Timeline for What makes two-stroke engines less fuel-efficient than four-strokes?
Current License: CC BY-SA 3.0
13 events
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| Apr 12, 2016 at 13:19 | comment | added | TMN | @IhavenoideawhatI'mdoing: I don't think we have any real data to go on. Engine inertia is going to be a negligible factor in motorcycle MPG, so if you really want to measure it you're going to have to run two similar unloaded engines at the same RPM and measure their fuel consumption. I think Anarach's assertion that a two-stroke consumes twice the fuel twice as often is wrong. If the cylinder size and compression ratio are the same, then the fuel/air mixture will be the same, not 2x. | |
| Apr 12, 2016 at 6:52 | comment | added | I have no idea what I'm doing | @TMN Even if that is the case, why an engine with less inertia needs more fuel to maintain speed? Less inertia means it has less weight, so less energy is needed to keep it moving, even if the power strokes are more frequent. This answer needs an explanation. | |
| Apr 11, 2016 at 16:54 | comment | added | TMN | @IhavenoideawhatI'mdoing: I think a four-stroke engine has considerably more inertia, due to the valve train, and it's not simple rotational inertia, either. | |
| Apr 11, 2016 at 12:13 | comment | added | Kickstart | The 2 stroke can produce more power than the 4 stroke for the same capacity, hence it needs less throttle (or a smaller engine) to produce the same amount of power. Many years ago I had a Honda H100S 2 stroke followed by a Honda CB100N 4 stroke. The H100S would manage about 95mpg however it was ridden, while the CB100N would manage about 80mpg in the same use. In general performance 2 stroke motorcycles produce their peak power at FAR lower rpm than equivalent capacity performance 4 strokes (company a CBR250 of ~1990, producing 45hp @ ~19000rpm) | |
| Jan 20, 2016 at 14:55 | comment | added | I have no idea what I'm doing | But why? Same capacity engines have more or less the same inertia, if you blast twice as much, the blasts should be half as weak to maintain the same speed, no? | |
| Jan 20, 2016 at 14:32 | comment | added | Shobin P | @IhavenoideawhatI'mdoing Well, in my example we are talking about same capacity engines so compared to a 4 stroke engine for similar cycle you will be spewing twice as often and twice as much. | |
| Jan 20, 2016 at 14:23 | comment | added | I have no idea what I'm doing | @Anarach You are spewing fuel twice as often, but not necessarily twice the amount, as I understand it. | |
| Jan 20, 2016 at 14:21 | comment | added | Shobin P | @IhavenoideawhatI'mdoing You are spewing in twice the amount of fuel than a relative 4 stroke engine which spews fuel only every other stroke for similar amount of work done and similar interval. | |
| Jan 20, 2016 at 14:18 | comment | added | I have no idea what I'm doing | I would also like an explanation of how the amount of power strokes per revolution is related to fuel efficiency. | |
| Jan 20, 2016 at 12:58 | comment | added | Zaid | MPG is not a good measure for this discussion because it brings in factors like gearing which I want to keep out of this discussion. | |
| Jan 20, 2016 at 12:58 | comment | added | JimmyB | "The higher fuel consumption of a two stroke engine is mostly due to the fact that it has a power stroke per revolution of the crankshaft." - Doesn't this statement support the opposite? More power strokes per revolution = less power wasted 'uselessly' moving the piston up and down without delivering power. | |
| Jan 20, 2016 at 12:52 | history | edited | Shobin P | CC BY-SA 3.0 |
added 119 characters in body
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| Jan 20, 2016 at 12:33 | history | answered | Shobin P | CC BY-SA 3.0 |