Audi S4


The Audi S4 is the high performance variant of Audi's compact executive car A4. The original Audi S4, built from 1991 until 1994, was a performance-oriented version of Audi's 100 saloon/sedan. All subsequent S4s since 1997 have been based on the Audi A4; and as the A4 has evolved from one generation to the next, so has the S4.
Like its regular A4 counterpart, all S4 variants have had longitudinally oriented, front-mounted engines. All versions of the S4 have their transmission mounted immediately at the rear of the engine in a longitudinal orientation, in the form of a transaxle, and like all Audi "S" cars, are only available as standard with Audi's quattro all-wheel drive system, using a Torsen-based centre differential system. A more powerful internal combustion engine, larger upgraded brakes, firmer suspension, larger wheels, and distinctive sheetmetal, styling cues and badging have always been amongst the many upgrades the S4 receives over its mainstream 100 and A4 siblings. In markets where the even higher-performance Audi RS 4 is not offered, the S4 is the top-of-the-line trim of the A4 family.
A single turbocharged 2.2-litre inline five-cylinder powered the original C4 version, and a 2.7-litre twin turbocharged V6 engine was found in the B5 generation. The B6 and B7 versions shared a common 4.2-litre V8 engine, the first time that a V8 engine was placed in a compact executive car, placing it in direct competition with the BMW M3 and Mercedes-Benz C32 AMG. The B8 generation uses a supercharged 3.0-litre V6 TFSI engine and competed with the BMW 335i, BMW 335i/340i xDrive, and Mercedes-Benz C350. The current B9 generation is powered by a turbocharged 3.0-litre V6 TFSI engine, with rivals including the BMW M340i xDrive and Mercedes-Benz C450 AMG/Mercedes-AMG C43 4MATIC.
All versions of the S4 have been manufactured at Audi's plant in Ingolstadt, Germany; they are, or have been available as a four-door five-seat saloon and a five-door five-seat Avant body styles since the model's inception in 1991. A two-door four-seat Cabriolet S4 variant was introduced as part of the B6 and B7 generation A4 lineups. The B8 Cabriolet has now been built off the A5 coupe body style and the "S" variant is marketed under the Audi S5 nameplate.

C4 (''Typ'' 4A, 1991–1994)

Factory production of the original Audi S4, usually known as Audi 100 S4, began in August 1991 to serve as the performance version of the newly updated, C4 platform, 100-series four-door, five-seat saloon. First shown to the public at the May 1991 Barcelona Show, it was designed to replace the outgoing C3-based Audi 200 turbo quattro 20V and retained its five-cylinder engine. The 200, Audi's first true sports-saloon, had been discontinued at the end of 1990. Being the first S4 model from Audi, it is commonly referred to as the Ur-S4, derived from the augmentive word.
Audi mildly updated the C4-based model line in 1994 and dropped the 100 nomenclature; all variants of the former Audi 100 line were now re-badged as the Audi A6. In line with the switch in model name, Audi temporarily discontinued the use of the S4 name and began selling an updated but fundamentally identical version of the car, based on the "new" A6 and badged as S6. Despite the change in name, differences between the outgoing S4 and incoming S6 were cosmetic and very light.
An all-new C5-based Audi A6 debuted for 1997, after which the S4 and S6 became distinctly separate models based on very different platforms.
The C4 variant S4 ended factory production after less than three years in July 1994.
One of its most renowned owners was Ayrton Senna who owned a silver Avant, not least because he was the Audi distributor for Brazil.

C4 powertrain

In standard form, the powertrain detail of the C4-based S4 was available with only one engine, a single turbocharged and intercooled version of Audi's 2.2-litre 20-valve inline five-cylinder engine This displaced and was equipped with an advanced Bosch Motronic electronic engine control unit. This engine, developed a motive power output of at 5,900 rpm and of torque at 1,950 rpm. With the five-speed manual transmission, it was able to accelerate from 0- in 6.2 seconds.
Both five- and six-speed manual transmissions were offered to European customers, but a five-speed manual was the only transmission available in North America; a four-speed automatic transmission was available as an option worldwide. Front and rear axle final drive ratio is either 4.111 or 3.889, and the rear axle uses a driver-selectable electro-pneumatic-mechanical switchable diff lock.
Audi's quattro four-wheel-drive system was standard on the C4 S4/S6; a first-generation Torsen-based system which used the "T-1" automatically biasing centre differential was used.
S4/S6 models equipped with a 4.2-litre all-aluminium alloy V8 engine became available to European customers as an option from October 1992, only with the six-speed manual gearbox, in either saloon or Avant body styles.

C4 steering, brakes, wheels & tires

All C4 S4s' came equipped as standard with a conventional fixed-assistance rack and pinion power assisted steering system. An electronically controlled 'servotronic' system, which varied the level of assistance in accordance with the road speed, was available as an option.
There were two different types of high performance brake systems on offer for the C4 S4. All S4s' initially had diameter by thick, radially ventilated disc brakes up front, each with an ATE single-piston sliding caliper inside a 'UFO' styled bell-shaped disc. With the introduction of the V8 engine, a new front brake setup became standard; again the discs used radial ventilation, but these front discs were now sized at by - with a conventionally mounted Lucas-Girling caliper in an external position over the disc. US models had smaller discs. The rear brakes, by and also radially ventilated - remained the same throughout C4 production; they used a Lucas-Girling single-piston sliding caliper with an integrated cable-actuated handbrake mechanism. A Bosch three-channel operation Anti-lock Braking System with a mechanical load sensing valve for the rear brakes was standard throughout production.
For wheel options, the standard five-arm "Fuchs" forged alloy wheels were 8.0Jx16H2 ET40, and were fitted with 225/50 R16 sized tyres. Several other tyre and wheel designs were optionally available: a 7.5Jx15H2 ET40 six-spoke with 215/60 R15 tyres, an 8.0Jx16H2 ET40 five-double-spoke, a 7.5Jx16H2 ET35 six spoke "Avus", and an 8.0Jx17H2 ET40 ten-spoke.

B5 (''Typ'' 8D, 1997–2002)

The second generation S4, also known as the Audi S4 quattro debuted in 1997, with factory production commencing October 1997, as part of the facelifted B5 platform Audi A4 line-up, although it was not available in North America until late 1999.
In addition to the saloon, an estate version –the Audi S4 Avant–was introduced into the lineup from 1998. Production of the B5 S4 ceased in September 2001, although it was still sold together with the next B6 platform generation through 2002 in North America. Examples produced June 2001 to end of production are 2002 Model Year cars, the 10th digit of the VIN being the number "2".

B5 powertrain

The powertrain details of the B5 S4 feature a 2.7-litre twin-turbo 90° third-generation V6 engine. Details of the powerplant include a cast iron cylinder block with two lightweight aluminium alloy cylinder heads. The valvetrain includes 30 valves, twin hybrid-driven double overhead camshafts and variable valve timing for the inlet valves. The intake air is pressurized by two parallel water-cooled BorgWarner K03-series turbochargers; the charged air is cooled by two side-mounted air-to-air intercoolers. It displaces, and is rated to produce a motive power output of at 5,800 rpm, and generates of torque at 1,850 rpm. Engine management was by way of a Bosch Motronic ME 7.1 electronic engine control unit, and helped it meet the European EU-3D emissions standard. In all US-market cars, the engine was detuned to meet US emissions regulations; output was reduced to and .
As in the previous S4, a six-speed C90 manual transmission was standard equipment, as was the Torsen T-2 quattro permanent all-wheel drive system. Final drive ratio is 4.111. A five-speed ZF 5HP19 tiptronic automatic transmission became available for the first time as an option.
The B5 S4 claims acceleration from in 5.7 seconds, and has an electronically limited top speed of, which made it both the quickest saloon/sedan in the Audi model line, and among the quickest saloon/sedans in the world at that time.

B5 suspension, brakes, wheels & tires

The B5 S4 is fitted with 4-wheel independent suspension. The front suspension is a multi-link design with four individual control arms per wheel. The rear suspension is an unequal length double wishbone design; the lower control arms are mounted to a subframe which also carries the differential housing. Shock absorbers, coil springs, and anti-roll bars are fitted front and rear.
The B5 S4 brake system consisted of radially ventilated discs, in diameter by thick up front, and by at the rear. Two-piston Lucas HP2 brake calipers at the front, with Lucas single-piston sliding brake calipers at the rear. A Bosch ABS 5.3 four-channel Anti-lock Braking System and Electronic Differential Lock - Later 2001.5 cars all came with ESP Electronic Stability Program and upgraded tires. The Avant became available as well in North America.
Standard wheels were Audi's die-cast aluminium alloy six-arm 'Avus' 7.5Jx17H2 ET45 wheels, fitted with 225/45 ZR17 performance tyres.

B5 colors & optional equipment

Available exterior colors included; Imola Yellow, Nogaro Blue w/pearl effect. Brilliant Black, Laser Red, Light Silver metallic Cactus Green w/pearl effect, Santorin Blue w/pearl effect, Hibiscus Red w/pearl effect and Casablanca White. The first two colors were exclusive to the S4 model. Solid aluminum mirror housings were standard on later 2001.5+ models. Interior leather was available in Onyx or Silver.
Available options included:
  • Bose premium sound system
  • Audi Navigation System
  • 6-disc CD changer
  • Hands free Motorola cellular telephone
  • Premium Package: Sunroof, HomeLink transmitter, auto dimming mirrors
  • Cold Weather Package: heated front seats, heated outside mirrors, expandable ski sack
  • Sport Package
Silver or blue Alcantara seat inserts with matching armrests in the door cards was a rare option.
The 'Sport Package' also replaced the wood-grain belt line trim with silver aluminum trim, and the wood grain finish around the shifter surround with black plastic. Carbon fiber trim was also available on some models
On the early 2000 models, the Alcantara inserts in the rear seats did not fully extend forward to the front edge of the seat.