The SPCCI engine combines the benefits of spark ignition and compression ignition, but how does it actually work?

The best looking hatchback is going to have the most modern four stroke engine that we've ever seen. Mazda's new Spark Controlled Compression Ignition (SPCCI) engine will be found in the new Mazda 3 hatchback, and it is the new engine design that promises to deliver more power while delivering better efficiency. How did they do it? By combining the benefits of both Spark Ignition (Otto cycle) and Compression Ignition (Diesel cycle) engines into one. Take a look at Mazda's video on how the SPCCI engine works below:

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If you're still confused as to how the SPCCI engine differs from traditional SI or CI engines, here are the main takeaways:

SPCCI Uses Spark Plugs Near The Fuel Injector To Achieve Compression Ignition

Unlike an SI engine which relies entirely on the spark plug to initiate combustion, the SPCCI engine uses the spark plug AND a super high pressure fuel injector to help increase the pressure within the cylinder, high enough to initiate combustion through compression.

How does that work exactly? Without getting into the engineering and chemistry background on how air/fuel mixtures and octane ratings work, just understand that the incoming air/fuel mixture in an SPCCI engine isn't enough to achieve a complete compression ignition on its own. To give it that little bit of boost, for a lack of a better term, that lean air/fuel mixture is supplemented by a high pressure fuel blast from the injector.

In other words, there's a little "fire ball" created from the additional fuel sprayed into the cylinder and the spark plug during the ignition stroke. It's small enough to set the whole air/fuel mixture off, to the point where it behaves like a Diesel engine. Essentially, the spark plug doesn't ignite the entire mixture, rather it increases the pressure to a high enough point where combustion occurs naturally.

SPCCI Engine Is All About Spark Timing, And There Are More Components Involved

To make SPCCI work the spark plugs and fuel injectors will have to cleverly decide when to go off. Therefore, the engine requires more components and sensors to analyze what's going on at all times at a real-time level of precision.

This is done via in-cylinder pressure sensors and temperature sensors that continuously monitor and affect the timing of the spark. Since SPCCI relies heavily on spark timing, the delaying or advancing of the spark plays a critical role on the engine functioning happily and cleanly. This critical point varies depending on how warm the engine is and how fast the engine is spinning.

There will also be a high pressure fuel system needed to deliver the mini "fire ball" that will set off the entire air/fuel mixture.

SPCCI Engine Will Have A Supercharger That Has A Clutch

The critical aspect of having a diesel like ignition is to ensure that combustion occurs everywhere within the cylinder, and not just by the spark plug. In other words, instead of having a flame front develop at the origin (the spark plug), the entire air/fuel mixture combusts. Therefore, it is important to have a homogeneous air/fuel mixture.

The SPCCI produces this homogeneous air/fuel mixture with the help of a supercharger that has a clutch. It has a clutch because the air supply has to also be controllable in order to achieve the proper lean air/fuel ratio depending on the engine speed. The high pressure air will ensure that there's a cyclone of air/fuel mixture within the cylinder as it's about to ignite. The additional high pressure fuel blast and the "fire ball" will ensure that combustion occurs all throughout the cylinder.

SPCCI Engine Will Make More Power And Have Better Fuel Efficiency

Mazda has proven that the new Skyactiv-X engine with SPCCI technology will produce more power and torque compared to prior versions of the Skyactiv engines. It's expected that the 2.0 liter engine will now produce 197 horsepower and 207 lb-ft of torque compared to the 155 horsepower and 150 lb-ft of torque.

We can also expect NOx emissions to go down because the air/fuel ratio runs a bit higher than traditional engines. Additionally, since the spark and the air/fuel ratio can be precisely controlled, we should expect a much cleaner burning engine overall.

What do you think about Mazda's new SPCCI engine? Is it going to be the amazing engine that they claim it to be? How reliable will all of these new components be? And how well will it age as the years, and perhaps decades, come?

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# mazda # spcci # engine # shiftinglanes # videos # skyactiv