Turbo-Charger

A turbocharger is actually a type of supercharger. Originally, the turbocharger was called a “turbo super charger.” Obviously, the name was shortened out of convenience.

A turbocharger’s purpose is to compress the oxygen entering a car’s engine, increasing the amount of oxygen that enters and thereby increasing the power output. Unlike the belt-driven supercharger that is normally thought of when one hears the word “supercharger,” the turbocharger is powered by the car’s own exhaust gases. In other words, a turbocharger takes a by-product of the engine that would otherwise be useless, and uses it to increase the car’s horsepower.

Cars without a turbocharger or supercharger are called normally aspirated. Normally aspirated cars draw air into the engine through an air filter; the air then passes through a meter, which monitors and regulates the amount of air that enters the system. The air is then delivered to the engine’s combustion chambers, along with a controlled amount of fuel from the carburetor or fuel injectors.

In a turbocharged engine, however, the air is compressed so that more oxygen will fit in the combustion chamber, dramatically increasing the burning power of the engine. The turbocharger is composed of two main parts: the compressor, which compresses the air in the intake; and the turbine, which draws the exhaust gases and uses them to power the compressor. Another commonly used term in relation to turbochargers is boost, which refers to the amount of pressure the air in the intake is subjected to; in other words, the more compressed the air is, the higher the boost.

Although the increase in power is advantageous to the car — and likely a source of enjoyment for the driver — a turbocharger has its drawbacks. First and foremost, a turbocharged engine must have a lower compression ratio than a normally aspirated engine. For this reason, one cannot simply put a turbocharger on an engine that was intended for normal aspiration without seriously undermining the life and performance of the engine. Also, a lower compression ratio means the engine will run less efficiently at low power.

Another major drawback of a turbocharger is the phenomenon known as turbo lag. Because the turbocharger runs on exhaust gases, the turbine requires a build-up of exhaust before it can power the compressor; this means that the engine must pick up speed before the turbocharger can kick in. Additionally, the inlet air grows hotter as it is compressed, reducing its density, and thereby its efficiency in the combustion chamber; a radiator-like device called an intercooler is often used to counter this effect in turbocharged engines.

SKYACTIV TECHNOLOGY

Highlights of the SKYACTIV technologies:

• SKYACTIV-G: a next-generation highly-efficient direct-injection gasoline engine with the world’s highest compression ratio of 14.0:1
• SKYACTIV-D: a next-generation clean diesel engine with the world’s lowest compression ratio of 14.0:1
• SKYACTIV-Drive: a next-generation highly-efficient automatic transmission
• A next-generation manual transmission with a light shift feel, compact size and significantly reduced weight
• A next-generation lightweight, highly-rigid body with outstanding crash safety performance
• A next-generation high-performance lightweight chassis that balances precise handling with a comfortable ride

– First product to be equipped with SKYACTIV technology will be a Mazda Demio featuring an improved, fuel-efficient, next-generation direct-injection engine that achieves fuel economy of 30 km/L.

Overview of the SKYACTIV technologies

1. SKYACTIV-G

A next-generation highly-efficient direct-injection gasoline engine that achieves the world’s highest gasoline engine compression ratio of 14.0:1 with no abnormal combustion (knocking)

• The world’s first gasoline engine for mass production vehicles to achieve a high compression ratio of 14.0:1
• Significantly improved engine efficiency thanks to the high compression combustion, resulting in 15 percent increases in fuel efficiency and torque
• Improved everyday driving thanks to increased torque at low- to mid-engine speeds
• A 4-2-1 exhaust system, cavity pistons, multi hole injectors and other innovations enable the high compression ratio

2. SKYACTIV-D

A next-generation clean diesel engine that will meet global emissions regulations without expensive NOx after treatments — urea selective catalytic reduction (SCR) or a Lean NOx Trap (LNT) — thanks to the world’s lowest diesel engine compression ratio of 14.0:1

• 20 percent better fuel efficiency thanks to the low compression ratio of 14.0:1
• A new two-stage turbocharger realizes smooth and linear response from low to high engine speeds, and greatly increases low- and high-end torque (up to the 5,200 rpm rev limit)
• Complies with global emissions regulations (Euro6 in Europe, Tier2Bin5 in North America, and the Post New Long-Term Regulations in Japan), without expensive NOx after treatment

3. SKYACTIV-Drive

A next-generation highly efficient automatic transmission that achieves excellent torque transfer efficiency through a wider lock-up range and features the best attributes of all transmission types

• Combines all the advantages of conventional automatic transmissions, continuously variable transmissions, and dual clutch transmissions
• A dramatically widened lock-up range improves torque transfer efficiency and realizes a direct driving feel that is equivalent to a manual transmission
• A 4-to-7 percent improvement in fuel economy compared to the current transmission

4. SKYACTIV-MT

A light and compact next-generation manual transmission with crisp and light shift feel like that of a sports car, optimized for a front-engine front-wheel-drive layout

• Short stroke and light shift feel
• Significantly reduced size and weight due to a revised structure
• More efficient vehicle packaging thanks to its compact size
• Improved fuel economy due to reduced internal friction

5. SKYACTIV-Body

A next-generation lightweight, highly-rigid body with outstanding crash safety performance and high rigidity for greater driving pleasure

• High rigidity and lightness (8 percent lighter, 30 percent more rigid)
• Outstanding crash safety performance and lightness
• A “straight structure” in which each part of the frame is configured to be as straight as possible. Additionally, a “continuous framework” approach was adopted in which each section functions in a coordinated manner with the other connecting sections
• Reduced weight through optimized bonding methods and expanded use of high-tensile steel

6. SKYACTIV-Chassis

A next-generation high-performance lightweight chassis that balances precise handling with a comfortable ride feel to realize driving pleasure

• Newly developed front strut and rear multilink suspension ensures high rigidity and lightness (The entire chassis is 14 percent lighter than the previous version.)
• Mid-speed agility and high-speed stability — enhanced ride quality at all speeds achieved through a revision of the functional allocation of all the suspension and steering components

DISI ENGINE

In developing the DISI engine, we aimed to cool the interior of the cylinder as much as possible by promoting fuel vaporization and uniform mixing of atomized fuel and air. This produces a high charging efficiency of the air-fuel mixture and a high compression ratio, which results in significant improvements in both torque and fuel efficiency.

Characteristics of the direct injection engine:

• Fuel is injected from a tiny nozzle into a relatively large cylinder, so it has a high latent heat of vaporization, which efficiently cools the air within (in-cylinder cooling effect).

• The air temperature in the cylinder decreases, which means:

• (1) more air may be charged into the combustion chamber, which produces increased torque.

• (2) the engine is less prone to knocking. This contributes to increased torque, and enables a higher compression ratio that also contributes to good fuel efficiency.

In a direct injection engine, however, the fuel skips the waiting period it would have to endure inside a standard engine and instead proceeds straight to the combustion chamber. This allows the fuel to burn more evenly and thoroughly. For the driver, that can translate to better mileage and greater power to the wheels.

In the past, direct injection posed too many technical hurdles to make it worthwhile for mass market gasoline automobiles. But with advances in technology and greater pressure to make cars run more cleanly and efficiently, it looks as if gasoline direct injection — or GDI as it’s referred to in industry lingo — is here to stay. In fact, most of the major car manufacturers make or plan to soon introduce gasoline cars that take advantage of this fuel saving and performance enhancing system.