Feedback

Carbuyer Tech 101: Mazda's Skyactiv X technology explained

Derryn Wong
08/06/2018


Mazda’s Skyactiv X is revolutionary because of the way it bangs – or why pressure makes things difficult inside a gasoline engine
Mine Proving Ground, Yamaguchi Prefecture, JAPAN-
Mazda’s new engine tech, the company claims, makes Skyactiv X the most fuel efficient gasoline engine in the world. But how did Mazda succeed when companies like Honda, Toyota, Mercedes-Benz and more failed to develop the same kind of tech?
READ MORE: We’ve test driven Skyactiv X in real life – and it really works.
Before delving further, we need a short recap on how engines work.
Almost all combustion engines use a four stage cycle to produce power, known as the Otto cycle, after the man who came up with it.
You can refer to our other explainer on how alternative cycle engines work, as it includes a preface on normal Otto cycle engines.
Suck, squeeze, bang, blow: Fuel/air mix is drawn into the cylinder as the piston moves down (suck), it is squashed as the piston moves back up (squeeze), it is ignited by a spark plug (spark ignition, or SI) and is pushed down, creating power (bang), and it moves backup to push out the byproducts of combustion (blow).
Both diesel and gasoline engines use the Otto cycle, but it’s how the banging happens that makes all the difference.

Diesel engines have no spark plugs, the explosion happens through compression or auto ignition. As gas is compressed, its potential for ignition increases until it reaches blowing point. Compression ignition (CI) is simultaneous and homogeneous, that is, the entire charge explodes at once.
In contrast, a gasoline engine’s charge is ignited by a spark, from a spark plug, so the explosion originates from one source and expands outward, or propagates. Watching something explode, it seems instantaneous, but if you watch stuff blowing up in slow-motion on YouTube, you’ll know it’s really not the case.

Mazda’s Skyactiv X engine uses compression ignition in combination with a spark, called Spark Controlled Compression Ignition, or SPCCI. It’s still a sub-type of Homogeneous Charge Combustion Ignition.
Compression ignition is superior to spark ignition because it burns the fuel cleanly and completely, so there is less pollution, and more work is extracted from each charge. The fact that diesels pollute more is due to nature of the fuel, which creates more soot (particulate matter) and oxides of nitrogen.
So why don’t we simply make a compression ignition gasoline engine, combining the benefits of diesel with the less-pollutive nature of gasoline?
Gasoline is a more volatile fuel than diesel – you can set gas on fire with an open flame, but not diesel. Controlling it when compressed is even more difficult. In fact, engineers have spent huge amounts of time and money getting gasoline to do exactly the opposite.

You may have heard the term ‘compression ratio’, it’s simply used to describe an engine that squeezes its fuel-air charge a lot. A high compression ratio means more power, but it also brings with it the chance of premature detonation, before the spark ignites. That’s bad, as it damages the engine, and causes power loss.
That’s where octane comes in. There’s a misconception that a higher octane rating (RON number) means a superior fuel, but it simply denotes how resistant it is to knocking. Most engines use 95RON, but when in doubt read your owner’s manual.

 
So if compression ignition is hard to control when you don’t want it to happen, it’s also hard to control when you do want it to happen, especially at the level of precision required for modern engines.
But Mazda has plenty of experience with this – its current Skyactiv G engines have among the highest compression ratios for modern mass market production engines, and is also a reason why they’re very efficient.
An average Japanese 1.6-litre has a compression ratio of around 10.0:1, while the 2.0 Skyactiv G has 14.0:1, with the Skyactiv X having a ratio of 16.0:1.
HCCI (homogenous charge compression ignition) has of course been experimented with by bigger car companies, and Mazda’s justifiably proud of Skyactiv X being a production ready tech.
“Larger companies like Honda, Toyota, Mercedes-Benz and Nissan have made HCCI prototype technology, but Mazda has gone ahead of them and made it real,” adds Mr Tokushige.
Mazda’s step forward was to make an engine that combined both ignition types, rather than just focusing on making a solely CI gasoline engine. It sounds almost simple when you say it like that, but Mazda did spend more than a decade and a lot of R&D money to get Skyactiv X a reality.

Tags:

efficiency future mazda skyactiv-x technology

About the Author

Derryn Wong

CarBuyer's chief editor brings 15 years of experience in automotive journalism. Previously, he was the editor for Top Gear Singapore, and a presenter for CNA's Cruise Control motoring segment. He's contributed to The Business Times, Today, and many other publications, and also covered technology as editor of Stuff magazine. An avid motorcyclist and photographer, he is the Chief Slave of two cats. Follow him on Instagram @werryndong

One thought on “Carbuyer Tech 101: Mazda’s Skyactiv X technology explained”

Leave a Reply

Your email address will not be published.

CarBuyer – Revolutionizing The Online Car Marketplace In Singapore

Buy Used And New Cars Online
Start your car buying journey with CarBuyer as we connect you seamlessly to the industry’s best CaseTrust-SVTA accredited car dealerships. As a one stop car online portal you can now buy your new ride, be it a pre-owned car or a brand new car from trusted dealers all over Singapore, all in one place. Our ever expanding listing of quality and covet-worthy cars, new and second hand, from both owners and trusted car dealers, will leave you spoilt for choice. Refine your search by vehicle type, registration year, price, mileage, engine type, transmission, annual depreciation value and more to find the car that best suits your needs, taste and lifestyle. You can even search for your car by dealer or directly by owner.

Sell Your Car In An Instant With Confidence
We all know how selling a car in Singapore can be a daunting task especially for a first time car seller; from trying to get a valuation for your car, finding a trusted dealer, to getting the best quote on your vehicle. CarBuyer understands the hassle and even the costs involved and have as such partnered with Huawei to develop a FIRST in Southeast Asia AI car valuation tool that is able to provide a car’s resale value at the snap of a finger. Backed with a consortium of trusted CaseTrust-SVTA accredited car dealers you can be assured that you are getting the best price for your vehicle and do not have to worry about any hidden costs.

The Ultimate Car Shopping Experience Online
CarBuyer platform is the first of its kind to be backed by Huawei’s Artificial Intelligence and cloud computing, enabling it to be able to offer users transparency and enhanced security, all with the one aim of enhancing customer experience. So come on over to buy and sell used cars online at the best prices at CarBuyer Singapore. Connect easily with dealers in real-time via our online video call feature, or schedule a test drive when you’re ready. Have some questions? Get them answered instantly with our chatbot moderated by our responsive team. Stay in the loop with our car-related tips, reviews and news. Learn the ins-and-outs of your car, as well as global and Singapore’s car updates at your own pace.