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Although there is a
significant horsepower difference between the two engine versions, they
have many similarities. Both have roller hydraulic camshafts for minimal
friction and canted valves for optimum breathing. Both come with long-life
platinum spark plugs. And both can be rigged by OEMs with an electronic
throttle kit from GM that enables fly-by-wire operation, similar to what’s
available on many diesels. This means the only thing connecting the engine
controls to the engine is an electrical cable, a feature that makes for
not only easier rigging but also easier operation. Moving through the
rpm range is generally smoother with electronic controls, and synching
engines can be done accurately and automatically. Moreover, fly by wire
opens up a world of electronic networking possibilities with equipment
such as autopilots and GPS navigators. Also standard on both engines is
a new coil-near-plug ignition system that increases ignition energy by
50 percent, improving reliability (there are no moving parts), increasing
fuel efficiency, smoothing idle, and reducing emissions. GM’s fourth-generation
ECM (electronic control module), the MEFI IV, is available to marinizers
(some have their own processors) and includes a more powerful computer
to more accurately control ignition timing and fuel delivery. Even the
firing order has been carefully selected. It’s 1-8-7-2-6-5-4-3, a
sequence GM says fires more evenly and so reduces stress on the crankshaft
by seven percent.
But technology is only
as good as what it’s attached to. The standard and high-performance
8100s start with a durable cast-iron block and cylinder heads. An integral
positive crankcase ventilation system is designed to trap pollutants before
they escape into your bilge, and a coated, cast-aluminum intake manifold
maximizes air flow to the injectors to increase mid-range torque. The
water pump used on both engines has a bronze impeller and is silicone-carbide-sealed
to extend life in the saltwater environment. In addition, the Vortec 8100’s
bottom-end and oil-pan designs allow for installation at a multitude of
angles, allowing it to easily fit into most engine rooms.
There are differences
between the standard and high-performance engines as well. The 375-hp
Vortec V-8 comes in at 732 pounds, while the high-performance engine weighs
eight pounds more, a difference attributable in part to their crankshafts.
The standard 8100’s is made of high-density nodular iron, while the
high-performance engine’s is forged steel, which is better able to
handle the engine’s increased output. Both engines’ crankshafts
are internally balanced, which means there are no external counterweights,
resulting in reduced stress on the crankshaft and bearings and a more
compact envelope.
Finally, and of prime
importance to boaters, both versions of the 8100 were engineered with
an eye toward durability. In fact, GM’s marine-engine standards surpass
those required for its truck applications. In one test the engine was
run in 60-minute cyclesÑwide-open throttle for 55 minutes, then idle for
five minutesÑnonstop for 300 hours, far exceeding the use the engine might
get under normal operation.
Now that GM has researched,
engineered, built, and tested the basic engine package, OEMs such as Crusader,
MerCruiser, and Volvo Penta are adding their own bells and whistles, such
as proprietary ECMs, exhaust manifolds, fuel/water separators, and auxiliary
pumps. (See “Primping Iron”, this issue.) So if you’re
looking for a gasoline engine that offers a tradition of excellence, the
newest technology, and saltwater toughness, GM has your V-8.
GM Powertrain (248) 857-0323. Fax: (248) 857-0045.
Next page > GM Vortec 8100, Part 3
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