October 1, 2009 12:00 AM
DETROIT -- Carmakers across the globe are already adapting their R&D to hit the new 35-mpg law by 2020--and now the Department of Transportation wants to speed up the fuel-economy boost by five years. Sure, we'll see plenty of hybrids, some plug-ins and even a few new clean-diesel rides. But as our video tour of GM's HCCI lab for Future Car Week demonstrates, the focus will likely remain on gasoline engines. So expect upgrades such as variable intake and exhaust valve timing, reduced engine friction, turbocharging with direct fuel injection, and light-load cylinder deactivation. Engines are also expected to downsize in order to save fuel, with more six-, seven- and eight-speed transmissions on the way, too--not to mention low-rolling-resistance tires and improved aerodynamics.To drive a little further in the green direction--and still keep costs within reason--here are a half-dozen future engine technologies we saw at this month's exclusive SAE World Congress that, if put into production, could boost the fuel economy of our next generation of gas-powered cars.
1.Multistage Oil Pump.
A regular oil pump has chambers for suction and a discharge chamber. But this one from automotive supplier Aisin, just introduced in some Toyota products, has two discharge chambers--one slightly smaller than normal, and another even smaller--so you can tailor pressure to when you actually need it, and divide the discharge in half. There's full pressure from both chambers at idle, some from both at medium speed with higher loads, and full pressure from just the main chamber with light load conditions. At high rpm, when a pump would provide more pressure than needed, the oil flow comes from both chambers but is reduced by bleeding pressure through the relief valve. So it essentially reduces the total amount of work the pump has to, well, pump out.
2.Shortened Cylinder Head
Automotive engineering consulting firm FEV has come up with a simple but ingenious method for saving weight while reducing valve size, to rev an engine higher and tune it better for performance and fuel economy: shorten the cylinder head by 0.6 in. Instead of a full-length valve-stem guide to hold the valve stem in alignment, FEV's system created a cylindrical bore around the top of the valve, and instead of just a cap holding the top of the valve spring to the valve, there's an inverted cover attached to the end of the valve stem. In valve operation, that metal cover slides through the cylindrical bore, where it holds the top of the valve and the spring in alignment. Cool.
3.Variable Compression Ratio
Take two cold, hard facts of automotive engineering: An engine's thermal efficiency improves if it carries a variable compression ratio, which in turn increases with light engine loads. In theory, then, you should get better fuel economy at constant freeway speeds when the load on the engine is light. In practice, FEV has a stop-step design for hollowing out a connection rod with an actuator that pushes on a cam built into the piston pin. The cam action raises the piston height by 2 mm, which boosts the compression ratio from 14:1 to 17:1. The actuator is moved by engine oil pressure, applied when the engine computer activates a small electric motor, which opens a flow-control valve in an oil passage.
4.Guided Spray Turbo
Rather than aiming its piezoelectric fuel injector from the side, FEV's 1.8-liter turbo four-cylinder engine uses a top-entry, with the spray aimed at an adjacent spark plug. The new design offers better distribution of the fuel mixture and 8 percent better fuel economy compared to conventional designs that essentially need to spray more fuel--and modifies piston heads and intake ports to get what's called the "tumble effect" to mix the air and fuel. FEV officials say this stratification of the air/fuel charge brings its fuel economy numbers within about 10 percent of a 1.8-liter turbodiesel, while still hitting 214 hp and 236 lb.-ft. torque. In a small sedan, the engine would have no problem hitting the 35-mpg standard.
5.Electromagnetic Valve Actuator
In this design, automotive supplier Valeo replaces the intake camshaft of a twin-cam engine with electro-magnetic valve actuators, instead of the more pricey and complex approach of replacing both camshafts with these cam actuators. The intake-only approach offers improvement in fuel economy between 16 and 19 percent--very close to the results with two sets of actuators. The improvement comes from infinitely variable valve lift and timing--without requiring a 42-volt system. This is still a comparatively expensive step, but it offers a big improvement and could be cost-effective down the road.
6.Hydraulic Power Electrification
To eliminate continuous power draw from engine-driven pumps, automakers are replacing conventional hydraulic power-steering pumps with all-electric systems or electric-motor-driven pumps that operate only when needed. Expect engine-driven water pumps across the industry to be replaced by electric ones--or at least by smaller engine-driven water pumps with auxiliary electric pumps for high loads. And look for stop-start engine technology to combine with electric-drive compressors (think full hybrids), so that you can shut off the engine and still keep your car cool. These compressors, which can continue a/c operation after the engine is brought to a fuel-saving stop, are found in Toyota and Honda hybrids, but not in European and U.S. mild hybrid cars with engine stop-start. Without the electric compressor, the engine must be kept running when the a/c is on--wasting fuel while keeping passengers comfy.
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