5 ms·

Unfortunately you can’t turbocharge or supercharge a two-stroke. There’s a material amount of time during the cycle where both intake and exhaust port are open

Unfortunately you can’t turbocharge or supercharge a two-stroke. There’s a material amount of time during the cycle where both intake and exhaust port are open at the same time. If you use any type of forced induction it would blow the fuel/air mixture straight out the cylinder before it could be ignited. You can however use a tuned pipe to cause a pressure wave to reflect back up the pipe and compress the mixture, but that’s usually limited to a pretty narrow powerband

rsj_hn 6y ago
Ahh, so the special regs only apply to 2 strokes? I thought they were based on displacement
- foepys 6y ago
  They're also valid for 4 strokes but generally speaking 4-strokes have lower torque at high rpm and since it's hard to get much power out of 50ccm anyways, they tend to be 2-stroke.
  - rsj_hn 6y ago
    I remember Honda made waves with low displacement four stroke engines. https://en.wikipedia.org/wiki/Honda_CB50 https://en.wikipedia.org/wiki/Honda_CB50 https://en.wikipedia.org/wiki/Honda_Super_Cub https://en.wikipedia.org/wiki/Honda_Super_Cub
- numpad0 6y ago
  I think he’s talking inherent technical limitations, not regulations. I wonder if it still applies if there was a pre-burning occurring in the middle of intake manifolds
swimfar 6y ago
You can have forced induction with two-strokes if you use direct injection. It ends up being pretty efficient because you can blow all the exhaust out of the cylinders and have clean air for the next cycle. You also don't need to add oil to the fuel because you don't use the crankcase to pressurize the air/fuel charge. This type of engine is really common in construction equipment and (older) big trucks, semis, buses, etc. Some were even supercharged and turbocharged.
- seryoiupfurds 6y ago
  In fact, I believe the supercharger is necessary for them to function. https://en.wikipedia.org/wiki/Two-stroke_diesel_engine https://en.wikipedia.org/wiki/Two-stroke_diesel_engine
deleted 6y ago
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rsj_hn 6y ago

Ahh, so the special regs only apply to 2 strokes? I thought they were based on displacement

foepys 6y ago
They're also valid for 4 strokes but generally speaking 4-strokes have lower torque at high rpm and since it's hard to get much power out of 50ccm anyways, they tend to be 2-stroke.
- rsj_hn 6y ago
  I remember Honda made waves with low displacement four stroke engines. https://en.wikipedia.org/wiki/Honda_CB50 https://en.wikipedia.org/wiki/Honda_CB50 https://en.wikipedia.org/wiki/Honda_Super_Cub https://en.wikipedia.org/wiki/Honda_Super_Cub
numpad0 6y ago
I think he’s talking inherent technical limitations, not regulations. I wonder if it still applies if there was a pre-burning occurring in the middle of intake manifolds

swimfar 6y ago

You can have forced induction with two-strokes if you use direct injection. It ends up being pretty efficient because you can blow all the exhaust out of the cylinders and have clean air for the next cycle. You also don't need to add oil to the fuel because you don't use the crankcase to pressurize the air/fuel charge. This type of engine is really common in construction equipment and (older) big trucks, semis, buses, etc. Some were even supercharged and turbocharged.

seryoiupfurds 6y ago
In fact, I believe the supercharger is necessary for them to function. https://en.wikipedia.org/wiki/Two-stroke_diesel_engine https://en.wikipedia.org/wiki/Two-stroke_diesel_engine

deleted 6y ago

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