Mazda’s Innovative Skyactiv-X review

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Mazda’s new petrol engine throws a lifeline to the doomed internal combustion engine. On the roads around Sofia Bulgaria we’ve been testing the Japanese firm’s new Skyactiv-X engine in the new Mazda3. The 2 litre engine is technically innovative, powerful yet capable of diesel-like fuel consumption with very low emissions. CO2 emissions fall around the 100g mark (NEDC) but more noteworthy is that NOX production is ultra low. The low nitrogen oxide level is thanks to the clever way it burns fuel. Nitrogen oxide is a truly nasty by-product of internal combustion.

When engines burn fossil fuel NOX is generated and it is extraordinarily tricky to reduce at the tailpipe. Older diesels are being demonised for dirty emissions even if their CO2 is relatively low but petrol engines are quite polluting too. Generally petrol engines produce higher CO2 while also generating NOX albeit not as much as diesel combustion. This is why car makers have had to resort to adding Adblue tanks to the current Euro6 crop of diesel engines to make them emissions compliant. European emission regulations are only going to tighten and innovation is needed. Thankfully Mazda is proving to be the bright spark of the industry with the world’s first commercially available spark controlled compression ignition engine or SPCCI for short.
Mazda has developed in the Skyactiv-X engine a more efficient way of controlling how petrol combusts. Ample power is generated in this case 180hp as opposed to the standard 2 litre Mazda Skyactive-G’s 120hp. Mazda says its new engine can be a sporty driver or an everyday thrifty commuter. The Skyactiv-X uses a very high fuel air mixture of 16.3:1 usually it’s 14.7:1. By carefully controlling when the spark ignites the mixture the X produces power with less heat generation – a key component in NOX generation. By running with greater thermal efficiency less harmful emissions are created. Traditionally a petrol engine uses spark plugs to ignite its highly flammable fuel and create power while a diesel engine ignites its less flammable fuel as a result of the high pressure the fuel is injected in to the engine. Petrol engines are often described as spark ignition engines while diesels are referred to as a compression engines. Mazda with Skyactive-X has married both methods.
Earlier in the summer we tested a pre production Mazda3 Skyactiv-X engine on the roads around Frankfurt. Its power and torque impressed but it did make a slightly odd sound. We have just tested the slightly tweaked production version in Bulgaria that now sounds just like a regular petrol engine. The X is lively and pulls very well. On a mix of motorway and rural roads the handsome Mazda3’s Skyactiv-X proved to be a fun machine to hustle along. Mazda says the new engine is not designed for performance driving alone but as a fuel efficient commuter too. The X delivers the best of both driving worlds as required. To enjoy enthusiastic dynamic performance you need to get the revs up.
Power output figures are good with the 2 litre four cylinder engine making 60hp more than the G engine with the same displacement. The torque figure is very good for a petrol unit at 224nm (213nm G). This pulling power is available from quite low down the engine rev range (3,000rpm). The new engine is quite smooth and responsive. It has a free revving feel that you don’t associate with an economical car. The X can be driven through a conventional automatic or six-speed manual gearbox. The manual gearbox reveals more of the engine’s nature. Hold on to the gears up through the rev range and enthusiastic performance is on tap. The trip computer does however remind the driver that this is not the most economical way to drive endorsing Mazda’s everyday use claim. A period of considered driving allowed our fuel consumption figures dip down in to the mid 4l/100km – close to Mazda’s claim.
The Skyactiv-X also features fuel and emissions saving cylinder on demand technology. Under a light load the car will tip along fueling just two of its four cylinders, when power is needed all four cylinders fire up. With Skyactiv-X the throttle is always open and never closed – allowing better intake of air to the cylinders. Both G and X engines used in the Mazda3 use the latest generation 24 volt ‘M hybrid’ mild hybrid system with integrated belt driven starter/generator. When you lift off the throttle energy is recouped to its small 600kJ lithium-ion battery allow the car run very smoothly. Mazda’s NEDC-2 emissions figures for the Euro6d compliant Skyactiv-X engine state a sub 100g CO2 figure of 96g/km with an average fuel consumption figure of 4.3l/100km (65.6mpg) for a Mazda3 saloon on 16 inch wheels. Mazda Ireland Won’t bring the poverty spec model in and so it lowest quoted CO2 figure is 102g/km NEDC-2 (€190 motor tax). Using 2020’s WLTP (2021 in Ireland) emission testing the CO2 figure rises to 127g/km. To put that in context the equivalent diesel saloon produces130g/km of CO2.
Mazda has a history of using engines that are the right size for its cars. If a conventional 2 litre is needed then it won’t build a 1.5 and add a turbocharger to bring the power back up just for the sake of reducing engine displacement. The Skyactiv-X 2 litre engine’s technology is scalable, so larger or smaller engine capacities may get it in the future. Production of the engine will run in parallel with Mazda’s G and others and will be built per customer demand. It has more costly components than the Skyactiv-G’s 2 litre and Mazda says it will be price accordingly. There are no plans to sell the new X engine to other manufacturers.

Mazda is famed for bringing the remarkable German Wankel piston-less rotary engine to the masses and its new SPCCI engine breakthrough could be as significant. The new Skyactiv-X proves there is still life in internal combustion despite many governments, including our own, planning to ban them in the not too distant future. The Mazda3 range starts from €26,295 for the Skyactive-G hatch. The entry grade Skyactiv-X Mazda3 is priced from €30,495.

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About Author

Michael Sheridan

Michael is Motorhub's Editor. Well known from TV and radio, Michael has been writing, presenting and judging cars since the mid 90's. He is a renowned Producer/Director and documentary film maker. Dozens of credits include: The Whole Way Round (Gay Byrne), The Shamrock Run (Alan Shortt), The Viking Run (Clodagh McKenna) and The Irish 66ers (David Mitchell) and The Climb for Kids (Colin Farrell). Print credits include: the RTE Guide (motoring editor 1999-2003), many national daily papers and Sundays including The Irish Times (freelance) plus other magazines. National radio credits include multiple at RTE Gerry Ryan show, the Mooney Show, The Dave Fanning Show, Drivetime etc. TV credits as a motoring expert include RTE's flagship current affairs show Primetime and TV3's Ireland AM. Michael also presented RTE's car show Drive! in the late 90s and directed some items in MPH2 on TG4. Michael contributes weekly on motoring issues to The Last Word show with Matt Cooper on Today FM. Michael has represented Ireland's motoring journalists in Motorsport at the International Mazda MX-5 endurance race series in Italy and the Arctic Ice Race. He has been a Car of the Year Judge for over 18 years and is a former Chairperson of the Association of Professional Motoring Press (APMP).

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