Quote:
Originally Posted by rmay635703
Plain and simple a smaller engine will always get better fuel economy if it is of equal efficiency as compared to a larger one.
Unless the small motor has terrible gears and poor fuel delivery there is just no comparison.
That is why the mother earth 40mpg full size trucks do so with their 5hp - 25hp engines.
Obviously drivability is removed but fuel economy is great.
This is of coarse removing P&G and obviously removing what happens if the motor is so small that you run it at redline to maintain 55mph
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Pick a power requirement i.e. a particular rate of acceleration or road speed for a vehicle. For the sake of this we'll assume a CVT and that the engine can operate at a single - ideal - load and speed.There is a "right size" for the engine that will provide that power with the greatest efficiency. Both larger and smaller engines will be less efficient, just on different sides of the peak of the BSFC island.
From the OP:
Quote:
Originally Posted by NoD~
Lets say you have a 1.0L engine VS a 2.0L engine. They both use the same technologies, such as fuel injection, cam specs, etc. ..... Efficiency is just about even on these engines....
...Here's my thoughts on it: If they both consume an equal amount of fuel to produce an equal amount of power and things like idling is thrown out of the equation, should engine size actually matter? And with gearing: As long as you stay in the appropriate RPM range (such as referenced to a BSFC), is there really any point in gearing changes as long as you don't cruise in a set gear?
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If they scale perfectly they won't produce the same power with equal efficiency across the whole speed and load range. If you are going to pulse and glide they could be equally efficient with the acceleration rates proportional to engine size.