Ask: Why two stroke engine compares four-stroke engine excessive consumption of fuel and oil, thank
" car knowledge " answer: Start function to make successive job, combustion, the order with need a series of movements to press certain repeats carry out. Above all gas mixture inside inspiratory air cylinder, generation of the combustion after gas is compressed expands, the gas that combustion produces from cylinder eduction.
Take energy of life so, compress, 4 movements repeat combustion, exhaust the process that have is called the job of engine circulates.
Two-stroke engine brace rotates 360 ° finish loop of a job, namely brace rotates circuit engine combustion does work, it is to rely on cylinder the mural mouth that sweep gas, vent is finished into, of exhaust process. Four-stroke engine brace rotates 720 ° finish loop of a job, namely brace rotates two rounds engine combustion does work, it is to rely on to deserve to enrage cam to control into, exhaust valve is finished into, of exhaust process.
Because two-stroke engine brace rotates,circuit does one second work, the brace of four-stroke engine rotates two rounds to do one second work, so the torque of the two-stroke engine relatively four-stroke engine is even; Fall in the circumstance of identical crankshaft rotate speed and same job cubage at the same time, the power that the two-stroke engine outputs is one times higher than four-stroke engine, but because the two-stroke engine has the loss that sweep gas, and effective job travel reduced when take a breath, so its actual output power compares four-stroke engine only tall 50% ～ 70% .
The 150 ° of 130 ° ～ that the two-stroke engine occupies crankshaft corner only into process of gas, exhaust, fresh mixture gas enters crankcase first, when piston be issued to lower levels, fresh mixture gas enters air cylinder firebox by the mouth that sweep gas, push residual gas a vent at the same time. To make waste gas eduction cleaner, inevitable meeting has a few fresh mixture gas pours out of vent along with waste gas, cause fresh the waste of mixture gas, make oily cost rises.
And the 360 ° that four-stroke engine occupies brace corner in all into gas, exhaust, the piston when exhaust goes up consummate dead centre, waste gas forcibly eduction, be issued to lower levels of the piston when taking energy of life comes next dead centre, those who enter is fresh mixture gas attends combustion entirely almost, what basically was not wasted is fresh mixture gas, because this is oily bad news is inferior.
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