Volkswagen AAZ Specifications
| Engine Model: Volkswagen AAZ |
| Engine Type: 4-cycle inline 4-cylinder SOHC 8-valve liquid-cooled diesel |
| Total Displacement: 115.7 cu.in (1.89 L) |
| Rated Engine Power: 60-75 Hp (44-55 kW) at 4400 rpm |
| Fuel System Type: Indirect injection (IDI) |
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The Volkswagen AAZ is a 1.9-liter,
four-cylinder, naturally aspirated and turbocharged diesel engine,
representing the final and most refined evolution of the venerable
1.6/1.9 D diesel family (VW's first-generation water-cooled diesel
engines). Introduced in the early 1990s, it was a significant step
forward from its 1.6 TD predecessor (HY/1Y), offering increased
displacement and, in its most common form, a wastegate-controlled
turbocharger for improved power and torque. The AAZ is a mechanically
simple, indirect injection (IDI) diesel with a Bosch VE rotary injection
pump, renowned for its durability, mechanical simplicity, and ease of
repair.
It was engineered for robustness, featuring a cast-iron block, a forged
crankshaft, and a non-interference valvetrain, making it highly tolerant
of neglect and a favorite for conversions and high-mileage use. While
not powerful or refined by modern standards, its legendary reliability,
mechanical fuel system independence from complex electronics, and
abundant parts supply have cemented its status as a classic workhorse
engine.
Engine Type: Inline-4 cylinder, liquid-cooled, turbocharged (or
naturally aspirated in rare variants), indirect injection (IDI) diesel.
Displacement: 1896 cc (1.896 L) / 115.7 cu.in.
Bore x Stroke: 79.5 mm x 95.5 mm / 3.13 in x 3.76 in.
Compression Ratio: 22.5:1 (turbo), 23.0:1 (naturally aspirated). Firing
Order: 1-3-4-2.
Direction of Rotation: Clockwise (viewed from the front/flywheel end).
Maximum Power Output (Turbo): 55 kW (75 hp) at 4400 rpm. Naturally
Aspirated: 44 kW (60 hp).
Maximum Torque Output (Turbo): 150 Nm (111 lb-ft) at 2400-3400 rpm.
Fuel Requirement: Diesel fuel.
Emission Standards Compliance: Pre-catalytic converter, meets
regulations of the late 1980s/early 1990s (e.g., Euro 1).
Material: Cast iron. Exceptionally robust and heavy, designed for high
durability.
Construction: Deep-skirt design with an integrated upper crankcase.
Features five main bearing caps. The block is drilled for both
mechanical and vacuum lift fuel injection pumps. A main bearing girdle
was used in later production for added rigidity.
Crankshaft: Forged steel, a key upgrade from the cast crankshaft in
earlier 1.6L engines. Supported by five main bearings. Main bearing
journal diameter: 60.0 mm / 2.362 in. Crankpin journal diameter: 47.8 mm
/ 1.882 in. Pistons: aluminum alloy pistons with a deep "Mexican hat"
shaped pre-combustion chamber in the crown, characteristic of indirect
injection diesels.
Connecting Rods: Forged steel I-beam connecting rods.
Material: Cast iron. A notable feature, providing strength but
contributing significant weight.
Head Construction: Single overhead camshaft (SOHC), 8-valve design (2
valves per cylinder). The camshaft is driven by a timing belt.
Valve Arrangement: Inline valves actuated directly by the camshaft lobes
via bucket tappets with shims for valve clearance adjustment. Critical
The AAZ is a non-interference engine; timing belt failure will not cause
valve/piston contact. Variable Valve Timing: None.
Valve Diameters: Intake: 40.0 mm / 1.575 in. Exhaust: 34.0 mm / 1.339
in.
Pre-Combustion Chambers: Threaded "plug-type" pre-chambers are installed
in the cylinder head for each cylinder, where fuel is injected and
initial combustion occurs before propagating to the main chamber.
Injection Type: Indirect injection (IDI) via pre-combustion chambers.
Injection Pump: Bosch VE rotary distributor-type injection pump,
mechanically governed. This is a fully mechanical pump with a built-in
vacuum-controlled fuel shutoff solenoid and a diaphragm for cold start
advance. The pump is driven by the timing belt.
Injectors: Pintle-type nozzles with an opening pressure of 130-135 bar
(1885-1960 psi). They are single-hole nozzles designed for the
pre-chamber system.
Turbocharger (if equipped): Garrett T2 or K14 wastegate turbocharger,
oil-cooled only (no water cooling). Maximum boost pressure is limited to
0.55-0.65 bar (8-9.5 psi).
Glow Plugs: Standard slow-glow plugs for cold starting, controlled by a
timer relay.
Type: Pressure-fed, full-flow filtration with a gear-type oil pump.
Oil Pump: Gear-type pump, driven by the crankshaft.
Oil Filter: Spin-on canister type.
Oil Cooler: Not standard on most passenger car applications. Often added
for heavy-duty or performance use. Oil Capacity (including filter): 4.5
L / 4.75 US qt.
Recommended Oil Grade: High-quality diesel engine oil meeting API CD/CE
or later. Modern CJ-4 synthetic 5W-40 is an excellent choice.
Mineral-based 15W-40 was common.
Operating Oil Pressure: 2.0 bar minimum at hot idle, 4.0-5.0 bar at 2000
rpm or 29 psi (idle minimum), 58-73 psi (2000 rpm).
Type: Pressurized, single-circuit system.
Water Pump: Centrifugal pump, driven by the timing belt.
Thermostat: Wax pellet type, opening temperature 87°C (189°F).
Coolant Capacity: 7.0 L / 7.4 US qt (entire system).
Coolant Type: Conventional ethylene glycol-based antifreeze (G11 or
equivalent).
0Electrical System: 12-volt negative ground.
Starting System: High-torque 1.4 kW or 2.0 kW starter motor.
Alternator: 70-90 amp output.
Vacuum System: Utilizes engine vacuum (from a pump on the injection pump
or alternator) for the turbocharger wastegate actuator, brake booster,
and interior controls.
Overall Length: 580 mm / 22.8 in.
Overall Width: 640 mm / 25.2 in.
Overall Height: 680 mm / 26.8 in.
Dry Weight: 145 kg / 320 lbs (turbo variant).
Engine Oil Change Interval: Every 7,500-10,000 km or 6-12 months. Severe
service: 5,000 km or 4,700-6,200 miles. Oil Filter Change: Every oil
change. Fuel Filter Change: Every 30,000 km (18,600 miles) or 24 months.
Critical to prevent water and contaminants from damaging the injection
pump. Air Filter Change: Every 30,000-60,000 km (18,600-37,300 miles) or
as inspected.
Timing Belt Replacement: CRITICAL for engine operation, though
non-interference. Replace belt, tensioner, and water pump every 60,000
km (37,300 miles) or 5 years. Valve Clearance Adjustment: Check and
adjust (via shims under bucket tappets) every 30,000-60,000 km.
Clearance (cold): Intake: 0.20 mm (0.008 in). Exhaust: 0.40 mm (0.016
in). Injection Timing: Should be checked and set (via pump rotation)
with a dial indicator every 60,000 km or after major service.
Cylinder Head Bolts: Tighten in a specific multi-step sequence. Final
torque: Step 1: 60 Nm (44 lb-ft). Step 2: +90° turn. Step 3: Final +90°
turn (180° total additional rotation). Bolts are stretch bolts and
should not be reused.
Main Bearing Cap Bolts: 80 Nm (59 lb-ft) + 90° turn (for stretch bolts).
Connecting Rod Cap Bolts: 55 Nm (41 lb-ft) + 90° turn (for stretch
bolts, replace).
Injector Hold-Down Clamp Bolt: 25 Nm (18 lb-ft).
Glow Plugs: 15 Nm (11 lb-ft).
Oil Drain Plug: 30 Nm (22 lb-ft).
Flywheel to Crankshaft Bolts: 100 Nm (74 lb-ft) + 90° turn.
Wheel Bolts: 120 Nm (89 lb-ft).
The AAZ engine was used in a wide range of Volkswagen Group vehicles in
the late 1980s and throughout the 1990s, primarily in Europe and Canada.
It was not sold in the United States.
Volkswagen Golf Mk2 (1G): Golf TD, Golf ECOdiesel.
Volkswagen Golf Mk3 (1H): Golf TDI (early, non-direct injection).
Volkswagen Jetta Mk2 (16V): Jetta TD, Jetta ECOdiesel.
Volkswagen Jetta Mk3 (1H): Jetta TDI (early, non-direct injection).
Volkswagen Passat B3 (3A2): Passat TD.
Volkswagen Passat B4 (3A5): Passat TDI (early).
Volkswagen Transporter T4 (7D): Multivan and Caravelle.
Volkswagen Caddy (9K): Pickup and panel van.
SEAT Toledo Mk1 (1L): As a diesel option.
The AAZ was also widely used as an industrial and marine engine due to
its robustness.
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