why do some smaller engines have lower gas mileage than some larger engines?
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Poor design or application. You could “technically” move a dump truck with a dirt bike engine and some insane stack of gearing but it would be hugely inefficient because to get the most out of it you would be running the engine at WOT all day.
It almost always makes more sense to have a more powerful engine that doesn’t need to constantly run at 100% output, not only for obvious wear&tear reasons but also because combustion engines are most efficient when operated in a specific range of speeds, and because it’s a hell of a lot easier to build and operate a vehicle where you can modulate the speed with the engine instead of having 50 gears or some overly complex and unreliable CVT. .
Ideally the engine will be designed (or at least selected) for the vehicles use (will it be towing or hauling heavy loads? Is it a tiny lightweight commuter vehicle meant to be as fuel efficient as possible? Is it an off-highway vehicle that doesn’t need to reach high speeds?). Other considerations like duty-cycle (will this engine be running 12-24 hours a day? It’s probably overbuilt and underpowered if so) and maintenance/service intervals come into play as well, although more commonly in industrial applications. For passenger vehicles, fuel efficiency and cost of production are by far the largest factors.
Poor design or application. You could “technically” move a dump truck with a dirt bike engine and some insane stack of gearing but it would be hugely inefficient because to get the most out of it you would be running the engine at WOT all day.
It almost always makes more sense to have a more powerful engine that doesn’t need to constantly run at 100% output, not only for obvious wear&tear reasons but also because combustion engines are most efficient when operated in a specific range of speeds, and because it’s a hell of a lot easier to build and operate a vehicle where you can modulate the speed with the engine instead of having 50 gears or some overly complex and unreliable CVT. .
Ideally the engine will be designed (or at least selected) for the vehicles use (will it be towing or hauling heavy loads? Is it a tiny lightweight commuter vehicle meant to be as fuel efficient as possible? Is it an off-highway vehicle that doesn’t need to reach high speeds?). Other considerations like duty-cycle (will this engine be running 12-24 hours a day? It’s probably overbuilt and underpowered if so) and maintenance/service intervals come into play as well, although more commonly in industrial applications. For passenger vehicles, fuel efficiency and cost of production are by far the largest factors.
Engines typically have a very efficient “efficient speed”, and a fairly poor “inefficient speed”.
When a tiny engine is being pushed too hard, it may be small, but it’s having to work extremely hard, in its inefficient range, to do so.
On the other hand, the lager engine can sit happily in its efficient range, doing the same work with less effort.
Engines typically have a very efficient “efficient speed”, and a fairly poor “inefficient speed”.
When a tiny engine is being pushed too hard, it may be small, but it’s having to work extremely hard, in its inefficient range, to do so.
On the other hand, the lager engine can sit happily in its efficient range, doing the same work with less effort.
A large heavy object takes less energy to maintain it’s velocity. So when a big car gets going on the highway it takes less gas to keep it moving. More gas to speed up but less while coasting. And since most long trips are mostly coastly you’ll get better mileage with a heavier engine. Roughly speaking.
A large heavy object takes less energy to maintain it’s velocity. So when a big car gets going on the highway it takes less gas to keep it moving. More gas to speed up but less while coasting. And since most long trips are mostly coastly you’ll get better mileage with a heavier engine. Roughly speaking.
Nowadays the size of an engine does not directly correspond to its efficiency. With modern engineering a small 3-cylinder can have more power compared to an old 4 cylinder one. Tighter tolerances, different means of getting the fuel-air mixture, different fuel, different gearing, all contribute to where the optimum working point lies of that particular engine. It will perform most efficient when it’s working on that optimum.
Nowadays the size of an engine does not directly correspond to its efficiency. With modern engineering a small 3-cylinder can have more power compared to an old 4 cylinder one. Tighter tolerances, different means of getting the fuel-air mixture, different fuel, different gearing, all contribute to where the optimum working point lies of that particular engine. It will perform most efficient when it’s working on that optimum.
Percentage efficiency doesn’t depend on engine size in a linear way, there are many factors it depends on
It’s those factors where you’re noticing the difference, rather than the engine size, but those aren’t usually listed on the specs for example
Percentage efficiency doesn’t depend on engine size in a linear way, there are many factors it depends on
It’s those factors where you’re noticing the difference, rather than the engine size, but those aren’t usually listed on the specs for example
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