High-BSFC Gasoline Powertrain Architecture via Stratified Injection, Extreme Long-Stroke Geometry, e-Turbocharging, and Multi-Ratio Transmission

1. Background & Problem Statement Conventional spark-ignition (SI) engines often compromise thermal efficiency at lower engine speeds (RPM) to achieve peak horsepower at high RPM. High compression ratios aimed at improving efficiency face significant physical limits, including narrow fuel flammability windows, destructive engine knocking (detonation), and excessive linear piston speed in long-stroke configurations. 2. Proposed Engineering Solution This paper proposes an integrated powertrain concept that combines four interdependent engineering variables: - Direct Stratified-Charge Injection: Utilizing high-pressure Gasoline Direct Injection (GDI) to create a dual-zone mixture inside the cylinder: a stoichiometric mixture near the spark plug electrode and an ultra-lean mixture (30:1 - 40:1) throughout the rest of the combustion chamber. This eliminates misfires while optimizing fuel consumption. - Extreme Long-Stroke Geometry (Under-Square Ratio): Utilizing an extreme stroke-to-bore ratio where stroke length significantly exceeds cylinder bore diameter. This maximizes crankshaft leverage to generate high low-end torque starting from 1,000 RPM, increases thermal efficiency, and provides optimal duration for fuel vaporization. - Instant Electric Boosting (e-Turbocharger / 48V e-Booster): Integrating a high-speed electric compressor to supply abundant oxygen instantly, independent of exhaust gas pressure. This completely eliminates turbo lag, stabilizes air delivery for stratified combustion, and supports throttle response at low RPM. - Multi-Ratio Transmission Matching (10+ Speed / CVT): To compensate for the linear piston speed limitations of a long-stroke configuration at high RPM, the engine is paired with a wide-ratio transmission (10+ Speed Automatic or CVT). Electronic mapping locks the engine within its optimal Brake Specific Fuel Consumption (BSFC) sweet spot (1,200 - 2,500 RPM) across various road speeds. 3. Expected Outcomes - Projected thermal efficiency exceeding 42–45%, approaching modern diesel efficiency. - Instant low-end torque delivery with EV-like throttle response. Significant reduction in CO2 and unburned hydrocarbon ( HC) emissions.