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Mazda Executive explains ground-breaking HCCI petrol engine

As reported last week, Mazda is set to roll out the world’s first compression ignition petrol engine in a production car. And today details of its global debut have been confirmed.

The ground-breaking diesel-style compression ignition petrol engine, more commonly known as the Homogeneous Charge Compression Ignition or HCCI engine, will launch in 2019, with first application expected to be the next-generation Mazda3, which is due for debut in the same year.

The revolutionary technology uses ultra high compression ratio – as much as 18.0:1 – in a petrol engine to initiate combustion without the use of spark plugs, just like in a diesel engine. Mazda’s production HCCI engine will operate on conventional spark ignition on start up or low temperature conditions, then automatically and seamlessly switch to compression ignition. It’s claimed that The lean-burn process is claimed to produce more efficient combustion, which reduces fuel consumption and emissions. It’s said to improve fuel efficiency by up to 30 per cent, sipping as little as 3.5L/100km and releasing no more than 95g/km in emission for a 2.0-litre engine, with no compromise in engine performance.

Called Controlled Compression Ignition, the technology will be deployed in the company’s next generation engines called SKYACTIV-X, which will enter production in 2019 and replace the current SKYACTIV-G engines.

Kiyoshi Fujiwara, Director and Senior Managing Executive Officer at Mazda today explains in detail the HCCI engine and its working principle.

Full press release below:

Good afternoon ladies and gentlemen.

I am Fujiwara, senior executive with oversight on R&D, MDI, and cost innovation.

As President Kogai earlier explained ‘Sustainable Zoom-Zoom 2030,’ our long-term vision for technology development, we need to help solve issues facing the earth and society, while at the same time enrich people’s mind and heart through fundamental appeal of the automobile. That is what people want seamlessly in their life.

Among those issues, what I would like to focus on today is concerning the reduction of greenhouse gas as a challenge for ‘the earth’ in order to address global warming.

To fulfill our mission in the automotive industry, we Mazda want to account the vehicles’ lifecycle and look at CO2 emitted during manufacturing, usage, and disposal of vehicles in order to put the first priority to greenhouse gas reduction.

During the vehicle usage, CO2 emission is especially large, but again we look at Well-to-Wheel CO2 emissions so that we can make a maximum contribution to CO2 reduction.

Given the energy source and how electricity is generated in each region of the world, we believe multiple solutions for power source are needed rather than just one if we want to reduce CO2 in an optimum way for each region.

We showed a graph in 2008 that plotted which power source would be utilized in the world. Now we feel the projection turned out to be almost correct. Although government’s policy in each country has some impact,   (click) we believe the forecast for 2035 as shown here.

For the future, internal combustion engines are still projected to stay as majority powertrains around the world, therefore we think it is an imperative and fundamental job for us to pursue ideal internal combustion engines thoroughly.

Of course electrification including systems such as mild hybrid is necessary, but a pursuit for ideal internal combustion engine should come first, then we combine electrification technologies with such engines. That is our unwavering, basic strategy.    

Around the world, SKYACTIVE-G and D are highly evaluated, and they will be continuously improved and upgraded to maintain their high competitiveness. The next generation technologies including the next generation gasoline engine, ‘SKYACTIV-X’ which was just introduced earlier, will be mounted in actual products in the fiscal year ending March 2019.

Together with G and D, it will add further uniqueness to Mazda’s engine lineup and will help us to respond to diversifying customer needs.

Based upon the evolution and improvement of internal combustion engines as the foundation, we will be taking further steps to adopt electrification technologies, evolving from i-Stop, i-eloop, to Mild Hybrid, EV, and P-HEV.  

Today I will focus on the first step and the highlight of our plan, the new generation gasoline engine ‘SKYACTIV-X.’ I will talk mainly about the technology concept as well as customer values. As for technological details, we will provide them together with the drive experience at a test drive event we are preparing soon.

To give you a recap, I would like to use the roadmap we have showen in 2009.

Mazda has always been striving to make ideal engines, and by identifying controlling factors, we steadfastly reached closer to deliver the ideal combustion.

What I am presenting now is a new combustion technology, which is the 2nd step toward the goal we have been aiming for since the first introduction of SKYACTIV; the goal to deliver an ideal internal combustion engine powered by gasoline.  

Let me give you a little more details.

In one word, our new engine is capable of combusting gasoline fuel by compression ignition just like a diesel engine does.

In other words, ‘SKYACTIV-X’ combines the characteristics of both gasoline and diesel engines. It is a new Mazda unique internal combustion engine that provides excellent environmental performance, power output and dynamic performance with no compromise on any of them, and fully supports Jinba-Ittai driving Mazda aspires for. It is an engine that stands by the earth and people.

We have been aiming to attain excellent real-world fuel economy, emission, and responsive driving that works well with human senses. We want to deliver all of them at high dimensions. The ideal combustion that helps us to meet this goal is called CCI (controlled compression ignition) .

The term may not sound familiar, I am afraid. CCI means completely ‘controlled ‘ compression ignition.’

There are two key words here.

The first is compression ignition, and the second is a capability to completely control the compression ignition, which is Mazda’s original technology.

Let me explain what compression ignition is.

CI (compression ignition) is a combustion method adopted for diesel engines. Trying to do the same combustion in gasoline engine is called HCCI (homogeneous charge compression ignition)

It is a combustion method where gasoline and air are completely mixed and ignited by compression temperature and pressure.  Very lean air-fuel mixture that is too lean to combust by spark ignition, can combust by this method cleanly and rapidly. It offers benefits such as better thermal efficiency, better fuel economy, with less NOx emissons.

What we are so obsessed with the compression ignition? There are mainly two reasons.

The first reason is to make a major breakthrough in lean combustion to burn thin air-fuel mixture.

If we want to improve fuel economy, we should reduce the amount of fuel to burn, Lean combustion has been applied to spark ignition combustion, but it has reached the leanest possible level already.

On the other hand, if compression ignition is realized, super lean combustion can be achieved with air-fuel mixture that is two times thinner,  far exceeding the stoichiometric air-fuel ratio. Spark ignition would not combust such a thin air-fuel mixture. Simply put, compression ignition can achieve combustion with a half amount of fuel compared to conventional combustion.

Secondly, right after the piston starts moving from the top dead center, combustion takes place spontaneously and rapidly in everywhere in the combustion chamber, which enhances the force to push the piston and does it for a longer time, which improves efficiency.

Realization of compression ignition in gasoline engine was said to be a dream for engineers. If deployed on a commercial product, we believe our engine will be the first to in the world.

There were, however, two large challenges in HCCI combustion.

Firstly, HCCI works only at a limited range (of RPM and load.)

Secondly, to overcome the first challenge, we needed to offer spark ignition along with HCCI. But in transient time or under a variety of different conditions, it was difficult to ensure stable switchover between spark ignition and HCCI combustion.

Due to these challenges, the technology was yet to be deployed in a commercial product in spite of attempts by many companies and engineers.

Therefore, our task was to expand the range where compression ignition combustion works and deploy technologies to completely control the switchover between different combustion methods with gasoline fuel.  This control technology is a breakthrough and an original technology proprietary to Mazda.

Next, I will briefly talk about the technology that completely controls compression ignition.

In order to have stable combustion at all range, it is necessary to have switchovers between SI and CI, which requires to have a spark plug in the structure. We turn that into advantage, and use the spark plug as a control factor to control the compression ignition. Except for a certain cold temperature conditions, CI combustion is feasible in almost all ranges.

In order to understanding this as a concept, I will explain it in a simplified way.

The actual system involves a lot more difficult controls, which will be explained separately, so please take this explanation as just a concept. 

Spherical flame expanded by the spark plug ignition serves as a second piston (air piston,) and further compresses the air-fuel mixture in combustion chamber to facilitate the necessary environment for compression ignition to take place. By controlling the ignition timing by the spark plug, we expand the compression ignition and make smooth switchover with spark ignition, realizing completely controlled compression ignition and spark ignition. 

This completely controlled compression and spark ignition are made possible by Mazda’s proprietary combustion method, SPCCI (stands for spark controlled compression ignition.) It is the combustion where compression ignition combustion is controlled by spark ignition.

Also, as a technology to help raise the ratio of compression ignition combustion, the new engine is equipped with air supply device that can send air into highly compressed cylinders.

In order to expand CI combustion to the mid to high load range, a large amount of air has to be taken in, and for that purpose, the air supply device helps and expands the range of CI, which contributes to both driving performance and fuel efficiency.

Thanks to these measures, as shown in the conceptual schematic, the ratio of compression ignition combustion is heightened to almost all range except for super low temperature condition, but  even at such a condition, transition to spark ignition combustion is made seamless.

We succeeded in realizing a clean engine that offers high torque and excellent fuel economy thanks to super lean combustion, which has never been possible with spark ignition.

Spark ignition kicks in when temperature is extremely low, but even in that condition the combustion is same as SKYACTIV-G we currently sell, proving the cumulative improvements of combustion technology we have made.  

Let me discuss customer values the new engine will offer.  There are mainly three values.

The first value its great driving as we promise to continue providing driving pleasure.

In SKYACTIV-X, air is forcefully pushed into cylinders to achieve compression ignition, which leaves no delay for intake air in entering into cylinders, and you can feel excellent driving response thanks to that.

When a customer is driving at a constant speed, pressing accelerator pedal 10%, and tries to overtake another car by speeding up with pressing the pedal 50%, the initial response for such scene is as good as that of diesel engine which uses the same compression ignition.

In this cartoon, it may appear a small difference, but psychologically it gives a driver a great confidence and provides a feeling that the car is part of his or her body. The car can merge into traffic without stress, which is a real tangible value of responsive driving. We believe that offering diesel engine’s benefits by a gasoline engine is going to be a great strength of SKYACTIV-X.

Another point, the gasoline engine’s strength, is its unconstrained feeling of expansion at high RPM, it is an advantage over diesel engine, and we believe it also provides a pleasure of driving too.

As a result, the torque curve runs like this. Thanks to the combination of SPCCI and the air assist mechanism, 10 to 30% of substantial torque improvement is achieved compared to SKYACTIV-G.

Its level of evolution is same or better than SKYACTIV-G.

The second value is a good fuel economy. There are two points of evolution there.

The first evolution is a substantial improvement in fuel consumption ratio.

With regard to fuel consumption, there is an improvement by 20% compared to SKYACTIV-G, attaining the best fuel economy for a gasoline engine in the world. (click)

Furthermore, in those regions where people drive at low speed quite often, the fuel economy is improved by maximum 30% or so thanks to super lean combustion. Compared to the I4 engine in 2008, the improvement is drastic 30 to 45%, and offering better or same fuel economy with the latest SKYACTIV-D diesel engine.

Its amazing improvement in fuel consumption at the light load range completely breaks the conventional notion that says  “large displacement is bad for fuel economy.

The second evolution is a flat characteristic of fuel consumption that shows small difference in real world driving.

This map shows fuel economy ratio. Look at the conventional engine. The lighter the color, the better the fuel economy is. The left one has the best fuel economy. Next is yellow green, then green, then light blue.. the fuel economy gets worse in this order.

When it comes to purpose-built engines for HEV, their discussions are only about the highest efficiency point, but in our case,  we went beyond that to improved fuel economy over in the orange colored range, and expanded to the yellow area to offer a flat fuel economy characteristic. From city streets to long distance highway driving, good fuel economy continues even under a variety of driving conditions with changing engine RPM and load. 

As such, the new engine has fuel economy characteristics that can expand to real world driving range, therefore whether it’s tested by WLTC, JC08 (cold mode), or NEDC, there is little difference in its fuel economy figure. (WLTC is only for cold mode, therefore we compared it with JC08 cold mode.)

The third point is to deliver both driving performance and fuel economy to realize driving pleasure.

This slide indicates how the merit of wide area of good fuel economy brings advantages to a car.

An engine drives a vehicle by transmitting power through a gear in the transmissions to move the wheels. The setting for the gear is a very important factor in terms of increase/decrease the driving force, and which range of engine RPM is used.

Please see the left diagram. This is for a current engine.

The red line shows the difference in gear ratio. There are A and B.  A is used as a base, and when you want to boost the driving force,  gear ratio B is selected. This is often referred to as lowering the final gear ratio.

In this case, if you are driving a car at 100k/h, the engine RPM goes up and you have to drive at a range where fuel economy is poor, as it moves from pale yellow green to green area.

In selecting gear ratio in conventional engine, fuel economy and driving performance were always in a trade-off relationship.

As you see on the right,  SKYACTIV-X, the yellow area of low fuel consumption is extremely broad,  and if you see A and B, they can be used at the same yellow fuel economy area. In other words, fuel economy does not change much even if the load changes, and that dramatically reduces the trade-off feeling by gear ratio between driving performance and fuel economy. It allows you to choose gear ratio that gives exhilarating, responsive driving without sacrificing fuel economy.

Leveraging such fuel economy and torque characteristic , in the case of Mazda3 2.0L , SKYACTIV-X can offer driving performance that is better than 2.5L, with lower fuel consumption than 1.5L.  In other words, transmission gear ratio that prioritizes driving performance can be selected without deteriorating the fuel economy.

In the same token, it is possible to improve fuel economy without much deterioration of driving performance.

Any changes in the market trend can be flexibly dealt with while delivering our brand value of driving pleasure.

In our evaluation of a prototype vehicle in real driving range, its CO2 emission was same as that of Mazda2 1.5L SKYACTIV-D, while its acceleration feel was same as that of MX-5 SKYACTIV-G 2.0L, which gave us a good confidence.

Lastly, I will talk about the positioning of this engine in our product strategy to summarize my presentation.

With regard to SKYACTIV-G engine introduced in 2011, they will be kept upgraded through our process such as the bundled planning and Monotsukuri Innovation, and product improvement actions will be taken one after another, so that we will be able to keep our dealer showroom filled with new and fresh products, and for that purpose we will continue to evolve SKYACTIV-G engines.

In Japanese market, SKYACTIV-D diesel engine is highly praised.

And in the US market, as shown here, SAE paper states that the US EPA gave a high evaluation to SKYACTIV-G gasoline engine from the third party.

It makes us believe that SKYACTIVE-G and D engines still have strong product marketability.  We will make small upgrades to continue the enhancement of their marketability.

As their cost competitiveness is getting stronger through efforts in sales and production over the last several years, we believe SKYACTIV-G, D, engines can still provide high value for money to customers for future.

We will continue to sell products mounted with SKYACTIV-G upgrade and D- upgrade engines as they are still fully competitive, and in addition to them, newly introduced  SKYACTIV-X will expand our lineup that has cost competitiveness, great driving and excellent fuel economy.

And we can combine these three strongly competitive engines with electrification technology, which will enable us to offer optimum combinations with products that will match regional and customer characteristics in each market, and contribute to grow our business.

We Mazda will protect the earth and enrich people’s life through driving pleasure, which is our company’s cause, and continue our challenge to pursue the ideal internal combustion engine.

We will combine the ideal ICE with evolved transmission, body, and chassis, and overlay the most critical control and electrification technology to deliver Mild Hybrid, EV, range extender, and PHEV to offer them as products.

Electrification technologies including EVs, motor control technology, and battery control technology, will be developed by model-based development method, to enable efficient development of high quality products with low investment.

Through such process innovations including Building Block Strategy, model-based development and Monotsukuri Innovation, we will do our best with our company size, to prepare multiple solutions in order to sustain our business toward 2020, and overcome the anticipated challenges toward 2025.

In terms of protecting the earth and to serve for our customers around the world, we will be ready to provide most optimal power source to each region and customers there.

Toward 2020 when Mazda will celebrate its centennial, we are committed to introduce those technologies every year together with prototype vehicles, and in 2021 when the next 100 years will begin, we are committed to deliver to our customers the total lineup of such products.

I would like to conclude my presentation today by making our pledge to complete  the preparation to start the next 100 years as Mazda.

Thank you very much for your kind attention.

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