Quote:
Originally Posted by PierrePHRWEAUX
I was wrong I confounded "Carnot cycle" with "Otto cycle". Indeed Carnot cycle is the 'perfect' thermodynamic cycle.
Otto cycle = 37%
Diesel cycle = 42%
(42-37)/37=13,5% difference. (I thought too fast)
I think the problem with diesel engine is that to have the best combustion possible and thus the best efficiency, the engine has to run slow. It's probably due to tha fact that fuel is injected in a very high pressure cyclinder which make it difficult to spread. That's why it burns in excess of air and produce NOx. The fact that it has to run slow make it very suitable for big engine (trucks) an for industrial applications.
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those are the theoretical efficiencies of each cycle and there are many variables involved in calculation of those values, the main factor being compression ratio which is obviously much easier to push the limits with in the diesel cycle. also those are just peak efficiency values, location and distribution of those with respect to drive cycle is what will determine your actual mpg performance. the benefits in efficiency and fuel economy are at least significant, not to mention a torque value in the 335d that provides just the kind of grunt that makes a sports car fun to drive around town, and i dont know about you but thats where i tend to spend my time. because i am an environmental nerd i cant help but love the diesel (also because i effin love the torque), but i have never driven a sporty diesel car, only trucks, so really as far as driving experience im talking out of mere speculation.. yes diesels rev more slowly and favor lower rpms but couldnt this be geared to give the driver a sporty experience? i really would like to know.. the 335d has gotten great reviews thus far. do they really have the sluggish feeling of a typical truck diesel?