The Mazda J Engine Is More Than Just a Rotary Engine

In the 1970s, Mazda’s rotary engine was a success story. Despite a few challenges, like devil’s claw marks on the inner rotor casing that would scratch and deteriorate quickly, the Mazda rotary engine became a major player in the American car market.

It was so successful that it made up half of Mazda’s vehicle production for the decade. The brand’s rotary philosophy still holds true today, blending reliability with stunning power.

Engine Performance

The Mazda J engine has an excellent reputation for being responsive, efficient and refined. But it has a lot more to offer than that.

For example, it is a world first that uses spark-controlled compression ignition to help achieve significant fuel economy and performance gains. This system is part of the automaker’s broader ‘well-to-wheel’ approach to reducing emissions.

It also works with the company’s future electrified vehicles. This includes a mild hybrid and plug-in hybrid prototype, due in the early 2020s.

The J engine is available in higher trims of the Mazda6 midsize sedan, as well as the CX-9 compact crossover SUV and the Mazda6 Signature model. It produces 310 lb-ft of torque at a low 2,000 rpm, which is more than many turbo-4 and V-6 engines produce.

Fuel Economy

Mazda J engine fuel economy is surprisingly good for the small-block V6 it employs in most of its cars. It’s EPA-rated at 29 mpg in front-wheel-drive models and 27 mpg with all-wheel drive.

That’s a huge improvement over what was attainable by turbocharging downsized engines that were touted as the only way to comply with corporate average fuel economy standards. The problem with downsizing engines is that they heat up and can also cause fuel to ignite prematurely, wasting energy.

Fortunately, Mazda has developed a new way to boost compression ratios without compromising power and efficiency. It’s called Spark-Controlled Compression Ignition, or SPCCI.

It involves a combination of higher pressures and an air compressor that boosts compression by spreading a large amount of pressurized fuel close to the spark plug. Eventually, it’ll be possible to raise compression ratios by up to 20 percent. It would make the engine’s thermal efficiency 56 percent, which Hitomi said is enough to reduce emissions to a level that makes the gasoline engine on par with an electric car.

Reliability

The Mazda J engine is a solidly reliable engine for a range of vehicles. It was built to deliver the best power-to-weight ratio possible, while still offering impressive fuel economy.

It is also one of the most efficient engines available in a compact vehicle. It can achieve up to 30 mpg on the highway while still producing a satisfying 181 horsepower.

While the Mazda J engine is a solidly reliable powerplant, it does have its drawbacks. It can develop misfires due to carbon buildup, especially if the spark plugs are not replaced properly.

This is not a problem for newer Mazdas, but older cars are more likely to have problems. The older CX-7s, for example, have a higher percentage of owner complaints related to their engines than their competitors.

Emissions

For decades, auto-makers have been chasing the holy grail of internal combustion: a homogeneous charge compression ignition (HCCI) engine. It promises a fuel efficiency equivalent to diesel engines without the soot or nitrogen oxide emissions that typically plague them.

However, HCCI engines require a high-pressure injection system that must be monitored in real time. They can only be reliably operated under a narrow band of temperature and pressure, and they’ve always posed technical challenges.

Mazda has finally solved those hurdles, though. It plans to offer a new type of engine, called Skyactiv-X, in the near future.

The two-litre SKYACTIV-X engine is expected to produce ten to 30 percent more torque than the current SKYACTIV-G, with better fuel efficiency and power. All this while preserving the fun-to-drive nature of the company’s cars. And it all happens without the need for heavy batteries or complex transmissions. That’s the Mazda way, and it looks to be a winning strategy for the long run.