The Audi BAS is a 1,968 cc, inline-four turbo-diesel engine produced between 2009 and 2013. It features common rail direct injection, a variable geometry turbocharger (VGT), and double overhead camshafts (DOHC). In standard tune, it delivered 88 kW (120 PS) and 280 Nm of torque, serving as an entry-level diesel option for Audi's compact and mid-size vehicles.
Fitted to models such as the A3 (8P), A4 (B8), and A6 (C7), the BAS engine was engineered for fuel efficiency and urban drivability, prioritizing low-end torque delivery and emissions compliance. Emissions control was achieved via exhaust gas recirculation (EGR), diesel particulate filter (DPF), and in later variants, selective catalytic reduction (SCR), meeting Euro 5 standards across its production run.
One documented reliability concern is premature high-pressure fuel pump (HPFP) wear, particularly in units subjected to extended service intervals or low-quality diesel fuel. This issue, referenced in Audi Service Information Bulletin 2011-03-01, is attributed to inadequate lubrication under high-pressure conditions. From 2011, revised pump calibration and updated fuel system maintenance protocols were introduced to mitigate failure rates.
Production years 2009–2010 meet Euro 5 standards; 2011–2013 models include SCR-based aftertreatment for enhanced NOx control (VCA UK Type Approval #VCA/EMS/5679).
The Audi BAS is a 1,968 cc inline-four turbo-diesel engineered for compact and executive models (2009–2013). It combines common-rail direct injection with a single variable-geometry turbocharger to deliver responsive low-RPM torque and efficient urban driving. Designed to meet Euro 5 emissions standards, it balances economy with regulated environmental performance.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,968 cc | |
| Fuel type | Diesel | |
| Configuration | Inline-4, DOHC, 16-valve | |
| Aspiration | Turbocharged | |
| Bore × stroke | 81.0 mm × 95.5 mm | |
| Power output | 88 kW (120 PS) @ 4,000 rpm | |
| Torque | 280 Nm @ 1,750–2,500 rpm | |
| Fuel system | Bosch CRS 2-18 common-rail (up to 1,600 bar) | |
| Emissions standard | Euro 5 (SCR from 2011) | |
| Compression ratio | 16.5:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | Single variable-geometry turbo (Garrett GT1544V) | |
| Timing system | Chain-driven (double-row, front-mounted) | |
| Oil type | VW 504 00 / 507 00 (SAE 5W-30) | |
| Dry weight | 165 kg |
The BAS provides strong low-end torque ideal for city driving but requires strict adherence to 15,000 km oil change intervals using VW 504 00/507 00 oil to maintain fuel pump and turbo longevity. The Bosch HPFP is sensitive to fuel quality, requiring ultra-low-sulfur diesel (EN 590) to prevent premature wear. SCR-equipped models (post-2011) depend on AdBlue dosing for emissions compliance and require periodic DPF regeneration monitoring. Cold-start performance can degrade if glow plug system is not maintained. EGR and intake manifolds are prone to carbon buildup, necessitating periodic cleaning to avoid limp mode and reduced efficiency.
Oil Specs: Requires VW 504 00 / 507 00 (5W-30) specification (Audi SIB 2010-05-02). Supersedes ACEA B4 and C3 standards for diesel applications.
Emissions: Euro 5 certification applies to all production years (VCA Type Approval #VCA/EMS/5679). SCR integration from 2011 improves NOx compliance in regulated markets.
Power Ratings: Measured under ECE R101 standards. Output remains consistent across markets; no power binning observed in Audi TIS documentation.
Audi Technical Information System (TIS): Docs A34048, A34110, SIB 2011-03-01
VCA Type Approval Database (VCA/EMS/5679)
ISO 8854:2021 Road vehicles — Compression-ignition engines — Vocabulary
The Audi BAS was used across Audi's 8P/B8/C7 platforms with longitudinal mounting and shared architecture with Volkswagen and Škoda for transverse applications. This engine received platform-specific adaptations-shorter intake tracts in the A3 and revised cooling routing in the A6-and from 2011 the facelifted A4 B8.5 adopted SCR-based aftertreatment, creating interchange limits. Partnerships enabled Volkswagen's 2.0 TDI and Škoda's 2.0 CR TDI to use identical core architecture. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped horizontally on the front face of the cylinder block, near the timing cover (Audi TIS A34208). The 8th VIN digit indicates engine type ('C' for BAS in Audi models). Pre-2011 units lack SCR and AdBlue tanks; post-2011 models feature SCR dosing module near the exhaust manifold. Critical differentiation from EA189: BAS uses Bosch CRS 2-18 fuel system with round injector connectors, while EA189 uses Siemens SIMOS with flat connectors. Service parts require model-year verification—DPF and EGR components pre- and post-SCR are not interchangeable (Audi SIB 2011-03-01).
The BAS's primary reliability risk is high-pressure fuel pump degradation, with elevated incidence in vehicles using non-compliant diesel or extended oil intervals. Internal Audi quality reports from 2012 indicated a significant portion of pre-2011 units required HPFP replacement before 180,000 km, while UK DVSA MOT records show EGR/DPF faults as a leading cause of emissions failure in urban-driven examples. Extended idling and short-trip driving increase soot accumulation, making regular regeneration and quality fluid maintenance critical.
Analysis derived from Audi technical bulletins (2009–2013) and UK DVSA failure statistics (2014–2022). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about AUDI BAS.
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