ABSTRACT

Are two stroke motorbikes poised for a comeback? With new development, they can compete with four stroke in emission cleanliness, full economy & rideability while retaining power, size & weight advantages.Now days this is the age of four-stroke engme. Because of its various advantageous like mileage, power and one of the greatest advantage is that it's emission.And therefore it is certify that it is cleanliness and made very low pollution. Because of this the two stroke engine is left out from the market. All the giant companies turn towards four stroke engines.At this stage were there is no demand for two stroke engine, because of the concentrated effort of an Australian base Orbital Engine Company take a giant leap, they took back two stroke engine technology, having advantageous over four stroke engine in all respect. And which is tie with greatest automobile companies like Peugot , Aprila and Bajaj also. This technology not restricted only for two-wheeler but also use in four-wheeler like BMW& Ford also.

INTRODUCTION

When two-stroke motorbikes comes to off road motor cross racing.Two stroke-powered bikes have always taken the lead. But its harmful emission forced the Environmental Protection Agency to ban them from rallies in America. Finally after a long wait two stroke returning to the circuit with a total redesign of engine, its fuel injection system, & working. This was possible due to the concentrated effort of an Australian organization, the Orbital Engine Company that pioneered the development of direct in cylinder fuel injection system, which reduces emission level but also increases power. In addition the redesign of the combustion chamber & valve mechanism by Honda & Bimota has enabled them to run the engine without spark plugs! In basic two stroke working cycle, fuel enter the cylinder through the intake port from one side of the cylinder & pushes spent exhaust gases out of the exhaust port on the opposite cylinder wall at the same time. This causes the fuel to mix with the exhaust gases. Some amount of exhaust gas invariably remains in the cylinder as the fresh charge comes in. When spark plug ignites the fuel mixture, some fuel is isolated from the flame by the exhaust gases still in the cylinder Goes not bum.Thus two basic disadvantages arise: incomplete combustion of fuel at low engine rpm, & expulsion at high engine rpm. Moreover the oil injected into the motor to lubricate the crankshaft is also bum off the combustion. This result more pollution than permissible limits. Some new technologies have been making waves in low emission high performance 2-stroke engine. The three different innovations competing for the right to save future Two-stroke are direct fuel injection, exhaust trapping valves & active radial combustion.

CONVENTIONAL TWO-STROKE ENGINE

The air or charge is sucked through spring loaded inlet valve when the pressure in the crankcase reduces due to upward motion of the piston during compression stroke. After the compression stroke, ignition & expansion takes place in the usual way. During the expansion stroke the air in the crankcase is compressed. Near the end of expansion stroke piston uncover the exhaust port.And the cylinder pressure drops to atmospheric as the combustion products leave the cylinder. Further motion of the piston uncovers the transfer port, permitting the slightly compressed air or mixture in the crankcase to enter engine cylinder. This causes the fuel to mix with the exhaust gases. Some amount of exhaust gas invariably remains in the cylinder as the fresh charge comes in. When spark plug ignites the fuel mixture, some fuel is isolated from the flame by the exhaust gases still in the cylinder & does not bum. For this some provision is done, the top of Next Generation 2-Stroke Engine the piston usually has a projection to deflect the fresh air to sweep up to top of the cylinder before flowing to the exhaust port. This serves the double purpose of scavenging the upper part of the cylinder of combustion product & preventing the fresh charge from flowing directly to the exhaust ports. The same objective can be achieved without piston deflector by proper shaping of the transfer port. During the upward motion of the piston from BDC, the transfer ports &then the exhaust port close & compression of the charge begins &cycle is repeated.

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