Category Archives: JDM

Subaru Turbocharger Explained Part 1

Subaru Turbocharger Explained:

Turbochargers are fairly simple in concept, but adapting the system to modern vehicles can be quite complex. This primer for those new to servicing turbos and review for veterans lays out the function and operation of turbocharging in Subaru vehicles.

Subaru Turbocharger: Starting with 2004 models, the WRX STi incorporates a water spray system to help cool the intercooler, thereby further cooling the intake air.
Subaru Turbocharger: Starting with 2004 models, the WRX STi incorporates a
water spray system to help cool the intercooler, thereby
further cooling the intake air.

The return of turbocharging in the 2002 Impreza WRX marked an absence of nearly a decade for Subaru vehicles. While the new generation has been around for half a decade, not everyone understands the function and operation of Subaru turbocharging systems.

Naturally, everyone knows these blowers are designed to get the maximum power out of engines by packing more air and fuel into the cylinders to get the biggest bang possible. Just how that is accomplished, however, may be a bit of a mystery to you. Here’s a primer on turbocharging and how it applies to Subaru vehicles.

Subaru Turbocharger Explained:

A Brief History of Turbochargers

Turbochargers were originally invented to increase the volume of air pushed into the cylinders of internal combustion engines, and, along with increased fuel, raise the level of energy produced by the combustion process

Historical references indicate that Swiss engineer Alfred J. Buchi adapted the turbines from steam engines to diesel engines as a method to improve air induction, and, therefore, smoother operation in internal combustion engines. In 1905, Buchi’s idea of powering the forced air induction by exhaust flow was granted a patent. Good idea or not, the fairly crude engines of the day could not sustain even or adequate boost pressures. Buchi worked another ten years before he could produce a working model of a turbocharged diesel engine. By that time, other companies had also produced turbocharging systems

The massive building boom of internal combustion engines to supply ships, trucks and airplanes for World War I saw technologies take a giant leap forward. The first turbocharged diesel engines for ships and locomotives appeared around 1920. Shortly thereafter, European car manufacturers began incorporating them into factory race cars and a few sporty luxury models.

The next milestone for turbocharging came with the military build-up for World War II, when turbo systems were fitted to fighter planes and bombers to allow them to fly at higher altitudes where the thinner air could be compacted into the engines to provide sufficient combustion. However, direct-driven superchargers quickly proved more reliable, efficient and more easily controlled, leaving turbochargers by the wayside.

It wasn’t until the mid-1950s when turbochargers started appearing on diesel trucks that modern turbos began to make a dent in the automotive market. Today, the vast majority of truck engines are turbodiesels.

When turbocharged vehicles began to dominate the international racing scene in the 1960s, car manufacturers began to use them in sporty models to appeal to performance-oriented drivers. By the 1980s, turbochargers for cars were a bona fide success, particularly in Subaru vehicles, due to improved metallurgy, intercooling and efficient boost controls.

The main components of a Subaru turbocharger system are a water-cooled turbocharger, an air-cooled intercooler, a wastegate control solenoid valve, sensors and a controller. Let’s review the individual components and the role they play in the system.

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LSD Mechanical DCCD Advantage Explained:

LSD Mechanical DCCD Advantage Explained:

LSD: Advantages of mechanical LSD

The mechanical LSD mechanism is advantageous in that it has good response of the LSD differential limiting force to the engine driving force and has direct vehicle operational stability allowing the driver to easily grasp changes in the vehicle behavior. This post discusses these advantages in comparison with conventional DCCD system.

LSD Mechanical Advantage: Controlling coil current based on driving force estimated from detected information. Time lag existent between a change in engine driving force and generation of LSD differential limiting force.
LSD Mechanical Advantage: Controlling coil current based on driving
force estimated from detected information.

LSD Advantage: The LSD differential limiting force exactly follows changes in the engine driving force.
LSD Mechanical Advantage: The LSD differential limiting force exactly
follows changes in the engine driving force.
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DCCD Subaru STi Explained

DCCD Subaru STi Explained:

The Driver’s Control Center Differential system is system that appropriately controls the differential limiting force of center differential LSD depending on running conditions of a vehicle. The DCCD system evolved provides controls that follow operations of the driver, while conventional DCCD system provides those based on conditions of the vehicle.

The system consists of a center differential of planetary gear type provided with LSD function, a steering angle sensor, a yaw rate sensor, a lateral G sensor, a DCCD control module and other components.

DCCD: The DCCD system evolved provides controls that follow operations of the driver, while conventional DCCD system provides those based on conditions of the vehicle.
DCCD: The DCCD system evolved provides controls that follow operations of the driver, while conventional DCCD system provides those based on conditions of the vehicle.

Hybrid LSD mechanism using conventional electromagnetic clutch LSD mechanism added with torque-sensitive mechanical LSD mechanism allows approximate coincidence between the vehicle acceleration/deceleration and LSD clutch differential limiting timings, resulting in linear LSD characteristics acquired through driver’s accelerator operation. Thus, the driver can more freely control the vehicle by easily grasping behavior of the vehicle.

In addition, the steering angle sensor let the DCCD control module know the driver’s intension of turning. In combination with the yaw rate and lateral G sensors, it adjusts the electromagnetic clutch LSD differential limiting force based on the running path imaged by the driver and the actual behavior of the vehicle. Thus, cornering in better accordance with the driver’s image is enabled, preventing occurrence of understeer and oversteer.

LSD MECHANICAL DCCD ADVANTAGE EXPLAINED

For balancing between the vehicle turning performance and traction during turning in a high order, the center differential driving torque is set to have distribution ratio 41:59.

 

DCCD: For balancing between the vehicle turning performance and traction during turning in a high order, the center differential driving torque is set to have distribution ratio 41:59.
DCCD: For balancing between the vehicle turning performance and traction during
turning in a high order, the center differential driving torque is set to have distribution ratio 41:59.

 

Manual mode switch/DCCD control dial

In manual mode, the DCCD control can be used to adjust the differential limiting force of the electromagnetic clutch LSD mechanism in the range from free to lock. Current settings of the control dial are displayed on the indicator in the meter.

DCCD: In manual mode, the DCCD control can be used to adjust the differential limiting force of the electromagnetic clutch LSD mechanism in the range from free to lock.
DCCD: In manual mode, the DCCD control can be used to adjust the differential limiting force of the electromagnetic clutch LSD mechanism in the range from free to lock.

 

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SI-Drive 2008+ STi Explained:

SI-Drive 2008+ STi Explained:

The 2008 Subaru Impreza WRX STI has a heritage of power and control. Previous models have been the foundations for countless racing victories and championships. The new WRX STI promises the same with it’s 305- horsepower, turbocharged, intercooled Boxer engine and a six-speed manual transmission.

SI-Drive: he new WRX STI promises the same with it's 305- horsepower, turbocharged, intercooled Boxer engine and a six-speed manual transmission.
SI-Drive: he new WRX STI promises the same with it’s 305- horsepower, turbocharged, intercooled Boxer engine and a six-speed manual transmission.

Power and control incorporate enchanced technology. As suggested by new switchgear on the dashboard and center console and my markings within the instrument cluster’s center-mounted tachometer, a driver has some things to learn before wringing out the most from the car.

Today’s electronics now allow the driver to tinker with engine response characteristics, the manner in which All-Wheel-Drive system fights for traction, and the degree to which braking and engine management help maintain vehicle stability. These capabilities are made possible by standard Vehicle Dynamics Control (VDC), Driver Controlled Center Differential (DCCD), and Subaru Intelligent Drive (SI-Drive).

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Legacy World Speed Records

Legacy World Speed Records:

Prior to launching the 1990 Legacy, Subaru drew attention to the car’s capabilities and durability by attempting to set world speed records with the Legacy. In an effort involving three Legacy RS Turbo Sedans, Subaru established a new 100,000 kilometer (62,137 miles) world speed record as well as 13 international records. Some of these records still stand today.

Legacy World Speed Records: For the 1990 model year, Subaru was launching the Legacy, a front-wheel drive model with optional 4-wheel drive. It was larger than previous Subaru models and had a 2.0-liter, 16-valve, turbocharged engine.
Legacy World Speed Records: For the 1990 model year, Subaru was launching the Legacy, a front-wheel drive model with optional 4-wheel drive. It was larger than previous Subaru models and had a 2.0-liter, 16-valve, turbocharged engine.

For the 1990 model year, Subaru was launching the Legacy, a front-wheel drive model with optional 4-wheel drive. It was larger than previous Subaru models and had a 2.0-liter, 16-valve, turbocharged engine. Since the car represented a new segment for Fuji Heavy Industries Ltd. (FHI), it wanted to demonstrate the vehicle’s performance, reliability, and durability. Thus began the quest for the 100,000 kilometer (62,137 miles) world record. That represents the distance typically covered during five years of hard driving.

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Cool Down WRX Turbo Procedure

Cool Down WRX Turbo Procedure:

It is not necessary to perform a cool down/idling procedure on Subaru WRX turbo models, as was recommended with past turbo models. “The current 2.0 liter turbo engine has a far greater cooling capacity and, coupled with technology advances, makes this practice no longer necessary. This explains why information about a cool down is not included in the Impreza Owner’s Manual.

Cool Down WRX Turbo Procedure: It is not necessary to perform a “cool down/idling” procedure on Subaru WRX turbo models, as was recommended with past turbo models.
Cool Down WRX Turbo Procedure: It is not necessary to perform a “cool down/idling” procedure on Subaru WRX turbo models, as was recommended with past turbo models.

The heat contained in the turbocharger begins to vaporize the coolant at the turbocharger after the engine is stopped. This hot vapor then enters the coolant reservoir tank, which is the highest point of the coolant system.

At the same time the vapor exits the turbocharger, coolant supplied from the right bank cylinder head flows into the turbo. This action reduces the turbocharger temperature. This process will continue until the vaporizing action in the turbocharger has stopped or cooled down.

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AWD: The five types of Subaru systems

AWD: The five types of Subaru systems

Back in 1972, Subaru introduced the Leone 4WD Station Wagon. It was the first fourwheel drive vehicle designed specifically for everyday driving, rather than for off-road or rugged use.The safety and driving performance aspects of the Leone 4WD proved popular and made the car successful. It quietly set the standard for Subaru to become the global AWD leader of today.

AWD Genesis: The safety and driving performance aspects of the Leone 4WD proved popular and made the car successful.
AWD Genesis: The safety and driving performance aspects of the Leone 4WD proved popular and made the car successful.

 

Subaru Symmetrical All-Wheel Drive:

Subaru calls its system of mating a horizontally opposed (boxer) engine to various types of full-time AWD “Symmetrical All-Wheel Drive.” This system is based on the balance of both the powertrain and the straight, nearly-horizontal, flow of power to the wheels.The weight of the flat boxer engine and the transfer components lie very low in the chassis, providing a lower center of gravity, resulting in excellent traction and stability.

The Five Types of Subaru Symmetrical All-Wheel Drive:

Subaru currently uses five different types of Symmetrical AWD. Each is specific to the Subaru model and transmission.The five types are:

■ Continuous All-Wheel Drive
■ Active All-Wheel Drive
■ Variable Torque Distribution (VTD) All-Wheel Drive.
■ Driver Controlled Center Differential (DCCD) All-Wheel Drive
■ Vehicle Dynamics Control (VDC) All-Wheel Drive

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Formula 1 Subaru Flat-12

Formula 1 Subaru Flat-12:

In 1990 Subaru took over the Coloni Formula One team, acquiring a 51% ownership stake, paying off the team’s debts, and supplying a new, unique engine. The engine was a flat-12 called the “MM” series, which in fact was penned by Carlo Chiti.

Formula 1 Subaru Flat-12: In late 1988, the Japanese commissioned Chiti to design a new Formula One engine with a "flat" layout, as used in their road cars.
Formula 1 Subaru Flat-12: In late 1988, the Japanese commissioned Chiti to design a new Formula One engine with a “flat” layout, as used in their road cars.

Chiti’s Motori Moderni company at Novara had supplied V6 turbo engines for the Minardi Formula One team from 1985 to 1987, and in 1988 Chiti had penned a naturally aspirated V12 engine that attracted Subaru. In late 1988, the Japanese commissioned Chiti to design a new Formula One engine with a “flat” layout, as used in their road cars.

The engine was completed in the summer of 1989, and was tested in a Minardi M188 chassis; due to a severe lack of power, Minardi lost interest. After a few months of searching, Subaru found the Coloni team. Eventually, the Subaru Coloni team was founded with Enzo Coloni staying on board as the man for operational business.

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