2018 Mazda 3 Skyactiv-X prototype review

This Mazda 3 prototype's clever Skyactiv-X engine mixes petrol and diesel tech to improve emissions and economy. It's only an early taster, but things look promising...

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Alan Taylor-Jones
21 February 2018

Priced from TBC Release date 2019

Although this appears to be an ordinary Mazda 3 with a shonky matt black wrap, what you’re actually looking at is potentially the next big thing in internal combustion technology. Underneath the familiar face is a brand new platform and a clever new engine that applies diesel technology to a petrol powerplant.

Now, we could spend the entire review explaining how this set-up works, but instead we’ll give you the abridged version. In Skyactiv-X (here applied to a 2.0-litre four-cylinder motor, although it will work on any size of engine), the aim was to use less fuel for any given quantity of air and to get this mixture to combust as it’s squeezed by the pistons, like a diesel, rather than be ignited by spark plugs.

Although Mazda still has to use spark plugs to start the combustion process, and at high loads, squishing this part-ignited mixture leads to a cleaner, more efficient and cooler burn of the petrol. In English, that means a big reduction in carbon and NOX emissions, plus greatly improved fuel economy. Mazda is suggesting improvements of at least 20%.

To ensure there's enough air in the cylinders regardless of altitude, temperature or throttle openings, there's a small supercharger bolted to the engine. Don't think of this as a device to squeeze more power out of the engine, though. The supercharger's pulley even has a clutch on it, so it isn't driven when it isn't needed, aiding efficiency even further.

2018 Mazda 3 Skyactiv-X prototype review

2018 Mazda 3 Skyactiv-X prototype on the road

The technology behind Skyactiv-X might sound daunting, but we doubt you’d be aware of the fancy-pants gubbins under the bonnet if you didn’t know about it. The engine idles with the smoothness of a typical petrol unit and has a pleasing amount of pull from low in the rev range.

Performance is currently on a par with the 3's regular 163bhp 2.0-litre petrol engine, with a touch more flexibility from just above 1000rpm. Impressively, it does this while making less noise and emitting fewer vibrations than its conventional forebear when under load. By the time the new engine reaches production, Mazda’s engineers are aiming for a healthy 190bhp.

Although Mazda was very careful to make sure we couldn’t see any trip computer fuel economy readouts, it had strapped an iPad to the dash that showed us exactly what mode the engine was running in. When driven gently and especially during a steady cruise, the Skyactiv-X ran predominantly in its high-efficiency mode, which reduces fuel consumption.

That bodes well for real-world economy, because the technology can do its thing over a wide range of engine speeds. This gives Skyactiv-X a strong advantage (on paper, at least) over the downsized turbocharged petrol engines that are increasingly popular in family cars. They may perform well in official tests, but when taken out of the narrow band in which they work most efficiently, they are often no more frugal than larger non-turbo engines – something we've found a lot in our True MPG testing.

The combination of the 3's new platform, slightly more compliant tyre sidewalls and a new seat design have an effect on the driving experience, too. Over cobbled streets, the new car is less jarring, a feeling that continues on less extreme surfaces. Impressively, that’s without any detriment to the 3’s handling.

2018 Mazda 3 Skyactiv-X prototype review

2018 Mazda 3 Skyactiv-X prototype interior

At this very early stage, there isn't much we can say about this, because very little of our test car's innards were representative. Indeed, the underpinnings may have been all-new, but the interior was a mixture of the current car’s, electronic control boxes and lashings of gaffer tape.

Let’s just say we’ll have to wait until nearer the car’s release to comment on what the new version is like inside.

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