Related: Automotive Powertrain
"We wanted to bring premium technical features to the entry level," says Eric Ridenour, executive vice president Product Development, Chrysler Group as he describes the GEMA (Global Engine Manufacturing Alliance) world engine. Available in 1.8-, 2.0-, and 2.4-liter displacements, the design will be shared with Hyundai and Mitsubishi and built in five plants around the globe with a total capacity of two million units. "It's the largest engine program in the history of the auto industry," says GEMA president Bruce Coventry. One that DCX claims will return $100-million in savings when it fully replaces the current four-cylinder engine family. Two of the engine plants are in Korea, one in Japan, and the remainder are in Dundee, Michigan. Each of the U.S. plants measures 450,000 ft2, and is capable of producing 420,000 engines annually. "Lots of effort went into making this engine easy-to-assemble," says Coventry, "and toward maintaining a common base engine design throughout the design and development process." Not only can any of the GEMA plants produce any version of the engine under this plan, any technology developed by the joint venture's members can be adopted by the others without a costly redesign of "their" engine.
Around The Block
Hyundai handled the initial block and cylinder head design and was the short-block lead, but JL French (www.jlfrench.com) will deliver the high-pressure die-cast aluminum block from its Sheboygan, WI, facility in fully machined form to the Dundee plants.The block is stout, has cast-in iron liners, and has been designed to support the naturally aspirated, turbocharged, and supercharged performance variants that inevitably will supplement the base engines. Ridenour says it has a 300 Hz natural frequency, is 30 lb lighter than it would be if made of cast iron, and boasts a 360ºº bell housing attachment flange to more tightly tie the transmission to the engine.
Ample water jackets surround each siamesed cylinder and leave enough structure to help the block take high boost pressures, resist twisting, and provide a stable sealing surface around the wedge-shape combustion chamber. Displacement is altered by fitting thicker liners or altering the stroke, and the pistons have short skirts and wear graphite patches to reduce friction. They connect to a forged steel crankshaft that sits above the balance shaft/oil pump module. It is delivered to the assembly plant as a complete unit, attaches to the bottom of the block, and draws oil from the composite (steel-plastic-steel) oil pan through its integrated single-stage oil pump. Each block is automatically measured and its pistons, main bearings and connecting rod bearings are matched to ensure the tightest tolerances. This eliminates a number of machining operations, and also contributes to a claimed low noise signature.
Inside The Head
The most talked-about feature of this engine is bound to be the electro-hydraulic dual variable valve timing system borrowed from the latest Mercedes E-Class V6.These units use pressurized oil to adjust the intake and exhaust cam phasing on a continuously variable basis, and sit at the end of each cam. "The timing is variable throughout the rev range," says Ridenour, "with little overlap at idle and more at speed. It gives us the flexibility to use more ‘natural' EGR"–through altered exhaust valve timing–"in order to reduce pumping losses." The intake cam phaser has a 40º range of motion, while the exhaust cam unit has a 35ºº range of motion.
The composite intake manifold has equal-length runners, and electrically triggered flow control valves. When closed, they block just over half of the intake port below 3,200 rpm in order to increase tumble by forcing air to curl back toward the intake as it fills the cylinder. The intake manifold is delivered to the line complete with the flow control valve unit and throttle body attached.
The cams ride on direct-acting steel bucket tappets that come in 47 thicknesses. The differences are measured in microns, say engineers, and the tappets are automatically measured and matched to each head. This eliminates the need for lash adjustment, and parallels the thought process that has the 4-3-4 cam-drive link chain ride on composite ramps within the front cover. Eliminating the need for external adjusters saved weight, cost and complexity, and helped the three automakers easily surpass their durability bogeys. The head is topped by a composite valve cover with elastomeric seals, isolated grommets, and rubber bumpers. It comes to the line with the seals, oil cap, EGR valve, and bolts in place. Coil-on-plug ignition is used across-the-board. Nemak (www.nemak.com) supplies the head castings from its facility in Monterrey, Mexico.