3 ms·
Nit pick, apologies up front. Two stroke motors are actually more efficient than four stroke motors, they just emit a bunch of pollution due to the oil in the g
by anonfornoreason 5y ago
Nit pick, apologies up front. Two stroke motors are actually more efficient than four stroke motors, they just emit a bunch of pollution due to the oil in the gasoline, which is a much dirtier combustion than gasoline.
A two stroke motor is considerably simpler than a four stroke, they often come in at around half the weight for an equivalent power output, and have less moving parts. This is why they are the default engine of choice for hand powered tools - almost no maintenance, very little warmup cycle, high power:weight ratio. The downside is dirty exhaust.
Modern two stroke dirt bikes have actually all started moving to fuel injection to help combat this. No premixed oil/gas, oil is injected at an optimal ratio given the load of the engine. Light cruise / idling, they run at 100:1, at heavy throttle they drop down to 50:1. Much more pleasant than something set to constantly run, via premixing, at 50:1 gas:oil.
Other note: large ocean freighters are two stroke engines: https://en.wikipedia.org/wiki/W%C3%A4rtsil%C3%A4-Sulzer_RTA96-C https://en.wikipedia.org/wiki/W%C3%A4rtsil%C3%A4-Sulzer_RTA9...
- Scene_Cast2 5y agoThere are different types of efficiency. I think you might be referring to power per weight, while the parent comment is talking about emissions per (unit of) power. To dig further, you can also differentiate between peak and sustained power; MTBF, maintenance (and dollars of maintenance) per hour of operation, volume, overall environmental effect (due to lifespan and manufacturing), etc etc.
- anonfornoreason 5y agoI am referring to both thermal efficiency, and power to fuel ratio. Meaning, for any given amount of work needed, a two stroke will produce more work for the same input of fuel as compared to an equivalent quality/design four stroke motor. Your point is a good one though, but I think the common use case of the word efficiency, when talking about vehicles, if fuel required to produce a given amount of work (miles, horsepower, etc).
- ansible 5y agoI actually was talking about thermal efficiency of two-stroke vs. 4-stroke, and believed that overall four-stroke does better. Reading about just a little bit, this may not be the case... depending on what application you are talking about. I would expect to be some differences between a 10-ton marine two-stroke on a ship vs. a 49cc two-stroke on a moped in terms of efficiency.