I guess what about having extra pistons makes mpg worse vs. 1.8L, 2.5L, 3.5L, etc.?
In: 168
I’ve wondered the same thing. The best I can come up with is, the smaller you make a cylinder/combustion chamber, the greater its perimeter area (i.e. sides and top/bottom) in comparison to its volume. The air/fuel mixture doesn’t burn as efficiently as in the center of the combustion chamber, and it loses heat faster, so it winds up being better to have fewer larger cylinders than more smaller ones. Also, the more cylinders you have, the more friction you’ll have (more bearings, more piston rings, more moving parts in general), so the smaller the engine, the more you benefit from having larger cylinders.
What I’m not clear on is how the scaling works. In other words, by the same argument, wouldn’t it be more efficient to make an engine for a large ship with, say, eight giant cylinders instead of the 18, 20, 24 they actually use? Maybe the vibration would be excessive with beer-keg sized pistons, or maybe that just makes the engine more easily scaled…eight cylinders for a smaller ship, sixteen for a medium-sized one, and 24 for a large ship, all using the same size components.
Latest Answers