Explain the engine modification on petrol and diesel engine required to use alternate fuel such as ethanol, LPG and biodiesel.?
John: Ethanol in a petrol engine
Ethanol in a petrol engine: To modify the engine, the may thing is changing the gaskets and seals of the fuel related parts to ethanol resistance materials. If not made of substances like Viton, they will tend to desintegrate and fail. Also contact with aluminum can be a problem. Carburetion or changes to the ECU can also be necessary in order to deliver a little bit more fuel for amount of air let into the intake. This may auto adjust in some closed-loop engines. LPG in a petrol engine: The entire fuel system has to be replaced with LPG components. If the car is carbureted, then it needs an LPG carburetor. If it's fuel injected then it needs gaseous fuel injectors and the ECU will need to be reprogramed. It will also need a pressure regulator and a way to warm it to prevent icing. Same with CNG. Also, the compression ratio and spark advance can be increased do to the higher octane of LPG and even more so with CNG. LPG or CNG in a diesel engine: Either the entire engine will need to be completely modified, or the engine can be made into a dual fuel engine. Sometimes just fumigating a small amount of LPG or CNG via a venturi tube into the intake will allow the engine to run on both fuels at the same time. Some have made such engines to run ok up to 50% gaseous fuels and 50% diesel, but the more gaseous fuels you use the more you risk destroying the engine. Biodiesel: Mainly you need methanol resistant materials in the fuel system, kind of like ethanol in a petrol engine. But another problem is bacteria proliferation in the fuel system Antibiotics might help, but periodically the fuel system may need to be disassembled and cleaned out. Another problem is in cold weather biodiesel can solidify. So you may have to either use normal diesel, or blended diesel, or install a system that will heat the entire fuel system, including the fuel tank.