"Dave Plowman (News)" wrote
DavidR wrote:

In principle is there any reason, other than the technical difficulty
in
implementation, why a petrol engine couldn't have a fuel demand valve
connected to the pedal with the engine management determining the
necessary throttle setting?

Because petrol can only burn satisfactorily within a small range of
fuel/air ratio.

That doesn't answer the question.

Then there's no point continuing.

Well it does seem odd when your replies essentially say "they're not
the same because they're different" but on consideration, I think I see
what you were trying to say.

In a diesel a droplet of fuel will spontaneously combust because the air
surrounding it is hot.

A petrol engine requires a chain reaction where the flame from one droplet
reaches the next and if the distance from one droplet to the next is too
great, the fire goes out. I guess that in a petrol lean burn engine keeping
fuel saturated air and plain air separate is the main stumbling block.

Apart from the differences in ignition, I would still say that the fact of
having excess air is the qualification for lean burn.