Next Mazda SkyActive Engine Will Have No Sparkplugs


The evolution of the internal combustion engine continues, even as electric cars are waiting in the wings for their grand entrance. Mazda has just announced that its next generation of SkyActive engines will have no sparkplugs. Instead, they will use something called homogeneous charge compression ignition, or HCCI. It is a blending of gasoline and diesel technology.

Mazda SkyActive engine

Cranking up the compression ratio to around 18 to 1, the mixture of gasoline and air will explode on its own without the need of a spark. Mazda claims the result is 30% better fuel economy with lower emissions. According to Japanese trade journal Nikkei, the new HCCI engine will debut on the next generation Mazda3 sometime in 2018 before making its way to other vehicles in the Mazda lineup.

Other manufacturers such as GM, Mercedes and Hyundai have dabbled with HCCI research but abandoned it because the costs of development were too high. Managing heat, fuel flow, and emissions in a modern engine is a very complex task with many trade offs. Mazda has not released any details about driveability or longevity but we can assume it has conquered the challenges involved if it is putting the new engine into its highest volume production car.

While the future of driving is electric, it will be several decades before internal combustion engines disappear from the roads. Mazda is keeping one foot firmly planted in the past until such time as electric cars  become the default choice for mainstream shoppers.

That doesn’t mean Mazda is not also thinking about the future. It is currently collaborating with Toyota on the development of battery electric and plug-in hybrid vehicles. The partnership puts Mazda in charge of creating the next generation of high efficiency low emissions gasoline engines, which leaves Toyota free to focus on electric power trains. 

Those Toyota developed powertrains will be made available to Mazda as needed. Nikkei says to expect a Mazda EV as early as 2019. Presumably, HCCI engines developed by Mazda will also find their way into various Toyota products as well. The internal combustion engine is dead. Long live the internal combustion engine!

Source: AutoBlog




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  • Ed

    It’s a Diesel…just using cleaner gasoline as the fuel. I am pretty sure it will face the same NOX issues as have plagued the current generation of Diesels, but should have greatly reduced particulates due to the refinined fuel. It will be interesting to see what kind of aftertreatment system Mazda uses.

    I think the Toyota/Mazda tie-up has the potential to do great thing when they get around to full electrics.

    • James Rowland

      HCCI has lower combustion temperatures than diesel and – as the name suggests – greater homogeneity than a conventional petrol engine, so NOx emissions are lower. I don’t doubt it will still need a catalyst though.

      TJI purportedly has an even greater advantage than HCCI, and with fewer control issues, though the system is more elaborate.

      I’d still rather have an electric motor and battery though. 🙂

      • Ed

        Typically, however, the higher the efficiency, the higher the peak combustion temperature. Yes, it can be tailored somewhat by the injection system, still, it is a huge challenge at that compression ratio.

        All of this work to extract more efficiency and cleaner exhaust in car engines looks and feels a lot like the tipping point in aircraft engines.

        • Steve Hanley

          Great info. Thanks.

        • James Rowland

          Yes, electrification’s obviously going to render all this effort improving ICEs irrelevant in a decade or so. I still find it fascinating though.

          The expectation for HCCI NOX emissions is that it will be lower than both diesel and conventional petrol, due to lower and, in the latter case, more uniform flame temperature. CO and hydrocarbon emissions will be higher though, due to the shorter and colder combustion process.

          NOx production is strongly dependent on temperature; reaction rate is near-zero below about 1600°C. The diffuse and uniform energy release in HCCI results in a lower peak temperature.

          Simultaneous combustion and higher compression ratio than spark ignition petrol also leads to shorter residence time, as the expansion ratio changes more quickly after ignition.

          Additionally, higher thermodynamic efficiency is effectively an emissions reduction in itself, as less fuel air mix is required for the same output.

          • Ed

            Great summary, James. Thanks.

          • Rguy

            Better fuel would help too. Mazda reduces its compression ratio on the skyactiv engines for the US because the US has lower octane fuels. ‘Premium Only’ engines have kind of faded away but they should be brought back and the fuel required to meet that standard. This would shave up to 10% off our oil consumption right there. Electric cars are interesting but something that has only 1% market share is more than a little ways from becoming a dominant player. Immediate 10% improvement with the stroke of a legal pen is possible.

  • kevin mccune

    This should help the efficiency of these particular ICEs ,it will be interesting how close to diesel torque and mileage you can get with gasoline , I am sort of afraid Diesel fuel is set to take a big out of proportion price hike again .
    How close is the “workhorse” truck to production now ? Hydrocarbon fuel has got me pretty jittery right now .

  • Rick Danger

    The argument has been that Mazda is too small a company to afford to develop BEVs and PHEVs, but they have the money to p*ss away on this????
    Ahh, Mazda… I knew thee well. I will raise a glass on the day you shut your doors.

    • Steve Hanley

      I thought I covered this in the story. Mazda is collaborating with Toyota. It is in charge of developing more fuel efficient engines that both will use. In return, Mazda will have access to hybrid, plug-in hybrid and battery electric powertrain technology from Toyota, which will save it the enormous costs of developing that technology independently.

      • Rick Danger

        I have a hard time believing that it’s harder to develop a decent PHEV than it is to try and design this Rube Goldberg contraption. This is like investing tons of money into better buggy whips in 1907. Now, if Mazda had teamed up with Tesla, I’d have a huge smile on my face, but Toyota is the Trump of EV automakers.

        • Rguy

          I suppose that’s why you aren’t an automotive engineer. You have a hard time imagining science. The idea that all development on better engines should stop is a bit naive. Two companies each with a certain set of strengths collaborating for the common good. That’s an outrage!

  • Samus Arin

    So like, how hard can it rev?