Third in a 6-part series exploring powertrain strategies for Japanese auto makers.

TOKYO – Honda Motor Co. Ltd. rolled out its next-generation engine lineup last autumn, highlighting, among other things, an all-new turbodiesel equipped with an innovative catalytic converter that allows the diesel to meet Environmental Protection Agency Tier II, bin 5 emission standards.

Honda says the new turbodiesel is fully compliant even without a separate urea-injection system to help reduce oxides of nitrogen emissions.

The new converter is simpler in design than current diesel exhaust systems with urea injection – and thus potentially less expensive, says Motoatsu Shiraishi, president of Honda R&D Co., the auto maker’s wholly owned research subsidiary. No urea tank, no urea heaters, no accompanying sensor and injector.

Honda’s system stores NOx in the catalyst and converts it into harmless nitrogen during normal engine operation.

NOx stored below the surface of the catalyst substrate is converted to ammonia (NH3) during a brief and controlled rich-combustion phase and moves to the platinum-coated catalyst surface, where it reacts to form harmless nitrogen and water.

Other factors contributing to the engine’s impressive emissions results include an improved combustion-chamber design, a 29,000-psi (2,000-bar) common-rail injection system with piezohydraulic injectors to speed injection times and patterns, and an upgraded exhaust-gas recirculation system.

Bottom line for Honda, says Shiraishi: “It enables diesel engines to rival gasoline engines in cleanliness.”

The auto maker plans to introduce a vehicle equipped with the engine into the U.S. market in 2009. While no model has yet been designated, analysts speculate it will be the CR-V compact cross/utility vehicle or Civic subcompact, both of which are built in North America.

Honda’s first turbodiesel, the iCTDi 2.2L DOHC 4-cyl., debuted for the European Accord in early 2004. Featuring a lightweight aluminum block, the 4-cyl. turbodiesel also now is available on the U.K-built CR-V, Civic and FR-V, European derivative of the Edix.

Researchers confirmed the iCTDi will be the base architecture for the new North American diesel.

Honda also has announced plans to introduce a V-6 turbodiesel in 2009. No details were disclosed other than it will exceed Tier II, bin 5 standards.

In a forecast at the 2005 Society of Automotive Engineers World Congress, Honda estimated clean diesels, gasoline-engine vehicles and hybrid-electric vehicles each will claim roughly 30% of the global market in 2020, with fuel-cell vehicles accounting for a portion of the remainder. A senior researcher predicted at the time FCVs will account for 5% of Honda’s North American sales.

Meanwhile, Honda will stick with its Integrated Motor Assist hybrid system and not introduce a more intricate Toyota Prius-type “full” HEV system in which one or both power sources, the internal-combustion engine or the electric motors, can propel the vehicle.

“We think our IMA system is more efficient, particularly for smaller vehicles,” says a Honda research executive. “For larger vehicles, we will consider diesels.”

Last September, Honda remodeled its Civic Hybrid, equipping the car’s 4-cyl. gasoline engine with a new 3-stage variable valve-timing design (including low/high rpm and idle) and an improved IMA system.

The result: 74 mpg (3.1 L/100 km) in city driving based on the Japanese “10-15” test cycle, along with substantially improved acceleration.

Japanese fuel-economy testing skews toward higher mileage because it does not include startup and warmup emissions, and running speeds only average 14 mph (22.7 km/h).

The Civic Hybrid still lags the Toyota Prius, which achieves a staggering 85 mpg (2.7 L/100 km), according to the Japanese test mode. In the U.S., the Prius has the best hybrid fuel economy, with a combined rating of 55 mpg (4.2 L/100 km).

Honda 2006 Hybrid Vehicle Sales
Japan Overseas* Total
Accord Hybrid 7,750 37,870 45,640
Civic Hybrid 0 6,150 6,150
Insight 85 745 830
Total 7,835 44,665 52,500
* Includes estimates for several countries. Source: Honda.

In the family-sedan segment, Honda’s V-6/IMA-powered Accord Hybrid ranks as best in class for both fuel economy and acceleration.

In fact, a Consumers Union research official says the car “delivers comparable acceleration to a V-8 with the fuel economy of a 4-cyl. model.”

In 2006, Honda sold nearly 53,000 HEVs globally, with the Civic Hybrid accounting for nearly 90% of sales, of which well over half were in North America.

Meanwhile, Honda is expected to introduce its next-generation Variable Valve Timing Electronic Control (VTEC) valvetrain system for an Accord-class vehicle in 2009.

A 2.4L prototype displayed last autumn features continuously variable valve timing, lift and phase controls which, according to Honda, will improve fuel economy 13% over existing i-VTEC engines.

A researcher says the engine could be modified to be used with Honda’s IMA system, but there are no immediate plans.

Nor will the engine, unlike the i-VTEC, be introduced throughout the auto maker’s model lineup, he says.

In other fields, Honda introduced a flexible-fuel version of the 1.4L Fit and 1.8L Civic in Brazil last year. The engines run on alcohol fuels with virtually no change in power and torque output.

In its FCV program, Honda is moving closer to completing the development of the FCX Concept, a mockup of which debuted at the 2005 Tokyo Motor Show.

Since the debut, Honda has reduced the fuel cell’s stack size 20% while cutting weight nearly 33%, or 396 lbs. (180 kg). Researchers add that the car’s powertrain, though 10% larger than the V-6 developed for the standard Accord, is slightly lighter.

Other Honda FCV advances include:

  • Lower-temperature operation. The fuel-cell powerplant now can be started at -22° F (-30° C), 10 degrees lower than the current generation FCX, Honda’s main FCV offering.
  • Improved motor power of 95 kW (127 hp), up from 80 kW (107 hp) in the FCX, by employing a new lithium-ion battery pack that produces 30 kW and enhances motor speed up to 12,500 rpm (up 1,500 rpm) and vehicle speed of 100 mph (161 km/h).
  • Extended driving range from 200 miles (322 km) to 270 miles (435 km). Honda’s eventual target is 300 miles (483 km) under all climatic conditions.
  • Improved fuel-to-wheel efficiency, from 55% to 60%, compared with 17% for Honda gasoline-engine cars and 30% for Honda HEVs.

Shiraishi credits the car’s ‘V-Flow’ fuel-cell stack design – whereby compressed hydrogen and oxygen flow downward from the top of the stack rather than horizontally, as is the case in other stack layouts – for both size reduction and improved low-temperature performance.

The V-Flow stack is located inside the car’s central tunnel. Its compact, coaxial-type traction motor and gearbox allow for a short front overhang. Shiraishi says the powertrain’s layout permits the same sort of packaging one might get with a standard sedan.

Honda’s 5-year targets for the car include a further 10% to 15% reduction in stack size from current 52 L, a 15% to 20% reduction in the power control unit’s size (no specifications provided), and the 300-mile driving range.

If the auto maker achieves these targets, it will focus on infrastructure problems, including developing a hydrogen refueling network.

“Only then,” a senior researcher advises, “will we work on bringing down (total vehicle) cost.”

Honda expects all technical developments to be completed by 2012, at which time cost-reduction work will begin in earnest. Researchers say they will not seek to lower starting temperatures, as “-30° is the same as for piston engines.”

Meanwhile, Honda’s 2020 price target for its FCV is ¥4 million ($35,000), roughly the same as an upper-grade Accord. If it achieves that target, management estimates FCVs will account for 5% of Honda sales in North America. No sales targets were offered for other markets.