NAMBA October 2020 Web.pub

Several other intake valves have been used to increase flow. They are the rear drum, rear disk, and bell valve. The bell valve has the best flow but is harder to make. All these valve systems can reduce crankcase volume. However, this isn’t necessarily important where the tuned pipe generates most of the pumping action. PROPWASH April 2020 11 Rear Drum Rear Disk Bell Valve Carbs Nitro carbs tend to be simple. They consist of a rotary barrel with a needle valve to control fuel flow. Control is by rotating the barrel. Fuel is usually fed into the carb with pressure from the tuned pipe. This gives a crude fuel injection system. As power increases, pipe pressure increases, increasing fuel flow. More elaborate carbs have air bleeds and/or multiple other adjustments for less than wide open performance. Allen Carb OS Carb I think fancy porting isn’t as important in smaller engines. Friction caused by mechanical issues causes more power loss. However, poor scavenging efficiency definitely limits power. The most modern nitro engine designs are following the best designs outlined above. The last part will be about what it takes to build the high-power nitro engine.

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