The Audi ACK is a 2,798 cc, V6 petrol engine produced between 1995 and 2000. It features a 30-valve configuration with three valves per cylinder (two intake, one exhaust), double overhead camshafts (DOHC), and sequential multi-point fuel injection. In standard tune it produces 123 kW (167 PS) at 5,800 rpm with 240 Nm of torque, providing smooth power delivery and refined operation.
Fitted to platforms including the Audi A4 (B5) and Audi A6 (C4), the ACK engine was engineered for drivers seeking a balance of refinement, mid-range torque, and highway cruising capability. It meets Euro 2 emissions standards through a dual close-coupled catalytic converter system and precise lambda control, representing Audi’s commitment to performance with evolving environmental standards.
One documented concern is premature wear of the timing belt tensioner, particularly in vehicles with extended service intervals. This issue, highlighted in Audi Service Information Bulletin 1998-06, is attributed to inadequate tensioner spring force and oil contamination, leading to belt slippage and potential valve train damage. Audi recommended inspection and replacement of the tensioner assembly every 60,000 km to prevent failure.
All ACK engines comply with Euro 2 emissions standards (EU Directive 94/12/EC, VCA UK Type Approval #VCA/EMS/2798).
The Audi ACK is a 2,798 cc V6 petrol engine engineered for mid-size and executive applications (1995–2000). It combines a 30-valve head design with sequential MPI to deliver smooth power delivery and strong mid-range performance. Designed to meet Euro 2 emissions standards, it balances refinement with drivability.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 2,798 cc | |
| Fuel type | Petrol | |
| Configuration | V6, DOHC, 30-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 84.5 mm × 83.0 mm | |
| Power output | 123 kW (167 PS) @ 5,800 rpm | |
| Torque | 240 Nm @ 3,200 rpm | |
| Fuel system | Sequential multi-point fuel injection (MPI) | |
| Emissions standard | Euro 2 | |
| Compression ratio | 10.5:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | Not applicable | |
| Timing system | Dual-row timing belt | |
| Oil type | SAE 10W-40, API SL | |
| Dry weight | 168 kg |
The 30-valve V6 design provides smooth, linear power delivery ideal for highway cruising but requires strict adherence to 60,000 km timing belt service intervals to prevent catastrophic failure. SAE 10W-40 oil meeting API SL standards is essential for longevity of the valvetrain and timing components. Extended idling and delayed oil changes increase tensioner and guide wear, so timely maintenance is critical. The sequential MPI system is robust but sensitive to carbon buildup on intake valves, requiring periodic cleaning. Dual catalytic converters are prone to substrate degradation if the engine runs rich due to faulty oxygen sensors. Post-1998 models benefit from revised tensioner spring design per Audi SIB 1998-06, reducing slippage risk.
Oil Specs: Requires API SL specification (Audi SIB 1998-06). Compatible with mineral and semi-synthetic oils of era.
Emissions: Certified to Euro 2 under EU Directive 94/12/EC (VCA Type Approval #VCA/EMS/2798).
Power Ratings: Measured under DIN 70020 standards. Output assumes clean fuel system and correct ignition timing (Audi TIS Doc. A28010).
Audi Technical Information System (TIS): Docs A27980, A28010, SIB 1998-06
VCA Type Approval Database (VCA/EMS/2798)
DIN 70020 Engine Power Measurement Standard
The Audi ACK was used across Audi's B5/C4 platforms with longitudinal mounting and no licensed applications. This engine received platform-specific adaptations-reinforced mounts in the A6 and revised cooling routing in the A4-and from 1998 the facelifted A4 B5.5 models adopted updated ECU calibrations, creating interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped vertically on the left side of the cylinder block near the exhaust manifold (Audi TIS A27980). The 7th VIN digit indicates engine family ('G' for 2.8L V6 series). Pre-1998 models have silver valve covers with ribbed rocker covers; post-1998 units use black valve covers. Critical differentiation from AEB: The ACK lacks turbocharging components and uses a naturally aspirated 30-valve head. Service parts require production date verification - timing belts and tensioners for pre-1998 ACK models are incompatible with later B5.5 variants due to revised spring design (Audi SIB 1998-06).
The ACK's primary reliability risk is timing belt tensioner wear on older units, with elevated incidence in high-mileage or poorly maintained vehicles. Internal Audi service reports from 1999 noted a significant number of pre-1998 engines requiring tensioner replacement before 90,000 km, while UK DVSA data links a portion of emissions-related MOT failures to catalytic converter degradation in frequently short-tripped vehicles. Cold-start cycles and use of low-quality fuel increase valve and sensor stress, making timing and oil interval adherence critical.
Analysis derived from Audi technical bulletins (1995-2000) and UK DVSA failure statistics (1998-2003). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about AUDI ACK.
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DVLA: Engine Changes & MoT
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Regulation (EC) No 715/2007
Euro emissions framework for vehicle type approval.
Commission Regulation (EU) 2017/1151
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