Audi CDHB Specifications
| Engine Model: Audi CDHB |
| Engine Type: 4-cycle inline 4-cylinder DOHC 16-valve liquid-cooled gasoline |
| Total Displacement: 109.7 cu.in (1.79 L) |
| Rated Engine Power: 158 Hp (118 kW) at 6200 rpm |
| Fuel System Type: Direct fuel injection |
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The Audi CDHB is a 1.8-liter, 4-cylinder turbocharged
petrol engine belonging to the EA888 Gen 2 family, a lineage recognized for its
balance of performance and efficiency through technologies like FSI direct
injection and forced induction. Produced between approximately 2008 and 2012,
this powerplant was designed for longitudinal installation, serving as a core
power unit for the Audi A4 (B8) and A5 model lines. It represents a
higher-output variant within its displacement class, distinguished from the
closely related CDHA engine by a specific engine control unit calibration that
yields a standard output of 160 hp.
The CDHB embodies a period of advanced engine development for Audi, combining a
robust cast-iron cylinder block with an aluminum cylinder head to manage the
thermal and mechanical stresses of turbocharging. While praised for its
responsive torque curve and fuel efficiency, this generation gained notoriety
for specific long-term reliability considerations, primarily concerning piston
ring design and timing chain tensioner durability, which are critical focal
points for maintenance and longevity.
Engine Code: CDHB.
Displacement: 1798 cc (109.7 cu.in).
Configuration: Inline 4-cylinder.
Valvetrain: Double overhead camshaft (DOHC), 4 valves per cylinder, 16 valves
total.
Bore x Stroke: 82.5 mm x 84.1 mm (3.25 in x 3.31 in).
Compression Ratio: 9.6:1.
Induction System: Single turbocharger with air-to-air intercooler.
Fuel System: Direct injection (FSI - Fuel Stratified Injection).
Camshaft Drive: Roller timing chain.
Max Power Output: 118 kW (160 PS / 158 hp) at 4500-6200 rpm.
Max Torque: 250 Nm (184 lb-ft) at 1500-4500 rpm.
Top Speed: Approx. 225 km/h (140 mph) - vehicle dependent.
Acceleration (0-100 km/h): Approx. 8.6 seconds - vehicle dependent.
Emission Standard: Euro 5.
Engine Oil Capacity: 4.6 L (4.9 qt).
Oil Specification: VW 502 00 or VW 504 00 (5W-30 or 5W-40 synthetic).
Cooling System Capacity: 8.4 L (8.9 qt) - with G12++ or G13 pink coolant.
Spark Plugs: NGK PFR7S8EG (standard gap: 0.8 mm / 0.031 in).
Firing Order: 1-3-4-2.
The cylinder block is constructed from grey cast iron
with an open-deck design, a configuration selected to provide superior
structural rigidity and thermal stability under the increased stress of
turbocharging. The open-deck architecture allows coolant to flow freely around
the upper portion of the cylinder bores, enhancing heat dissipation from the
cylinder head interface. The bore dimensions are set at 82.5 mm (3.25 in),
machined to a precise finish to accommodate the high-silicon aluminum alloy
pistons.
Within the block, the crankshaft is supported by five main bearings, each fitted
with steel-backed aluminum shells to ensure durability and consistent oil film
formation. The engine incorporates a forged steel crankshaft with eight
counterweights, contributing to smooth operation and resistance to torsional
vibrations. A structural aluminum oil pan, bolted to the underside of the block,
serves not only as an oil reservoir but also as a structural component to
increase overall powertrain stiffness.
The cylinder head is manufactured from lightweight
aluminum alloy, utilizing a cross-flow design to optimize intake and exhaust gas
routing. It houses a dual overhead camshaft (DOHC) arrangement, where the intake
and exhaust camshafts are driven by the timing chain. Each camshaft actuates the
16 valves through low-friction roller finger followers.
Valve diameters are optimized for forced induction: intake valves measure 34.0
mm (1.34 in) in diameter, while exhaust valves are 28.0 mm (1.10 in). The
valvetrain incorporates a continuously variable valve timing system on both the
intake and exhaust camshafts, a technology designated as Audi Valvelift System
on the exhaust side in some applications, allowing for precise control over
valve overlap to enhance low-end torque, reduce emissions, and improve fuel
economy.
The valves are sealed with three-piece stem seals to minimize oil consumption
into the combustion chambers. The direct-injection fuel injectors are mounted
centrally within the cylinder head, positioning the injector nozzle directly
into the combustion chamber to facilitate stratified and homogeneous combustion
modes.
The fuel system is a high-pressure direct injection
architecture, branded as FSI (Fuel Stratified Injection). A low-pressure fuel
pump, located within the fuel tank, delivers petrol to a high-pressure fuel pump
mounted on the cylinder head. This high-pressure pump, driven by a cam lobe on
the intake camshaft, generates fuel pressures up to 150 bar (2176 psi).
The pressurized fuel is then routed through a stainless steel fuel rail to
six-hole solenoid injectors that spray fuel directly into the combustion
chambers. This system enables precise fuel metering, stratified charge operation
during light loads to improve thermal efficiency, and homogeneous operation
under higher loads for maximum power. The high-pressure system necessitates
meticulous cleanliness during service to prevent injector fouling or internal
pump damage.
The lubrication system is a pressurized wet-sump design
with a capacity of 4.6 L (4.9 qt). A gear-type oil pump, driven directly by the
crankshaft, provides a high volume of oil flow to critical engine components.
The pump is equipped with a pressure relief valve to maintain stable oil
pressure across the engine speed range. Oil is filtered through a full-flow
paper element filter, integrated into a filter housing that incorporates an
anti-drain-back valve to ensure rapid oil pressure buildup on cold starts.
The system is designed to supply a high-pressure oil circuit for the camshaft
phasers and the timing chain tensioner, making the choice of correct oil
viscosity (VW 502 00 or 504 00 specification) critical for proper operation of
these components. An oil cooler, integrated with the filter housing, uses engine
coolant to stabilize oil temperature.
The cooling system is a pressurized, liquid-cooled
setup with a total capacity of 8.4 L (8.9 qt). It employs a water pump driven by
the toothed rubber belt from the crankshaft, circulating G12++ or G13 ethylene
glycol-based coolant. The system includes a dual-circuit configuration to manage
thermal demands of the engine block and cylinder head independently,
facilitating faster warm-up and reduced friction.
A map-controlled thermostat allows the engine control unit to actively regulate
coolant temperature for optimal performance and efficiency. The turbocharger is
integrated into the cooling circuit with a dedicated coolant supply line, and
after engine shutdown, a separate electric auxiliary water pump continues to
circulate coolant to the turbocharger bearings to prevent localized overheating
and oil coking.
Engine Management: The engine is governed by a Bosch
Motronic MED 17.5 engine control unit (ECU), which manages fuel injection,
ignition timing, boost pressure, and valvetrain actuation based on inputs from a
network of sensors including a wideband lambda sensor, manifold absolute
pressure (MAP) sensor, and knock sensors.
Ignition System: The ignition system utilizes a coil-on-plug (COP) design, with
an individual ignition coil mounted directly over each spark plug, eliminating
the need for high-tension leads and ensuring a strong, consistent spark under
high cylinder pressures.
Exhaust System: The exhaust manifold is integrated into the cylinder head, a
design that reduces weight and allows the exhaust gases to reach the
turbocharger more quickly, improving catalyst light-off and reducing turbo lag.
The system includes a close-coupled three-way catalytic converter and oxygen
sensors for closed-loop emission control.
Overall Length (including ancillaries): 650 mm (25.6
in)
Overall Width: 620 mm (24.4 in)
Overall Height: 700 mm (27.6 in)
Engine Weight (dry): 145 kg (320 lb)
Engine Oil Change Interval: 15,000 km (9,300 mi) or 12
months, whichever occurs first. Use oil meeting VW 502 00 or VW 504 00
specifications. Oil Filter Replacement: Replace at every oil change. Spark Plug
Replacement Interval: 60,000 km (37,300 mi). Electrode gap: 0.8 mm (0.031 in).
Timing Chain Inspection: Inspection recommended every 80,000 km (49,700 mi) due
to known tensioner vulnerabilities. The early-style mechanical tensioner is a
critical service item; upgrade to the revised "K-version" tensioner is strongly
advised. Coolant Replacement: Replace at 5-year intervals. Use only G12++ or G13
pink coolant.
Air Filter Replacement: Replace every 60,000 km (37,300 mi) or earlier in dusty
conditions. Fuel Filter: The fuel filter is a maintenance-free unit integrated
with the low-pressure fuel pump assembly in the tank. Valve Clearance: Not
adjustable due to hydraulic roller finger followers. Carbon Cleaning: Intake
valve cleaning is a recommended maintenance procedure beyond 80,000 km (49,700
mi) to address carbon deposits from direct injection.
Cylinder Head Bolts (Stage 1): 40 Nm (30 lb-ft)
Cylinder Head Bolts (Stage 2): 90-deg turn
Cylinder Head Bolts (Stage 3): 90-deg turn
Main Bearing Cap Bolts (Stage 1): 50 Nm (37 lb-ft)
Main Bearing Cap Bolts (Stage 2): 90-deg turn
Connecting Rod Cap Bolts (Stage 1): 30 Nm (22 lb-ft)
Connecting Rod Cap Bolts (Stage 2): 90-deg turn
Camshaft Bearing Cap Bolts: 10 Nm (7 lb-ft)
Timing Chain Tensioner Bolt: 10 Nm (7 lb-ft) + 45-deg turn
Intake Manifold Bolts: 10 Nm (7 lb-ft)
Exhaust Manifold Bolts: 20 Nm (15 lb-ft)
High-Pressure Fuel Pump Mounting Bolts: 10 Nm (7 lb-ft)
Engine Mount to Block Bolts: 45 Nm (33 lb-ft) + 90-deg turn
Spark Plugs: 30 Nm (22 lb-ft)
Oil Filter Housing to Block: 25 Nm (18 lb-ft)
Audi A4 (B8) - 2008 to 2012 model years
Audi A5 (8T) - 2008 to 2012 model years
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