DCCD | Subaru Idiots (2024)

The Winter season brings cold weather to many parts of the country, and with it the traditional driveability problems.

Before you push the panic button on Subaru cold weather and driveability problems, remember:

• No vehicle runs as well when it is cold as it does when it is at normal operating temperature.

• You have been operating the vehicle in more moderate temperatures and has gotten accustomed to the way it has been running. Now it is colder and things are not working the same.

• Some areas of the country may be using gasoline blended for warmer temperatures. These fuels normally do not atomize as well in cooler temperatures.

• Oxygenated and reformulated fuels that are in use in many parts of the country are normally harder to ignite in cold cylinders.

• Many drivers get their gas at one station because it may be close to home or work. Question them about this and if this is true, suggest they try a different brand of gas. It may take a couple tanks before any improvement is noticed. Different manufacturers blend their fuels differently.

• The 4EAT has a temperature sensor in the ATF and the Transmission Control Unit (TCU) will not allow an up-shift into 4th gear until the ATF has reached a specific temperature. This 4EAT design characteristic may be interpreted as a driveability problem by a driver who is not familiar with 4EAT operation.

There are many reasons for Subaru cold weather and driveability issues during cooler weather. Spending a few minutes with your Subaru and look over the points listed above should eliminate misconceptions about the Subaru cold weather performance and driveability characteristics of Subaru vehicles.

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.

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.

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’saccelerator 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.

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.

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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.

Power and control incorporate enhanced 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).

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.

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

Front Differentials:
02-07 WRX: open
04 STi: “SureTrac” LSD
05-07 STi: “Helical” LSD

Rear Differentials: R160, R180
These were originally used in the Datsun 510, 610 and other IRS Datsuns. The “R” stands for Fuji Heavy Industries. The R180 was used in the front axle of Datsun 4×4 trucks (720, etc). The number represents the ring gear size in millimeters.

R160 – 52lbs. WRX rear differential. It has a viscous LSD which is no better than an open differential since the unit is so tiny in this differential.
02-05 have a 3.54 gear ratio
06-07 have a 3.70 gear ratio
R160’s on 2.2L Legacy/Impreza’s have a 3.9 gear ratio

R180 – 64lbs. STi rear differential. It has a mechanical clutch type LSD.
04-05 R180’s have a 3.90 gear ratio
06-07 R180’s have a 3.54 gear ratio

Center Differentials:
02-07 WRX: Viscous coupling type
02-05 has a 1.1:1 gear ratio
06-07 has a 1:1 gear ratio
04-07 STi: DCCD (Driver Controlled Center Differential)
04-05 has a 1:1 gear ratio
06-07 has a 1.1:1 gear ratio

Do I need different front axles?
02-early 04 WRXs have female axles and need to use stubs that go inside the transmission . Late 04-07 WRXs use male ended axles that slide inside the front differential so there is no need for stubs. For the female axles, you need axle stubs, circlips, and seals to reuse the WRX axles (check out the seal differences link for part numbers). You can use the stubs from your 5MT. For the male ended axles, they just slide right into place with the correct seals and circlips. 04 STi front axles will work too.

A limited edition of 1000 Japanese MY04 WRX STI‘s with DCCD were exported to celebrate victory in the 2003 WRC drivers’ championship. 500 were sold in Europe, Australia and South Africa as the Petter Solberg edition; the other 500 were further modified by Prodrive and sold in the UK as the WR1. They had 316 bhp (236 kW) and 309.8 ft·lbf (420.0 N·m), an incredible 0-60 mph time of only 4.25 seconds and a top speed of 155 mph (249 km/h) (electronically limited). They were equipped with Prodrive WRX STI springs, Pirelli PZero Nero tires, mesh grilles, special Ice Blue metallic paint and Prodrive PFF7 Pewter wheels. The new ECU and exhaust were not EU-hom*ologated, so they were fitted after registering the car. The retail price was £29,995.

The Cusco team have been campaigning a heavily modified STi with a rear drive conversion as required by regulations since the late nineties and having no two-door model available at present, the Super GT committee gave a special permit for them to race with a four-door model instead of a two-door one. The rear drive conversion rule was lifted in 2006, and since then they returned to all-wheel drive with a transaxle gearbox.

In 2008, Cusco’s Impreza won the first GT300 race in Sepang. It marked the first AWD car victory in Super GT/JGTC history. Even though they were having very impressive results(with 1 win and 2 podiums) that season, Cuscho announced that they would not participate in the 2009 season as they want \ The performance of Cusco was outstanding even though they were using a 4-door car, it later lead the Super GT committee to officially allow all 4-door model cars to participate the series. The Toyota Corolla Axio followed suit in 2009.

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