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

TOKYO – Mazda Motor Corp. strives to coordinate powertrain development with Ford Motor Co. in hopes of introducing new technologies at an affordable cost.

While largely achieving this objective, management often must delay marketing of advanced systems until Ford, Mazda’s largest share holder, gives the green light.

Until then, Mazda does without continuously variable transmissions and hybrid-electric or flex-fuel vehicles, though some of these systems are technically ready.

Instead, Mazda’s focus has been on direct-injection gasoline engine and variable valve-timing technologies. In 2005, the auto maker introduced its 2.3L DISI (Direct Injection Spark Ignition) 4-cyl. for the Mazdaspeed6 performance sedan.

The same DISI 4-cyl. since has been adopted by the Mazdaspeed3 and CX-7 cross/utility vehicle. In Japan, it is available in the MPV minivan and Premacy wagon, the domestic version of the Mazda5.

The new 2L DISI 4-cyl. for the Premacy/Mazda5 is naturally aspirated. All other models, each with 2.3L variants of the DISI family, are turbocharged.

Meanwhile, Mazda, which has 17 engines in its lineup, was among the leaders in introducing high-pressure, common-rail fueling for diesels.

In 2002, it adopted a 26,000-psi (1,800-bar) common-rail system supplied by Denso Corp. for European export models of the 2L MPV and Mazda6. The 2L turbodiesel with the high-pressure injection system also now is available in the Mazda5.

Elsewhere, Ford soon will discontinue production of the Mazda2 at its Valencia plant in Spain, returning production to a Mazda plant in Japan.

As a result, the Japanese auto maker likely will source the new-generation Mazda2’s 1.3L turbodiesel directly from PSA Peugeot Citroen’s Douvrin plant; that diesel engine family was co-developed with Ford.

Mazda’s own 2L turbodiesel, also using a Denso-developed high-pressure common-rail injection system, is installed in European export models of the Mazda6.

Unlike Honda Motor Co. Ltd. and Mitsubishi Motors Corp., Mazda has no plans to introduce a “clean-diesel” vehicle in the U.S. market.

“We are not big enough to do it on our own, thus we’ll have to work with Ford,” says Seita Kanai, director-technical development.

Nor will Mazda develop a hybrid-electric vehicle on its own – although it has a “smart” mild- hybrid system featuring idle-shutdown technology that is ready to go.

Here, too, it will rely on Ford technology, specifically, the system developed for the Escape and Mercury Mariner HEVs. Nevertheless, Kanai expects HEVs to make “big inroads” in the coming 10-15 years.

From the middle of this year, the auto maker will launch a Tribute Hybrid CUV in the U.S. A variant of the Ford Escape Hybrid, Mazda’s Tribute Hybrid will be powered by a 2.3L gasoline engine and 70-kW electric motor. Engineers say the vehicle’s 4-cyl. mill will produce 131 hp and 123 lb.-ft. (167 Nm) of torque.

Kanai declines to speculate on which HEV system – “strong” such as the Toyota Prius or mild such as Honda’s Accord Hybrid and Civic Hybrid – will prevail.

“A bigger question for Mazda is, what sort of engine future hybrids will be based on: Gasoline? Diesel? Even rotary? At this point we see no clear direction. A rotary hybrid would be fantastic, however,” he says. Mazda is the only auto maker with a rotary in production.

In future-fuel endeavors, Mazda began leasing a dual-mode (gasoline and hydrogen) rotary-powered car last April.

Based on an RX-8 sports car, the RX-8 Hydrogen RE can run 60 miles (97 km) with its rotary burning pure hydrogen; 400 miles (644 km) using both fuels. Hydrogen gas is stored in a supplemental high-pressure fuel tank in the car’s trunk.

To date, the auto maker has leased five RX-8 Hydrogen REs in Japan, including two in the private sector, to companies.

Mazda researchers note that conventional piston engines tend to misfire when running on hydrogen, as the gas hits the hot intake valves. In contrast, the rotary’s unique layout – with intake and exhaust areas located in separate chambers – is much more suitable for hydrogen fuel.

Meanwhile, Mazda currently is testing an HEV using a rotary. A prototype displayed at the 2005 Tokyo Motor Show in a Premacy minivan employs the same dual gasoline-hydrogen system that is installed in the RX-8 Hydrogen RE.

Unlike the RX-8 Hydrogen, however, the Premacy Hydrogen’s dual-fuel rotary engine is augmented by an electric motor powered by a nickel-metal hydride battery pack.

Its hydrogen fuel tank is slightly larger than the RX-8 Hydrogen unit, enabling the model to run 125 miles (201 km) using only hydrogen fuel, double the distance of the RX-8 Hydrogen.

Kanai says Mazda’s hydrogen rotary has greater mid-term future potential than fuel cells because its cost is “more realistic.”

Mazda is relying on Ford to take the lead in developing fuel-cell technology through its partnership with DaimlerChrysler AG and Ballard Power Systems Inc.