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 750HLSaab Combustion Control (SCC) System. The main goal of the SCC system is to keep the air/fuel ratio as close to the ideal for catalytic converter efficiency as much as possible, even during transient conditions. To do this, Saab uses a strategy of running very high amounts of exhaust gas recirculation (EGR), up to 60-70 percent. The amount of air ingested by the engine varies accordingly but the amount of fuel used never exceeds one percent. To do this, Saab uses air-assisted fuel injectors which have an integral spark plug with an extended ground electrode. Depending upon the operating conditions, the spark will either jump to this electrode or to the piston dome itself. Saab claims this system allows it to meet the future ULEV II standards by reducing HC and CO by about 50 percent, while NOx is reduced over 75 percent. This is accomplished with no loss in performance and with an eight to ten-percent improvement in fuel economy; CO2 is also lower.BMW 750 HL. The use of hydrogen-powered fuel cells is considered by many to be the ultimate low-emission technology, since it uses a renewable fuel which produces no tailpipe emissions. There are considerable issues with supply and overall commercial feasibility that remain to be resolved, but BMW is taking a novel approach to doing so. BMW believes that an internal-combustion engine run on hydrogen fuel should be used for propelling the vehicle, while a hydrogen-powered fuel cell should handle the electrical loads. To this end they have developed the 750 HL, an interim step in getting to this goal. The HL is currently a dual-fuel vehicle: it can run on both gasoline or hydrogen. As such it is a compromise in terms of performance. The HL’s 5.4-liter V-12 is rated at 204 hp versus the gasoline model’s 326 hp. The latter meets LEV emission standards while the former emits primarily water from its tailpipe. When a dedicated hydrogen version of the HL is developed, BMW believes it would make about 340 hp. The current bi-fuel model reaches 62 mph in 9.6 sec. so the extra hp will be appreciated for those who want the ultimate “clean” driving machine. With a 37-gallon cryogenic fuel tank, which keeps the liquid hydrogen at a temperature of minus 423 0F, the HL has a range of 220 miles. Not bad, but this too will have to improve with the dedicated version for hydrogen to be a viable alternative.
Saab Combustion Control ConceptEnlarge Photo
BMW 750HLEnlarge Photo