Category Archives: Drivetrain

Drivetrain, Ej20, EJ257, gc8, Impreza, JDM, Legacy, STi, Subaru, Turbo, USDM, WRX

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.

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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2.5RS, Drivetrain, Ej20, EJ25, EJ257, forester, Impreza, STi, Subaru, Turbo, USDM, WRX

Engine noise when cold (Winter is coming)

Engine Noise When Cold:

Beginning with the 1997 model year, the 2.2 and 2.5 engines were made more fuel efficient, more powerful, and were given a flatter, more usable torque curve than in previous years. To achieve these objectives, it was necessary to make improvements and modifications to the Subaru engine lineup. The following are some of those improvements:

• Mechanical valve lash adjusters (reduces friction).
• Lightweight pistons (reduces inertia).
• Short skirt, Molybdenum coated pistons (reduces friction).
• Increased compression ratio (improved power output).
• Improved cylinder head design (improved cooling).
• Improved induction system (improved breathing).

Engine Noise when cold: As a result of these enhancements, some Subaru engines may exhibit some engine noise during the warm-up period after a cold startup.

As a result of these enhancements, some Subaru engines may exhibit some engine noise during the warm-up period after a cold startup. This engine noise is a consequence of the engine improvements and is not, in any way, an indication of any engine problem.

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2.5RS, AWD, DCCD, Drivetrain, forester, gc8, Impreza, JDM, Legacy, STi, Subaru

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.

 

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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2.5RS, AWD, Drivetrain, forester, gc8, Impreza, Legacy, STi, Tuning, Turbo, USDM, WRX

OBD-II Subaru Diagnostic Systems

OBD-II Subaru Diagnostic Systems:

The Environmental Protection Agency (EPA) now has regulations in place that establish requirements for on-board diagnostic (OBD-II) systems on light-duty vehicles and light-duty trucks. The purpose of the OBD-II system is to ensure proper emission control system operation for the vehicle’s lifetime by monitoring emission-related components and systems for deterioration and malfunction.

OBD-II Subaru Diagnostic Systems:
The Environmental Protection Agency (EPA) now has regulations in place that establish requirements for on-board diagnostic (OBD-II) systems on light-duty vehicles and light-duty trucks.

There’s a big difference between detecting only hard faults (OBD-I) and having the ability to actively monitor the system for proper operation, deterioration or a malfunction (OBD-II).

Engines in today’s vehicles are largely electronically controlled. Sensors and actuators sense the operation of specific components (e.g., the oxygen sensor) and actuate others (e.g., the fuel injectors) to maintain optimal engine control. An on-board computer, known as the “powertrain control module,” controls all of these systems.

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Drivetrain, forester, gc8, Impreza, Legacy, STi, Subaru, WRX

R-134a A/C refrigerant guide

R-134a A/C refrigerant guide for Subaru cars:

Since 1996, original equipment manufacturers have been using R-134a in all automotive air conditioning systems. R-134a is now the refrigerant of choice. This short article will help you learn proper safety procedures regarding the use of R-134a. Also, to stress the importance of refrigerant identification for OEM automotive A/C systems, we will explain some of the specific system component changes, and discuss important changes to A/C service equipment.

You may already be familiar with R-134a, A/C retrofits, and proper procedures. If you are confident of your abilities and retrofit knowledge, try answering the 20 question quiz that ends this article. If you are not sure about your R-134a retrofit knowledge, read this article first.

R-134a A/C refrigerant guide for Subaru cars:
Since 1996, original equipment manufacturers have been using R-134a in all automotive air conditioning systems. R-134a is now the refrigerant of choice.

What Is R-134a?

R-134a does not contain suspected ozone-depleting chlorofluorocarbons. The chemical compounds and molecular structures of the old refrigerant R-12 and the new refrigerant R-134a are completely different. However, the temperature/pressure relationships of the two are very similar. Automotive publications, equipment manufacturers, and refrigerant suppliers, provide technical specifications and properties for R-134a.

R-134a and R-12 are not compatible. Under no circumstances should they be mixed. Vehicle and service manufacturers have gone to great lengths to prevent cross-charging or contamination of these two refrigerants. For instance, R-12 systems use a small high-side service port, and a large low-side service port. R-134a service fittings are completely different. The high side service port is now the larger of the two. These quick disconnect fittings will not work with R-12 service equipment.

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2.5RS, Drivetrain, Ej20, ej20G, EJ25, EJ257, forester, gc8, Impreza, JDM, STi, Subaru, Turbo, UK, USDM, WRX

Subaru Engine Block Piston Size Identifier:

Subaru Engine Block Piston Size Identifier:

The picture below of this paragraph shows the location of piston size and main journal size information on all Subaru engines. As the figure illustrates, it is possible to have more than one piston size in the same engine.

Subaru Engine Block Piston Size Identifier:
The picture on the bottom shows the location of piston size and main journal size information on all Subaru engines. As the figure illustrates, it is possible to have more than one piston size in the same engine.
2.5RS, AWD, Drivetrain, exhaust, forester, gc8, Impreza, Legacy, STi, Subaru, Suspension, Transmission, Turbo, UK, USDM, WRX

Maintenance Inspections for Subaru:

Maintenance Inspections for Subaru:

Subaru vehicles are more reliable than ever before. To assure their continued reliability, a schedule of inspection and maintenance (I & M) services is prescribed by Subaru of America for every Subaru vehicle sold. A copy of this schedule can be found in the Warranty and Maintenance Booklet located in the vehicle glove compartment.

Maintenance Inspections for Subaru:
Subaru vehicles are more reliable than ever before. To assure their continued reliability, a schedule of inspection and maintenance (I & M) services is prescribed by Subaru of America for every Subaru vehicle sold.

Subaru vehicle maintenance inspections services are divided into recommended intervals beginning with three months or 3000 miles (whichever comes first). Each additional level in the maintenance schedule (7,500/15,000/ 30,000 miles) adds more maintenance and inspection steps to the process. The 15,000 (15 month) and 30,000 mile (30 month) services are ‘major’ services, and include the most comprehensive range of component checks, part replacements and adjustments.

If you are already familiar with Subaru vehicles, you may have developed a routine when performing a vehicle safety maintenance inspections. Following a set routine allows you to start at one end of the vehicle and end up at the other end, having performed all of the necessary safety inspection steps along the way.

Repetition of the safety inspection may also allow you to commit the steps to memory, but a checklist can be a helpful addition that leaves nothing to chance (or memory). Checking items off the checklist provides a written record that can be shared with the customer and retained for your service records as well.

Recommended steps in a Subaru Safety Maintenance Inspections  are also spelled out in the owner’s Warranty and Maintenance Booklet. Some of the steps overlap services performed during the scheduled maintenance program. It could be argued that any scheduled maintenance should always include a Safety Inspection. Most of the Safety Maintenance Inspection steps are based on common sense, but it’s surprising how frequently these simple suggestions are ignored.

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2.5RS, Drivetrain, EJ25, EJ257, forester, gc8, Impreza, STi, Subaru, USDM, WRX

Valve Adjustment DOHC Engine Part 2

Valve Adjustment Tool and
Adjustment Procedures:

As we mentioned, it takes a special tool to work within the limited clearance area between the cylinder heads and the frame rails. The ST 498187 is a three part tool. One part wraps around the cam lobes, a second touches the outer edges of two shim buckets, and a third eccentric bolt exerts the necessary pressure to push a pair of shim buckets away from the cam lobe to make shim removal and replacement possible.

The tool installed in the three steps:

• Wrap the first half of the tool (part A) around the lobes.
• Attach the second half (part B) to part A by sliding its pins through the slotted holes in part A.
• Install the eccentric bolt (part C) into the hole in part A.

Valve Adjustment Tool and Adjustment Procedures: As we mentioned, it takes a special tool to work within the limited clearance area between the cylinder heads and the frame rails.

The eccentric bolt forces parts A and B away from one another. Because part A can’t move (it’s wedged against the cam lobes), the only thing that can move is part B. Part B moves by forcing the shim buckets downward, away from the camshaft.

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