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The methodical pursuit of fuel efficiency improvement
Using an engine that synergistically works with motor output and achieving high-efficiency operation and comfortable cruising through the synergistic effect of high-torque motor output
High-Expansion Ratio Cycle
A 1.5-liter engine is used, which achieves high efficiency by using the Atkinson Cycle, one of the most heat-efficient, high-expansion ratio cycles. Because the expansion ratio ((expansion stroke volume + combustion chamber volume)/combustion chamber volume) is increased by reducing the volume of the combustion chamber and the chamber is evacuated only after the explosion force has sufficiently fallen, this engine can extract all of the explosion energy.
*1 Expansion ratio: (expansion stroke volume + combustion chamber volume)/combustion chamber volume
*2 Compression ratio (compression stroke volume + combustion chamber volume)/combustion chamber volume
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In conventional engines, because the compression stroke volume and the expansion stroke volume are nearly identical, the compression ratio ((compression stroke volume + combustion chamber volume)/combustion chamber volume) and the expansion ratio are basically identical. Consequently, trying to increase the expansion ratio also increases the compression ratio, resulting in unavoidable knocking and placing a limit on increases in the expansion ratio. To get around this problem, the timing for closing the intake valve is delayed, and in the initial stage of the compression stroke (when the piston begins to ascend), part of the air that has entered the cylinder is returned to the intake manifold, in effect delaying the start of compression. In this way, the expansion ratio is increased without increasing the actual compression ratio. Since this method can increase the throttle valve opening, it can reduce the intake pipe negative pressure during partial load, thus reducing intake loss.
High Functionality
VVT-i (Variable Valve Timing-intelligent) is used to carefully adjust the intake valve timing according to operating conditions, always obtaining maximum efficiency. Additionally, the use of an oblique squish compact combustion chamber ensures rapid flame propagation throughout the entire combustion chamber. High thermal efficiency, coupled with reductions in both the size and weight of the engine body through the use of an aluminum alloy cylinder block, and a compact intake manifold, etc., help improve the fuel efficiency.
Output Improvement
The engine's top revolution rate has been increased from the 4,500 rpm in conventional engines to 5,000 rpm, thereby improving output. Moving parts are lighter, piston rings have lower tension and the valve spring load is smaller, resulting in reduced friction loss. Furthermore, the increase of 500 rpm produces faster generator rotation, increasing the driving force during acceleration and further improving fuel efficiency.
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