Saving fuel with minimal compromise

Interview with Tom Odell, GM's Technology Planning Manager, on the Two-Mode Hybrid system

By Justin Pritchard,

Thursday, March 26, 2009

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GM's award-winning Two-Mode Hybrid system is proving its ability to save owners fuel with minimal compromise. Justin Pritchard talked to Tom Odell, a Two-Mode Hybrid expert at GM, about the various ins and outs of the system, and how its users can maximize their mileage.

Tom Odell, Technology Planning Manager, Canadian Programs, General Motors of Canada, Oshawa, Ontario

J.P.: In a nutshell, how does the Two-Mode Hybrid system work?

T.O.: The GM Two-Mode System is a hybrid drive system that can operate on gasoline-only, electric-only, or a blend of gasoline and electric power. It is called "Two Mode" because the system can operate in a low speed range and a high speed range through unique combinations of electric drive and fixed gears.

At lower speeds in mode 1, power from the gas engine and electric drive is split via a planetary gear set. The split allows pure electric drive and then a continuously variable combination of gas and electric. It's called 'input split'.

At higher speeds and loads in mode 2, another planetary gear set is used to apply continuously variable combinations of gas and electric drive power, and fixed ratio drive for high load conditions. It's called 'compound split'.

The heart of the system is the Electrically Variable Transmission (EVT). It's a fully automatic, variable-speed, electronic-controlled transmission. It has 3 planetary gear sets, 4 clutch assemblies, and 2 internal 60 kilowatt electric motors.

The advanced EVT and a 300-volt nickel-metal hydride Energy Storage System (ESS) work in concert with the standard 322 hp, 6.0L V-8 gasoline engine with Active Fuel Management (AFM) and Late Intake Valve Closing (LIVC) technology.

GM's hybrid technology system not only enables the vehicle to launch and drive up to 48 km/hr on electricity alone, it also allows the Vortec 6.0L V-8 engine to operate in its more economical 'V-4' mode for longer periods.