55 Miles Per Gallon: How Honda Did It

Back in 1976, Hideyo Miyano decided to take a peek at the goings-on over at Honda Motor Co. A diesel-engine designer for a rival carmaker, Miyano hoped a job interview at Honda would let him gather a little intelligence. He didn't even bother to wear a tie to the meeting, a casualness almost unheard of in Japan. But Nobuhiko Kawamoto, then Honda's engine-design manager and now its president, ignored the irreverence and turned the discussion to the diesel-exhaust technology Miyano had patented. "We talked as engineers, nothing else mattered," Miyano says. He was so impressed that he switched jobs--though it meant a 20% cut in pay.

Miyano settled in at Honda's research lab. There, in 1984, he started looking at "lean-burn" technology, which boosts fuel efficiency by raising an engine's air-to-fuel ratio above the standard 15:1. Lacking a budget, he persuaded Honda's fabrication shop to make bootleg test parts from his drawings. "The beginning stages of research are extremely fragile," says Kawamoto, who by then was head of research and development at Honda but had only an inkling of what Miyano was up to. "We let small leaves grow in the dark for a while first."

Such nurturing paid off. On Sept. 10, after many trips to the drawing board, Honda became the first carmaker to introduce a lean-burn engine that doesn't sacrifice power. Two 1992 Civic models with the new VTEC-E motor will be sold in Japan. And on Sept. 27, Honda will unveil its Civic VX hatchback with the engine in the U. S. That car will meet California's strict emissions standards only with adjustments that cut the engine's fuel economy by 7%. But elsewhere, the VX will boast 48 mpg in town, 55 on the highway, the Environmental Protection Agency estimates. That's a 35%-plus jump from the 31/35 mpg for the three-door 1991 Civic--with little trade-off in performance or weight. Even with the California shortcomings, "it's a hell of an achievement," says Robert Brooks, an engine-technology consultant in Waukegan, Ill. "Japan is pursuing the state of the art with more diligence and speed than we are."

'EVERYTHING WE KNOW.' Lean-burn technology has long tantalized carmakers, most of whom are working on it. Such engines burn less fuel at a lower temperature and thus emit fewer oxides of nitrogen. Power always suffered, however, because no way could be found to ensure stable combustion or to precisely control the air-fuel ratio. Detroit's Big Three had always insisted that only a major breakthrough would make a lean-burn engine a success.

All Miyano needed was imagination and existing technology. He borrowed the variable valve-timing and lift system from Honda's $60,000 NSX sports car. At low engine speeds, one of the two intake valves in each four-valve cylinder stays shut, making for an optimum swirl of air and fuel through the chamber. At higher speeds, the valves open to deliver full power. A sensor usurped from Honda's Formula 1 racing engine helps maintain a precise air-fuel ratio of 22:1 at low engine speeds. "We just pulled together everything we know," shrugs Miyano.

Back in 1987, as Honda's Civic team began its four-year product-development cycle, none of this even seemed possible. Still, project leader Kenzo Suzuki realized that concern was growing worldwide over energy efficiency and the environment. He made a gut decision: At least one of his 1992 Civics would be a superhigh-mileage model.

That was the opening Miyano needed. He approached the design team, which showed cautious interest in his 218-pound motor. Then, in the fall of 1988, he installed a prototype engine in a Civic and shipped it to California for a road test. "It seemed to us the engineers were on the right path," says Thomas G. Elliott, executive vice-president of American Honda Motor Co. in Torrance, Calif. Indeed, with Miyano's prototype, a five-passenger Civic beat the mileage of the CRX-HF two-seater Honda had on the market. The problem was that the lean-burn system, plus a new transmission designed for it, would have hiked costs for the two by 10%. The team scaled back to an existing transmission.

Still, in mid-1989, 27 months to D day, the fuel-miser Civic was in jeopardy. Low oil prices had spurred demand for muscle cars, and some marketing types argued that fuel economy was a weak selling point. "Some people didn't think we needed this car," recalls chief engineer Kazushige Toshimitsu. In the end, top management kept the engine but turned down a sleek body the team wanted for maximum mileage. That saved millions on retooling for plants in Suzuka, Japan, and Alliston, Ont., where the model is assembled.

The next step was to adjust Miyano's prototype for mass production. The piston crown got a more dishlike shape, which made it easier to maintain production quality, notes Hideji Oura, who as head of bench tests for the Civic engine chose Miyano's model from in-house competitors. The valve-timing mechanism had to be coaxed to open both intake valves at 2,500 rpm, instead of 6,000 as in the NSX. And the control unit for the hijacked racing sensor had to be adapted to the new system.

At 18 months and counting, Toshimitsu and a few others returned to California with a prototype car. But the revised, mass-production model was a flop. It surged and vibrated and made strange noises. Dismayed, the team trudged back to Honda's development center in Tochigi, Japan. They fiddled with the transmission, lowering the gear ratio in each of the five speeds by up to 5%. That smoothed out the ride but cut mileage by 1% to 2%.

'IN TROUBLE.' As it turned out, the lean-burn drama wasn't over. With a year to go until mass production, the Tochigi team was about to hand over its drawings to the Suzuka plant for a test run. But a horrified engineer noted that the swirl ratio, which determines combustion speed, was far off target. "We were really in trouble," says Oura, who had kept his team so on-the-ball that he had time to play with his kids on weekends.

A brainstorming session led to alterations in the culprit--an intake port on the cylinder head. Even a 0.5-millimeter variance throws off the swirling motion, and late into the night the team tried to get things right by slapping clay on here, shaving it off there. They rushed new drawings to Suzuka last September, then bit their nails as production geared up on the revised design.

Finally, at dawn one Friday last January, the group had a truck waiting to snatch the first cylinder head off the line and race it 270 miles to Tochigi. They tested all day--stopping for 10 minutes to gulp down a curry-rice lunch. By 3 p.m., the engine had a passing grade. Jubilant, Toshimitsu, Oura, and six others headed for town to drink and sing karaoke until 3 a.m. The lead designer never made it home that night, sleeping off his celebration in the train station.It was a smooth ride from there to full production six months later, and for the engineers the VTEC-E is a triumph. But the true test will be customer reaction. In the U. S., Elliott wants to sell up to 18,000 units a year--about 25% of hatchback sales. Back home, Honda aims for 10% of Civic three- and four-door sales. Honda hopes to keep the VX's still-secret U. S. price under $10,000, vs. $9,400 for the CRX-HF it replaces.

SMALL STEP. The lean-burn engine still faces obstacles. Today's catalytic converters can't do their normal job of removing the oxides of nitrogen it emits, so the technology is limited now to small, 1.5-liter engines that inherently spew less NOX. They will meet standards in Japan and in 49 states. But to sell the engine in the California market, where Honda gets up to 25% of its U. S. sales, it had to leave the air-fuel ratio at the standard 15:1.

This cuts efficiency by only 4 mpg. But Honda wants that back, since it expects Congress to one day pass higher mileage standards. "The direction is inevitable," says Kawamoto. "We'd rather take even a small first step, instead of waiting for regulations." In fact, Honda is on step No. 2. It is experimenting with a new catalytic converter that can soak up NOX from lean-burn combustion, and with a much leaner engine. If these work, lean-burn engines might show up across Honda's product line.

That could leave U. S. auto makers far behind. They're developing two-stroke engines, a variety of lean-burn technology, but these won't be ready for several years. Detroit's stopgap strategy is to delay higher mileage rules with determined lobbying. And keep its fingers crossed that consumers aren't quite ready for Honda's latest innovation.


1984 Engine designer Hideyo Miyano begins research on an unauthorized fuel-efficient engine, cajoling colleagues into making prototypes from his drawings. Research head Nobuhiko Kawamoto, now Honda's president, looks the other way, giving tacit approval to the bootleg project

FALL, 1987 The Civic development team starts planning the 1992 model line. With new fuel-economy standards possible in the U.S., high mileage is a must for the new car

FALL, 1988 Miyano brings a prototype of the "lean-burn" engine to Honda's U.S. headquarters in California for testing. Performance is on track, but projected high production costs leave it on shaky ground

FALL, 1989 The cost problems are largely solved. But low oil prices have dampened demand for small, high-mileage cars. After heated debate, Honda decides to push ahead, and Miyano's engine is chosen for a super-fuel-efficient variation of the Civic

SPRING, 1990 Full of high hopes, Honda chief engineer Kazushige Toshimitsu takes a lean-burn Civic prototype to California. But the engine surges noisily and vibrates--a disaster. The Civic team returns to Japan to make the necessary changes, which boost performance but cut mileage

FALL, 1990 A last-minute problem crops up in the air-fuel mixture, unleashing a mad dash to redesign parts of the engine and put performance back on target

JANUARY, 1991 Successful production of new engine head for lean-burning VTEC-E

SEPTEMBER, 1991 Honda launches new Civic lineup in Japan on Sept. 10. The U.S. introduction is set for Sept. 27