"Martin Underwood" wrote in message
s.com...
"Nick Finnigan" wrote in message
...
"Martin Underwood" wrote in message
s.com...

I've always wondered: is it the fact that diesel engines use compression
ignition or the fact that they use different fuel which gives rise their
greater efficiency and their greater torque at lower engine revs?

It is quite possible to design an 'inefficient' diesel engine, but
no-one would buy a car with one instead of a petrol engine.

Do you have examples of greater torque at lower revs?

1.8i 16V Zetec
1.8 Duratorq TDCi

1.8 16v petrol
2.0 HDi diesel

Maybe the difference is partly due to the diesels being turbo-charged and
the petrols not being.

Yes, of course it is, the function of a turbo is to increase torque,
by increasing the amount of air per stroke.

Could this be a fairer comparison?
1.4 16v petrol

1.9 SDI diesel

Still different amounts of air per stroke.