The 'Supercar' may have a diesel under the hood
Washington, DC--Despite the allure of electric vehicles, the promise of propane, and the vision of "Mr. Fusion," the vast majority of us will be driving gasoline-powered cars over that bridge to the 21st century.
However, a prototype fuel-efficient and clean "Supercar" may be waiting just around the bend--powered by the venerable diesel engine.
More radical solutions are stymied by a number of factors: The internal-combustion engine works really well. Nearly everybody can afford one. There is a huge infrastructure in place to support it. Gas is currently plentiful and cheap (in the U.S., at any rate). Economic forces alone suggest internal combustion engines will be around for the foreseeable future.
Facing reality, the Partnership for a New Generation of Vehicles (PNGV), an organization that includes the Big Three automakers, members of the research and business communities, and the federal government, aims to develop and commercialize technologies that will enable vehicles to operate more efficiently and with fewer harmful emissions. As it stands, the organization plans to produce a prototype "new generation" car by 2004 that is three times more fuel-efficient than a corresponding car today.
The Big Three back developing a variety of diesel compression-ignition, direct injection (CIDI) engines as the powerplant for the PNGV prototype. Current diesel designs feature a 40% peak thermal efficiency and are easy to manufacture. Nevertheless, emissions are still higher than for gasoline engines, a fact that doesn't sit well with the government.
"The majority of the government's investment in this project has been, and will continue to be, directed to long-range, higher-risk research, including solutions other than the internal combustion engine," Vice President Al Gore told the Sixth Automotive Technical Symposium for the PNGV this past Summer.
Examples of these "higher risk" research areas include: fuel cells, gas turbines, hybrid engine configurations, flywheels, and ultracapacitors in the power plant and energy storage areas, in addition to new lightweight automotive-grade materials. This leaves the Big Three and company to work on "real world" ways to make an old friend more environmentally friendly.
Die-hard diesel. The fuel efficiency of diesel engines has re-awakened industry interest in this technology. While consumers flirted with diesels during the oil crises of the 1970s, they never embraced them long enough for a convenient supporting infrastructure to develop. Furthermore, environmentalists have never been fond of the high sulfur content of diesel emissions.
Nevertheless, engineers at Chrysler, Ford, and General Motors are convinced they can develop a well-behaved diesel engine that burns low-sulfur fuel in an optimized combustion system equipped with an after-treatment device that reduces nitrogen-oxide (NOx) and particulate emissions. In particular, the Big Three, which together comprise the United States Council for Automotive Research (USCAR), have identified the CIDI diesel engine as the key to achieving PNVG's goals of a cleaner, more fuel-efficient, and affordable mid-sized car.
"We recognize that emissions reduction and customer-oriented attributes, such as reduced noise and improved performance, are key challenges for CIDI technology," says William Powers, vice president of research for Ford, speaking on behalf of USCAR. "We are attacking each of these technical challenges from a full systems perspective, including the engine, fuel, and after-treatment devices."
In order to meet those challenges, USCAR is developing a high-pressure, common-rail injection system for the CIDI that precisely controls fuel amount and rate, reducing NOx and particulate formation during combustion. Electronic engine control devices and sensors monitor the combustion process and optimize the fuel-air ratio, exhaust gas recirculation, and exhaust gas composition.
Another problem is CIDI engines have higher firing pressures than gas engines and must be made heavier to accommodate them. Research is aimed at developing alternative engine design architectures that make greater use of lightweight materials.
A prototype CIDI engine fitted with quartz windows and a laser diagnostics system give researchers at Sandia National Labs with a look at how fuel mixes with air in the combustion chamber. Detailed observations provide insight into how fuel/air mixtures ignite, burn, and how NOx is formed. Results are contributing to the redesign of fuel injectors that will introduce less fuel into the cylinder under more controlled conditions.
Researchers also are studying how to make more with less using so-called "lean-burn" engine technology. Such engines use higher air-fuel ratios (AFR) mixtures. While this enables less fuel to be used and decreases particulates, the challenge here is to deal with the NOx emissions that result. Unfortunately, current catalytic converters do not work with lean-burn engines because they require stoichiometric engine operation with a comparatively-rich 14.65 AFR.
In order to reduce NOx emissions, the U.S. Department of Energy, in partnership with USCAR and Lockheed Martin Energy Systems, is developing new catalysts for catalytic converters. A large number of catalyst formulations are being considered, including aerogels. Candidates are coated onto testbeds that are incorporated into vehicles for evaluation. The Oak Ridge National Lab is categorizing the material properties of the catalyst formulations.
Emissions reduction efforts may also receive a boost at the tail end. USCAR is working on treating emissions from lean-burn CIDI engines with ionized gas. This plasma treatment is expected to reduce emissions even further.
In addition, dimethyl ether (DME) is being evaluated as an alternative, low-emissions fuel. DME can be produced from natural gas and produces almost no particulates when burned.
Although an advanced CIDI is the leading candidate for the Supercar, the final decision has still not been made. However, even if a diesel CIDI is not chosen by PNGV, better diesel engines could benefit many sectors of the economy. According to Ken Oscar, assistant secretary of the Army, all military ground vehicles in the U.S. inventory are diesel-powered. In addition, diesel engines move the bulk of U.S. ground freight and bus traffic. Almost half of the new passenger cars sold in France and Belgium have diesel engines.
FEA models transmission groove flow
Livonia, MI--Journal bearings, or bushings, play a major role in Ford's bearing support strategy for automatic transmissions. Directly integrated into the bearing-and-support strategy of most rotating components, journal bearings frequently lie directly in the path of the transmission hydraulic circuitry. Fluid flow through or along the bearings is critical.
"We're frequently trying to get fluids from one end of the transmission to the other and need to move the fluid through the journal bearings, which can represent quite an obstruction in the fluid path," explains William Hoge, design engineer at Ford's Advanced and Pre-Program Transmission Engineering. "For this reason, we design circular, semi-circular, and/or trapezoidal grooves into the journal bearings to facilitate fluid flow to the various parts of the lubrication circuit."
Hoge recently began working closely with engineers from the University of Michigan and Ford-bushing-supplier Federal-Mogul to develop mathematical models for solving groove-flow problems. He uses PDEase2D FEA software to model and calculate groove-flow rates by solving partial differential equations (PDEs).
"Fluid flow through the cross section of a groove can be generalized as a Poisson problem with boundary conditions," Hoge explains. "Exact solutions to this problem can be derived for rectangular and semi-circular groove cross sections. Other geometries require a numerical solution. PDEase2D is a natural tool for this type of problem because it allows us to state the problem as a set of PDEs."
PDEase2D forces the engineer to stay in close touch with the physicality of the problem, continues Hoge. With conventional finite elements, the physical problem can become reduced to an abstract numerical exercise, he says. "PD-Ease2D pushes the engineer to understand and appreciate the governing equations and boundary conditions for the problem at hand, and that's a definite advantage in any design application."
Sleek seals streamline Malibu
Farmington Hills, MI--As new cars become more aerodynamic, headlamp designs become more challenging. That was the case when it came to designing the headlamp close-out seals for Chevrolet's new Malibu. The problem: closing the gap between the headlamp and exterior of the vehicle while achieving a sleek appearance.
Magneti Marelli Lighting Div. designed the seals. For the project, the firm's engineers selected a thermoplastic rubber over EPDM rubber to meet GM's demanding long-term weatherability specifications. The seals, made of Santoprene rubber supplied by Advanced Elastomer Systems, L.P., Akron, OH, not only won't fade or bloom, but cut the overall part cost substantially versus EPDM rubber.
Use of Santoprene also offered Marelli other advantages:
Greater design flexibility.
Reduced processing cycle times.
Greater dimensional stability.
And there's one more advantage, according to Marelli engineers. The parts are easier to install.
Micro PLC moves monster truck into high gear
Laurelville, OH--Dan Patrick had a problem: A missed shift on his monster truck during a race last year cost him $10,000 in body and rear axle damage--in addition to bruised ribs on his body. He mentioned this while visiting one of his equipment suppliers, Central Industrial, in nearby Chillicothe. By the time he arrived home, Steve Shapeshair, Central's high-technology specialist, was on the phone with the solution--a Rockwell Automation Allen-Bradley (Milwaukee, WI) Micro-LogixTM micro programmable logic controller (PLC).
Patrick's Samson truck has three shift-on-the-go gear boxes in an in-line configuration to form a four-speed transmission. The gear change for each box is affected by solenoids activating pneumatic valves to lock each box. The original "manual" system used repeated presses of a push button to walk up the gears by activating relays. Pressing another "downshift" button reversed the gearchange. Patrick says in a helmet and driving suit within the five-point racing harness it's impossible to see the buttons at his gloved hand. An accidental push of the downshift caused his mishap. Also, mechanics had to change the timing relays every month or two due to shock and vibration.
Shapeshair knew a Micro-Logix industrial automated controller could replace such hardwired controls. The right PLC had to accommodate requirements encompassing four input signals (select timed "automatic" or manual shifting; activate the timed sequence; effect a manual shift; and reset the transmission for total downshift) and one output for each gear plus a spare output.
These requirements had to accommodate Patrick's need for speed, reliability, and ease of use. "To win, it is imperative that the truck is at maximum speed in fourth gear for most of the race," notes Shapeshair. "Dan has approximately 1.5 seconds to make all four shifts in a five-second straight-line race, which he found he couldn't do." The MicroLogix 1000 can shift with the needed quickness and repeatability--executing a 500-instruction program in 1.56 msec. "I can concentrate on driving," says Patrick, "not pushing buttons."
For straight-line competitions, Patrick makes several preliminary runs. He then programs a shift-timing pattern, which may include skipping a gear, into the controller to give maximum torque and no wheel slipping. The controller can store different sequences for various courses and conditions, such as mud or dry grass. In obstacle races around a circuit that last as long as half a minute, Patrick currently uses the manual mode.
"With only 10 minutes between each race, there's no time for major changes or troubleshooting. This demands the solution be very reliable," says Patrick. "He adds, "We flipped the truck, and the controller broke out of its mount and still worked."
Other advantages of using a PLC instead of the relay system include: less transmission wear, improving overall reliability such that transmissions need changing every 10 to 15 runs rather than every 5; engine rpm limiting; and a fail-safe shut off if power is lost. The PLC is also easy to install, use, and maintain, and does not require Patrick to have any computer experience or training. Its hand-held programmer features a trace key to quickly troubleshoot faulty output sources.
In the future, Shapeshair and Patrick may incorporate the return-to-center function for rear steering into the Micro-Logix unit. Another possibility: tuning the motor during a race.
PC-based vehicle tester loses DAQ boards
Houston--A palmtop computer is all Texas Micro needs for the new in-vehicle tester it designed for one of Detroit's Big Three automakers. That's because the tester uses SmartLinkTM modules from Keithley Instruments, Cleveland, OH, to directly connect to automotive sensors and send digitized signals directly to the palmtop via the Universal Serial Bus (USB).
USB provides an easy, flexible means of creating a local network of measurement instruments. Unlike ISA bus-based hardware, instruments with USB ports do not require users to install a data-acquisition board in the PC. Result: Texas Micro's USB-based system doesn't demand the availability--or even the presence--of a PC expansion slot. Thus, the company could base its test system on slotless rugged palmtop PCs.
The systems test new cars off the production line to finetune engine-management, climate-control, suspension, transmission, and other systems. They use two types of SmartLink modules: temperature and high-speed dc volts. The latter is a hybrid isolated unit containing four channels, each of which has its own analog-to-digital converter, sampling at 100 ksamples/sec.
In addition to doing away with the need for a data-acquisition board, the Keithley modules offer small size--6.7 inches tall. This feature makes them easy to deploy within the tight confines of the typical in-vehicle test set-up--for example, under the dashboard or seats or in the trunk.
SmartLink modules connect via a four-wire cable to the palmtop's USB port and are automatically configured once connected to the network. Transmission speed is up to 12 Mbps. The modules can be daisy-chained or configured using dedicated USB hubs having one input and four outputs. Hubs enable one PC to connect with a network of up to 127 USB devices and results in a significant reduction in cabling.
Keithley offers 16 SmartLink modules with USB data communication. Prices range from $574 to $2,655. Other communications options include four types of Ethernet, RS-232, RS-422, and RS-485.
Electric scooters scoot onto French traffic scene
Paris--If you plan a trip to France soon, you may see more scooters on the streets of Paris. EDF, the French national electricity board, has teamed with STIQ and Peugeot Motorcycles to promote the use of electric scooters in an effort to cut down on air and noise pollution.
Both companies offer new electric scooter models: Peugeot with its ScootElect, and STIQ with the Barigo. The scooters compare favorably on most accounts with their internal-combustion-powered counterparts. They also could provide an answer to urban traffic problems.
The vehicles offer equivalent technical performance in terms of speed (28 mph, the speed limit in urban areas), acceleration, mobility, and range (which varies between 40 and 60 km, or 25 to 37 miles). Their use considerably reduces driver constraints, including problems related to oil and gasoline odors, as well as noise. Moreover, maintenance doesn't pose a problem. The batteries need to be topped with water only three times a year.
A 220V socket is all that's required to recharge the scooters. It takes about two hours to reach 95% of the total electrical capacity. A complete recharge requires four to five hours.
The electric scooters have another advantage over their gasoline-propelled counterparts. The extra expense to purchase an electric model (about 20,000 vs. 10,000 francs, U.S. $3,200 vs. $1,500) is recovered in just three years--a battery recharge costs only two francs (35 cents) in France. Moreover, prospective buyers shouldn't overlook insurance cost-cutting. French insurance companies have agreed to substantially reduce premiums on the electric scooter, the result of manufacturers integrating an anti-theft device connected to the ignition.
Roof rack consolidates parts
Macomb, MI--A prototype for an automotive luggage roof rack made from a nylon resin features one-piece assembly, which shortens lead times and makes it possible to have one materials supplier.
The rack, designed by John M. Heuchert, tooling and technology manager at Jac Products, Macomb, MI, won first place in the 1997 AlliedSignal Plastics "Take Your Best Shot" NPE Design Contest, which is held every three years. The design was featured at the National Plastics Exposition in Chicago this summer. AlliedSignal Plastics' Capron® 8267 nylon resin, which is a nylon 6 gas and mineral filler, is key to the unit's design.
Heuchert formed the roof rack using the gas-assist process, which involves injecting nitrogen into the partially filled mold and coring out hollow and thick sections. The material's other applications include mirror housings, Heuchert says.
The rack's one-piece construction provides many benefits, including no assembly, one supplier for materials, improved fit and finish, and a better paint matchup since the roof rack only has to be painted once as a unit rather than having several components painted separately. Also, the rack is handled only one time rather than several as with the regular component assembly process. "We're trying to get away from metal screws and bolts," Heuchert says.
New LEDs make auto lighting a snap
San Jose, CA--While LEDs for automobile lighting are nothing new, recent evolution of the technology may see these long-lived, lower-power devices become the dominant light sources for non-headlight uses. Such applications include: turn signals, rear combination lamps, and marker and clearance lights. The slim profiles now possible with LED assemblies make them easy to mount on a car body.
| The thin profile of SnapLEDs permits shallow lighting cavities that take up less internal volume and lowers the number of large openings in body panels.
Using LEDs instead of incandescent bulbs saves 2 to 4A per rear-signal light cluster, according to Hewlett-Packard Automotive Lighting Organization Manager Dave Zabrowski. This translates into lower wiring weight and cost, and could also result in lower alternator costs. And with nonfilament LED lifetimes longer than that of the average car, replacement is a thing of the past.
The first application of HP's marrying the latest LED materials to a unique mounting process is now in showrooms. SnapLEDs use the high-output flux per LED of the company's transparent-substrate aluminum indium gallium phosphate LED material, mounted onto a thin, flexible, stamped copper-alloy assembly frame. High flux--5 to 10 times older LEDs--means fewer LEDs and even less power, perhaps down to 10% of the incandescent lighting equivalent.
The broad, flat lead frames on the SnapLED snap into the nesting frame, eliminating wave soldering of previous LEDs to circuit boards. Without the heat of soldering, reliability increases. The wide lead frames efficiently dissipate heat from the higher current lighting.
But the greatest advantage is that the thin array of LEDs on metal can conform to body contours, and form narrow lines such as stripes and circles. Engineers are free to place lights where they can be most effective or stylish, and devise new applications, such as remotely activated underbody security lighting. Previously, says Zabrowski, "car makers couldn't design a rigid substrate onto a complex, curved design."
Lower LED bulk eliminates cutouts and deep cavities in body panels used to hold incandescent lighting; only indentations are needed. This translates into more trunk-space and less assembly-cost. "Stamping and tools for cutouts are eliminated," Zabrowski notes, "and attachment is simpler since you don't need to laser weld."
Lastly, LED brake lights cut stopping distances. A University of Michigan Transportation Research Institute study shows quicker motorist response to LED lighting on the car ahead. An incandescent light takes 200 msec to illuminate; an LED tens of nanoseconds, says Zabrowski, reducing stopping distance about one car length at highway speeds.
Auto parts win powder-metal awards
Chicago--Two of the grand prize winners in the Metal Powder Industries Federation's 1997 P/M Part-of-the-Year design competition got a big assist by incorporating powders and process technology from Hoeganaes Corp., Riverton, NJ. The winning parts included a warm-compacted P/M torque converter turbine hub and a stainless-steel auto exhaust system.
The hub, made by Chicago Powdered Metal Products for Ford, became the first automotive powertrain application to use Hoeganaes's ANCORDENSE® warm-compaction technology in the manufacturing process. The component makes up part of Ford's E40D transmission for its 6.8l and larger engines in F-150 trucks, Econoline vans, and large sport-utility vehicles. It replaces a machined and heat-treated forged part at a cost savings of more than 30%, plus an assembly savings of more than 50%.
SSI Technologies Inc.'s Sintered Specialties division produced the stainless-steel exhaust system flanges used on exhaust manifolds. The flanges employ Hoeganaes's stainless-steel powder. The three-level manifold flange connects the manifold to the exhaust pipe leading to the catalytic converter. The exhaust converter outlet flange connects the exhaust pipe leading from the catalytic converter to a flange welded to the manifold.
In the application, P/M replaced a two-piece stamped and welded assembly that leaked exhaust fumes. Compared with the welded assembly, the P/M component dramatically reduced exhaust leakage at the manifold/exhaust system junction. Improved tensile, corrosion, and oxidation properties also reportedly resulted from using the P/M part.
The ANCORDENSE process allows P/M fabricators to produce parts with enhanced performance characteristics using a single compaction operation, which is not feasible with conventional P/M processing, according to Dennis M. Jackson, Hoeganaes's vice-president, sales and marketing. It provides P/M densities that previously required a double-press/double-sinter or copper infiltration process, he explains.
Auto seats focus of design competition
Boulogne, France--Seats may not be the major selling point when a customer makes that final decision to buy a new car. But a seat that reflects comfort, safety, and style may help turn the tide--all other things being equal.
That's why Bertrand Faure, a major automotive seat manufacturer in France, decided to promote research and innovation inherent to the automotive seat trades by conducting an industrial design competition. The idea also resulted in the development of stronger relationships between the company and industrial design schools. The project involved the design of an individual front or back seat, other than the driver's seat.
Hélène Boga of the Ecole Nationale Supérieure des Arts Décoratifs walked off with the top prize in the contest. She conceived her winning design around three main principals:
Ensuring a visual comfort as much as a physical comfort. The winning result brings a contrast between the metal structure and the body support elements of the award-winning design.
Creating an environment that enables passengers to sit in different positions, while allowing contact with other areas of the car interior through the use of transparent material, and by providing a visual effect of lightness.
Ensuring the kinematics of the seat with built-in mechanisms and slides that remain accessible from the electronic controls in the door panel.
Second prize went to Magali Borgers and Vincent Muracciole of Ecole Nationale Supérieure de Création Industrielle. Their TSIO (Two Seats in One) design features modular lateral wings on both the seat and the seat back to enable the passenger to adapt to different driving conditions.
Third-prize winner was François Tarinquecostes of Ecole Nationale Supérieure des Arts Appliqués et des Métiers d'Arts. This design integrates the following functions:
Comfort through the absorption of vibrations by an air cushion.
Ergonomics that permit a wide view and ease of movement.
Security through the use of an airbag in the seat back and a three-point seat belt.
Quality through the use of such materials as aluminum alcantara.
Conservation of natural resources by making the seat lightweight and requiring less materials.
Daniel Dewavrin, Bertrand Faure CEO, presided over the awards jury. Other jury members included: Yves Dubreil, projects manager at Renault, and Roger Garnier, industrial manager of Sogedac.
Automated-highway research meets the road
by Julie Anne Schofield, Senior Editor
San Diego--"The driver will purposely veer off the road to demonstrate the lane-departure warning"--not exactly words of comfort when you're barreling down the highway in a bus that's driving itself.
Regardless of whether you think automated highways and vehicles are a good idea, it was clear this summer that the technology exists today. At the National AHS (Automated Highway System) Consortium's Demo '97, car companies, technology firms, research facilities, and government teamed up to deliver six scenarios of what driving might be like in 20 years.
My bus was part of the Free-Agent, Multi-Platform demonstration put on by Carnegie Mellon University and Houston Metro. The demo, which comprised two buses, two Oldsmobile Silhouette minivans, and two Pontiac Bonnevilles, illustrated how automated and nonautomated vehicles might one day operate together.
Each vehicle was fitted with a Pentium-based PC; video cameras; forward-looking radar; short-range radar units on the sides; laser rangefinders on the rear; displays; motors to actuate the throttle, brakes, and steering; an on/off switch for automated control; and a button for changing lanes.
Human "safety drivers" drove the vehicles to the specially outfitted section of I 15, then let the automation take over. As I sat powerless in the bus, vehicles automatically changed lanes, a minivan got out of the way of a faster car, vehicles switched lanes to avoid a barrel and warned vehicles behind them of the obstacle, and all six vehicles come to a smooth stop at the end of the course. The entire ride was basically uneventful--and that was just the point.
Why do we need automated highways? National Highway Traffic Safety Administration statistics show that crashes on U.S. highways cause more than 40,000 fatalities and more than 5 million injuries each year, costing more than $150 billion. In 9 out of 10 crashes, human error--usually fatigue--plays a leading role. Further, travel increased 65% between 1970 and 1990 and is expected to double between 1990 and 2020.
The dual goals for an AHS are to improve safety by reducing crashes attributed to driver error and to relieve traffic congestion by increasing the capacity of existing freeways.
In 1991, Congress directed the Department of Transportation to develop an automated highway and prototype vehicle by 1997. To date, the federal government has invested $1.2 billion dollars in the Intelligent Transportation Systems program, said Secretary of Transportation Rodney E. Slater during Demo '97. And there's more money coming. The Clinton administration has proposed investing another $250 million in 1998.
Core participants--in partnership with the U.S. Department of Transportation Federal Highway Administration--include: Bechtel, the California Department of Transportation, Carnegie Mellon University, Delco Electronics, General Motors, Hughes, Lockheed Martin, Parsons Brinckerhoff, and the University of California PATH Program.
CMU researcher Dean Pomereau predicts that the first commercially available technology to come from AHS research will be collision warning and avoidance systems. Using radar, such a system would detect obstacles and other vehicles in the road and either warn the driver or apply the brakes. Other near-term applications could include adaptive cruise control, which senses vehicles ahead and alters speed accordingly, and lane-keeping systems, which use sensors to track magnets in the road or radar-reflective tape on the pavement to warn drivers when their vehicles are drifting across a lane boundary.
Although the key buzzword in San Diego was "incremental deployment," NAHSC officials say that operational tests involving the public could begin within 10 years. I can only hope they choose Massachusetts as the next testbed. As someone who regularly deals with Boston drivers, I can't imagine that a computer could do much worse.
Automakers aim to remove cast iron liners from aluminum engines
by Charles J. Murray, Senior Regional Editor
Fond du Lac, WI--Twenty-five years ago when General Motors unveiled an all-aluminum block engine in the new Chevrolet Vega, the nation's engineers viewed it with a jaundiced eye. Over time, they said, it wouldn't stand up to heat and friction.
Sure enough, Vega's all-aluminum block didn't wear as well as cast iron. Although engineers later announced that the problems were caused by deficiencies in the Vega's cooling system, the all-aluminum block had suffered a blow. Since then, post-Vega aluminum engines have employed cast iron cylinder liners.
Now, however, that's changing. The Porsche Boxster, unveiled earlier this year, employs an aluminum alloy block engine with high silicon aluminum liners. BMW offers a linerless aluminum block in its 8- and 12-cylinder engines. And now, one major automaker and a motorcycle manufacturer reportedly have entered into programs with Mercury Marine Division of Brunswick Corp. to develop linerless aluminum block engines.
| Silicon particles in the cylinder bore, along with a nickel phosphorous/boron nitride piston coating, enhance the durability of the aluminum block.
Removing cast iron liners from aluminum engines could mean major financial savings for engine manufacturers. By most estimates, cast iron liners cost $4 to $6 per cylinder, meaning that a V-6 engine builder could save between $24 and $36 per engine by eliminating them. It could also lead to better performance and lower emissions because an engine made from a single material could be designed to tighter tolerances. "Because you would have less parts in a linerless engine, it would probably be easier and less expensive to make," notes David Cole, director of the Office For The Study Of Automotive Transportation at the University of Michigan. "But you need to be sure first that you have confidence in the aluminum bore."
At Mercury Marine, engineers have developed extraordinary confidence in the viability of the aluminum bore. Over the past 12 years, the company has developed and tested a hypereutectic aluminum-silicon block technology known as Mercosil. Mercosil employs 30-µm-diameter silicon particles throughout the aluminum alloy to enhance the wear resistance of the bore. Using Mercosil, the company built 500 test engines in 1985, 1,000 test engines in 1991, and went into production with a linerless aluminum engine in 1994. Next spring, it plans to introduce its biggest version yet, the 125-hp MERC 125 all-aluminum, two-stroke engine. "All of the engines--even the early models--have exhibited very good durability," says Raymond J. Donahue, director of advanced materials for Mercury Marine.
On the Merc 125, Mercury Marine plans to use a special NCC nickel phosphorous/boron nitride piston coating made by Daubert Chemical Company Inc., Chicago. Donahue describes the solid lubricants in the NCC-coated piston as "a technical breakthrough" that further enhances the robustness of the hypereutectic aluminum-silicon block.
Ultimately, engine manufacturers may be forced to take a harder look at the technology. As the Environmental Protection Agency continues to crank up emission regulations on engines for automobiles, boats, snowblowers, and lawnmowers, manufacturers may see economic advantages to eliminating the cast iron liner. Because cast iron liners have a different thermal expansion coefficient than aluminum, engineers typically design for wider tolerances, which can cause higher emissions. Switching to a homogeneous block would enable engineers to design to tighter tolerances.
Similarly, concern over weight issues may drive the technology, since aluminum blocks on average weigh about 20%-30% less than cast iron counterparts. "In all forecasts, we foresee a significant increase in the use of aluminum blocks," Cole says. "A bare bore technology could help accelerate it."