Wednesday, October 17, 2012
Liquid Petroleum Gas, Direct Injection Manual guide
The high exhaust emissions and poor fuel economy of carbureted, crank-case scavenged two stroke engines are well documented. Despite their high fuel consumption and poor emissions they remain a popular power source for small transports especially in developing countries due to their low cost and high power to weight ratio. To meet more ridged emissions requirements some two stroke manufacturers have switched from carburetors to Direct fuel Injection (DI). Direct Injection of the fuel greatly reduces the emissions and simultaneously improves the fuel economy of the vehicle.
This technique is even being applied at a retrofit to existing vehicles. DI systems for small two-stroke engines are typically the air-assist Orbital system, which requires an air pump, separate fuel pump and both an air and fuel injector. In some countries another attractive alternative exists, namely the direct injection of a gaseous fuel such as Compressed Natural Gas (CNG) or Liquid Petroleum Gas (LPG). Many developing countries have an existing LPG infrastructure as it is often used for cooking. Also many developing countries have natural gas reserves, and it is a potentially renewable resource in the form of biogas. In some countries both LPG and CNG may have lower costs than the equivalent amount of gasoline.
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