When asked about developments in engine materials technology, Chinu Bahavsar, senior staff technical specialist for vehicle technologies at Ford, was quick to repeat that favorite saying of the engineering community: "Evolutionary rather than revolutionary." The driving force behind this evolution has clearly been ever-more stringent government regulations: CAFE standards and California Air Resources Board (CARB)-influenced emissions regulations have forced automotive powerplants to become more efficient. Of course, the bean counters have had their say, as well (after all, in their eyes, materials like titanium have a price point that's only suitable for golf clubs).
While the easiest way to make regulators happy may be to cut weight from the engine, contrary to what most anti-government, regulation-haters might think, there are other reasons for changes to more lightweight materials. Front-wheel-drive vehicles handle better with lighter engines due to a better front-to-rear weight balance. Reducing friction in the internals gets more horsepower to the flywheel without reducing fuel economy. And, of course, there's always the hope that new materials can make engines less costly to manufacture, usually by virtue of parts reduction through integration.
Below, you'll find Bahavsar's analysis of engine materials. (And just so there's no confusion, the Lincoln LS 3.0L V6 diagram may or may not contain the noted technologies.)
A. Intake Manifolds
A composite intake manifold not only reduces weight, but allows for the integration of sensors, engine controls, throttle body, fuel rail, injectors, air filter and intake into a single plastic unit. With all of these items integrated, the "fuel-air delivery module" would reduce part counts and simplify assembly, as it could be injection-molded with snap-fit characteristics and use self-tapping fasteners. This would have cost advantages over traditional cast and machined aluminum or steel. However, there are still a few issues to be worked out before all of these parts get incorporated into a composite intake manifold. First, as Bahavsar explains, steel advocates have made great strides in improving manufacturing methods to cut cost and weight. Steel also holds an edge when it comes to recyclability. Furthermore, an integrated composite fuel rail might have a problem with emissions. Since all plastics are permeable to some extent, the potential for fuel evaporation through a composite fuel rail exists. Regulators who are concerned with the emissions of a single drop of gas spilled outside of a fuel tank will not be happy about this. Another rub on plastic is that while most engineers are fairly adept at designing aluminum manifolds, plastics can give them headaches. Plastics have a low modulus, which causes them to transmit much more noise from the engine. Despite these drawbacks, intake manifolds are ripe with opportunities for plastic components even if it is on a piece-by-piece basis, rather than an integrated module.
B. Camshaft/Valve Covers
Aluminum or composites are both desirable because they're lightweight materials. Magnesium is another potential, but it's too expensive to widespread application.
Powdered metal cam lobes allow for better lubrication because of the porosity of the material and its improved adhesion to oil. Bahavsar explains that with the right chemistry, the strength of powdered metal can even be very close to that of forging. By near-net forming the lobes, then assembling them under pressure to a steel tube, machining is reduced compared to a traditional camshaft. The hollow tube lightens up the camshaft, reducing reciprocating weight, thereby improving horsepower. Bahavsar says that making camshafts in this fashion will soon be the industry norm.
Aluminum heads are now being used on nearly all gasoline engines. Those that don't have them will soon, according to Bahavsar. Diesel engines, however, are a different case. Because of the higher pressure in the head of a diesel engine, aluminum is a somewhat problematic material. Diesel's move to aluminum for heads will be a much more gradual shift, but it should still happen.
Blocks are made from either cast iron or aluminum. Cast iron is cheap and tough, while aluminum is desirable because of its lighter weight. More cylinder blocks are being made from aluminum every year, as methods for reinforcing cylinder liners have improved. Since pressed-in cast iron liners still carry a weight disadvantage, the future will see widespread use of sprayed or plated metallic liners. Bahavsar is also working with carbon fiber liners—incredible strength and very light, but very expensive, too.
F. Connecting Rods
Using powdered metal for connecting rods allows for better control over part geometry, meaning less machining and reduced manufacturing cost. It also allows Ford to employ a fracture-split process to fit the rod on the crankshaft. A machine "cracks" the bearing caps off the rods so when they're reassembled, this natural fracture means that the rods can only be bolted back together one way, ensuring a perfect fit and a very strong assembly.