Update on the AVL ECO TARGET Diesel Mild-Hybrid

6 October 2004

Some more details and corrections on the AVL ECO TARGET diesel mild-hybrid powertrain (earlier post) from the presentation of the concept at the 16th Engine & Environment Conference.

The ECO TARGET consists of a 60 kW (80 hp) 1.2-liter diesel engine matched with a 6-speed transmission and a 10kW (13 hp), 42V electric motor connected to the transmission via an intermediate gearbox, rather than being fitted to the crankshaft as in some other designs.

By keeping the electric motor as an independent unit, AVL claims, it is better able to optimize the system and to fit into different form factors—such as a car with a front transverse engine. (“Transverse” refers to an engine in which the crankshaft is oriented side-to-side relative to the wheels of the vehicle. Most front-wheel drive vehicles use this orientation.)

The power electronics are bolted to the intermediate gearbox. Rather than a 42V battery, the ECO TARGET uses a supercapacitor located above the gearbox and fixed to the chassis. The use of a supercapacitor enables short-term very-high current operation of the electric motor both for drive and braking. However, the amount of energy stored in the supercapacitor is smaller than that for a battery, with the result that the system is not designed for extended operation.

The ECO TARGET electric motor therefore does not provide extended boosting (drive assistance). Instead, the boost function is limited to brief periods such as acceleration from launch through to the engine speed for maximum torque (2000 rpm). The electric motor also delivers supportive motive force during gearshifts.

It seems like there are still some issues the AVL team needs to work through, such as cooling, before the system is ready to present to automakers as a powertrain package. One estimate suggested another 2 years of work.