We've already seen (and driven) the new Lexus mid-size luxury sedan in its GS 350 gasoline-powered guise, but today's unveiling at Frankfurt of the GS 450h hybrid exhibits more than just swoopy bodywork and handling prowess. Its powertrain is now equipped with a second-generation Lexus Hybrid Drive, a system expected to offer fuel consumption improvements of more than 30 percent.
Key to this is the 3.5-liter V-6's adoption of Atkinson Cycle combustion, akin to that making the Synergy Drive in such a frugal package. The Atkinson Cycle features a delayed compression, brought about by relatively late closing of its intake valves. This combination of high expansion ratio combined with less compression translates into reducing the engine's inherent pumping losses and enhancing its efficiency.
Another feature, Lexus's D-4S injection technology, combines with the engine's extremely high compression ratio (geometrically, 13.1:1 versus the previous non-Atkinson's 11.8:1) to wring out even more efficiency. D-4S has one fuel injector spraying into the intake port and a second one performing direct injection into the combustion chamber itself. The result yields benefits of each, the inherent charge cooling of direct injection combined with the quelled noise of port injection at engine idle. Other D-4S innovations include new slit-type injector nozzles functioning at an increased fuel pressure.
The new GS 450h loses just a tiny bit of power, a total-system peak of 338 hp compared with the current non-Atkinson's 340, an excellent trade in exchange for its expected fuel-consumption advantages of more than 30 percent. (The current GS 450h's EPA numbers are 22 mpg city/25 mpg highway.) Lexus claims the new car's 0-60-mph time is a tad extended as well, 5.6 seconds versus the current less frugal car's 5.2. Like the previous version, the new GS 450h is expected to qualify as a SULEV II, as in Super Ultra Low Emissions Vehicle II. (more)
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Photos: 2013 Lexus GS 450h >>