Mahle made: engine supplier Mahle becomes its own customer by developing its own 3-cylinder powerplant

Automotive Industries, May, 2004 by Jonathan Walker

If an engine component specialist has a program which covers all but two major parts of the whole, how strong is the temptation to develop a complete engine?

In the case of Stuttgart-based Mahle Group, the answer was "irresistible," and the result was on show at last year's IAA--the first "Mahle Motor."

During a press conference at the Mahle Motorsport works in Fellbach, Germany, the company recently revealed full details of the engine and, more importantly, its rationale--it is to serve as a combination of "technology" demonstrator," racing engine and a research and development project designed to release a broad array of synergies within Mahle among its various product groups.

"The racing aspect centers on 'Formula SAE' an international competition run by America's Society, of Automotive Engineers," notes Mahle CEO, Prof. Heinz Junker. "Also known as 'Formula Student' the competition is open to academic institutions in all parts of the world, who build and race their own single-seater as a 'hands-on' learning project.

"(On the R&D side, we had long wanted to try our hand at developing a complete engine, both to demonstrate our existing overall know-how and to add to this fund of knowledge, especially regarding the interplay of the components and subsystems we produce. At our product groups pistons and piston assemblies, cylinder components, valve train, air and liquid filtration, we develop world-leading technologies for the world's best engines. Developing a complete engine was a logical next step."

A happy combination of circumstances made possible this "quantum leap" to engine developer status, noted Mahle Motor project leader Dr. Adolf Wunsche. "Our involvement in Formula SAE arose from our close contacts with the Technische Hochschule Aachen, with whom we cooperate closely in R&D projects. Aachen has an excellent reputation in engines and vehicle dynamics, and when we heard of their plans to participate in Formula SAE we felt well placed to assist.

"First, no engine component manufacturers is better equipped--in principle, the crankshaft and the cylinder head casting are the only major engine components not in our range. Second, we enjoy a leading position as a supplier of components for racing engines, notably in Formula One and endurance racing, and Aachen's Formula SAE project revolves around a race. We also see our support as a contribution to developing the next generation of engineers at a time when technical professions have lost some of their popularity,."

Dr. Uwe Mohr, head of Research & Development detailed Formula SAE's specifications and stressed that the Mahle Motor is a completely new design in both architecture and features. "While leaving free the configuration and number of cylinders, the SAE Formula prescribes natural aspiration, a four-stroke cycle, a maximum 610 [cm.sup.3] displacement and a maximum 20 mm diameter inlet restrictor on the basic engine. To this the students may add the options of turbocharger or supercharger, carburetor or fuel injection with electronic engine management. The intake system might consist of filter, carburetor/throttle body, air restrictor, charger and engine.

Mahle went for a 3-cylinder, in line configuration with swept volume of 609 [cm.sup.3]. Rated output is around 60 kW (80.4 hp) at 9,500 rpm and maximum torque 65 Nm (48 lb. ft.) at 7,000 rpm. The 3-cylinder inline design gives short inlet tracts in view of the 20 mm restrictor rule, and keeps down overall engine length. This minimized costs and with bore and stroke dimensions of 70.8 x 51.5 ram, cylinder dimensions are close to those of commercial engines, making acquired data and findings widely applicable. The requirement for the engine to form part of the vehicle structure necessitated a balance shaft to compensate the "rocking couple' inherent to an inline three."

With its role as technology demonstrator Mahle has clearly taken pride in developing innovative solutions on its engine. With its deep involvement in competition engines, a number of solutions borrow straight from current motorsport practice. "Solutions to which, in many cases, Mahle

has made a vital contribution," Junker says.

For example, the engine block is an interesting light alloy design using Mahle's NIKASIL coating on parent bores. "The block is a two-piece structure and its halves locate the crankshaft and form a stiff "tunnel" capable of withstanding thermal and mechanical distortion," Mohr says. "This prevents cylinder distortion and Rives addition al structural strength. The main bearing caps are in ferrous material to maintain tight clearances and are integral to the lower half of the crankcase. A broad based, integral oil sump lends additional stiffness and a low center of gravity. To minimize hydraulic losses, it is connected to the crankcase by a series of windows and oil strainers."

The cylinder head is a also two picot structure, allowing the camshaft covers to form its bearing caps. "It features four valves per cylinder with a central spark plug," notes Dr. Martin Lechner, Mahle's head of pre-development.