In their expansion the four stroke defeat two stroke cause by emission gas. But in four strokes engine also has problem of mechanical & process loss. That is only 40% remain power to turn the wheel.
Totally there are six loss of four strokes engines,
1. Compression Ratio loss.
The compression ratio can not be increase due to tendency to knocking caused by the rapid increase temperature of combustion chamber.
2. Air-Fuel Ratio (AFR) loss.
To created ideal comparison of air-fuel ratio and how to mixture of them is not easy.
3. Combustion Period loss.
How long the mixture of air and fuel.
4. Combustion Timing loss.
How can to define the ignition time, if not right knocking can created.
5. Pumping loss.
The condition where camshaft can not created opening and closing valve as a variation of load engine. This problem solved by variable camshaft.
6. Mechanical loss.
This is about friction.
Mazda Skyactiv claim that they can decrease consumption of gasoline until 15% or equal to modern diesel engine.
Also the torque power can increase until 15%. So 60% of gasoline engine loss can be taken back.
Mazda Skyactiv solution to answer the six losses are high compression ration can created high temperature at combustion chamber so the fuel can ignition by itself before ignition of spark plug.
The effect of that the engine will loss of torque power. Mazda Skyactiv install the exhaust system with 4-2-1 to reduce the temperature . This system is effective in reducing emission gas flow from one cylinder to another cylinder.
The temperature of exhaust gas can be increase by take slowly of ignition by piston with hole at the center.
Mazda skyactiv fuel injection system can hold the fuel to not enter the combustion chamber before the right time.
This hold time is using to mixture air-fuel. And the created time of ignition, the tendency of knocking almost impossible happen.
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