Are we comparing exactly the same weight/aerodynamics/rolling resistance car here, with just different powered engines? Or complete different cars like a metro, corolla, and a ferarri.
I think for otherwise identical cars, a medium sized engine (but smaller than what most cars come with nowdays) will get better mileage, because it can accellerate fast enough to get out of the fuel dumping acceleration, and into more fuel efficient cruising faster. But if it's to large, it's less efficient at cruising speed because of low part load efficiency. And if it's too small, it it always trying futiley to accellerate, instead of cruising. Also, due to real fixed ratio transmissions, a less powerful engine may spend more time at a higher RPM, where the fuel efficiency in grams/kWh is less, whereas a higher power engine could downshift sooner. There is also the human factor, that a more powerful car will entice lead footedness and speeding, and thus get worse gas mileage than an underpowered car that you just accept your slowness.... On 9/13/05, Michael Redler <[EMAIL PROTECTED]> wrote: > > > > > > > (theoretically) True > > > (IMHO) Engine efficiency and engine size are almost mutually exclusive (very > few things are perfectly scalable). > > If your throttle control is nothing more than a request for more or less > power AND there is a correlation between a demand for power and a demand for > fuel AND the thermal efficiency of the two engines are the same, why not? > > The only note I would make is repeating Kirk's point, that the > characteristics of the engine requires the operator to take full advantage > of the engines ideal running conditions. > > Of course, this too is debatable because of the number of variables. > However, I think that semantics aside, the other factors are negligible. > > Mike > > Kirk McLoren <[EMAIL PROTECTED]> wrote: > > The fuel efficiency of an engine is not a constant. At high throttle > settings economy is sacrificed for power. ie the grams of fuel used per > horsepower hour increases. That is why infinite ratio transmissions would be > worthwhile. And ideally - lossless. > > At low loads the fixed burden of the engine becomes significant. Most > diesels look best around 70% of design max. > > Kirk > > Greg and April <[EMAIL PROTECTED]> wrote: > > > > True or False > > Underpowered vehicles can be just as inefficient as overpowered vehicles. > > Why or why not? > > > > Greg H. > _______________________________________________ > Biofuel mailing list > Biofuel@sustainablelists.org > http://sustainablelists.org/mailman/listinfo/biofuel_sustainablelists.org > > Biofuel at Journey to Forever: > http://journeytoforever.org/biofuel.html > > Search the combined Biofuel and Biofuels-biz list archives (50,000 > messages): > http://www.mail-archive.com/biofuel@sustainablelists.org/ > > > > _______________________________________________ Biofuel mailing list Biofuel@sustainablelists.org http://sustainablelists.org/mailman/listinfo/biofuel_sustainablelists.org Biofuel at Journey to Forever: http://journeytoforever.org/biofuel.html Search the combined Biofuel and Biofuels-biz list archives (50,000 messages): http://www.mail-archive.com/biofuel@sustainablelists.org/
