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Mar. 10, 2015 - Updated 04:16 UTC



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Low Tech, Low Emissions

Yuko Fukushima

Oct. 30, 2015

Japanese automaker Mazda has come up with a new approach to making eco-friendly clean diesel cars. With all the negative publicity surrounding the Volkswagen emissions scandal, diesel cars were in the spotlight at the recent Tokyo Motor Show.

European automakers don't seem to be fazed by the scandal and they're standing by their emission control technology. It remains to be seen whether consumers are convinced or regulators, for that matter.

In the meantime, Mazda has come up with a very different approach to clean diesel cars.

The technology used by VW is called exhaust emissions control. Following computer commands, it filters out pollutants before they leave car. The problem is these systems are expensive to make and operate and that is one reason Volkswagen cheated on the emissions test.

A company based in Hiroshima has taken a different road. Mazda sells diesel engine cars that don’t need emission control devices and it claims they're clean.

Mazda is a mid-ranking automaker, with less than 3% share of the global market. It's been through some troubled times. Bad management decisions put the company on the brink of bankruptcy.

At one time, it operated under US carmaker Ford. Recovering from those setbacks, Mazda is staking its future on a simple strategy make affordable cars that are fuel efficient and eco-friendly. To do that, it cut production costs to the bone.

Factory workers at Mazda are making thousands of tiny efforts to make their production line more efficient and cut costs. For example, they are using plastic bottle as weights.

Recycled bottles that are filled with scrap waste is hardly state of the art equipment. But it works. And it's cheap.

Other companies invest huge sums developing next generation transport, like hybrids and fuel-cell cars. But Mazda chose to focus on a less fashionable project improving the diesel engine.

“We aren’t a big company. Our funds are limited," said Mazda chief engineer Eiji Nakai. "We had no choice but to concentrate whatever resources we had on improving engine efficiency.”

Diesel engines mix air and fuel in a combustion chamber just like a gasoline engine. The difference is there's no spark plug. Instead, diesel combustion relies on high temperatures to ignite the mix.

This is achieved by squeezing the air. But getting the right combination of fuel and air can be tricky. Too little or too much of either leads to incomplete combustion. That creates pollutants, the most troublesome being Nitrogen Oxide.

Mazda's team decided to go back to the drawing board. They began a search for optimum combustion conditions.

The first attempts failed. Then they struck on the idea of lowering the compression ratio. Most diesel engines compress air to about a 15th to 20th of its original volume. Mazda engineers decided to see what happens when air is compressed as low as a 14th of its volume.

It turns out lower compression does help create a better mix of air and fuel before ignition. The result is fewer harmful substances.

Mazda engineers say this white cloth over the tailpipe is evidence of what they have achieved: no soot.

A more efficient engine means Mazda can do away with an emission control device.

Mazda’s CEO says there's no danger of the Volkswagen scandal tainting his company. He stresses the technology is very different.

"We have been researching ways to purify toxic gas emitted from the engines for a very long time," said Mazda CEO Masamichi Kogai. "We will never run into a problem like that. So I want our customers to be assured our cars are perfectly fine."

Zero-emission vehicles may be the future. But Mazda says there's still a lot of mileage in the conventional engine. It looks like clean diesel cars are just warming up.

Yuko Fukushima discussed Mazda's progress with NHK's Sho Beppu.

Beppu: Mazda is obviously proud of its technology. But has their engine really solved all the problems of dirty diesel?

Fukushima: As I mentioned in the report, the engine does emit pollutants, just very few compared to other clean diesel engines. And Mazda's engines didn't come without challenges. Low compression engines have trouble starting in cold weather. The engineers came up with a number of solutions. One was to tweak the way fuel is injected into the engine. They adjusted the amount and timing. Another was to funnel hot exhaust air back into the engine housing. And they say their work is not over. They're now aiming for a new type of engine that will combine the best of both gasoline and diesel. And rest assured they're sticking to their low-cost strategy. So we'll see what they come up with.