here is likely to change on a daily basis, please use only as
a guide. If you would like to participate in the creation of
this document please get in touch.
Links within document
|For the story from
start to finish see - Subaru
and the Impreza
For other subaru models (Historic) see - 360,
For the performance version see, WRX,
For Subaru VIN Codes see VIN
For information on AWD
- What is it?
For differential information see - Differentials,
LSD ~(Limited Slip)
For flat-4 configuration information see - Flat-4
What is it?
For TurboCharge see - Turbo
Charger - What is it?, Turbo
For BOV (Blow off Valve) see - BOV
For Intercooler information see - Intercoolers
For information about Brake Horse Power see- BHP
For information about Fuji Heavy Industry See-
For information about Engine Knocking see - Engine
For a list of Acronyms please see - Acronym
Subaru and the Impreza
Subaru, a Japanese car company, is a subsidiary of Fuji Heavy
Industries. General Motors is a 20% minority shareholder. "Subaru"
is the Japanese word for the star cluster Pleiades that is depicted
in the company logo. While an automotive minnow compared to
many of its competitors, Subaru has been a highly profitable
company for many years. It is noted for the production of conventional-bodied
cars with full-time all wheel drive (in fact, in many markets
its entire product range has this feature) and its use of the
horizontally-opposed boxer engine (flat engine).
Subaru's best-known vehicles are high performance turbocharged
versions of its Legacy (known as Liberty in Australia), and
Impreza, which offer outstanding performance and handling at
relatively affordable prices. Modified versions of the Impreza
have been competing successfully in car rallies and the World
Rally Championship for many years. Several endurance records
were set in the early and mid-ninties by the Legacy.
Subaru cars (especially Imprezas) are sometimes affectionately
referred to as "Scooby-Doos," "Scoobies", or "Scoobarus," due
to the similarity in pronunciation between "Subaru" and "Scooby
Recently GM has developed the Saab 9-2X model, based on the
Subaru Impreza WRX
The Subaru Impreza is a compact car that was first introduced
by Subaru in 1993. In addition to filling the small-car market
segment among Subaru's offerings in the Japanese, U.S., European
(and various other) markets, the Impreza chassis rose to prominence
in rally racing more effectively than Subaru's previous contenders.
Formerly, Subaru had fielded its larger, mid-size car, the Legacy,
for rally purposes. However, as rally competition shifted toward
smaller and lighter chassis, Subaru needed a smaller and faster
car-a role in which the Impreza was immediately successful and
in which the Impreza continues to compete effectively, albeit
in more powerful versions than were initially introduced.
In 1993, the Impreza was offered in either front-wheel drive
or all-wheel drive versions and only as a four- or five-door
sedan. In later years, the two-door coupé was introduced, although
production of the coupé ended with the introduction of the redesigned
2003 model year. The engine that came in the car initially was
a naturally-aspirated 1.8 flat-4 (the EJ18), followed in successive
years by larger and turbocharged engines. The basic turbocharged
motor, the EJ20, produces 211 bhp.
Starting in 1994, Subaru introduced Subaru Tecnica International
versions of the Impreza in the Japanese and European markets,
which were upgraded in many categories, including performance-tuned
engines and suspensions. The STI
versions of the Impreza were immensely successful in rallies
and popular among street racers. Its top speed is electronically
limited at 250 km/h (155 mph) and it has a 0-100 km/h time of
4.7 seconds. In the United States, release of the basic turbocharged
Impreza (the WRX)
did not occur until the 2002 model year, and the Impreza WRX
was delayed until the 2004 model year; furthermore, the U.S.
version of the STI
includes various departures from the Japanese and European counterparts
(such as a standard-turbo 2.5 L motor in the U.S., rather than
the twin-scroll turbo 2.0 L motor sold elsewhere).
The Impreza brought Subaru three consecutive World Rally Championship
titles (1995-7) and was considered the fastest car in the championship.
The Impreza was Wheels magazine's Car of the Year for 2000.
As of late 2004, the most recent overhaul of the Impreza occurred
with the 2002 model year, with controversial "bug-eyed" styling
for its headlamps, and the discontinuation of the two-door coupé
version. Some customers' and the press's negative reaction to
the look forced Subaru to facelift the car by 2003, with less
unconventional, squarer headlamps.
Models offered in Australia in 2005 include the GX (2.0 L engine,
this model has become the baseline Impreza in Australia), RV
(2.0 L engine, styled for active lifestyles), RS (2.5 L engine,
sport model) along with the WRX
version thereof. The RX model has been abandoned in Australia,
and its position in the Impreza lineup has been subsumed by
the GX (which had formerly been a sparsely outfitted budget
Subaru used the Impreza chassis for the mechanical underpinnings
of the Subaru Forester, a small SUV designed to compete in the
segment comprising the Honda CR-V and Ford Escape; also, the
hatchback-or Impreza Wagon-formed the basis of the Saab 9-2X
released in 2004 (given the tongue-in-cheek moniker, "Saabaru").
The Subaru 360 was the first automobile mass produced by Fuji
Heavy Industries in Japan. Production ran from 1958 to 1969.
The Subaru 360 featured an air-cooled, 2-stroke cycle engine
of 356 cc capacity mounted transversely at the rear. The engine
was designed with a capacity of less than 360 cc so that the
Subaru 360 would qualify for Japan's Keicar class. The body
was of monocoque construction and featured a fiberglass roof
panel, which was considered very advanced in 1958.
When introduced in 1958, the Subaru 360's 356 cc engine turned
out 16 hp and Subaru claimed 71 mpg fuel economy-by the end
of production power had increased to 25 hp with a 36 hp twin
carb engine was an option.
Several variants were produced, including a station wagon (called
the Custom), a convertible, and two sports models known as the
Young S, and the Young SS. A truck and van called Sambar were
also produced using the 360's engine.
The Subaru 360 was replaced by the less popular but more advanced
R-2 which was quickly superseded by the long-lived Subaru Rex
The 360 is the original mass-production Subaru, and for many
years the company searched for ways to capture the car's heritage
in a new model. A string of city car concepts in the 1990s were
tied to the 360 in various ways. In the Subaru Jusmin from the
1991 Tokyo Motor Show, this was simply a yellowish paint color
reminiscent of the 360's. Later concept cars such as the 1997
Elten and 1999 Elten Custom proposed a modern remake of the
360. However, it's not until the subaru R1's release in January
2005, that a production Subaru blatantly cites influence from
the 360. The R1's Motor Show teaser, the R1e, wore a 360-like
The Subaru 1600 can trace its origin back to the Subaru 1000
of 1966, the first front wheel drive Subaru. The Subaru 1000
evolved into the 1100 (also known as the FF-1), which in some
markets was called the Subaru Star. The Star soon added an optional
1300 cc engine-and then came the 1400, and then the 1600 and
The Subaru XT, XT6, and Alcyone are sporty coupes sold from
1985 to 1991. The XT was sold in New Zealand and it and the
XT6 were sold in North America and Europe. The Alcyone was sold
in Japan. All were available in front wheel drive or four/all-wheel
drive (depending on the year) but the all-wheel drive XT was
the only model sold in NZ.
The XT was replaced by the Subaru SVX in 1992.
The Alcyone is named after the brightest star in the Pleiades
star cluster, on which the Subaru logo is based.
Subaru Alcyone SVX
The Subaru Alcyone SVX (also known in the United States simply
as the Subaru SVX) was a mid-sized coupe sold from 1992 to 1997.
Built as a successor to the first-generation Alcyone (also called
the XT), it had a 6-cylinder boxer engine and a unique appearance.
In contrast to the boxy XT, the SVX had unusual, curvy lines
designed by Giorgetto Giugiaro of ItalDesign. Like all Subarus
at the time, it was available in all wheel drive, though many
front wheel drive examples were also produced. The SVX is most
easily recognized by its unconventional split windows.
Subaru BRAT is a pickup version of the regular Subaru 1600
car from the 1970s. The BRAT was developed directly from the
company's four wheel drive station wagon model and was first
introduced as a 1978 model. Similar in concept to the Chevrolet
El Camino, American versions also had Astroturf carpet and welded-in
jumpseats in the cargo area as a tax dodge, as passenger cars
imported into the US were charged a 2.5% tariff, while that
on trucks was 25%. The BRAT was restyled in 1981 and the jumpseats
were removed after 1985. Production continued into the early
1990s but ceased to be imported to North America around 1987.
Subaru FF-1 G
The Subaru FF-1 G (also sold as the 1100 and 1300) was a compact
car from the 1970s, replacing the FF-1 Star. It was a front
wheel drive vehicle with a typical Subaru flat-4 engine. A fully
independent torsion bar suspension and rack and pinion steering
were impressive for the time. The inboard front drum brakes
was an oddity. Also strange were the dual radiators - the car
used only a small radiator (which was also the heater core)
on starting, speeding warmup.
The 1.1 L (1088 cc) and 1.3 L (1267 cc) engines found in the
1100 and 1300 had no cooling fan. An electric fan on the small
radiator cooled the engine. The engines shared the same short
60 mm stroke, but the larger unit was bored to 82 mm rather
than 76 mm. The small engines produced an impressive 80 hp (JIS).
Even in 1972, Subaru boasted about the foul-weather handling
of their cars, and they were quite successful. Priced at just
over US$2,000 and achieving 29 mpg, the Subaru quickly became
one of the top-selling import cars in the United States.
Subaru FF-1 Star
The Subaru FF-1 Star was a development of the original front
wheel drive Subaru, the 1000 with an 1100 cc engine. The FF-1
was marketed as the Star in the United States in 1970 and 1971
model years, and was replaced by the FF-1 G in 1971.
The Subaru Justy is a compact hatchback automobile produced
in the late 1980s and early 1990s.
The Justy was equipped with a 1.2 L three-cylinder engine and
either a standard manual transmission or a novel type of automatic
transmission known as a Continuously variable transmission,
or CVT. The CVT technology was employed because with a conventional
automatic transmission performance would have been unacceptable,
due to the small 3-cylinder engine.
The manual transmission version of the Justy had excellent
mechanical reliability and fuel economy. However, it was small
and noisy as one would expect of an economy hatchback. The five-speed
manual transmission worked reliably, but was far from smooth
to operate because its synchronizers were not very good.
The CVT version was actually able to get reasonable acceleration
out of the small engine, but was unfortunately quite unreliable.
Since the novel automatic transmission was so unreliable, and
the manual transmission, while reliable, was not enjoyable to
operate, the Justy was never a very popular model, and Subaru
abandoned it in many export markets after a few years. This
is especially true due to the fact that its 1990 model was the
last car in the United States that was still carbureted.
In Europe, Suzuki Motors built the Justy for Subaru at its
Hungarian plant. It was merely a rebadged Suzuki Swift. In 2004,
the Justy name continued in European markets on a rebadged Suzuki
The Subaru Leone is a compact automobile produced from June
1971 to February 1989 when it was replaced by the Subaru Loyale,
which was essentially the same car, only with a different name.
The Leone was known as the "GL/DL" in North America. The Leone
was offered in sedan format from launch and station wagon format
starting in September 1972.
The Leone soon became a success in areas where people wanted
four wheel drive (4WD), but didn't want a larger car. It soon
became the world's top-selling 4WD. The car is powered by a
water-cooled, horizontally-opposed, 4-cylinder OHV engine.
The first Subaru Legacy was originally intended to be a Leone
replacement, but the car was moved upmarket. The Leone soldiered
on in Japan. It did not have a direct replacement until the
Subaru Impreza launched in October 1992.
Subaru Loyale was the name given to the former GL and
DL model series in 1990. The name change was triggered
by the introduction of the entirely new Legacy line of cars.
Subaru GL/DLs became very popular in the 1980s in snowy areas
due to their adaptability to extreme cold (you can count on
a Subaru to start at 40 degrees below zero, this cannot be said
of all cars), low price, good fuel economy, and most importantly,
the four wheel drive option. As Subaru GL/DLs were purchased
as utilitarian vehicles, mainly for their practicality in icy
environments, it is rare to find front wheel drive examples
in areas where GL/DLs were popular, and almost as rare to find
sedans or coupes.
However, though these may be the cars that gave Subaru their
popularity in northern climates, they were not perfectly well
adapted to the cold. CV axles and related parts on these vehicles
(even more so than most front wheel drive and four wheel drive
cars) had a tendency to break or wear out quickly in cold weather,
and were relatively expensive to replace (compared to many other
makes). Also, in part due to the width of the boxer engine,
which made access inconvenient, repairs to the engine could
be notoriously difficult, to the point that even in some areas
where these vehicles were very common you could find mechanics
who would refuse to work on them at all.
GL/DL-type names had been in use since the mid 1970s. All GL/DLs
were powered by 1.6 or 1.8 liter carburated flat-4 engines.
2WD models were all fuel injected (with the exception of the
STD and GL Hatchbacks, which remained carbureted until 1989)
starting in 1986 (85 for California) and 4WD models were fuel
injected in 1987 (1986 in California) although 87 4WD models
with carburetors do exist, as the changeover was mid-year.)
The Loyale was similar to the GL-10, althuogh their range of
options ranged from DL to GL-10 levels. (For example, some Loyales
did not have a console surrounding the gear shift, while others
had power everything and a sunroof. Turbo Loyales were only
available in 1990, which also saw the end of the production
of the 3-door coupe, wihch was available as an RS model which
was basically an RX without the turbo.
- DL - Base model, with few options. Manual transmission
most common, although in later years automatics were available.
Most examples were front wheel drive. DL models did not have
a tachometer, oil pressure gauge, or voltage gauge (With the
exception of the DL XT, which did have a tachometer, but no
volt or oil gauges) although most other GL options such as
power windows were available. Most 80-84 models were equipped
with the 1600cc engine, although some models were available
with the 1800cc engine on 4WD models.
- GL - More options than the DL, power windows and
locks available, larger engine available on early models,
turbo option available on later models. Air conditioning,
automatic transmission, and power steering available. 1800cc
engine was only available with the automatic transmission
in 1980, but was available with the manual in 1981, although
it was more common on the 4WD models. Starting in 1985, the
new EA82 overhead cam engine was introduced, which replaced
the EA81 and EA71 cam-in-block engines, except in the 85-89
hatchbacks and the 85-87 Brats.
- GL-10 - Radios, power door locks and windows, power
moonroofs standard. Turbo option available on all years, and
very common on later models.
- RX - GL-10 without a moonroof, but with an upgraded
suspension, standard turbo, and a 5 speed manual transmission
and dual-range 4WD standard. Comparatively rare. There were
two major versions: a sedan and a coupe, which differed mechanically
as well as in body-style. 85 and 86 RX models were part-time
4WD with "shift on the fly" 4WD, that is the vehicle could
shift in and out of 4WD while the vehicle was in motion. It
was also possible to shift between "high" and "low" with the
vehicle in motion, provided the clutch was depressed. Starting
in 1987, the RX switched to a "full time" dual range 4WD in
which a center differential was utilized to allow the vehicle
to remain in 4WD at all times for added traction. A "Diff
Lock" switch allowed the center differential to be locked,
to provide a 50/50 power split for added traction. An automatic
transmission was available in 1989, although it was not very
common. Full time 4WD was also available on the Turbo wagon,
sedan, and 3 door coupe but it was only offered with dual
range on the RX
- Loyale - Replaced all GL and DL models. Essentially
the same as a GL-10, but with a different name.
Turbo models (with the exception of the RX) were not dual range
from the factory, rather they had a vacuum-operated pushbutton
4WD system, with a 4WD switch integraded into the gear shift
knob. It was possible to special order a Turbo model with the
dual range RX transmission, but they didn't come standard that
way. Loyales never came with low range, all were pushbutton
or full-time 4WD.
Production of the Loyale ended in 1994.
The Subaru Rex is a subcompact automobile produced from 1972
The Rex was the replacement for the Subaru R-2, which was meant
to be the replacement for the long lived, but outdated Subaru
360. Because the R-2 was based largely on the 360, it lasted
only a few years. In contrast, the 360 was produced for 11 years
and the Rex was produced for 20.
The Subaru Rex represented a fresh start, having little do
with the Subaru 360, although they did share a rear-engine layout.
The Rex featured a 358 cc rear-mounted two-cylinder, water-cooled,
4-stroke cycle engine, upgraded from the 2-stroke cycle engine
used by the 360 and R-2 models). In 1981, the Subaru Rex became
front wheel drive, and the engine was enlarged to 665 cc in
1982. The end for the Rex came in 1992, when it was replaced
by the Vivio.
The Subaru Vivio is a car. It was introduced in March 1992,
as a 660 cc small car (K-car) manufactured by Subaru.
The name Vivio is a reference to the number 6 6 0 written in
Greek, and also inspired by the word vivid. The Vivio replaced
the Subaru Rex nameplate. It was available in 3 and 5 door versions.
The "Vivio Bistro" is a variation with a retro theme, with Mini-esque
front and rear-end, upholstery of a matching theme and modifications
to the dashboard. The Bistro series was popular and Japan would
see a string of modern small cars modified to appear retro.
Like the larger Subarus, the Vivio was available with a variety
of supercharged 4 cylinder engines, with an emphasis on performance.
The Vivio T-top is a limited production, coupe-convertible
version. It is a two-seater with detachable roof (in two halves).
In October 1998, the keicar regulation changed, prompting manufacturers
to release new models. The Vivio was replaced by the Subaru
Pleo at this time. The Pleo was subsequently replaced by the
Subaru R2 in December 2003.
The Subaru Impreza WRX
is a high-powered, turbocharged version of the Subaru Impreza,
a small all wheel drive sedan. The WRX
has become a popular choice for automobile enthusiasts wherever
it is sold for its high performance, excellent grip and handling,
practicality, and relatively affordable price (approximately
$45,000 Australian, or $25,000 US).
Originally introduced in 1992 in Japan, then shortly afterwards
in Australia and Britain, the WRX
had a turbocharged flat-4 2.0 L engine producing 155 kilowatts
of power (208 horsepower). Compared to the base Impreza, the
had wider low-profile tyres, larger brakes (further improved
in later versions with the fitment of four-piston calipers and
larger discs), and firmer, higher quality suspension components.
Offering the performance and handling of vehicles of far higher
cost, it rapidly became popular with enthusiasts worldwide.
Indeed, it gained a reputation as a popular getaway car for
robberies because the car's precise, yet forgiving, handling
meant that even inexperienced drivers were able to handle it
at high speeds.
The current WRX
is based on the Peter Stevens designed Subaru Impreza WRC. The
now famous instructions given by Prodrive boss David Richards
were to make a car that "looked like it was doing 100 mph, even
when it was standing STIll
in a car park".
A series of low-volume versions with even greater power and
grip were built by Subaru's in-house modifier, Subaru Tecnica
versions of the Impreza, which produces 300 horsepower (224
kW) from new, are often raced, largely unmodified, in production
car circuit racing and stock classes of car rallies to great
success. Introduced in 1994, the STI
has proven to be a very popular high(er)-performance machine
in the Japanese domeSTIc
In the 2002 model year, an all-new version of the car was released,
finally appearing in the United States, with an engine rated
for 227 hp (169 kW) and 217 ft·lbf (294 N·m) of torque. To celebrate
the debut of the STI
in the European market, 1,000 special "ProDrive" models were
produced with exclusive ProDrive interior items designed by
Peter Stevens. The Impreza WRX
was on Car and Driver magazine's Ten Best list for 2002 and
While the new model was more refined and handled better, it
was not as popular with enthusiasts since its greater weight
(approx 3100 lb or 1400 kg) hampered performance slightly. A
higher-powered engine (310 hp or 230 kW) fitted to the Japanese
market version remedied that problem somewhat. In addition to
the sedan model, a 5-door wagon was offered, and met with brisk
sales. Even so, the exterior styling was widely regarded as
somewhat unattractive. As a result, in an unusually early revamp,
Subaru updated the style again for the 2004 model year.
In the 2004 model year, Subaru began selling the highly performance-tuned
in the United States, with a 2.5 L engine with AVCS producing
300 hp (224 kW).
The Subaru Impreza WRX
is used as the basis for the Saab 9-2X.
The Subaru Impreza WRX
(also referred to as simply, STI)
is a high-performance version of the WRX">Subaru Impreza WRX,
tuned by Subaru Tecnica International. Originally sold only
in Japan and Europe, Subaru began selling the STI
in North America in 2004. Available in the Japanese domeSTIc
market with a 2.0 L engine, the North American STI
features a 2.5 L powerplant. The STI
weighs in at nearly 3300 lb.
All US, Japanese, and European models claim 300 hp at
6000 rpm and 300 ft·lbf of torque at 4000 rpm,
although the US claim 0-60 mph times of 4.6 s whereas
the Japanese And European models claim 5.1 s.
has these changes over the standard WRX:
Manual transmission only
Modified body aerodynamics (Including rear spoiler)
Larger Hood Scoop
2.5L (US) Engine (Compared to 2.0L)
300HP (vs. 257)
Driver Controlled Center Differential
Larger disc brakes
High Intensity Discharge headlights
is the only new Impreza not being produced with a San Remo
Red body paint option.
Subaru Tecnica International
is Subaru's motorsports division, similar to RalliArt for Mitsubishi,
TRD for Toyota, AMG for Mercedes-Benz, etc. STI
specializes in the preparation of a variety of vehicles for
rallies such as the World Rally Championship (WRC). It was founded
in 1998 by Subaru to promote the company identity. In recent
years, the WRC has been predominantly won by the heavily modified
555 Impreza, beating many of its rivals such as the Mitsubishi
Lancer Evolution. STI
is an acronym for Subaru Tecnica International, most people
misspell Tecnica with Technica.
The Subaru Impreza WRX
also comes in a high performance STI
edition, designed by STI.
Subaru Vin Codes
The line type is specified in character four of the Subaru
VIN for passenger cars.
The body style is specified in character five of the Subaru
VIN for passenger cars.
The engine type is specified in character six of the Subaru
VIN for passenger cars.
The model is identified in character seven of the Subaru VIN
for passenger cars.
The restraint type is specified as character eight of the Subaru
VIN for passenger cars.
The plant and transmission type is specified in character eleven
of the Subaru VIN for passenger cars.
Plants and transmission types
SIA=Subaru-Isuzu of America FHI=Fuji Heavy Industries
- What is it?
Four wheel drive, 4WD, 4x4, all wheel drive, and AWD
are terms used to describe a four-wheeled vehicle with a drivetrain
that allows all four wheels to receive power from the engine
simultaneously. While many people think exclusively of off-road
vehicles, powering all four wheels provides better control on
slick ice and is an important part of rally racing on mostly-paved
Four wheel drive (4WD or 4x4 for short) was the original term,
often used to describe truck-like vehicles that required the
driver to manually switch between a two wheel drive mode for
streets and a four wheel drive mode for low traction conditions
such as ice, mud, or loose gravel. The "all wheel drive" term
for short) was invented to diSTInguish
vehicles that are capable of driving all four wheels on normal
roads without causing poor control and excessive tire and drivetrain
Flat-4 - What is it?
A flat-4 is a four cylinder internal combuSTIon
engine where the cylinders are arranged in a flat configuration.
This is not a common configuration, but some brands of automobile
have favoured such engines and it is a common configuration
for smaller aircraft engines such as made by Lycoming. Although
they are considered to be superior to "inline-fours" in terms
of refinement and vibration, they have largely fallen out of
favor because their larger overall dimensions are not suited
to modern small cars. The shape of the engine suits it better
for rear engine designs, where the low center of gravity is
an advantage; in front engine designs the width interferes with
the ability of the front wheels to steer.
The open and exposed design of the engine allows air cooling
over water cooling, and in air cooled applications fins are
often seen machined into the external cylinder block walls.
Volkswagen used air-cooled flat-4s extensively in their early
days, in the VW Beetle and most early VW designs. Porsche also
used the VW engine in the early Porsche 356. This engine was
replaced by a Porsche designed Flat-4 in the late 356s and the
912. The 914 that replaced the 912 was built in partnership
with VW using a VW engine.
Citroën used an air-cooled flat-4 on the GS and GSA.
Alfa Romeo introduced a water cooled flat-4 on the Alfasud.
That engine was later used on the Alfa Romeo Arna, the Alfa
Romeo 33, the Alfa Romeo Sprint, the Alfa Romeo 145/146.
Lancia also used a water cooled flat-4 on the high-end Lancia
Subaru produces water-cooled front mounted flat-4 engines that
are confusingly marketed as H-4, by which they mean Horizontal
rather than the H cross-section normally meant by H engine.
When powering two wheels simultaneously, something must be done
to allow the wheels to rotate at different speeds as the vehicle
goes around curves. When driving all four wheels, the problem
is much worse. A design that fails to account for this will
cause the vehicle to handle poorly on turns, fighting the driver
as the tires slip and skid from the mismatched speeds.
One could avoid the following mechanical complexity by simply
using one electric motor per wheel, with speeds under computer
control. This is not normally done though, so...
A differential allows one shaft to drive two output shafts
with different speeds. The differential distributes torque (angular
force) evenly, while distributing angular velocity (turning
speed) such that the average for the two output shafts is equal
to that of the input shaft. Each powered axle requies a differential
to distribute power between the left and right sides. If all
four wheels are to be driven, a third differential can be used
to distribute power between the front and rear axles.
Such a design would handle very well. It distributes power
evenly and smoothly, making it unlikely to start slipping. Once
it does slip though, recovery will be difficult. Suppose that
the left front wheel (of a design that drives all four wheels)
slips. Because of the way a differential works, the slipping
wheel will spin twice as fast as desired while the wheel on
the other side stops moving. (the average speed remains unchanged,
and neither wheel gets any torque) Since this example is a vehicle
that drives all four wheels, a similar problem occurs between
the front and rear axles via the center differential. The average
speed between front and rear will not change, torque will be
matched, torque goes to zero, speed at the rear goes to zero,
and the speed at the front goes to double what it should be...
making the left front wheel actually turn four times as fast
as it should be turning. This problem can happen in both 2WD
and 4WD vehicles, whenever a driven wheel is placed on a patch
of slick ice or raised off the ground. The simpliSTIc
design works acceptably well for a 2WD vehicle. Since a 4WD
is twice as likely to have a driven wheel on an icy patch, the
design is usually considered unacceptable.
Limited Slip Diferential (LSD)
A Limited Slip Differential (LSD) is a modified or derived type
of differential gear arrangement that allows for some difference
in rotational velocity of the output shafts, but does not allow
the difference in speed to increase beyond a preset amount.
In a car or automobile, such limited slip differentials are
sometimes used in place of a standard differential, where they
convey certain dynamic advantages, at the expense of greater
The main advantage of an LSD is found by considering the case
of a standard differential where one wheel has no contact with
the ground at all. In such a case, the contacting wheel will
remain stationary, and the non-contacting wheel will rotate
at twice its intended velocity - the torque transmitted will
be zero and the vehicle will remain stationary. In normal everyday
use on typical roads, such a situation can usually be assumed
to have a vanishingly small probability, and so a normal differential
suffices. For more demanding use however, such as driving off-road,
or for high performance vehicles, such a state of affairs is
undesirable, and the LSD can be employed to deal with it. By
limiting the velocity difference between a pair of driven wheels,
useful torque can be transmitted as long as there is some friction
available on at least one of the wheels.
Turbocharger - What is it?
A turbocharger is a compressor used in internal-combuSTIon
engines to increase the power output of the engine by increasing
the mass of oxygen and fuel entering the engine. A key advantage
of turbochargers is that they offer a considerable increase
in engine power with only a slight increase in weight.
A disadvantage in gasoline engines is that the compression
ratio should be lowered (so as not to exceed maximum compression
pressure and to prevent engine knocking) which lowers engine
efficiency when operating at low power. This disadvantage does
not apply to specifically designed turbocharged diesel engines.
However, for operation at altitude, the power recovery of a
turbocharger makes a big difference to total power output of
both engine types. This last factor makes turbocharging aircraft
engines considerably advantageous-and was the original reason
for development of the device.
Principle of operation
A turbocharger is an exhaust gas driven supercharger. All superchargers
have a gas compressor in the intake tract of the engine which
compresses the intake air above atmospheric pressure, greatly
increasing the volumetric efficiency beyond that of naturally-aspirated
engines. A turbocharger also has a turbine that powers the compressor
using waste energy from the exhaust gases. Compressor and turbine
have the same shaft, similar to a turbojet aircraft engine.
The term supercharger is very often used when referring to
a mechanically driven supercharger, which is most often driven
from the engine's crankshaft by means of a belt (otherwise,
and in many aircraft engines, by a geartrain), whereas a turbocharger
is exhaust-driven, the name turbocharger being a contraction
of the earlier "turbo-supercharger"
The compressor increases the pressure of the air entering the
engine, so a greater "charge" (fuel/air mixture) enters the
engine in the same time interval (the increase in fuel is required
to keep the mixture the same ratio). This greatly improves the
volumetric efficiency of the engine.
The increase in pressure is called "boost" and is measured
in pascals, bars or PSI. The energy from the extra fuel leads
to more overall engine power. For example, at 100% efficiency
a turbocharger providing 100 kPa (1 bar or 14.7 PSI) of boost
would effectively double the power of the engine. However, there
are some parasitic losses due to heat and exhaust backpressure
from the turbine, so turbochargers are generally only about
80% efficient because it takes some work for the engine to push
those gases through the turbocharger turbine (which is acting
as a restriction in the exhaust).
For automobile use, normal maximum boost pressure is 80 kPa
(0.8 bar), but it can be much more. Because it is a centrifugal
pump, a typical turbocharger, depending on design, will only
start to deliver boost from about 2500 engine rpm (1800 in automotive
turbo-diesel engines), while a supercharger will supply some
boost at most engine speeds.
A main disadvantage of high boost pressures for internal combuSTIon
engines is that compressing the inlet air increases its temperature.
This increase in charge temperature is a limiting factor for
petrol engines that can only tolerate a limited increase in
charge temperature before pre-ignition occurs. The higher temperature
is a volumetric efficiency downgrade for both types of engine.
The pumping-effect heating can be alleviated by intercooling
or aftercooling, or both.
When a gas is compressed, its temperature rises. It is not
uncommon for a turbocharger to be pushing out air that is 90
°C (200°F). Compressed air from a turbo may be (and most commonly
is) cooled before it is fed into the cylinders, using an intercooler
or a charge air cooler (a heat-exchange device).
A turbo spins very fast-10,000 to 150,000 rpm depending on
size (using low inertia turbos, 190,000 rpm), weight of the
rotating parts, boost pressure developed and compressor design.
Such high rotation speeds would cause problems for standard
ball bearings leading to failure in a turbo. Most turbo-chargers
use a fluid bearing. This is a flowing layer of oil that suspends
and cools the moving parts. The oil is usually taken from the
engine-oil circuit and usually needs to be cooled by an oil
cooler before it circulates through the engine. Some turbochargers
use incredibly precise ball bearings that offer less friction
than a fluid bearing but these are also suspended in fluid-dampened
cavities. Lower friction means the turbo shaft can be made of
lighter materials, reducing so-called turbo lag or boost lag.
Some car makers use water cooled turbochargers for added bearing
Turbochargers with foil bearings are in development (see picture
above). This design eliminates the need for bearing cooling
or oil delivery systems.
To reduce the possibility of damage to the engine and to also
reduce the amount of time required for the turbo to spool-up
and increase the boost after the quick increase in throttle
opening, turbocharged engines are usually equipped with a blowoff
valve or a bypass valve. This allows the upper-deck air pressure
to be maintained within limits that ensure engine efficiency
To manage the upper-deck air pressure the turbocharger's exhaust
gas flow is regulated with a wastegate that bypasses excess
exhaust gas entering the turbocharger's turbine. This regulates
the rotational speed of the turbine and the output of the compressor.
The wastegate is opened and closed by an electromagnetic coil
or oil pressure that is regulated by pressure of the compressed
air from turbo (the upper-deck pressure) through some form of
Automatic Performance Control or the engine's electronic control
As long as the oil supply is clean and the exhaust gas does
not get too hot (ultra-lean mixtures) a turbocharger can be
very reliable but care of the unit is important. Replacing a
turbo that lets go and sheds its blades will be expensive. The
use of synthetic oils is recomended in turbo engines.
After high speed operation of the engine it is important to
let the engine run at idle speed for two to three minutes before
switching off. Saab, in its owner manuals, recommends only 30
seconds. This lets the turbo rotating assembly run down in speed
and cool from the lower gas temperatures in both the exhaust
and the intake tracts. Not doing this will also result in the
critical oil supply to the turbocharger being severed when the
engine stops while the turbine is STIll
turning at high speed, leading to coking (burning) of the lubricating
oil trapped in the unit and, later, failure of the supply of
oil when the engine is next started causing rapid bearing wear
and failure. Even small particles of burnt oil will accumulate
and lead to choking the oil supply and failure. A turbo timer
is a device designed to keep an automotive engine running for
a pre-specified period of time, in order to execute this cool-down
Diesel engines are much kinder to turbos because their exhaust
gas temperature is much lower than that of gasoline engines
and because most operators allow the engine to idle and do not
switch it off immediately after heavy loading.
A lag is sometimes felt by the driver of a turbocharged vehicle
as a delay between pushing on the accelerator pedal and feeling
the turbo kick-in. This is symptomatic of the time taken for
the exhaust system driving the turbine to come to high pressure
and for the turbine rotor to overcome its rotational inertia
and reach the speed necessary to supply boost pressure. The
directly-driven compressor in a supercharger does not suffer
this problem. Conversely on light loads or at low RPM a turbocharger
supplies less boost and the engine is more efficient than a
Lag can be reduced by reducing the rotational inertia of the
turbine, for example by using lighter parts to allow the spin-up
to happen more quickly. Ceramic turbines are a big help in this
direction. Another way to reduce lag is to change the aspect
ratio of the turbine by reducing the diameter and increasing
the gas-flow path-length. Increasing the upper-deck air pressure
and improving the wastegate response help but there are cost
increases and reliability disadvantages that car manufacturers
are not happy about. Lag is also reduced by using a precision
bearing rather than a fluid bearing, this reduces friction rather
than rotational inertia but contributes to faster acceleration
of the turbo's rotating assembly.
Another common method of equalizing turbo lag, is to have the
turbine wheel "clipped", or to reduce the surface area of the
turbine wheel's rotating blades. By clipping a minute portion
off of the tip of each blade of the turbine wheel, less restriction
is imposed upon the escaping exhaust gases. This imparts less
impedance onto the flow of exhaust gasses at low RPM, allowing
the vehicle to retain more of its low-end torque, but also pushes
the effective boost RPM to a slightly higher level. The amount
a turbine wheel is and can be clipped is highly application-specific.
Turbine clipping is measured and specified in degrees.
Other setups, most notably in V-type engines, utilize two identically-sized
but smaller turbos, each fed by a separate set of exhaust streams
from the engine. The two smaller turbos produce the same (or
more) aggregate amount of boost as a larger single turbo, but
since they are smaller they reach their optimal RPM, and thus
optimal boost delivery, faster. Such an arrangement of turbos
is typically referred to as a "twin turbo" setup.
Some car makers combat lag by using two small turbos (like
Toyota, Maserati, Mazda, and Audi). A typical arrangement for
this is to have one turbo active across the entire rev range
of the engine and one coming on-line at higher RPM. Early designs
would have the smaller turbocharger active up to a certain RPM
limit, after which the exhaust gases were shunted away from
the small turbo to the larger one. Being individually smaller
they do not suffer from excessive lag and having the second
turbo operating at a higher RPM range allows it to get to full
rotational speed before it is required. Such small/large combinations
are referred to as "sequential turbos". Sequential turbochargers
are usually much more complicated than single or twin-turbocharger
systems because they require what amount to three sets of pipes-intake
and wastegate pipes for the two turbochargers as well as valves
to control the direction of the exhaust gases.
Lag is not to be confused with the boost threshold, however
many publications STIll
make this basic mistake. The boost threshold of a turbo system
describes the minimum turbo RPM at which the turbo is physically
able to supply the requested boost level. Newer turbocharger
and engine developments have caused boost thresholds to steadily
decline to where day-to-day use feels perfectly natural. Putting
your foot down at 1200 engine rpm and having no boost until
2000 engine rpm is an example of boost threshold and not lag.
For racing the motor avoids <2000rpm and therefore spool-up.
A variable geometry avoids variable rpm for the rotor and therefor
Boost refers to the increased manifold pressure that is generated
by the intake side turbine. This is limited to prevent detonation
by controlling the wastegate which shunts the exhaust gasses
away from the exhaust side turbine
A wastegate is a valve that diverts exhaust gases away from
the turbine wheel in a turbocharger. Diversion of exhaust gases
causes the turbine to lose speed, which in turn reduces the
rotating speed of the compressor. The primary function of the
wastegate is to stabilize boost pressure in turbocharger systems.
Blow Off Valve
A blowoff valve is a vacuum operated valve that is located after
a turbocharger on an internal combuSTIon
engine, but before the throttle body butterfly valve and intake
manifold. Its use is to vent extra pressure being developed
by the turbocharger when the throttle is closed, such as during
a shift. During a shift in a car with a manual transmission,
the throttle plate is closed. The pressure from the turbocharger
has nowhere to escape to. The pressure pressing against the
throttle plate will produce a pressure wave in the opposite
direction, causing possible damage to the turbocharger turbines
and may also slow or even stop the turbine, thus causing turbo
lag when the throttle is pressed again.
A blowoff valve is connected by a vacuum hose to the intake
manifold after the throttle plate. When the throttle is closed,
a strong vacuum develops in the intake manifold after the throttle
plate and "sucks" the blowoff valve open. The excess pressure
from the turbocharger is vented into the atmosphere or into
the intake. Blowoff valves have a very diSTInguised
"psshh" sound that is desired by many who own turbocharged cars.
Some blowoff valves are marketed with trumpet shaped exits that
amplify the "psshh" sound. It is also sometimes called a "dump
valve", "bypass valve" or "hooter valve".
Blowoff valves are generally not required on automatic transmission
vehicles. Automatic transmission vehicles shift without closing
the throttle but are STIll
fitted by a lot of manufacturers, this is so the is able to
provide boost sooner if if the throttle is only releasd for
An intercooler is a device used on turbocharged
and supercharged internal combuSTIon
engines to improve the volumetric efficiency and increase the
amount of charge in the engine, thereby increasing power. The
inter in the name refers to its location compared to the compressors;
the coolers were typically installed between multiple stages of
supercharging in aircraft engines. Modern automobile designs are
technically aftercoolers because they appear at the very end of
the chain, but this name is no longer used.
Turbochargers and superchargers compress incoming air, causing
it to become heated (see the universal gas equation). Since
hot air is less dense than cooler air, the total charge delivered
to the cylinders is less than it could be. By cooling the charge
after compression, even more charge can be delivered, increasing
power. Additionally, intercoolers help to increase the total
amount of boost allowable prior to the beggining of detonation
in the cylinder by decreasing the temperature of the air charge.
An intercooler is essentially a radiator tuned for high flow
rates and the increasing density of the charge as it cools.
Most designs use ambient air for cooling, flowing through the
radiator core, and often colocated with other radiators for
oil or cooling fluid. An alternate design, often referred to
as a charge cooler, uses water to cool the charge, then cools
the water in a separate radiator. While heavier and more complex,
charge coolers can often make arranging the rest of the engine
Intercoolers need to be mounted so as to maximize air flow
and promote efficient cooling. Cars such as Saab or Mitsubishi
Lancer Evolution use front-mounted intercoolers mounted vertically
near the front bumper, in line with the car's radiator. In contrast,
cars such as the Subaru Impreza WRX
mount the intercooler horizontally on top of the engine and
use a hood scoop to force air over the intercooler. Some World
Rally Championship cars use a reverse-induction setup, where
air from ducts in the front bumper is forced up over a horizontally-mounted
intercooler and then vented through ducts in the top of the
BHP - Brake Horse Power
Brake horsepower was a term commonly used before the 1970s in
the United States, and is STIll
common in the United Kingdom. It indicates the brake, the device
for measuring the true power of the engine. Stating power in
'bhp' gives some indication this is a true reading, rather than
a calculated or predicted one. However, several manufacturers
started to strip their engines of essential ancillaries for
the purposes of getting a high horsepower figure to use in marketing
Knocking (also called pinking or pinging)-technically detonation-
in internal combustion engines occurs when fuel in the cylinder
is ignited by the firing of the spark plug and smooth burning
proceeds but some of the unburned mixture in the combustion
chamber explodes before the flame front can reach it, combusting
suddenly before the optimum moment of the four-stroke cycle.
The resulting shockwave collides with the rising piston, creating
a characteristic metallic "pinging" sound.
The fuel/air mixture is normally ignited slightly before the
point of maximum compression to allow a small time for the flame-front
of the burning fuel to expand throughout the mixture, so that
maximum pressure occurs at the optimum point. The flame-front
moves at about 1100 feet/second during normal combustion. It
is only when the remaining unburned mixture is heated and pressurized
by the advancing flame front for a certain length of time that
the knocking effect occurs. It is caused by an instantaneous
ignition of the remaining fuel/air mixture in the form of an
explosion. The cylinder pressure rises dramatically beyond design
limits. If allowed to persist detonation will cause vibration
and damage to engine parts.
Detonation can typically be prevented by:
The use of higher octane petrol
The addition of octane-increasing "lead", isooctane, or other
Reduction of cylinder pressure by increasing the engine revolutions
or reducing the load on the engine, or both
Reduction of in-cylinder temperatures (such as through cooling
or compression ratio reduction), or
Retardation of spark plug ignition.
Adding water in the form of humidity to the air.
Proper combustion chamber design which concentrates mixture
near the spark plug and generates high turbulence to promote
fast even burning.
Correct ignition timing is essential for optimum engine performance
and fuel efficiency. Modern automotive and small-boat engines
have sensors that can detect knock and delay the spark plug
firing to prevent it, allowing engines to safely use petrol
of lower octane ratings, with the consequence of reduced power
These knock sensors work by using a small piezoelectric microphone
connected to the ECU. Spectral analysis is used to detect the
trademark frequency produced by detonation at various RPMs.
When detonation is detected, ignition timing is retarded, reducing
the knocking and protecting the engine.
Detonation is a different phenomenon from pre-ignition, which
occurs when the air/fuel mixture in the cylinder (or even just
entering the cylinder) ignites before the spark plug fires.
Pre-ignition is caused by an ignition source other than the
spark. Heat can buildup in engine intake or cylinder components
due to improper design or maintenance, or overheating of the
air/fuel mixture during compression. This heat buildup can only
be prevented by eliminating the overheating (through redesign)
or the compression effects (by reducing the load). As such,
if pre-ignition is allowed to continue for any length of time,
power output reduces drastically and engine damage can result.
Pre-ignition may lead to detonation and detonation may lead
to pre-ignition or either may exist separately.
A coilover is an automobile suspension device. It consists of
a shock absorber with a coil spring encircling it. This provides
for optimal damping without torsional loads. Many coilovers
are adjustable for ride height as well using a simple threaded
perch similar to a nut. Note that coilovers are not the same
as struts - the former are not designed as wheel-location devices,
while the latter are integral to this function.
Fuji Heavy Industries,
A descendant of the Nakajima Aircraft Company (est. 1917), Fuji
Heavy Industries (FHI) was established on July 15, 1953 when
five Japanese companies joined to form one of Japan's largest
manufacturers of transportation equipment. Currently, FHI employs
more than 15,000 people worldwide, operates nine manufacturing
plants and sells products in 100 countries. It is currently
20% owned by General Motors.
FHI has four main divisions. The automobile division, Subaru,
has been manufacturing and selling automobiles since 1958 and
now has 1,970 dealers in 100 countries. The aerospace division
is a contractor for the Japan Defense Agency and markets and
sells both commercial and defense-related aircraft, helicopters
and target drones. The industrial products division manufactures
and sells equipment under the Robin brand. Finally, the transportation
equipment division builds several types of buses, garbage trucks,
and prefabricated housing.
The company's four divisions all share their technological
advancements with one another, which has made FHI a leader in
innovation. In particular, they apply a great deal of their
aircraft technology to their automotive division, the most notable
example being the horizontally-opposed boxer engines used in
all modern Subaru automobiles.
Acronym - Subaru Impreza
1. ABS = Antilock Braking System
2. BOV = Blow Of Valve - VTA = Vent To Atmosphere
3. FMIC = Front Mounted InterCooler
4. TMIC = Top Mounted InterCooler
5. DCCD = Driver Control Centre Differential
6. LSD = Limited Slip Differential
7. ECU = Electronic Control Unit (computer
8. ITC= Ignition Timing Controller
9. STI = Subaru Technical International
10. RPM=Revolution per minute
11. MPH= Miles Per Hour
12. MAF= Mass Air Flow Sensor
13. PPP = Prodrive Performance Pack
14. D/P = down pipe
15. DECAT-Decatted Exhaust Pipe
16. BHP= Break Horse Power
17. OB=Octane Booster
18. JDM=Jap Domestic Market
19. MAP = Manifold Air Pressure (sensor
20. MBC = Manual Boost Controller
21. RB5 = A limited edition Impreza produced in 1999? (was it?)
22. VIN = Vehicle Identification Number
23. P1 = Limited Edtn Prodrive Impreza
24. WR1=Limited Edtn NewAge Impreza
25. 555=sponsors of the Subaru World Rally Team
26. SWRT=Subaru World Rally Team
27. NM's (of torque)= Newton Metres
28. TPS=Throttle Position Sensor
29. MY= My Year of Car (Example MY99 would be a 1999 year of registration)
30. GANGY= Green anorak no girl friend yet... for all the other spotters out there
31. WRC= World Rally Car
32. WRB= World Rally Blue
33. PSI= Pounds per squair inch (measure of pressure)
34. USDM= US domestic market
35. VC= viscous coupling
36. VDC= vehicle dynamic control ............Subaru version of Yaw control
37. WRB= world rally blue
38. WRC= world rally championship
39. WRX= world rally experimental
40. WTB= want to buy
41. WTF= what the Funck
42. YMMV= your mileage may vary
43. TT= twin turbo
44. TT= turbo timer
45. TSB= technical service bulletin
47. TDC= top dead centre
48. T/C = turbo charger
49. TACHO= tachometer
50. SOHC= single overhead camshaft
51. SEMA= speciality equipment markerters association
52. PS= German measure of horse power= Pherdestdrke
53. PSI= pounds per square inch
54. R&D= Research and development
55. RHD= right hand drive
56. RON= research octane number
57. RS= rally sport
58. RWD = rear wheel drive
59. RTFM= read the flipping manual
60. RWHP= Rear wheel horse power (Rolling road measure)
61. RR= rolling road
62. SAE= society of automotive engineers
63. S/C= super charger
64. SEDAN= saloon
65. MAS= mass air flow meter
66. MT= manual transmission
67. NA= normaly aspirated (non turbo)
68. NASIOC= North American Subaru Impreza owners club
69. Nm= Newton Meters (a measurement associated with torque)
70. NOS= Nitrous oxide supplier
71, NOX= Nitrous oxide
72. O2= Oxygen
73. OEM= original equipment manufacturer
74. HID= high density discharge lights
75. IAC= idle air control
76. ICE= in car entertainment
77. JTCC= japanese touring car chapionship
78. KPH= kilometers per hour
79. Kw= Measurement of power (Kilo-watt)
80. LHD= left hand drive
81. EFI= Electronic fuel injection
82. EGR= exhaust gas recirculation
83. EJ20= engine 2.0 litre
84. EJ25= engein 2.5 litre
85. FHI= Fuji Heavy Industries (Subaru parent company)
86. FF= Front engined front wheel drive
87. GT= Grande Tourismo
88. H-4= horizontaly oposed four cylinder engine (boxer engine)
89. Boxer= see above
90. Cd= Coefficient drag (measurement of drag)
91. CE= check engine light
92. CV= constant velocity (joint)
93. Diff= Differential gear
94. DOHC= double overhead camshaft
95. DYNO= Rolling road measuring device
96. EBC= electronic boost controller
97. 5MT= five speed gearbox
98. 6MT= Six speed gearbox
99. AT= Automatic transmission
100. BAR= barometric pressure measurement 1bar=14.7 PSI at sea level 1 atmosphere
101.USDM =US domestic market
102. 22B = Not an acronym, but a special model Impreza released in 1998
103. VVT = Variable Valve Timing
104. DC = Direct Current
105. AVC = Actuator Valve Controller (the thing that bleeds off air that goes to the wastegate actuator
Not an acronym but Applied VIN Chassis Codes
106. GF4 = 2.2L Impreza Wagon
107. GD2 = 2.0L Impreza WRX saloon
108. GC5 =1.8L Impreza saloon
109. GC8 =2.0L Impreza WRX saloon
110. GGA. =2.0L Impreza WRX Wagon
111. GDB. = 2.0L Impreza WRX STi saloon
112. GFC. = 2.2L Impreza Wagon
113. GME. = 2.5L Impreza Coupe
114. GD7. = 2.5L Impreza WRX STi saloon
115. GD2 = 2.0L Impreza WRX saloon
116. GDF. = 2.5L Impreza WRX STi
117. GM6.= 2.5L Impreza Coupe
118. Gatso= revenue collection machine posing as safety device (who's bitter!)
Not an acronym but Applied Model codes
119. GC = Classic Impreza saloon
120. GM = Classic Impreza Coupe
121. GF = Classic Impreza Wagon
122. GD = New Age Impreza saloon:
123. GG = New Age Impreza Wagon
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