Environmentally friendly, or “green,” vehicles have gotten a lot of play over the past few years. At the 2001 North American International Auto Show in Detroit, though, there was noticeably less talk of new pollution-reducing technologies. For the most part, they insist, they’re doing it, and not talking about it as much.
For example, getting certified as an LEV (Low Emission Vehicle) is not as big a deal now, because so many vehicles — including larger trucks — now meet this level. Fully 92 percent of Toyota’s U.S. product line is certified at the LEV level or better; some smaller manufacturers may be able to claim 100 percent. Even the new 195-mph Porsche 911 GT2 meets the LEV certification standard.
You have to meet at least the ULEV (Ultra Low Emission Vehicle) standard (roughly a 50-percent reduction in terms of HC and CO versus LEV) to get any real attention these days. Yet there are only two gasoline-powered vehicles (the Nissan Sentra CA and a California Honda Accord) which meet the even more stringent SULEV (Super Ultra Low Emission Vehicle) standard.
This will all change as emission standards continue to go lower by law. The biggest changes will come by the 2004 model year, when the second generation of California’s Low Emission Vehicle program known as “LEV II” kicks in.
In the meantime, there were some pretty interesting low-emission technologies to look at in Detroit, even if they didn’t get as much hoopla as they have in the past. The majority were based on gasoline powerplants since it looks like alternate fuels are still a ways off. Diesel is big in Europe and may see a resurgence in the U.S. once we have cleaner diesel fuel and some regulatory relief. Natural-gas vehicles are pretty much niche players for now; only centrally serviced fleets seem to have any inclination to regularly use these fuels in quantity. Hydrogen and/or methanol may be longer-term solutions when fuel cells become commercially feasible, but they have infrastructure issues which will impede their near-term use.
Thus, gasoline engines will continue to improve so they can meet the more stringent environmental requirements being imposed upon them. The technologies that follow are some examples of how these various approaches may be improved and implemented:
Saab Combustion Control Concept BMW 750HL
Saab Combustion Control Concept
Cadillac LQ9 V-8 (Escalade). This new 6.0-liter V-8 engine is remarkable not only because it has 345 hp and 380 lb-ft of torque (both at 5200 rpm) but because it meets ULEV emission standards. To do this, it uses small volume exhaust manifolds and close-coupled, low-density catalytic converters with heavier precious metal loading; secondary air injection is not needed. The compression ratio is a respectable 10:1 and other hot-rod tricks like a larger 75mm throttle body, optimized intake and exhaust ports and low-restriction mufflers are used to improve performance without an emissions penalty. Aluminum heads allow more spark advance to be used for better combustion quality, while an electronically-controlled throttle smooths out deviations in air/fuel ratio as it also improves pedal feel and throttle response.
Mercedes’ New V-6/V-8/V-12 Engines. All of these new “V” engines use three-valve technology, which Benz claims can reduce emissions during the warm-up phase by up to 40%. This is especially critical since about 80 percent of the tailpipe emissions measured during certification occur during warm-up. Benz has successfully reduced the warm-up period from over two minutes to less than one through the use of this three-valve technology coupled with very lean air/fuel ratios and about 5-10 degrees of spark retard during warm-up. The three-valve technology alone is responsible for about a 12-second reduction in catalyst light-off time, due in large part to its 30-percent reduction in exhaust port area, which raises the exhaust temp at the catalyst inlet by about 125 0F. The use of phased dual spark plugs allows these engines to tolerate very lean mixtures and higher EGR levels, which further reduce emissions. The ignition system also employs an ion current sensing strategy that is used not only to prevent misfires but to improve combustion quality. Lastly, the V-12 has a cylinder deactivation capability which improves fuel economy by more than 20 percent versus the previous V-12. All engines use lightweight componentry.
Ford Hybrids (Escape HEV/Explorer with ISG). The concept behind Ford’s Integrated Starter Generator (ISG) is simple: recover some of the energy lost as heat/friction during braking, store it, and then use it to assist and/or replace the combustion engine under certain circumstances. The key benefit is being able to shut the engine off at traffic lights, etc., thus saving fuel and lowering emissions. You can also use the ISG as an “electric supercharger” to add power (especially torque) to the IC engine, thus allowing either the use of a smaller engine for the same performance with lower emissions and improved mpg. You could also keep the engine the same size and get better performance while still reducing emissions and fuel consumption somewhat due to the “smoothing” effect of the electric assist (you can minimize high transient loads on the engine which require rich fuel mixtures and thus increase emissions). Ford claims their 2003 Escape HEV with a four-cylinder engine will get 40 mpg and perform as well as the V-6 model. The Explorer with ISG will use a V-6 that will at least equal the performance of the V-8 model and get about 27 mpg versus the current 20 or so. Use of the ISG will require a 42v electrical system, which will facilitate use of other technologies such as purely electric power steering and, someday, even electric brakes. A small 12-volt battery will still be used for lower power consumption items like radios, etc., and to maintain long bulb life.
GM ParadiGM Hybrid Electric System. The GM approach to “mild” hybrids is unique in that it uses two electric motors instead of one. GM claims this gives them additional flexibility, which results in lower emissions and improved fuel economy by allowing them to run off of the motors, only more often. An example of this is that they can use one motor to run the air conditioning while the combustion engine is shut down and still have a second motor ready to restart the engine when needed. Other hybrids run the A/C off of the engine and thus can’t shut the engine off if the A/C is turned on. Since GM uses two motors and drives the A/C from the transaxle, not the engine, they can run the A/C in a zero-emissions mode, which saves fuel and makes best use of the recovered electrical energy.
GM plans to bring the ParadiGM system out in a production SUV in 2004. It will likely use a 3.6-liter V-6 engine, will be targeted to get 35 mpg and will use the gasoline engine to drive the front wheels while the motors will drive the rear wheels. Total horsepower will be about 252 (220 for the V-6, 32 for the two motors). GM claims they will be the first to bring hybrid technology to the masses by implementing ParadiGM over a large number of vehicles so they can make money doing so. They do not plan to roll out a few specific applications, which barely make (or lose) money. They believe the greatest benefit is on larger, high fuel consumption vehicles since the amount of fuel saved (and emissions reduced) is greater, even though the improvement in terms of mpg maybe smaller. They believe commercial customers with high annual fuel bills will be most interested in hybrid technology and have thus targeted buses and other large vehicles for hybrid technology as well. They already have several hybrid demonstration buses that use their Allison Division’s hybrid technology (called the “E System”) in use.
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