The L850 is a combination of design compromises, engineering trade-offs, and various technologies intended to please buyers on six continents.
Attracting those buyers has become a greater challenge in recent years thanks to a new generation of super-smooth four-cylinder engines from European and Asian competitors. The L850's committee realized early on that without certain basic design elements, the engine had no chance for success in any market.
For a start, it had to be quiet and refined. That's a challenge in larger-displacement engines. In these powertrains, the heavier moving parts can increase the natural tendency of in-line four cylinders to vibrate.
Like many of its competitors, the L850 uses balance shafts to stamp out these vibrations. Located in the block just above the crankshaft, these shafts are weighted unevenly and turn at twice the speed of the crankshaft. As they turn, they generate opposing vibrations to counteract the vibrations caused by the moving pistons.
Another goal for the L850 was compactness.
True, the engine's first home is the cavernous engine bay of the 2000 Saturn LS - effectively a revamped Vectra - which must also swallow a V-6. But smaller vehicles such as the Opel/Vauxhall Astra will follow, and older GM models are also being considered for possible retrofit.
To avoid the expense of re-engineering those vehicles, the L850 had to be no larger than GM's other four-cylinder engines.
Engineers created a three-dimensional packaging 'envelope' for the L850 by overlaying the schematics of GM's current lineup of four cylinder engines. The composite included the 1.9-liter Saturn SL/SC engines and the current family of Opel Ecotec engines. It established dimensional borders for the L850 which could not be crossed.
To make the engine fit inside the 'envelope,' engineers shaved millimeters wherever possible. For example, the pistons are tightly spaced thanks in part to iron cylinder liners with walls just 1.5mm thick.
One result of all this cutting and shaving is reduced weight. The L850 weighs 148.5kg fully 'dressed' with accessories, compared with over 188kg for a dressed 2.4-liter LD9, a bulky engine used in the Pontiac Grand Am.