Southwest Research Institute® (SwRI®) News
Printer Friendly VersionHybrid Powertrain Achieves 79 Miles per Gallon in Fuel Economy Test
For immediate release
San Antonio, Texas -- March 5, 2001 -- A parallel hybrid gasoline-electric powertrain for medium-size cars, developed by engineers at Southwest Research Institute® (SwRI®), achieved combined highway and urban average fuel economy of 79 miles per gallon.
Dynamometer tests of the Parallel Hybrid Electric Combination of Speeds (PECOS) powertrain were conducted to determine full acceleration performance and fuel economy over the urban and highway driving profiles.
The PECOS powertrain accelerates a vehicle with a mass of 1,265 kilograms,, aerodynamic drag coefficient of 0.34, and frontal area of 2m2 from zero to 60 miles per hour in 14.9 seconds.
The powertrain achieved fuel economy of 77 miles per gallon for city driving and 82 miles per gallon for highway driving, resulting in a combined fuel economy of 79 miles per gallon.
SwRI engineers recently completed prototyping and testing of the patented hybrid powertrain. Its simple design consists of off-the-shelf components, including a 40 kW (peak), 1-liter spark ignition engine, a 53 kW (peak) and 32 kW (continuous) permanent magnet brushless DC motor, a power splitting planetary gear box, and a lead acid battery pack (312 volt bus).
The planetary gearbox contains one sprag (one-way) clutch and one wet clutch. The sprag clutch and wet clutch transition the PECOS powertrain from one mode of operation to another. Four operating modes are possible: pure electric, a battery pack charge mode, motor assisted engine, and regenerative braking.
The engine can either be coupled to the road or decoupled from the vehicle's speed. The controller automatically switches the powertrain from one mode of operation to another using a fuzzy logic rule-based strategy based on road conditions. This control strategy minimizes mode transition instabilities.
The PECOS system has several advantages over conventional powertrains. It does not require a clutch to launch the vehicle. The engine does not require a starter, since the electric motor starts the engine. Finally, no transmission is required except for a differential.
For further information on the SwRI PECOS powertrain, licensing opportunities, or patent details, contact Ashok Nedungadi in the SwRI Engine, Emissions and Vehicle Research Division, (210) 522-3965, fax (210) 522-5720, or Joe Fohn, Communications Department, (210) 522-4630, fax (210) 522-3547.
