Industry experts at SEMA rate the fuel-economy options

  • 20-Nov-2009 06:03 EST

One of the cars on display at SEMA was the Prius Aerius with a Five Axis Design aero kit.

SEMA (Specialty Equipment Market Association) provides the leading forum for driving performance, at its annual Las Vegas meeting and show. However, SEMA also recognizes the national need to reduce oil consumption. Its “Driving Green" super session enables OEMs, suppliers, industry observers, and the aftermarket to share views on how to do it.

It will be primarily with gasoline, said Brett Smith of the nonprofit Center for Automotive Research (CAR), which forecasts that even at $6/gal in 2011, diesels would represent just 5% and gasoline hybrids just 10% of the market, and by 2015 hybrids perhaps only would double the 2011 level. He said lithium-ion battery technology isn't ready for high-volume all-electrics, and even at $6/gal CAR sees just a half million sold by 2015.

Dean Tomazic, Vice President, Performance and Emissions, FEV, sees more technical diversification, with six-, seven-, and eight-speed transmissions and dual-clutch gearboxes playing larger roles. Although there will be more diesels, he said, they will still be sold at relatively low volumes in the U.S. He also predicts two-stage turbocharging, currently used on diesels, will come to smaller gasoline engines to improve performance.

Aftermarket performance parts supplier Gale Banks, whose Banks Power specializes in diesels, said he sees them and hybrids as both eventually stabilizing at 8-10% of vehicle sales.

However, even if fuel prices remain low, legally mandated fuel-economy improvements will continue to drive the car manufacturers.

Toyota has a major commitment to gasoline-electric hybrids and invests to make them cost-effective. But because they are available throughout the Toyota and Lexus lines, performance of their hybrids also becomes important. This still is largely Toyota's department, although some aftermarket companies are offering engine air filter and muffler kits. A Prius show car, the Aerius, with an aero kit by Five Axis Design, a custom design company, was displayed at the SEMA show by Toyota, which noted the kit just maintained the vehicle's 0.25 Cd.

Justin Ward, Toyota Advanced Powertrain Program Manager, discussed evolution of the company's hybrid system and broadening of applications, from the original front-drive Prius of 1997 with its power-split device for delivery of either or both mechanical and electrical power to the wheels.

Among the key MY2010 Prius engineering changes he cited was redesign of the transaxle and the motors to reduce size and weight and increase power. The new traction motor now spins up to 13,000 rpm, almost twice the previous model's, producing 60 kW vs. the previous model's 50 kW. The power-split device is combined with a planetary-type traction motor speed-reduction unit, so the higher-rpm motor operation is smoothly integrated with engine power.

Redesign of the motor for higher rpm does cut torque in half—from 400 N·m (295 lb·ft) to 207 N·m (153 lb·ft). But the 2010 engine is larger (1.8 vs. 1.5 L) and produces 20% more torque—143 N·m (105 lb·ft) vs. 111 N·m (82 lb·ft)—so total hybrid system torque still is V6-class. And the 1.8-L develops a third more power than the 1.5-L—98 hp (73 kW) vs. 76 hp (57 kW). Further, dc bus voltage continues to rise, from 274 V in 2000 to 500 V in 2003, to 650 V in 2010, permitting reductions in current flow. The results are less copper needed and less motor heat generated, which reduces cooling loads. Although doubling motor speed could increase losses caused from crystal formation in the iron core, Toyota was able to optimize the motor for that issue, Ward added.

The new transaxle reduces torque losses 20%, and there is no continuous power draw from engine drive belt-driven accessories; all are electric-motor-driven. Bottom line: enough torque and more power to the wheels.

A more complex system in the Lexus LS 600h L and GS 450h features a two-stage planetary gearset for traction motor speed reduction, so these rear-drive cars accelerate even more smoothly to maximum speed. They also have optional four-wheel drive, which adds a center differential with a Torsen limited-slip feature, and output shaft to the front wheels. The GS 450h, Ward said, accelerates from 0-60 mph (0-97 kmh) in about 5.5 s.

Toyota demonstrated performance potential with the Supra HV-R hybrid racecar, which won the 2007 Tokachi 24-hour race in Japan, Ward noted. That vehicle has two traction motors driving the front wheels and one motor driving the rear wheels.

Ford Motor Co. already markets two gasoline-electric hybrids and plans more by midterm, plus an all-electric. However, near-term (to 2011) and midterm (2011-2020) plans feature gasoline turbo direct injection, said Dan Kapp, Ford director of Powertrain Research and Advanced Engineering, during the SEMA Driving Green session.

"Ford has to be both green and deliver performance," Kapp said, but "people aren't willing to pay a lot extra for fuel economy." Near- and midterm, he said, Ford will increase applications of EcoBoost, its brand name for turbo gasoline direct injection that already is deployed on the 3.5-L V6 in the Taurus SHO, Lincoln MKS sedan and MKT crossover, and Ford Flex. It delivers 355 hp (265 kW)—365 hp (272 kW) in the SHO—replacing V8s for improved fuel economy.

EcoBoost next goes onto four-cylinder engines for midsize sedans, likely even an F-150 pickup, replacing naturally aspirated V6s. Further, Ford has scheduled an almost total changeover to electric power steering to eliminate parasitic losses. Four- and five-speed automatics are being replaced with a six-speed, and even some dual-clutch automatics will be in the picture, Kapp said. Smaller improvements will come from 12-V charge-management systems and aerodynamic improvements, he added. "We have to be on the value curve."

Ford's midterm goal for weight reduction is 250-750 lb, which means smaller vehicles and unibody crossovers replacing SUVs, said Kapp. These steps would align with reductions in engine displacement and EcoBoost availability in 90% of Ford products by 2013. 

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