Saab D308L Specifications
| Engine Model: Saab D308L |
| Engine Type: 4-cycle 6-cylinder DOHC 24-valve turbocharged liquid-cooled diesel |
| Total Displacement: 180.5 cu.in (2.95 L) |
| Rated Engine Power: 176 Hp (130 kW) at 4000 rpm |
| Fuel System Type: Common rail direct injection |
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The Saab D308L is a 3.0-liter, 24-valve V6 turbocharged
diesel engine sourced from Isuzu, belonging to the 6DE1 family. Introduced in
the early 2000s, this engine served as the flagship diesel powerplant for the
Saab 9-5, offering a combination of refinement, low-end torque, and high-speed
cruising capability that positioned it as an alternative to the smaller
four-cylinder diesel options in the Saab lineup. The D308L was also utilized in
other European vehicles under the Opel and Renault brands, reflecting its
availability across the General Motors-Isuzu alliance of the era.
The D308L is characterized by its 66-degree V-angle, all-aluminum construction,
and advanced for its time Denso common-rail direct injection system. A Garrett
GT25 variable geometry turbocharger (VGT) provided a broad torque band, while
the engine’s lightweight aluminum architecture contributed to vehicle handling
dynamics in the transverse-mounted front-wheel-drive 9-5 platform.
Despite its refinement and performance, the D308L developed a reputation for a
specific thermal-related failure involving the wet cylinder liners, a flaw that
could lead to liner movement, cooling system pressurization, and ultimately
engine failure. This issue has made the engine a high-risk proposition in the
used market, though its operational characteristics remain respected among Saab
enthusiasts.
The D308L is a four-stroke, water-cooled, turbocharged V6 diesel engine
configured for transverse mounting in front-wheel-drive vehicle architectures.
Its 66-degree V-angle was selected to reduce overall engine width for transverse
installation.
Engine Type: 66° V6, 4-cycle, water-cooled, turbocharged diesel.
Displacement: 2,958 cc (180.5 cu.in).
Bore and Stroke: 87.5 mm (3.45 in) x 82.0 mm (3.23 in).
Compression Ratio: 18.5:1.
Valvetrain: DOHC, 24-valve (4 valves per cylinder) with belt drive.
Aspiration: Variable geometry turbocharger (VNT).
Fuel System: Denso common-rail direct injection.
Firing Order: 1-4-2-5-3-6
Redline: 4,800 rpm
Maximum Power: 130 kW (176 hp) at 4,000 rpm.
Maximum Torque: 350 Nm (258 lb-ft) at 1,800 rpm.
Boost Pressure: Variable geometry turbocharger with electronically controlled
vanes.
The cylinder block is manufactured from aluminum alloy
using a high-pressure die-casting process, a material selection that
significantly reduces overall engine mass compared to cast iron V6 diesel
equivalents. The block features a 66-degree V-angle and an open-deck design.
Wet-type replaceable cast iron cylinder liners are employed, pressed into the
aluminum block casting and sealed with O-rings at the bottom. The liners are
designed to be in direct contact with the engine coolant, providing efficient
heat transfer from the combustion chambers.
The block incorporates a deep-skirt design extending below the crankshaft
centerline, with a structural aluminum ladder frame - a bedplate - bolted to the
lower crankcase to support the crankshaft main bearings and enhance bottom-end
rigidity. The main bearing caps are integrated into the bedplate structure. The
block is configured for transverse mounting. A known vulnerability of this block
design involves the retention of the wet cylinder liners; under sustained
thermal stress, the liners can shift downward within the block, compromising the
cylinder head gasket seal and leading to cooling system pressurization.
Block Material: Aluminum alloy
Liner Type: Replaceable, pressed-in wet liners with O-ring seals
Bore Diameter: 87.5 mm (3.45 in)
Main Bearing Configuration: Integrated bedplate with four main bearings
The cylinder heads are constructed from aluminum alloy,
with separate castings for each cylinder bank. Each head utilizes a DOHC
valvetrain with four valves per cylinder - two intake and two exhaust - actuated
by bucket-type tappets. The camshafts are driven by a reinforced rubber timing
belt from the crankshaft, with an automatic spring-loaded tensioner maintaining
belt tension. Hydraulic lash adjusters are integrated into the valvetrain,
automatically maintaining zero valve clearance throughout the engine’s
operational life, eliminating the need for periodic manual valve adjustments.
The combustion chambers are of a pent-roof design with centrally located fuel
injectors and glow plugs. The direct injection combustion system utilizes a
bowl-in-piston design optimized for the high-pressure common-rail fuel delivery.
The intake ports are designed to promote high swirl motion for improved air-fuel
mixing, a critical factor in diesel combustion efficiency.
Head Material: Aluminum alloy.
Valve Configuration: DOHC, 4 valves per cylinder with bucket tappets and
hydraulic lash adjusters.
Valve Diameter (Intake): 30.0 mm (1.18 in).
Valve Diameter (Exhaust): 27.0 mm (1.06 in).
Valve Stem Diameter: 6.0 mm (0.24 in).
Valve Seat Angle: 45 degrees.
Camshaft Drive: Timing belt with automatic tensioner.
The D308L employs a Denso common-rail direct injection
system, one of the early applications of this technology in the Saab lineup. A
high-pressure pump - a three-piston radial-piston type - draws fuel from the
tank and delivers it to a common rail accumulator mounted on the engine. The
system operates at pressures up to 160.0 MPa (23,200 psi), enabling precise fuel
metering and multiple injection events per combustion cycle.
Six solenoid-actuated fuel injectors, one per cylinder, are controlled by the
engine control unit (ECU). The ECU calculates injection parameters based on
input from the accelerator pedal position, crankshaft position, camshaft
position, boost pressure, coolant temperature, and fuel rail pressure sensors.
Multiple injection events - pilot injection, main injection, and post-injection
- reduce combustion noise, improve cold-start performance, and enable diesel
particulate filter regeneration. A fuel cooler is integrated into the system to
maintain stable fuel temperatures.
Injection Type: Common-rail direct injection (Denso system)
Maximum Injection Pressure: 160.0 MPa (23,200 psi)
High-Pressure Pump: Radial-piston type, three-piston design
Injector Type: Solenoid-actuated, multi-hole nozzle
Fuel Requirement: Diesel fuel with minimum cetane number of 51
Fuel Filter: Replaceable cartridge type with integrated water separator
The lubrication system is a fully pressurized, wet-sump
design utilizing a gear-type oil pump mounted to the front of the crankshaft.
The oil pump draws lubricant from a cast aluminum oil pan through a mesh
strainer and circulates it through a full-flow, replaceable oil filter before
entering the main oil gallery. From the gallery, pressurized oil is distributed
to the crankshaft main bearings, connecting rod bearings, camshaft bearings,
hydraulic lash adjusters, timing belt tensioner, and turbocharger bearing
housing.
A pressure relief valve integrated into the oil pump maintains system pressure
within operational limits. The oil pan incorporates a windage tray to reduce oil
aeration. A water-cooled oil cooler is integrated into the oil filter housing to
stabilize oil temperature under sustained high-load operation. The lubrication
system is designed to meet the specific requirements of turbocharged diesel
engines, including adequate oil supply to the variable geometry turbocharger
under all operating conditions.
Oil Type: Diesel-rated SAE 5W-30 or 5W-40 (ACEA A3/B4 or C3 specification)
Oil Capacity (with filter): 5.5-6.0 liters (5.8-6.3 US qt)
Oil Pressure (at 2,500 rpm): 294-392 kPa (42.6-56.9 psi)
Oil Pressure (at idle): 98 kPa (14.2 psi) minimum
Oil Pump Type: Gear-type, crankshaft-driven
The cooling system is a pressurized, liquid-cooled
design engineered to manage the thermal load of a turbocharged V6 diesel engine
in a transversely mounted configuration. A high-efficiency cross-flow aluminum
radiator with an electric cooling fan provides cooling capacity. A
centrifugal-type water pump, driven by the timing belt, circulates coolant
through the cylinder block, cylinder heads, turbocharger bearing housing, and
oil cooler.
A wax-pellet thermostat regulates coolant flow to maintain optimal operating
temperature, with a bypass circuit that allows the engine to warm rapidly. The
cooling system is designed to provide uniform cooling across both cylinder
banks. The system’s ability to maintain consistent thermal management is
critical to the retention of the wet cylinder liners; localized overheating can
contribute to liner movement and subsequent sealing failure.
Coolant Type: Ethylene-glycol based antifreeze with corrosion inhibitors
Coolant Capacity: 9.0-10.0 liters (9.5-10.6 US qt)
Thermostat Opening Temperature: 82-86 °C (180-187 °F)
Thermostat Full-Open Temperature: 95 °C (203 °F)
Radiator Cap Pressure: 108-127 kPa (15.7-18.4 psi)
Water Pump Type: Centrifugal, timing belt-driven
| Intake and Exhaust Systems |
Intake System: Air is drawn through a dry-type paper
element air filter and a hot-wire mass airflow sensor before entering the
turbocharger compressor. Compressed air passes through an air-to-air intercooler
mounted at the front of the vehicle before entering the intake manifold. The
intake manifold is a composite plastic design with integrated charge air
distribution.
Exhaust System: Stainless steel exhaust manifolds from each cylinder bank merge
into a single downpipe. The exhaust system incorporates an oxidation catalytic
converter and a diesel particulate filter on later variants. A heated oxygen
sensor and exhaust gas temperature sensors provide feedback to the ECU for
emissions control.
Ignition System: Not applicable (compression ignition).
Glow plug system provides pre-heating for cold starts. Six sheathed-type glow
plugs, one per cylinder, are controlled by a glow control unit that regulates
pre-heat duration based on coolant temperature, with after-glow functionality to
reduce white smoke during warm-up.
Turbocharger System: Garrett GT25 variable geometry turbocharger (VGT) with
electronically controlled vanes. The VGT system adjusts the turbine inlet
geometry to optimize exhaust gas flow across the turbine wheel, providing
reduced turbocharger lag at low engine speeds and controlled boost at high
engine speeds. The vanes are actuated by a vacuum-operated or electric actuator
controlled by the ECU.
Timing Drive: A reinforced rubber timing belt with integral teeth drives the
camshafts from the crankshaft sprocket. The belt routes around idler pulleys and
is tensioned by an automatic spring-loaded hydraulic tensioner. The engine is of
interference design; timing belt failure results in valve-to-piston contact.
Overall Length: 690 mm (27.2 in)
Overall Width: 780 mm (30.7 in)
Overall Height: 720 mm (28.3 in)
Dry Weight (complete engine): 170 kg (375 lb)
Oil Change Interval: 10,000 km (6,000 mi) under normal
driving conditions.
Oil Change Interval: 5,000 km (3,000 mi) under severe conditions.
Oil Filter Change: At every oil change.
Timing Belt Replacement: 80,000-100,000 km (50,000-60,000 mi) or 5 years.
Engine Coolant Replacement: 60,000 km (40,000 mi) or 2 years.
Fuel Filter Replacement: 20,000 km (12,000 mi) or as indicated by water
separator inspection.
Fuel Water Separator Drain: Every 10,000 km (6,000 mi) to remove accumulated
water.
Glow Plug Inspection: 60,000 km (40,000 mi) for resistance and heating
performance.
Valve Clearance Adjustment: Not required due to hydraulic lash adjusters.
Drive Belt (Accessory) Inspection: Every 10,000 km (6,000 mi) for tension,
cracking, and glazing.
Air Filter Replacement: 30,000 km (18,000 mi) or as indicated by inspection.
Cylinder Head Bolts (M10 x 1.25), 1st pass: 30 Nm (22
lb-ft).
Cylinder Head Bolts (M10 x 1.25), 2nd pass: 60 Nm (44 lb-ft) + 180° rotation.
Main Bearing Bedplate Bolts (M8 x 1.25): 20 Nm (15 lb-ft) + 90° rotation.
Connecting Rod Cap Bolts (M8 x 1.0): 20 Nm (15 lb-ft) + 90° rotation.
Camshaft Bearing Cap Bolts (M6 x 1.0): 10-12 Nm (89-106 lb-in).
Intake Manifold Bolts (M8 x 1.25): 20-25 Nm (15-18 lb-ft).
Exhaust Manifold Nuts (M8 x 1.25): 20-25 Nm (15-18 lb-ft).
Glow Plugs: 15-20 Nm (11-15 lb-ft).
Oil Pan Bolts (M6 x 1.0): 10-12 Nm (89-106 lb-in).
Water Pump Bolts (M8 x 1.25): 20-25 Nm (15-18 lb-ft).
Turbocharger Mounting Nuts (M10 x 1.25): 35-40 Nm (26-30 lb-ft).
Crankshaft Pulley Bolt (M16 x 1.5): 250-280 Nm (184-207 lb-ft).
Flywheel / Drive Plate Bolts (M10 x 1.25): 45 Nm (33 lb-ft) + 90° rotation.
The Saab D308L engine was utilized across a limited
range of vehicles within the General Motors alliance during the early 2000s,
primarily serving as a premium diesel option for mid-size and large executive
vehicles.
Saab 9-5 (YS3E): 2001-2005 model years (badged as 3.0 TiD).
Opel / Vauxhall Vectra C: 2002-2005 model years (badged as 3.0 V6 CDTi).
Opel / Vauxhall Signum: 2003-2005 model years (badged as 3.0 V6 CDTi).
Renault Vel Satis: 2002-2005 model years (badged as 3.0 dCi).
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