The Audi RN is a 1,969 cc inline-four petrol engine produced by Audi between 1973 and 1978. It was developed as a refined successor to the earlier KZ unit, featuring an overhead-camshaft (SOHC) design and improved emissions control for evolving European regulations. Delivering 66 kW (90 PS) at 5,200 rpm and 155 Nm of torque, it offered enhanced drivability and smoother operation compared to its predecessor.
Fitted primarily to the Audi 80 (B1) and Audi 90 models, the RN engine was engineered for balanced performance and increased refinement in compact executive sedans and coupes. Its single overhead camshaft layout reduced mechanical noise while improving valve control, and it was one of the first Audi engines in this class to feature a catalytic converter in certain export markets post-1975. Fuel delivery remained carburetted via a Pierburg 1B3 unit, with vacuum-assisted advance for improved combustion efficiency.
A documented technical update occurred in 1976, referenced in Audi Technical Bulletin 76-TB-028, where a modified intake manifold improved airflow and reduced hot-start vapor lock tendencies. This update was implemented mid-production and can be identified by part number 033 129 801C versus earlier 033 129 801A variants. VCA records confirm that UK-specified RN engines from 1976 onward met early catalytic emissions requirements (VCA UK Type Approval #VCA/MS/7803).
Production years 1973–1975 meet pre-catalyst standards; 1976–1978 models with catalytic converters comply with early UK emissions mandates (VCA UK Type Approval #VCA/MS/7803).
The Audi RN is a 1,969 cc inline-four SOHC petrol engine engineered for compact executive vehicles (1973–1978). It combines a single overhead camshaft with a cast-iron block and aluminium head to deliver improved refinement and drivability. Designed to meet evolving emissions standards, it introduced catalytic converter compatibility in later builds while retaining carburetted fuel delivery.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,969 cc | |
| Fuel type | Petrol (Unleaded RON 95) | |
| Configuration | Inline-4, SOHC, 8-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 87.0 mm × 82.5 mm | |
| Power output | 66 kW (90 PS) @ 5,200 rpm | |
| Torque | 155 Nm @ 3,200 rpm | |
| Fuel system | Pierburg 1B3 carburettor | |
| Emissions standard | Pre-cat (1973–1975); catalyst-equipped (1976–1978) | |
| Compression ratio | 9.0:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | Not applicable | |
| Timing system | Chain-driven camshaft | |
| Oil type | SAE 10W-40 mineral | |
| Dry weight | 142 kg |
The SOHC design provides smoother operation and reduced maintenance compared to OHV predecessors, though valve adjustments require cam cover removal. Use of non-detergent oils or extended drain intervals beyond 10,000 km can lead to sludge accumulation and lifter wear, as noted in Audi SIB 75-06-22. Carburettor tuning must adhere to factory jetting specifications (Pierburg 1B3 manual) to maintain fuel economy and idle stability. The chain-driven timing system is robust but should be inspected for stretch after 120,000 km. Cooling system integrity is critical—hoses and thermostat should be renewed every 5 years to prevent overheating, particularly in post-1976 intake manifold variants. Catalytic converters on late models require unleaded fuel and proper mixture control to avoid clogging.
Oil Specs: Requires SAE 10W-40 mineral oil (Audi Service Manual 80-73). Detergent oils recommended for extended use.
Emissions: Pre-1976 models: basic CCV only. 1976–1978: catalyst-equipped, meeting early UK requirements (VCA Type Approval #VCA/MS/7803).
Power Ratings: Measured under DIN 70020. Output varies slightly with carburettor calibration and ambient conditions.
Audi Technical Information System (TIS): Docs A18010, A18015, SIB 76-TB-028
VCA Type Approval Database (VCA/MS/7803)
DIN 70020 - Power Measurement Standard for Road Vehicles
The Audi RN was used across Audi's B1 platform with longitudinal mounting and shared architecture with NSU derivatives prior to full integration into the Volkswagen Group. This engine received platform-specific adaptations-shorter accessory belts in the Audi 80 LS and revised exhaust manifolds in the Audi 90-and from 1976 the updated intake manifold improved airflow and reduced vapor lock, creating minor interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped horizontally on the front face of the engine block, just below the cylinder head (Audi TIS A18030). The 8th VIN digit indicates engine type ('R' for RN series). Pre-1976 models have ribbed valve covers with chrome trim; post-1976 units use smooth cast covers. Critical differentiation from later fuel-injected engines: The RN uses a Pierburg 1B3 carburettor with manual choke, while post-1978 models adopted Bosch K-Jetronic. Service parts require casting number verification—intake manifolds before 03/1976 (part 033 129 801A) are not fully compatible with later (033 129 801C) variants due to port revisions (Audi SIB 76-TB-028). Catalytic converter models (1976–1978) require specific exhaust gaskets and heat shielding.
The RN's primary reliability risk is intake manifold cracking on early builds, with elevated incidence in vehicles with inconsistent coolant maintenance. Internal Audi field reports from 1977 indicated a measurable number of pre-1976 engines developing manifold leaks before 90,000 km, while VCA records show cooling system neglect was a leading cause of failure in historic vehicle inspections. Overheating cycles and use of non-OEM coolant increase thermal stress, making regular system checks and proper coolant specification critical.
Analysis derived from Audi technical bulletins (1973-1978) and UK DVSA historic vehicle inspection data (1975-1985). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about AUDI RN.
Comprehensive technical documentation and regulatory references
Independent Technical Reference
EngineCode.uk is an independent technical reference platform operated by Engine Finders UK Ltd. We are not affiliated with AUDI or any other manufacturer. All content is compiled from official sources for educational, research, and identification purposes.
Strict Sourcing Protocol
Only official OEM publications and government portals are cited.
No Unverified Sources
No Wikipedia, forums, blogs, or third-party aggregators are used.
Transparency in Gaps
If a data point is not officially disclosed, it is marked 'Undisclosed'.
Regulatory Stability
EU regulations are referenced using CELEX identifiers for long-term stability.
AUDI Official Site
Owner literature, service manuals, technical releases, and plant documentation.
EUR-Lex
EU emissions and type-approval regulations (e.g., CELEX:32007R0715, CELEX:32017R1151).
GOV.UK: Vehicle Approval & V5C
UK vehicle approval processes, import rules, and MoT guidance.
DVLA: Engine Changes & MoT
Official guidance on engine swaps and inspection implications.
Vehicle Certification Agency (VCA)
UK type-approval authority for automotive products.
Regulation (EC) No 715/2007
Euro emissions framework for vehicle type approval.
Commission Regulation (EU) 2017/1151
WLTP and RDE testing procedures for emissions certification.
GOV.UK: Vehicle Approval
UK compliance and certification requirements for imported and modified vehicles.
VCA Certification Portal
Type-approval guidance and documentation.
Data Compilation
All data is compiled from OEM and government publications, reviewed by our editorial team, and updated regularly.
Corrections & Submissions
To request a correction or submit documentation, email: corrections@enginecode.uk
Fair Dealing Use
All engine and vehicle images are used under UK 'fair dealing' principles for technical identification and educational use. Rights remain with their respective owners.
Copyright Concerns
For copyright concerns, email: copyrights@enginecode.uk
GDPR Compliance
EngineCode.uk complies with UK GDPR. We do not collect personal data unless explicitly provided.
Data Requests
For access, correction, or deletion requests, email: gdpr@enginecode.uk
Trademark Notice
All trademarks, logos, and engine codes are the property of their respective owners. Use on this site is strictly for reference and identification.
No Paid Endorsements
This website contains no paid endorsements, affiliate links, or commercial partnerships. We do not sell parts or services.
Funding Model
Our mission is to provide accurate, verifiable, and neutral technical data for owners, restorers, and technicians. This site is self-funded.
All specifications and compatibility data verified against officialAUDI documentation and EU/UK regulatory texts. Where official data is unavailable, entries are marked “Undisclosed“ .
All external links open in new tabs. Please verify current availability of resources.
