This review has been translated from the Bahasa Malaysia version, written by our colleague Izwaashura Sadali and published on

Since Mazda announced details of its next-generation SkyActiv petrol engine, SkyActiv-X, many enthusiasts – especially Mazda loyalists – have been eager to find out just how effective Hiroshima’s radical new technologies would be.

Expected to make its production debut next year, the company’s new engine was initially supposed to use a technology called Homogeneous Charge Compression Ignition (HCCI), which does away with the spark plug completely – only using compression pressure itself to ignite the fuel/air mixture, like a diesel. However, the finalised version will instead retain the use of a spark plug to control ignition timing at specific periods.

Called Spark Controlled Compression Ignition (SPCCI), the technology is still in prototype stages, but Mazda has confidence in its SkyActiv-X engine. At a time when other carmakers are moving to plug-in hybrids and electric vehicles, it insists on soldiering on with internal combustion engines – not just because it wants to go against the grain. Instead, the company believes the ICE can still be relevant on the market.

Mazda is so excited of its technology that it recently invited motoring journalists from the Asia Pacific region – including from Malaysia, Thailand, Philippines, Indonesia and Vietnam – to Fukuoka, Japan for its Mazda ASEAN Tech Forum 2018, with a test drive of a next-generation Mazda 3 prototype fitted with the SkyActiv-X engine billed as the highlight of the event. Read on to find out how it drives.

What is SkyActiv-X, and how does it work?

It’s no secret that Mazda has long aimed to build an engine with compression ignition, as part of the company’s long-term goal for its SkyActiv umbrella of technologies. Compression ignition allows for a much leaner air-fuel ratio (more than 30:1 as opposed to the stoichiometric ratio of 14.7:1 on a typical petrol engine, Mazda claims), which vastly improves efficiency.

The only problem is that there is no way to control the timing of the ignition, so it can really only be used under very light loads.To solve this, Mazda reduced the compression ratio of the engine just enough so that the fuel doesn’t spontaneously ignite.

To kickstart the combustion process, a spark plug ignites a small amount of rich mixture around it; the resulting flame kernel raises the pressure within the combustion chamber, burning the rest of the mixture that is leaner. Mazda calls this Spark Controlled Compression Ignition (SPCCI).

Also fitted is a supercharger, but it’s not there for extra power. Rather, the blower is there only to increase the amount of air in the cylinders while running the same amount of fuel, in order to run an even leaner air-fuel mixture.

The technology is so effective, the company says, that the 2.0 litre SkyActiv-X engine’s fuel efficiency equals or even exceeds that of the 1.5 litre SkyActiv-D diesel engine. The mill is also claimed to offer improved response and between 10 to 30% more torque compared to the 2.0 litre SkyActiv-G engine, which Mazda says is equivalent to the larger 2.5 litre motor.

The prototype SkyActiv-X engine was installed within the bodyshell of a current left-hand drive Mazda 3. According to Mazda, the C-segment hatchback was used to give an idea of the engine’s performance from a 2.0 litre capacity, which is identical to the donor car’s original SkyActiv-G mill.

“However, we can produce a variety of engine capacities for the SkyActiv-X engine such as 2.5 litres in the future. But for the launch, we have chosen a 2.0 litre engine capacity,” said deputy general manager of Mazda’s powertrain development division, Tsuyoshi Goto.

After we were given a presentation of Mazda’s roadmap for the future and details on the SkyActiv-X engine, we were let loose in a SkyActiv-G-powered Mazda 3 before getting behind the wheel of a prototype with the SkyActiv-X, both in manual and automatic transmission flavours. The Mazda Proving Ground in Mine, Yamaguchi was the prime location for getting a feel of Mazda’s latest powertrain technologies.

Before that, we were reminded to respect the track’s speed limits as well as to follow the marshalling vehicle in front. We were also informed that the SkyActiv-X prototype was not fitted with traction control, stability control or airbags, so due caution was requested.

Stepping into the prototype, we noticed a tablet affixed to the dashboard, which displayed the mode the engine was currently in using a traffic light system. Red meant that the engine was in regular spark ignition mode, while yellow indicated that SPCCI was in action. The green light, on the other hand, showed that the engine was in lean fuel mode, using its fuel in the most efficient way possible.

However, it was difficult to establish the current engine mode as we had to follow the speed of the car in front, and our focus was also placed on the direction of an unfamiliar track. We could only really keep track of the modes when we were driving at a slow speed, around 50 km/h.

In this writer’s experience, the torque delivery was quicker with the SkyActiv-X engine when throttle was applied, compared to the SkyActiv-G. Not only that, the newer mill also felt freer, more muscular, with plenty of zeal even at higher speeds.

With the manual transmission, the loud roar of the SkyActiv-X unit, even at speeds of between 30 to 40 km/h, was almost urging this writer to shift to a higher gear. However, we were told that a lower gear ratio has little effect on fuel economy, and as such, we were encouraged to use fourth or fifth gear instead of sixth and stay in compression ignition mode while improving engine response – handy in the city, for example. It’s like having both Sport and Eco modes at the same time, Mazda claims.

Even when using compression ignition, the engine remains smooth. According to Mazda, you’d have to pay close attention to tell which ignition mode is in operation, depending on the driving conditions. On smooth roads at low speeds, there’s a slight diesel-like tune, but once you get up to speed or driving over coarser road surfaces, it becomes unnoticeable.

During our testing, the yellow light on the tablet was lit around 60% of the time, indicating that the engine was mainly running in compression ignition. It was quite difficult to light up the green light, especially when using the manual transmission. It may actually be possible, just that the driving conditions at the time prevented this writer from achieving it more regularly.

The SkyActiv-X engine prototype uses a 16:1 compression ratio, compared to 14:1 on the SkyActiv-G. SkyActiv-X also uses high-pressure direct injection as well as a pressure sensor that allows the engine to accurately adjust the injection and spark timing to control the SPCCI system.

As the engine is still in prototype stages, there are still a number of issues present, and these were shared with Mazda employees when we were asked. Many of us noticed a knocking sound, especially when switching between compression ignition and spark ignition. Mazda said that it was aware of this problem and promised to resolve it before the production version is introduced next year.

Mazda said that the SkyActiv-X can use fuel grades as low as 87 octane. Using a more premium grade, however, would allow the engine to get up to peak torque faster – even though there’s no change in the torque figure itself – transforming the engine’s character.

Due to our short time with the prototype, it was hard to know how much fuel the technology saved, although Mazda claimed that the SkyActiv-X uses up to 30% less fuel compared to SkyActiv-G. Of course, SPCCI plays an important role in reducing fuel consumption, as well as improving performance by using fuel in a more efficient manner.

For the SkyActiv-X, Mazda estimates outputs of 188 hp and 230 Nm of torque from a 2.0 litre unit. Contrast that to the similarly-sized SkyActiv-G mill in the current Mazda 3, which makes 162 hp and 210 Nm, as well as the 185 hp/250 Nm 2.5 litre SkyActiv-G in the Mazda 6.

There’s still a year or so left before Mazda introduces the new engine in a production vehicle. The company’s engineers will undoubtedly be working hard to resolve any issues currently present in these prototypes. As such, there are high expectations that will be placed on Mazda’s shoulders to see it succeed.

Based on the short feeler we’ve had, Mazda’s against-the-grain effort does indeed look promising. Whether car buyers would accept this new kind of a large capacity, (mostly) naturally-aspirated petrol engine while virtually the rest of the industry is moving towards small capacity turbo motors and/or electrification, we’ll have to wait and see.

How about you, though – would you choose Mazda’s left-field tech over the norm? Let us know in the comments section below.