Budny 3:00 PM ​ ​ ​ ​ R09

Disclaimer: This paper partially fulfills a writing requirement for first year (freshman) engineering students at the University ​ of Pittsburgh Swanson School of Engineering. This paper is a student paper, not a professional paper. This paper is based on ​ ​ publicly available information and may not provide complete analyses of all relevant data. If this paper is used for any purpose other than this author’s partial fulfillment of a writing requirement for first year (freshman) engineering students at the University of Pittsburgh Swanson School of Engineering, users are doing so at their own risk. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Skyactiv-X: Mazda’s Holy Grail ​ ​ ​ ​ ​ ​ Thomas Benson ([email protected]) ​ ​ ​ ​ ​ ​

As government regulations tighten around the the cylinder as room must be left for the valve injecting the automotive industry, manufacturers are struggling to fuel to open. Diesel engines have no throttle body. The improve the efficiency of their engines. One of the most throttle within a diesel car instead controls the amount of pressing issue in the automotive industry is that of fuel fuel added into the mixture to change the amount of power efficiency and environmental impact. As more people began [3]. to look for vehicles with little effect on the environment, and How It Works ​ ​ ​ ​ for cars that need to be filled up less often, companies must scramble to provide for the market in order to remain in How exactly does Skyactiv-X combine technologies of business. One of the biggest advancements is the diesel both diesel and traditional gasoline engines? It does this by engine. Diesel engines offer up to twenty percent better using both spark ignition (SI) and compression ignition (CI) efficiency on the highway compared to a similar gasoline [4][5][6]. On the intake stroke fuel is injected into the engine [1]. However, diesel is expensive and has distinct cylinder to mix with air, creating a super lean mixture. The disadvantages when compared to a regular gasoline engine. compression stroke then compresses the mixture to a Mazda originally aimed to create a Homogenous Charge speculated ratio of 18:1. Right before the power stroke the Compression Ignition (HCCI) engine, but ran into problems engine injects a second burst of fuel into the mixture that is doing so [2]. Instead, Mazda now hopes to overcome then ignited by the spark plug [2]. This ignition leads to an disadvantages of both engine types by combining the expansion of the mixture, which pushes it over the threshold technologies in its new engine platform, Skyactiv-X. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ of ignition. This ensures that the remaining fuel is ignited all at once much like a diesel engine’s mixture. Mazda is Diesel v. Gasoline ​ ​ ​ ​ calling this type of ignition Spark Plug Controlled Compression Ignition (SPCCI). SPCCI provides levels of In order to understand why Skyactiv-X is such a torque similar to that of a diesel engine due to all the fuel revolutionary engine, we must first look into the differences igniting at once. This design also overcomes the between a traditional gasoline engine and a diesel engine. A disadvantage that a diesel engine faces in terms of typical four stroke gasoline engine works by filling the compression as the valve does not need to open. Currently chamber with a mixture of gasoline and fuel which is then there is no information on how power will be controlled, compressed and finally ignited by a spark plug. This ignition whether through a standard throttle body or through controlling the fuel to air mixture. then sends the piston down, generating power to move the ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ vehicle. It is also important to note that a gasoline engine is HCCI And Why It Doesn’t Work controlled through airflow. The throttle in a car manipulates ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ a butterfly valve in the throttle body, manipulating the amount of air going into the engine. A diesel engine Earlier in this paper I mentioned that Mazda wanted to manages ignition much differently. Ignition is created by create a HCCI engine, but was unable to. The main reason compressing air within the cylinder to a certain point at behind wanting to create a HCCI engine is that it would be which it is enough to ignite the fuel that is sprayed into the able to combust ultra-lean air-fuel mixtures, which in turn cylinder towards the top of the stroke. This allows a diesel would allow for large gains in engine efficiency. However, engine to ignite almost all of its fuel at once as opposed to a there are several problems with HCCI engines. They gasoline engine which takes a slightly longer time to ignite function much like a diesel engine, but with a few major all the fuel in the piston. It is because of this a diesel engine differences. The most prominent difference is that fuel is not is able to put out more torque and run a leaner fuel mixture injected into the cylinder at the top of the compression than a traditional gasoline engine. However, because of the stroke. Rather, it is mixed in with air during the first stroke need to inject fuel into the cylinder at the top of the stroke, of the engine. This means that air and fuel are compressed, the piston cannot compress the air all the way to the top of University of Pittsburgh, Swanson School of Engineering 1 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 10.31.2017 Thomas Benson ​ ​

which changes the pressure required to ignite the mixture a 2.0 liter version of a Skyactiv-X engine. A 2.0 liter [3]. This leads to a couple of problems. For one, it is Skyactiv-G engine makes 155 crank horsepower and 150 incredible difficult to modulate the amount of fuel present ft-lb’s of torque. The Skyactiv-X makes similar power to the within the cylinder to the degree required. If the mixture is 2.5 liter 4 cylinder found in the Mazda 3 [2]. These off the mixture may ignite too soon or not at all, leading to performance gains hint at a strong future in the world of unreliable performance. Another issue that HCCI engines motorsport, especially in endurance racing. ​ ​ ​ ​ ​ ​ ​ ​ face is that as the engine heats up the timing suffers further. Traditional gasoline engines manage timing through the use Why I Care ​ ​ ​ ​ of spark plugs, while diesel engines manage timing through the use of the fuel valve. It is because of these issues that I have two main interests in the Skyactiv-X engine. The Mazda has decided to use a spark plug to help time ignition first stems from its efficiency. I personally don’t care much [2]. for electric cars. While I appreciate their technical aspects and what they offer the world, I much prefer the internal Why Is This A Big Deal? ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ combustion engine. I love the challenge that they offer in terms of driving. Having to work within specific RPM The question remains, why is this such a big deal? For ranges to achieve the best performance around a track is one, it has the possibility to be the most environmentally something that I love. I also love manual gearboxes, friendly engine created to date. Diesel vehicles release more something that will no longer be needed with the rise of the particulate matter and NO than a traditional gasoline electric car. Mazda’s innovation to improve engine ​x engine. These would both be negated, as the Skyactiv-X efficiency is something that will help to prolong the life of engine is a gasoline engine. An issue with traditional the internal combustion engine. The other interest that I have gasoline engines is that they aren’t able to run lean air-fuel in this engine are the performance gains. Because this engine mixtures like a diesel engine can. However, Skyactiv-X has puts out power well above its displacement size, cars can be the ability to do so, which in turn increases fuel economy. lighter and put out similar power. This means better Mazda claims that the engine will be twenty to thirty percent responding and faster cars, something that is always good in more efficient than its current engines. During test drives of my opinion. The motorsport aspect is also exciting. Should cars equipped with prototypes of the engine, Jalopnik writer Mazda bring a race-spec Skyactiv-X engine to a race such as David Tracy was able to gain between thirteen to fifteen Le Mans it should prove to be an exciting race. This engine percent gains in fuel economy over a traditional Skyactiv-G will also drive other companies to innovate with their engine [7]. Another major draw of the Skyactiv-X engine is engines, only pushing performance further.This engine has the possible performance of said engine. By igniting the fuel the possibility to spark a new race between manufacturers to in a way that allows most of the fuel to ignite at the same catch up to Mazda and see how far they are able to push time torque and power is increased. This means that the their engines. ​ ​ technology used in the Skyactiv-X engine could prove to be very useful in the world of motorsports. Having a powerful Acknowledgements engine that is more efficient than the competitor’s engine could mean the difference between winning and losing in a I’d like to thank my friend Evan Gzesch for giving me long distance race, as you would require fewer pit stops. The ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ the idea to do this paper on Skyactiv-X. I’d also like to thank engine will also provide major performance gains. Mazda ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Steve Schultz for being my inspiration. predicts 188 crank horsepower and 170 ft-lbs of torque from ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Sources

[1] D. Sclar “The Pros and Cons of Diesel Engines” Dummies. Accessed 10.26.2017. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ http://www.dummies.com/home-garden/car-repair/diesel-engines/the-pros-and-cons-of-diesel-engines/ [2] A. Stoklosa “Driving Mazda’s Next Mazda 3 with Its Skyactiv-X Compression-Ignition Gas Engine” Car and Driver. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 2017. Accessed 10.26.2017. ​ ​ ​ ​ ​ ​ https://www.caranddriver.com/reviews/2019-mazda-3-with-skyactiv-x-compression-ignition-gas-engine-prototype-drive-revi ew [3] A. Singh “Combustion characteristics of diesel HCCI engine: An experimental investigation using external mixture ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ formation technique” November 2012. Accessed 10.25.2017. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ http://www.sciencedirect.com/science/article/pii/S0306261912002802

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[4] J. Fenske “Gasoline vs. Diesel - 4 Major Differences” Youtube. 3.9.2016 . Accessed 10.26.2017 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ .https://www.youtube.com/watch?v=rXVJG9n6BAs ​ [5] J. Fenske “Mazda Creates the Holy Grail of Gasoline Engines - HCCI Skyactiv-X” Youtube. 8.13.2017. Accessed ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 10.25.2017. https://www.youtube.com/watch?v=9KhzMGbQXmY ​ ​​ [6] “Next Generation Gasoline Engine Skyactiv-X: SPCCI” Youtube. 10.24.2017. Accessed 10.25.2017. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ https://www.youtube.com/watch?v=RBlBrxT-Xy4 [7] “Vehicle Emissions” Air Pollution. Accessed 10.25.2017. http://www.air-quality.org.uk/26.php ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​​ [8] D. Tracy “I Drove Mazda’s Holy Grail of Gasoline Engines And It Was Incredibly Impressive” Jalopnik. 9.07.2017. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Accessed 10.24.2017 https://jalopnik.com/i-drove-mazda-s-holy-grail-of-gasoline-engines-and-it-w-1800874806 ​ ​ ​ ​​

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