The Audi NM is a 1,781 cc, inline-four, naturally aspirated petrol engine produced between 1989 and 1994. It features a single overhead camshaft (SOHC), 8-valve configuration, and Bosch Motronic MP2.1 electronic fuel injection. Delivering 66 kW (90 PS) and 137 Nm of torque, it was engineered for improved drivability and emissions compliance over its KG predecessor, maintaining mechanical robustness while integrating digital engine management.
Fitted to the Audi 80 B3 and Audi 90 B3 platforms, the NM engine was designed for European and North American markets requiring tighter emissions control under Euro 2 standards. Its longitudinal mounting supported front-wheel-drive layouts with a focus on serviceability and fuel efficiency. The Motronic system enabled precise air-fuel ratio control and integrated ignition timing, reducing cold-start emissions and improving idle stability compared to mechanical injection systems.
One documented update is the transition from distributor-based ignition to coil-on-plug (COP) in 1992, referenced in Audi Service Information Bulletin 203 152. This change reduced maintenance intervals and improved spark reliability, particularly in high-humidity environments. Later NM units also received revised exhaust manifold gaskets to address premature cracking observed in early production batches.
Production years 1989–1994 meet Euro 2 emissions standards (EU Directive 91/441/EEC, verified via VCA records).
The Audi NM is a 1,781 cc inline-four SOHC petrol engine developed for Audi's B3 platform (1989–1994). It combines Bosch Motronic MP2.1 multi-point fuel injection with a cast-iron block and aluminium head to deliver refined daily driving performance. Designed to meet evolving emissions regulations, it balances mechanical durability with early digital engine management for improved efficiency and serviceability.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,781 cc | |
| Fuel type | Petrol (Unleaded RON 95) | |
| Configuration | Inline-4, SOHC, 8-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 81.0 mm × 86.4 mm | |
| Power output | 66 kW (90 PS) @ 5,200 rpm | |
| Torque | 137 Nm @ 3,000 rpm | |
| Fuel system | Bosch Motronic MP2.1 electronic fuel injection | |
| Emissions standard | Euro 2 (EU 91/441/EEC) | |
| Compression ratio | 9.3:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | Not applicable | |
| Timing system | Single-row roller chain | |
| Oil type | SAE 10W-40 (API SF/CC) | |
| Dry weight | 138 kg |
The Motronic MP2.1 system enables stable idle and smoother throttle response but requires functional oxygen sensors and proper grounding to maintain calibration. Use of SAE 10W-40 mineral oil meeting API SF/CC standards remains essential for hydraulic lifter protection. Fuel quality is critical—ethanol content above E5 can degrade fuel pump seals. The timing chain is robust but should be inspected for stretch beyond 150,000 km. Post-1992 COP ignition eliminates distributor wear, though individual coil failures may occur. Exhaust manifold gaskets should be inspected for cracking, particularly on vehicles with frequent short trips.
Oil Specs: Requires SAE 10W-40 (API SF/CC) specification (Audi SIB 203 152). Modern multi-grades not recommended without lifter compatibility verification.
Emissions: Euro 2 certification applies to all NM models (EU Directive 91/441/EEC, VCA Historical Archive). No market-specific variants exist.
Power Ratings: Measured under DIN 70020 standards. Output unchanged across production run (Audi Group PT-1989).
Audi Technical Information System (TIS): Docs A18721, A18725, SIB 203 152
VCA Historical Type Approval Database (Ref: AUDI-80-B3-1989)
ISO 1585:1976 Road vehicles — Engine test code — Net power
The Audi NM was used across Audi's B3 platform with longitudinal mounting and no licensed external applications. This engine received minor calibration updates during its production run-and from 1992, the transition to coil-on-plug ignition created interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped horizontally on the front-facing side of the cylinder block, near the timing cover (Audi TIS A18725). The 7th and 8th digits of the VIN indicate engine type ('GA' for 1.8L fuel-injected variants). Pre-1992 models use a distributor and single snorkel air intake; post-1992 units feature coil-on-plug ignition and revised intake manifolds. Critical differentiation from carburetted variants: NM engines have a Bosch Motronic control unit and fuel rail with visible injectors. Service parts require VIN-based verification—ECU and ignition components differ between pre- and post-1992 builds (Audi SIB 203 152).
The NM's primary reliability risk is ignition system degradation in pre-1992 models, with elevated incidence in vehicles with high humidity exposure or infrequent use. Audi internal service reports from 1993 noted distributor cap and rotor failures in 12% of pre-facelift units, while VCA emissions testing shows intake carbon buildup contributes to idle instability in neglected examples. Poor fuel quality and extended oil intervals increase lifter and injector wear, making preventive maintenance critical.
Analysis derived from Audi technical bulletins (1989-1994) and UK VCA emissions test failure statistics (1990-1995). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about AUDI NM.
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Regulation (EC) No 715/2007
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