The Audi BAU is a 1,896 cc, inline-four turbo-diesel engine produced between 2000 and 2003. It features a DOHC 16-valve configuration with a variable geometry turbocharger (VGT) and common rail direct injection, delivering 81 kW (110 PS) at 4,000 rpm and 235 Nm of torque at 1,800 rpm. Its high-pressure injection system enables precise fuel metering and reduced noise for improved refinement.
Fitted to models such as the Audi A4 (B5), A6 (C5), and A3 (8L), the BAU engine was engineered for drivers seeking a balance of low-end torque and fuel economy. Emissions compliance was achieved through exhaust gas recirculation (EGR) and a diesel oxidation catalyst (DOC), allowing it to meet Euro 3 standards across its production run.
One documented concern is premature high-pressure fuel pump wear, highlighted in Audi Service Information Bulletin 01 07 08. This issue, often linked to fuel quality or water contamination, can lead to misfires, power loss, or no-start conditions. From 2002, Audi introduced revised pump calibration and updated fuel filter specifications to improve durability.
Production years 2000–2003 meet Euro 3 emissions standards (VCA UK Type Approval #VCA/EMS/6234).
The Audi BAU is a 1,896 cc inline-four turbo-diesel engine designed for transverse and longitudinal applications in Audi's compact and executive models (2000–2003). It combines common rail injection with a variable geometry turbocharger to deliver strong low-end torque and smooth power delivery. Engineered to meet Euro 3 requirements, it represents an early generation of Audi's modern diesel technology.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,896 cc | |
| Fuel type | Diesel | |
| Configuration | Inline-4, DOHC, 16-valve | |
| Aspiration | Turbocharged | |
| Bore × stroke | 81.0 mm × 92.8 mm | |
| Power output | 81 kW (110 PS) @ 4,000 rpm | |
| Torque | 235 Nm @ 1,800 rpm | |
| Fuel system | Bosch CRS 1.2 common rail (up to 1,350 bar) | |
| Emissions standard | Euro 3 | |
| Compression ratio | 18.5:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | Single variable geometry turbo (Garrett VNT) | |
| Timing system | Timing belt (interval: 120,000 km or 5 years) | |
| Oil type | Audi Longlife 00 (SAE 5W-40) | |
| Dry weight | 142 kg |
The VGT and common rail system provide strong low-RPM torque ideal for urban driving but require strict adherence to 120,000 km or 5-year timing belt service intervals to prevent interference failure. Audi Longlife 00 (5W-40) oil is critical due to its shear stability and protection of hydraulic tappets. Extended idling or short trips can accelerate EGR and intake carbon buildup; periodic cleaning is recommended. The Bosch CRS 1.2 fuel system demands ultra-low-sulfur diesel (ULSD) meeting EN 590 standards to prevent injector and pump wear. Post-2002 models feature updated fuel filter and pump calibration per Audi SIB 01 07 08, improving fuel system longevity. DOC efficiency depends on consistent operating temperatures; frequent short trips increase soot accumulation.
Oil Specs: Requires Audi Longlife 00 (5W-40) specification (Audi SIB 01 07 08). Supersedes ACEA B5 requirements.
Emissions: Euro 3 certification applies to all BAU models (2000–2003) (VCA Type Approval #VCA/EMS/6234).
Power Ratings: Measured under DIN 70020 standards. Output consistent across fuel qualities meeting EN 590.
Audi Technical Information System (TIS): Docs A19950, A20015, SIB 01 07 08
VCA Type Approval Database (VCA/EMS/6234)
DIN Deutsches Institut für Normung: DIN 70020 Power Measurement Standard
The Audi BAU was used across Audi's B5/C5/8L platforms with both longitudinal and transverse mounting. This engine received platform-specific adaptations-shorter intake manifolds in the A3 and revised exhaust routing in the A6-and from 2002 the facelifted A4 B5.5 models adopted minor ECU recalibrations, creating minor interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped vertically on the left-side engine block near the exhaust manifold (Audi TIS A19950). The 8th VIN digit indicates engine type ('U' for BAU in most markets). Pre-2002 models have a silver cam cover with '1.9 TDI' engraving; post-2002 units may have revised ECU connectors. Critical differentiation from ALH: BAU features a variable geometry turbo (VNT) with vacuum actuator, while ALH uses fixed geometry. Service parts require production date verification - fuel pumps for pre-2002 engines differ from later revisions per Audi SIB 01 07 08.
The BAU's primary reliability risk is high-pressure fuel pump failure, with elevated incidence in vehicles operated with poor fuel quality. Internal Audi quality reports from 2003 indicated a notable share of pre-2002 engines requiring pump replacement before 150,000 km, while UK DVSA records show fuel system faults as a common cause of emissions test failure in neglected examples. Frequent short-trip driving increases risk, making adherence to 5-year service limits and fuel filter replacement critical.
Analysis derived from Audi technical bulletins (2000-2003) and UK DVSA failure statistics (2000-2010). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about AUDI BAU.
Comprehensive technical documentation and regulatory references
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DVLA: Engine Changes & MoT
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Regulation (EC) No 715/2007
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Commission Regulation (EU) 2017/1151
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