unit of fuel than a decent piston engine and thats only
when they're running at constant rpm.

B2003