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SKYACTIV: Keeping the Zoom in Zoom-Zoom

Mazda takes a total approach to design.
Thursday, July 31, 2014 - 06:00
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What is Mazda’s SKYACTIV technology? Let’s break it down. “SKY” is about preserving the environment by lowering CO2 emissions. “ACTIV” is about preserving the excitement of driving by making the driver an active part of a system Mazda disguised as a car.

I am amazed at the new technology and the twists taken on some old ideas you see in Mazda’s SKYACTIV technology. One of the ideas that really caught my eye was raising the compression ratio of the gasoline engine to 14:1 and the lowering of their diesel engines to 14:1 compression ratio. Looking into how they could do this and make it work was very interesting.

Background
Mazda launched its SKYACTIV technology for model year 2011. Mazda took on the challenge to promote driving pleasure while being environmentally friendly and providing outstanding safety for its vehicles’ occupants. Mazda began the redesign around 2008 with the idea that by 2015 it could increase fuel economy by 30 percent over 2008 models, without decreasing driving pleasure or safety.

Mazda believes the internal combustion engine is still going be a major player in the future. It made the decision to position itself to seamlessly merge the internal combustion engine with present and future technologies such as electric drive, while keeping the driving experience alive. Mazda believes in the concept of having the engine, transmission, body and chassis all work as a system, including the driver. Some of the problems Mazda faced were improving already highly efficient engines, improving both automatic and manual transmissions and giving the vehicle a rigid body and chassis while maintaining safety from a lighter weight car for improved fuel economy.

We all know that an internal combustion engine is not efficient. Somewhere in the neighborhood of 70 to 80 percent of the energy produced is actually lost either through heat or friction. First, Mazda took a hard look at both its gasoline and diesel engines. It went back to the drawing board to figure out how to pull more useful energy from the engines. One of first things it considered was gasoline direct injection (GDI) technology. That was just not good enough, though; it wanted to improve it. All hot-rodders know that high compression engines typically put out more power, but the problem is that squeezing the air that tightly costs energy (pumping losses), just like the power it takes to run an air compressor. Mazda engineers also took aim at reducing internal engine friction and weight.

SKYACTIV-G (Gasoline Engine)
Engineers have been chasing Homogenous Controlled Combustion Ignition (HCCI) engines for a while. Gasoline Direct Injection (GDI) is the newest step toward getting more energy from combustion. GDI is a gas engine designed much like a diesel. The gas is injected under higher pressures (500 to 3,000 psi) directly into the combustion chamber allowing for a more complete burn. The air in the cylinder is directed toward the spark plug located in the center of the cylinder head where gas is sprayed just before ignition.

Mazda asked the question, “How do you get more power with less fuel?” The answer is to increase combustion expansion ratio. This means a smaller combustion area, thus increasing down pressure on the piston. This is why Mazda increased the compression ratio to 14:1. As you know, engine knock robs power, increases emissions and causes engine damage so they first went about lowering cylinder temps. Mazda decided to remove more residual exhaust gases from the cylinder.

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