Anonymous asked in Home & GardenMaintenance & Repairs · 2 months ago

why are they called "2 stroke" engines when there is only 1 cylinder and 1 piston in the engine?

have a leaf blower that is called a "2 stroke" engine, but it is like a "hybrid 2 stroke and is like a 4 stroke too"..i dont understand it, but anyways, it has only 1 piston and 1 cylinder. so why any engine that has this is called a "2 stroke"? what means?


BTW, I need to adjust the valves /rocker arms on this engine, and need to know how to determine "TDC" without seeing any marks on the flywheel. would i need to just turn the flywheel until the piston is at the very top of the cylinder?  would that be "TDC"?

thanks for any guidance!

4 Answers

  • 2 months ago
    Favorite Answer

    Strokes are the operation of each piston.

    4 stroke, (1) Intake stroke, draws fuel into cylinder (2) Compression stroke, compresses fuel, (3) Combustion stroke, after spark, (4) Exhaust stroke, discharges exhaust.

    In a two-stroke engine, the end of the combustion stroke and the beginning of the compression stroke happen simultaneously, with the intake and exhaust (or scavenging) functions occurring at the same time.

    TDC can often be determined through the spark plug opening.

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    • dtstellwagen
      Lv 7
      2 months agoReport

      You didn't specify brand, but some hybrids operate combustion cycles like a 4 cycle, but draw mixed fuel/oil through crankcase like a two-stroke that lubricates when tipped side to side and even sometimes upside down.  

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  • elhigh
    Lv 7
    2 months ago

    The number of strokes, either upward or downward in the cylinder, between ignition events, determines the number of strokes to describe the engine.

    Typical Otto cycle (four stroke) engines use an individual stroke to do each thing:

    Intake (piston traveling downward, intake valve/s open)

    Compression (piston traveling upward, all valves closed)

    Combustion (piston traveling downward, all valves closed)

    Exhaust (piston traveling upward, exhaust valve/s open)

    Two stroke engines combine some functions:

    Combustion (at the top of the stroke) becomes exhaust (near the bottom of the stroke) as fresh intake air is pulled in at the top of the cylinder.  NOTE 1.  As the piston reverses direction, the exhaust ports at the bottom of the cylinder are covered.  Intake, which is from the pressurized crankcase, continues until equilibirum is achieved, and the intake reed valve closes.  Compression cycle continues as the piston travels upward.

    Ignition, and cycle repeats.

    Two strokes are far less efficient than four-strokes in terms of power per unit of fuel, since some of the power stroke is lost to the uncovering of the exhaust ports while some expansion still remains.  They are also a lot more polluting.  They have to have some kind of pressurization on the intake cycle to make them really effective.  This is achieved by having the fuel-air mix drawn through the crankcase in small engines (which is why you need oil in the fuel, since you can't have the crankcase with its own oil that way - it would get aspirated by the engine, run dry and seize after just a few minutes).  But it also means you wind up with an engine that can be operated in any position.

    Less efficient, but generally a lot more powerful than a four-stroke of the same size, since it has twice as many power strokes per revolution than a four stroke.  Having essentially twice as many kabooms is also why, even at low revs, a two-stroke engine sounds so much buzzier - you're hearing a higher frequency of kabooms.

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  • 2 months ago

    If you would like a more detailed answer check out the link below

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  • Anonymous
    2 months ago

    One stroke simultaneously gets rid of the old gases and bring in fresh fuel and air.  The next stroke the air/fuel is ignited for the power stroke and then you start all over.

    2 stroke.

    On a 4 stroke engine in your car, one 1 in 4 strokes of the piston does it create power.

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