Is it possible to have a piston engine run backwards and generate electricity?

Such as a one-piston lawn mower engine.

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lemonie8 years ago
2-stroke engines will run in reverse (timings adjusted) but this is no use to you. What are you trying to to (in more detail)? L
dagenius (author)  lemonie8 years ago
nothing, really, just a question that I thought was worth asking...... or not
The 2-stroke cycle reads the same in both directions, obviously 'cos there are only 2 of them (121212121). Small petrols have valves ports in the cylinder walls, so timings go on where the piston is, and it still moves the same way regardless of the direction of the crank rotation. The only thing that causes a problem is the ignition timing, which tends not to be exactly top-dead-centre (but that can be adjusted). L
Yay! Lemonie got it! I knew someone here would know about the 2-strokes! I've got an old Bultaco that I can almost drive backwards! But as far as producing electricity....? I'm not sure running one backwards would help anything.
Risuji8 years ago
Unlike inducing motion on a motor to produce electricity, running an engine backwards that works by burning petrol will not produce electricity, because the movement is mechanical rather than electromagnetical. And, unfortunately, it won't produce petrol/gas for you either.
dagenius (author)  Risuji8 years ago
but, like deisel engines, if you compress gass enough, it will combust, and maybe you could use that...
NachoMahma8 years ago
. I don't understand. . Do you want to have a gasoline engine run counter to its designed rotation and drive a generator? Might work, but would most likely be much less efficient than running it the way it was designed. . Have another power source (eg, wind turbine, water wheel) drive the engine to produce electricity? Won't work. . Something else?
dagenius (author)  NachoMahma8 years ago
no, I want to generate power with it.
Picture it as a critical failure of public education. They think that a gas engine run backwards will become a generator, probably because they heard that an electric motor can be used as a generator : P
The kicker is his username: "Da Genius"
. I thought he was Swedish.
robotguy48 years ago
Short answer: No.

You can only do this with a DC electric motor, and you need to supply it with rotation (spin the shaft) to generate power, not run it backwards. What you are describing (in the case of a lawn mower) is an internal combustion engine, which uses small explosions in the cylinders to move a piston up and down, thus moving the crankshaft. (seethisfor more info) "Running it backwards" just moves the pistons up and down, and (maybe, but probably not, due to the set up of the valves) force some air out of the pistons.

If you want to generate electricity with your engine, you will also need an electric generator or that DC motor I was talking about earlier. Take a gander at this for more info.
Sparkington8 years ago
well why dont you add a dc motor on to the output shaft and use the motor as it came out of the factory :)
kelseymh8 years ago
No, of course not. A piston engine, as several other people have pointed out, burns gasoline mixed with air in the cylinder (piston chamber) to produce motion. Running such a thing "backwards" would imply converting the exhaust (combustion products) back into gasoline plus air. There are just a few chemical and physical impossibilities there, in case you hadn't figured that out already. Obviously, you could hook your gasoline engine up to a permanent-magnet-based electric motor, and use it to spin the motor stator to produce electricity. That's exactly what a gas-powered generator is. If you think about that for more than, oh, half a second, you'll realize that it pretty much defeats the purpose of the electric motor.
electro8 years ago
A piston engine uses petrol (or gas !!) to run. I dont see how running it backwards will generate electricity. It will however still produce the electricity required to produce the spark for the ignition. If you were to fit an alternator it wouldnt matter if the engine were running back or forward as, like the ignition spark generation, it will work in either direction.
fwjs288 years ago
runs backwards:possible create energy: not that i know of.
Rotten1948 years ago
No, not that I know of. Does it use gas?