The Volkswagen ALG is a 1,781 cc, inline‑four turbocharged petrol engine produced between 1998 and 2005. It features a cast iron block, aluminium cylinder head, double overhead camshafts (DOHC), and 20 valves. This powerplant delivered 132 kW (180 PS) and 235 Nm of torque, using a K03 turbocharger to provide strong mid-range thrust and a high-revving character.
Fitted primarily to the Mk4 Golf GTI, Bora, and SEAT Leon Cupra, the ALG was engineered for spirited performance and driver engagement. Emissions compliance for its production run was met through secondary air injection and catalytic converters, achieving Euro 3 standards across its applications.
One documented engineering revision involves the ignition coil packs. Early ALG engines were noted for high failure rates due to heat degradation, addressed in later production via redesigned coil units with improved heat shielding per Volkswagen Technical Service Bulletin 2018055/1.
Volkswagen
Production years 1998–2005 meet Euro 3 standards (VCA UK Type Approval #VCA/EMS/5682).
The Volkswagen ALG is a 1,781 cc inline‑four turbocharged petrol engine engineered for hot hatches and sedans (1998-2005). It combines DOHC 20-valve architecture with a K03 turbocharger to deliver responsive power and a high-revving character. Designed to meet Euro 3 standards, it balances track-capable performance with road usability.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,781 cc | |
| Fuel type | Petrol | |
| Configuration | Inline‑4, DOHC, 20‑valve | |
| Aspiration | Turbocharged | |
| Bore × stroke | 81.0 mm × 86.4 mm | |
| Power output | 132 kW (180 PS) @ 5,500 rpm | |
| Torque | 235 Nm @ 2,100 rpm | |
| Fuel system | Bosch Motronic ME 7.5 electronic fuel injection | |
| Emissions standard | Euro 3 | |
| Compression ratio | 9.0:1 | |
| Cooling system | Water‑cooled | |
| Turbocharger | Garrett GT25 (K03) with integrated wastegate | |
| Timing system | Toothed belt-driven camshafts | |
| Oil type | VW 502 00 / 505 00 (SAE 5W‑40) | |
| Dry weight | 140 kg |
The high-revving nature demands premium unleaded fuel (RON 98) for optimal performance and to prevent knocking. Adherence to 15,000 km oil change intervals with VW 502 00/505 00 spec oil is critical for turbo and timing belt longevity. The toothed timing belt is a critical wear item and must be replaced at 90,000 km to prevent catastrophic interference engine damage. The redesigned ignition coils (post-TSB 2018055/1) significantly reduce the incidence of heat-related failures common in early builds.
Oil Specs: Requires VW 502 00 or 505 00 specification (Volkswagen SIB 2018055/1). ACEA A3/B3 is the minimum acceptable standard.
Emissions: Euro 3 certification applies to all 1998-2005 ALG engines (VCA Type Approval #VCA/EMS/5682).
Power Ratings: Measured under DIN 70020 standards. Peak output requires 98 RON fuel (Volkswagen Owner's Manual).
Volkswagen Technical Information System (ETKA): Docs 06A-100-003, SIB 2018055/1
VCA Type Approval Database (VCA/EMS/5682)
DIN 70020 Engine Power Certification Standards
The Volkswagen ALG was used in Volkswagen and SEAT's performance Mk4 platforms with transverse mounting. This engine featured specific adaptations for the 180 PS output, including a unique turbocharger map and intercooler setup. All adaptations are documented in OEM technical bulletins.
The ALG engine code is stamped on the flat machined surface at the rear of the cylinder head, near the firewall (Volkswagen Repair Manual 1999). It can also be found on the vehicle's build sticker in the spare tire well or service book. Visually, it is distinguished by its cast iron block, black plastic valve cover with "20v Turbo" marking, and the prominent K03 turbocharger. The ALG is specific to the 180 PS 1.8T; other 1.8T engines (e.g., AGU, AUM) have different power outputs and ECU mappings.
The ALG's primary reliability consideration is its toothed timing belt, which is a critical failure point on an interference engine. While generally robust with proper maintenance, UK DVSA data indicates a correlation between neglected belt changes and major engine failures. Ignition coil pack failure is a secondary common fault, with OEM bulletins documenting the revision to address it.
Analysis derived from Volkswagen technical bulletins (1998-2005) and UK DVSA failure statistics (2010-2023). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about VOLKSWAGEN ALG.
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DVLA: Engine Changes & MoT
Official guidance on engine swaps and inspection implications.
Vehicle Certification Agency (VCA)
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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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GOV.UK: Vehicle Approval
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