Crankcase Supercharging Question

  • Thread starter Morgan3
  • Start date
In summary, there is a four stroke Model Airplane Engine made by Yamada (YS) that uses a rotary valve to compress a fuel/air mixture before it is admitted by the intake valve, resulting in about 14lbs of boost. YS claims a 30% increase in power/weight compared to naturally aspirated motors. The question is whether this technique has been applied to larger boxer engines, such as those used in BMWs. There are concerns about the waste of energy and potential pumping losses with this method. However, if the crankcase is sealed, there may not be much loss in compressing and expanding the air quickly. Ultimately, it remains to be seen if the benefits of the boost outweigh any potential drawbacks.
  • #1
Morgan3
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There is a four stroke Model Airplane Engine made by Yamada (YS) that uses a rotory valve in the back of the crankcase to compress a fuel/air mixture for two rotations in the valve cover, before it is admitted by the intake valve. The fuel contains oil which lubricates the bottom end. Excluding pumping losses, this would make about 14lbs of boost. YS claims 30% increase to power/weight figures compared to nat. aspirated motors.

My question is whether this has been done with larger boxer engines, like a BMW. It would seem a huge waste of energy to blow and suck the total displacement of the engine overboard with every revolution. Even with pumping losses, it seems a waste of energy. With standard oiling, one could just pump air and use EFI to add fuel at the valve.

Am I missing something or has this been done and proven to be not useful.

PhilD
 
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  • #2
If the crankcase is sealed there wouldn't be much loss compressing and expanding the air quickly. Pumping it through a valve like your engine would be a different story though.
 
  • #3
so, with pumping losses, heating, and other issues, is there a net gain with the boost provided?
 

1. What is crankcase supercharging?

Crankcase supercharging is a method of increasing the power output of an engine by forcing additional air into the crankcase, which then enters the combustion chamber and allows for a larger fuel charge to be burned.

2. How does crankcase supercharging work?

In crankcase supercharging, a blower or compressor is connected to the crankcase of the engine. As the crankshaft rotates, the blower/compressor draws in air and compresses it before sending it into the crankcase. The compressed air then mixes with the fuel in the combustion chamber, resulting in a more powerful explosion.

3. What are the benefits of crankcase supercharging?

Crankcase supercharging can increase the power output of an engine without significantly increasing the engine's size or weight. It also allows for better fuel-air mixing, resulting in more efficient combustion and improved performance.

4. Are there any downsides to crankcase supercharging?

One potential downside of crankcase supercharging is the risk of increased heat and pressure within the engine, which can lead to increased wear and tear on engine components. It may also require additional maintenance and monitoring to ensure optimal performance.

5. Is crankcase supercharging commonly used in modern engines?

Crankcase supercharging is not as common in modern engines as other forms of forced induction, such as turbocharging or supercharging. However, it is still used in some high-performance and racing engines. New advancements in technology and materials may lead to a resurgence in crankcase supercharging in the future.

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