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This page contains answers to some of the most frequently asked questions in the Subaru world. If you should have any questions, comments, or suggestions, please feel free to email me.

Engine and Drivetrain
Suspension, Brakes, Rims, and Tires


About Subaru

In February 1954, FHI announced its prototype passenger car called the P-1. The P-1, named the Subaru 1500 the following year, used the first Japanese-manufactured monocoque body. This passenger car provided excellent riding comfort and driving stability with its front-wheel wishbone-type independent suspension; a coil spring and double-action oil damper combination, and rear-wheel rigid axle suspension with a three-leaf spring and double-action oil damper combination. Unfortunately, sales had to be suspended because of difficulties in funding the factory equipment and sales network. Nevertheless, this vehicle proved to be of great value in the later developments of the Subaru 360 and Subaru 1000. That was the starting point for Subaru.

But why "Subaru"? Subaru is the name of a star cluster in the Taurus constellation, which is called Pleiades in the West. Six of its stars are visible to the naked eye, but about 250 bluish stars can be seen if one uses a telescope. Credit for naming the company goes to Kenja Kita, the first president of Fuji Heavy Industries. As Fuji Heavy Industries had just taken over 5 of 12 companies resulting from the breakup of the old Nakajima Aircraft Company, Kita saw this unique name as the ideal symbol to express the unification of these 5 Fuji companies -- "Subaru".

About Subaru Tecnica International

Subaru Tecnica International (STi) was founded in April 1988 by Fuji Heavy Industries, Ltd. Its purpose was promote Subaru cars around the world by participating in motorsports. STi identified rallying and endurance speed records as two types of motorsports that Subaru should participate in. The newly launched Legacy set two world records and 13 international records in the 100,000km FIA World Speed Record in January 1989. The World Rally Championship project evolved from Subaru's involvement in Japanese rallying but became a full scale factory effort when STi joined forces with the British-based Prodrive company. The initial objective was to pose a serious challenge to the established manufacturer teams competing in the World Rally Championship.

About Prodrive

Prodrive was formed in 1984 by David Richards and Ian Parry. In 1985 they formed their first motorsport team, the Rothmans Porsche Rally Team. In its first year it wins the Middle East Rally Championship and comes second in the European Rally Championship. In 1990, Prodrive begins its rallying relationship with Subaru. In 1991 and 1992, Colin McRae was on top of the podium, winning 2 consecutive British Rally Championships in Prodrive built Legacy RS. In 1993 Prodrive prepped Impreza make its debut for the new 555-sponsored Subaru team in the World Rally Championship taking second place in the 1000 Lakes Rally. With the help of Prodrive, Subaru captured the Manufacturers' World Rally Championship in 1995, 1996 and 1997. Colin McRae won the World Rally Championship in 1995 driving the Prodrive built Impreza. in 2000, Prodrive still maintains its close relationship with Subaru and STi and helps the Subaru World Rally Team to be one of the most competitive rally teams in the World. Prodrive worked closely with MG, Porsche, BMW, Honda, Ford and Alfa Romeo and helped them to become "the" cars to beat on the racetracks. In 1999 the World saw, what most magazine called "The Best Impreza Ever", Subaru Impreza P1. It was a street version of Impreza extensively modified by Prodrive and STi. Prodrive also makes many performance parts for any Impreza. Anything from wheels, seats to exhaust systems can be purchased at most dealers around Europe.

About Subaru Of America

Subaru of America, Inc., (SOA) was founded in 1968 in Philadelphia, Pennsylvania. Subaru 360 Mini became the first Subaru to be sold on the North American continent. In 1986, SOA relocated its headquarters to Cherry Hill, New Jersey. SOA has 5 regional offices (Aurora, CO -- Central Region, Itasca, IL -- Mid-America Region, Austell, GA -- Southeast Region, Moorestown, NJ -- Penn-Jersey Region, Portland, OR - Western Region) which are responsible for all regional operations, including distribution of parts and cars, service, local advertising, merchandising, sales incentives and dealer relations within their territories. 5 Regional Distribution Centers supply parts and support fixed operations efforts. They are located in Atlanta, GA, Denver, CO, Moorestown, NJ, Peru, IN and Portland, OR. 2 Port Offices of Subaru Of America located in Vancouver, WA and Lafayette, IN, receive imported and US-produced Subaru vehicles and ship them to dealerships. Three independent distributors represent Subaru and oversee all activities within certain geographical territories. Subaru Distributors Corp located in Orangeburg, NY serves NY and Northern NJ. Subaru of New England, Inc. located in Norwood, MA serves CT, ME, MA, NH, RI and VT. Finally, Schuman Carriage Co. from Honolulu, HI, serves HI. Subaru Research And Development, Inc., a subsidiary of Fuji Heavy Industries Ltd., is located in Ann Arbor, MI and is involved with advanced design and conducts prototype and emissions testing. Spanning the continental U.S., Subaru is represented by nearly 600 franchised dealerships.

Q: What is a GC8/GDA/etc.?
A: Please visit the Acronym List for any questions about acronyms used on this site.

Q: What is a Trunkmonkey?
A: The Trunkmonkey concept had been floating around the labs for quite a while before anyone actually decided to implement it. Consisting solely of a trained monkey and a steady source of ice cold high-quality import ale or lager, the Trunkmonkey lives in the trunk of any Subaru Impreza, Legacy, Forester or SVX platform vehicle and helps to automate weight transfer at the rear wheels during spirited driving maneuvers. See for more information.

Q: What are popular first mods?
A: Popular first mods would include upgrading your tires, the installation of a larger rear swaybar, short shifters, and cold-air intakes. Common modifications to a WRX include manual boost controllers and the addition of a boost gauge.

Q: What is the "break in period" and if I don't do it, will it hurt my car?
A: The break in period for Subaru is the first 1,000 miles. During this time, you should vary the RPM and speed of the vehicle as much as possible, without racing the engine or exceeding 4,000 rpms unless needed in an emergency situation. The idea is that this allows the engine to wear-in under a variety of conditions without abusing it, giving the seals time to expand and do their job. This is a hot topic of debate as to being necessary or not, though it is strongly recommended by Subaru.

Q: Where can I find a good shop manual, and why are the Subaru shop manuals so expensive?
A: There are no Chilton's or Haynes manuals yet available for the Impreza RS or WRX. The Legacy GT manual is of some help to RS owners, as the Legacy GT does share the same engine. The factory service manuals are the very best thing to have, as they are the same manuals the service department uses when working on your vehicle and are full of the most accurate, up to date information about your car.

Q: Will installing aftermarket parts void my warranty?
A: It is up to the manufacturer to prove that the aftermarket parts directly caused the problem that is under warranty consideration in order to deny warranty work. They cannot void the whole warranty, nor deny warranty work on the alternator for having an aftermarket suspension. However, if your brake rotors warp and you have aftermarket pads, likely expect a warranty claim on the rotors to be denied. There is a federal statue know as the Moss-Magnusson Warranty Act that can be used in defense of a legitimate denied warranty claim:

    Moss-Magnusson Warranty Act
    (15 U.S.C. 2302(C))

    (c) Prohibition on conditions for written or implied warranty; waiver by Commission
    No warrantor of a consumer product may condition his written or implied warranty of such product on the consumer's using, in connection with such product, any article or service (other than article or service provided without charge under the terms of the warranty) which is identified by brand, trade, or corporate name; except that the prohibition of this subsection may be waived by the Commission if -
    • (1) the warrantor satisfies the Commission that the warranted product will function properly only if the article or service so identified is used in connection with the warranted product, and

    • (2) the Commission finds that such a waiver is in the public interest. The Commission shall identify in the Federal Register, and permit public comment on, all applications for waiver of the prohibition of this subsection, and shall publish in the Federal Register its disposition of any such application, including the reasons therefor.

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Q: What is a proper way to break in a new car or a car with a brand new engine?
A: The break in period for Subaru is the first 1,000 miles. During this time, you should vary the RPM and speed of the vehicle as much as possible, without racing the engine or exceeding 4,000 rpms unless needed in an emergency situation. The idea is that this allows the engine to wear-in under a variety of conditions without abusing it, giving the seals time to expand and do their job. This is a hot topic of debate as to being necessary or not, though it is strongly recommended by Subaru.

Q: Where do I wire-in my Air/Fuel Sensor?
A: Most Air/Fuel gauges are designed for narrow-band oxygen sensors (0 to 1 volt). On a WRX, you would tap into ECU connector B135 (28 pin connector) wire 17 (it is solid white). On an 98 RS, it is wire 23 (yellow/blue wire) on the one big connector on the ECU. For 99+ RS, it is wire 18 on connector B136 (30 pin connector) and is solid white in color.

Q: Where do I tap in for my EGT sensor?
A: Conventional wisdom dictates to install the EGT probe 4" away from the hottest running cylinder. On a naturally aspirated vehicle, it can be installed just below the collector on either the driver side or passenger side exhaust header. On a turbocharged vehicle, it is generally advised to place it 4" from the turbocharger instead.

Q: Every time I shift, I hear this "clunk" from the back of my Impreza. Is it normal?
A: Yes, your rear differential is making that noise. It can also be caused my slight free play movement of the driveshaft.

Q: When my car is in gear, I hear a distinctive whine from where the shifter is. Is it normal?
A: Yes, your center differential is making this noise. It is being transferred through the shifter. Cars with aftermarket shifter kits tend to have more/louder noise, due to harder shifter bushings.

Q: What is clutch shudder and how can it be fixed?
A: Clutch shudder is a sometimes violent vibration when releasing the clutch pedal, and is generally worse when it is cold and damp. It can be attributed to a glazed clutch disk, a weak pressure plate, or condensation on the clutch disk face. It is generally a very difficult problem to replicate for the dealership, and not all dealerships will even acknowledge that it is a problem. The most effective way to prevent clutch shudder is to upgrade/replace the clutch disk and pressure plate. Of course, this is an expensive proposition if it is not covered by the factory warranty.

Q: I hear a "ticking" sound after shutting the engine down. What is causing this?
A: Due to the expansion and contraction of the metals used in the manufacture of the exhaust system, you may hear a crackling sound coming from the exhaust system for a short time after the engine has been switched off. This sound is normal.

Q: Can I used leaded fuels in my car?
A: Only if you want to replace an expensive set of O2 sensors and ruin your catalytic converter.

Q: What is a dogbox?
A: The "dog" in dogbox does not refer to the gears at all, but the the shifting mechanism. You can have a dogbox without straight cut gears. And you you can have a straight cut gearbox with synchronizers. Production car gearboxes have helical cut gears to keep them quiet. Straight cut teeth are ususally bigger but there is backlash and the teeth knocking together produce the distinctive gear whine. Production gearboxes also use synchronizers to provide smooth, quiet shifting. The synchro's job is to "grab" the gear when you are shifting and match it to the same speed as the driven shaft to provide a smooth silent shift with no grinding. This happens as you move the lever into the gate for that particular gear. The trouble with synchros is they slow down the shifting process and they have little teeth which aren't so strong compared to the mysterious "dogs". The engaging teeth on the gears are equally small so you could potentially strip all the synchro engaging teeth off the gear and have no more drive in that gear even though all the gear teeth are in perfect condition! A dogshift box does without the synchronizers. Instead you have 6 or 8 big dog "teeth" on the gear. On the shift slider you may have a corresponding number of "slots" that the dogs fit into. The are other designs as well. When you shift since there is no synchro to make the gear speeds match you have to match revs with a blip of the throttle for a smooth shift. But that's not necessarily accurate, really, because you can crash it right in. That's why they are also known as "crashboxes". The clutch is not required when shifting. When accelerating a quick, partial lift of the throttle will do. When downshifting a blip of the throttle to match revs will ensure a smooth shift. A dogbox will shift as fast as you can move the gear lever! No waiting for synchros. Also, the dog mechanisms don't take up as much room as synchros so a wider gear can be fitted.

Q: Can you use a WRX transmission in an RS and vice versa?
A: The RS transmission bell housing is totally different from the WRX. Prop shaft and half shafts are the same between both except the WRX sedan because of wider track. In addition, the WRX runs a 3.90 differential in the front versus the 4.11 for the RS.

Q: Where is the fuel filter?
A: It is located on the driver side front strut tower in the engine bay. It is a small silver or black cannister with several black fuel lines running into it.

Q: What's the difference between turbo back and cat back?
A: A cat-back exhaust system replaces everything from the rear catalytic convertor out to the tailpipe (ie: the midpipe and the exhaust cannister). A turbo-back exhaust would replace everything from the outlet side of the turbo to the tailpipe (ie: the downpipe, midpipe, and cannister).

Q: Whats the torque spec for my spark plugs?
A: Approximately 15 ft-lbs of torque.

Q: When is the best time to switch to synthetic motor oil?
A: The general rule of thumb has been to allow the engine to break in for five to ten thousand miles on "dino" oil before switching to synthetic, to allow the seals to expand. No real evidence of long-term problems has arise from switching from much earlier however, including going to synthetics from day one.

Q: What is an Up-pipe, Down-pipe, and/or Mid-pipe?
A: An Up pipe is the pipe that leads from the exhaust header collector up to the turbocharger. A down pipe leads from the exhaust side of the turbocharger down to meet the midpipe of the exhaust. The Midpipe is the center pipe leading from the catalytic convertor or downpipe to the exhaust cannister.

Q: How do you reset the ECU?
A: There are two methods to achieve this:
    Method One
    With the engine at operating temperature, turn the engine off. Place gear shift lever into park (auto transmission) or out of gear (manual transmission). Locate the two ECU check connectors, for most cars they are located under the steering column and consist of a black plastic male and female connector, and a green male female connector. The exact location of the connectors varies with the different year models, but generally they are located under the steering column on the drivers side (note: sometimes they are still taped over with some small amount of plastic tape). With the ignition OFF connect black to black and green to green. Turn on ignition, do not start the engine, (and for auto transmission, cycle the gearshift lever from park to neutral and back to park ), depress the accelerator pedal to full throttle and hold for a few seconds, and then release. Start engine and then drive for at least one minute, keeping road speed above 10mph. ECU is now re-set. At this point the check engine light should start to flash the all clear signal (steady 1/2 second interval flashes). If the check engine light does not flash, or indicates some other sequence, there is a fault present in the system, and should be professionally checked for necessary repairs. Stop the car, turn off the engine, and disconnect the plugs.

    Method Two
    According to conventional wisdom, you need to disconnect the battery for at least 30 minutes. Reconnect the battery after this time, and then idle the car until the cooling fan cycles at least once to reset the timing maps (approximately 10 minutes). Drive the car as usual.

Q: Where is the ECU?
A: It is under the passenger side foot well. Pull back the carpet and remove the metal plate any you will see it.

Q: Should I replace the crush washer every oil change?
A: Yes. The washer is meant to form a seal between the pan and the oil drain nut, so that you do not have to overtorque the nut to prevent leaks. They cost very little, and should be changed with every oil change.

Q: Whats the K&N Filter Part # for the WRX or RS?
A: RS: 33-2154, WRX: 33-2031-2

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Q: Can I remove the backing plates from my hoodscoop (perhaps to use for an intake) and/or hoodvents?
A: Most modifications to make use of the hoodscoop remove the stock airbox from the intake path, and result in a great deal of low-end power loss for a very small gain in high-end performance. That coupled with the problems of water getting into the filter usually keep people from bothering with trying to use the hood scoop for air intake- it really was designed to feed cool air to a top-mount intercooler, and that is what it does best. Removing the blocking plates will not do any real harm, other than making your engine bay a bit dirty. Alot of people seem to think the plates completely block water off, which they don't, as they have holes in them for drainage. Plenty of water comes into the engine bay via the radiator and front grill openings besides what hits it from below. There are no worries to removing the vent plates, and in fact there is a benefit in removing hot air from the engine bay. Visceral proof of that is available here. The vents on the RS hood are the same as those used on the STi Versions overseas, so no upgrade of the vents themselves is really required for them to be functional.

Q: I hear a 'whistling' noise at high speed- it sounds like it is coming from my passenger side mirror.
A: It's air passing through the crack in the folding mirror. You could put felt or something in there, or have it filled/painted by a body shop.

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Q: Any way to fix my rearview mirror vibration?
A: An owner submits the following suggestion:
    1. Remove the plastic cover which sits on the roof to cover the mirror mounting screws.
    2. Remove all three of the mounting screws to release the mirror arm from the roof.
    3. Remove the central screw holding the plastic spacer onto the mirror arm mount.
    4. Super glue the spacer back onto the arm and quickly refit the central screw , nice and tight but not enough to crack it.
    5. Refit the mirror onto the roof mount with the three screws, again quite tight.
    6. Leave this to dry full-, 24 hours is best.
    7. Now test with a highway drive and you will find the vibration has disappeared!

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Q: Why won't my parking lights shut off?
A: That switch is known as the "parking light switch". One of the greatest Subaru features requires that switch. When you turn the car off, the lights go off too. In order to be legal in some countries - you must be able to put the parking lights on (while parked - imagine that). The switch is there so you don't have to leave the car running.

Q: Why shouldn't I use high-wattage headlamp/foglamp bulbs?
A: In the stock headlamps, the reflectors are chromed plastic, and they are not capable of handling the large amounts of heat created by higher wattage bulbs. In addition, the stock wiring is not up to the task of handling the current draw created by higher wattage bulbs. Upgrading the wiring harness and/or the headlamps themselves enables you to run higher wattage bulbs safely.

Q: What are the size of the stock headlamp/foglamp bulbs?
A: RS Headlamp- H4, Foglamp- H3; WRX Headlamp- 9007, Foglamp H3

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Q: What is understeer?
A: Understeer is when the car plows into a corner. The wheels are turned, yet the car is still going straight.

Q: What is oversteer?
A: Oversteer is when the rear of the car swings outward towards the corner. This is also known as "tail out" and "fish tailing".

Q: What are coilovers?
A: Coilovers are an adjustable spring (or coil) mounted over the dampener. Using a threaded collar - you can adjust the springs up or down on the strut. Raising or lowering the car, and changing the dampening effect.

Q: What is camber?
A: Camber is the angle of the wheels from top to bottom. The more negative camber - the more the top of the wheel is pointed towards the car. A degree or two of negative camber is good for hard turns as the outside wheel is angled to take the force of the corner and keep the car planted in the turn.

Q: What is toe?
A: Toe is the left right angle of the wheels. Sometimes the rear wheels of other cars are placed "toe in" to make the car more stable at high speeds. Where the left wheel is turned right a degree, and the right wheel is turned left a degree.

Q: What are camber plates?
A: Camber plates sit at the top of the strut, and allow the strut to be adjusted in several directions. Changing the attitude of the wheels. You will also see the term pillowball mounts used when discussing camber plates.

Q: What are pillowball mounts?
A: A pillowball mount is basically a ball bearing mounted in stiff rubber - or similar material. These sit on top of your struts, and allow the wheels, struts, and springs to turn when you steer the car.

Q: What is offset?
A: The offset of a wheel is the distance from its hub mounting surface to the centerline of the wheel.

The offset can be one of three types:
  • Zero Offset

  • The hub mounting surface is even with the centerline of the wheel.

  • Positive

  • The hub mounting surface is toward the front or wheel side of the wheel. Positive offset wheels are generally found on front wheel drive cars and newer rear drive cars.

  • Negative

  • The hub mounting surface is toward the back or brake side of the wheels centerline. "Deep dish" wheels are typically a negative offset.
If the offset of the wheel is not correct for the car, the handling can be adversely affected. When the width of the wheel changes, the offset also changes.

Q: Whats the right offset for wheels for my car?
A: The recommended offset for most Subarus is +53mm in a 7" wide wheel. The correct offset is dependent upon the width of the wheel (ie: a +48 offset is acceptable for a 7.5" or 8" wide rim).

Q: Can I use wheel spacers to get the proper offset?
A: Wheel spacers have the opposite effect you are looking for- to get a +50mm offset to a +55mm, you need to remove material. Adding a 5mm spacer to a +50 offset nets you a +45 offset.

Q: What do stainless steel brake lines do and are they worth getting?
A: Stainless steel lines simply do not expand like the stock rubber hoses under extreme pressure when you press your brak pedal. When the rubber hose expands, you waste some of the pressure in your braking system and therefore loose some brake system performance.

Q: What are the torque specifications for wheel lug nuts?
A: Lug nuts should be torqued down to between 58 and 72 ft-lbs.

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