The name “Superturbo” sounds like it belongs to a character from a comic book, not something found under the hood of a car. The reason for this technology–a pairing of a supercharger and turbocharger on a single engine–is to provide boost across the full rev range of a downsized engine. This gives full-size engine power without affecting fuel economy. Come to think of it, maybe it is a comic book superhero, but without the cape and tights.
“The concept was in development for almost three years,” says Grant Terry, customer manager, New Business Development, Eaton Automotive Air Management Operations (Marshall, MI), “and will help manufacturers meet future emission and fuel economy regulations and give a 15% to 20% increase in both fuel economy and performance while aggressively downsizing their gasoline engines.” The idea–which has been developed for inline engines, mainly those with four cylinders–pairs an Eaton M24 supercharger with a garden variety turbocharger with an integral wastegate. The supercharger provides boost from just off idle until its clutch progressively disengages near mid-range. At that point, the turbocharger begins to take over and carries on to the redline.
“There’s a step-up gear in the supercharger so it produces full boost at one-half engine speed,” says Terry, who notes that the M24 unit is normally used for engines in the 800-cc to 1.0-liter range, not the 1.5 liter envisaged. “We use the smaller unit because we’re only covering half the rpm range, and its smaller size makes it easier to manage the thermal output.” Coupling the supercharger, turbocharger and electronic throttle under a single electronic controller eliminates torque spikes by trading off boost production between the two units. “All the customer feels is uninterrupted power,” claims Terry. In the case of the 1.5-liter engine, power that is equal to or superior to that found in a 2.0-liter engine.
The idea isn’t limited to gasoline engines, however. Eaton says the Superturbo concept can be applied to diesel engines as a way to meet future emission requirements. However, Eaton claims, its real talent lies in the fact that–on a systems basis–a Superturbo gasoline engine is less expensive than a turbo diesel while providing similar fuel economy. Also, automakers can use the technology to decrease costs by using a two-valve head in place of more expensive four-valve technology on a gasoline engine.
Paired to gasoline direct injection technology, the Superturbo concept makes it possible to aggressively downsize the engine, eliminate low- to mid-rpm turbo lag, and more efficiently scavenge residual gasses for greater torque. These are all items that are high on the list of Eaton’s development partner, Volkswagen. A Superturbo engine using components sourced from Eaton’s plant outside of Gdansk, Poland, will enter production in the last quarter of 2005 for use in the 2006 VW Golf GT. The 1.4-liter engine produces 168 hp and 177 lb-ft of torque (available from 1,750 to 4,500 rpm), and returns a claimed average of 39.2 mpg. Rather than use the “Superturbo” moniker, VW refers to the Golf GT’s engine as the “Twincharger.” It claims 0-62 mph acceleration of 7.9 seconds and a top speed of 136 mph for the Golf GT fitted with this engine. The Golf-based Touran MPV will get its own version of the Twincharger, though it will produce 138 hp and a maximum of 162 lb-ft of torque, numbers more in line with its role as a family hauler. VW also is expected to include the Twincharger unit in a future variant of the Jetta sedan, and may offer it outside of Europe.
VW’s Golf GT is the first vehicle to use the Eaton Superturbo concept. Eaton will supply components for the engine from its plant near Gdansk, Poland. The 1.4-liter engine has a broad torque curve that greatly reduces the need for changing gears, and returns exceptional fuel economy.