Audi CTUB Specifications
| Engine Model: Audi CTUB |
| Engine Type: 4-cycle 6-cylinder DOHC 24-valve supercharged liquid-cooled gasoline |
| Total Displacement: 182.8 cu.in (2.99 L) |
| Rated Engine Power: 329 Hp (245 kW) at 6500 rpm |
| Fuel System Type: Direct fuel injection |
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The Audi CTUB is a 3.0-liter, six-cylinder,
supercharged petrol engine belonging to the EA837 Gen 2 family, marketed under
the “3.0 TFSI” designation. Despite the “T” in its name, which denotes a
turbocharger in Audi nomenclature, this engine utilizes a Roots-type twin-vortex
supercharger. Representing a high-output variant within the EA837 range, the
CTUB was engineered to deliver a broad, flat torque curve and high specific
output, characteristics befitting its placement in Audi’s “S” performance
models.
Deployed between 2012 and 2017, this engine powered the B8.5 generation S4, the
facelifted 8T S5, and the first-generation SQ5, marking a significant step in
performance for these vehicles. Its architecture combines a compact 90-deg
V-angle with a supercharger nestled within the V-valley, creating a low center
of gravity and a responsive power delivery that distinguished this generation of
Audi performance models.
The CTUB displaces 2995 cc (182.8 cu.in), derived from a bore of 84.5 mm (3.33
in) and a stroke of 89.0 mm (3.50 in). The engine configuration is a 90-deg V6
with a double overhead camshaft (DOHC) valvetrain operating 24 valves, four per
cylinder. The geometric compression ratio is set at 10.3:1.
Induction is forced via a Roots-type Twin-Vortex Supercharger (TVS) manufactured
by Eaton. Fuel delivery is managed by a direct injection system (FSI). The
camshaft drive utilizes a timing chain located at the rear of the engine, a
characteristic feature of the EA837 family.
Peak power output is 245 kW (329 hp) at an engine speed between 5500 and 6500
rpm. Maximum torque is 440 Nm (325 lb-ft), sustained from 2900 to 5300 rpm. The
engine complies with Euro 5 or Euro 6 emission standards depending on the market
of sale. The required fuel is premium unleaded, with 98 RON recommended and 95
RON permissible as a minimum.
The cylinder block is manufactured from cast aluminum
alloy, a design choice made to minimize overall engine weight. The cylinder
bores are finished with a sophisticated process using a silicon-aluminum alloy,
creating a wear-resistant surface without the need for conventional cast iron
liners. The block is of a closed-deck design, enhancing structural rigidity
under high cylinder pressures generated by the supercharger system.
A structural aluminum oil pan is attached to the lower block assembly,
contributing to the engine’s overall stiffness and noise, vibration, and
harshness (NVH) characteristics. The 90-deg V-angle permits a compact
installation, with the supercharger mounted within the valley between the two
cylinder banks.
The cylinder heads are constructed from aluminum alloy
and feature a four-valve-per-cylinder configuration (24 valves total) arranged
in a pent-roof combustion chamber design. The DOHC arrangement per cylinder bank
operates the valves via roller cam followers, which incorporate hydraulic lash
adjusters for automatic valve clearance maintenance.
The intake and exhaust valves are manufactured from heat-resistant steel.
Variable valve timing is employed on both the intake and exhaust camshafts
across all four camshafts. The camshafts are driven by a single timing chain
located at the rear (flywheel end) of the engine, a layout that reduces
front-end engine length and aids in vehicle weight distribution.
The fuel system is a high-pressure direct injection
system, branded by Audi as FSI (Fuel Stratified Injection). A high-pressure fuel
pump, mounted on the engine and driven by a camshaft lobe on the right cylinder
bank, generates fuel pressures up to 150 bar (2176 psi).
Fuel is delivered directly into the combustion chamber through solenoid-type
injectors. This system allows for precise fuel metering, contributing to the
engine’s power output and efficiency. The engine management system utilizes a
Bosch Motronic MED 17.1.1 control unit, which governs fuel delivery, ignition
timing, and supercharger bypass valve operation to manage boost pressure.
0The lubrication system is a pressurized, wet-sump
design with a capacity of 6.8 liters (7.2 qt). The engine uses a
variable-displacement oil pump, which adjusts its output based on engine speed
and load to reduce parasitic power loss and improve efficiency.
The oil cooler, which uses engine coolant, is integrated into the oil filter
housing assembly. Approved oil specifications are VW 502 00 for fixed service
intervals or VW 504 00 for flexible (long-life) service intervals. Recommended
viscosity grades are 5W-30 or 5W-40 synthetic engine oil.
The cooling system is a pressurized, water-cooled
design with a total system capacity of 11.0 liters (11.6 qt). The primary
coolant loop serves the cylinder block, cylinder heads, and the oil cooler. A
secondary, low-temperature cooling circuit is integrated for the supercharger’s
charge-air cooler. The supercharger unit itself contains an integrated
water-to-air intercooler located within the intake manifold, directly beneath
the supercharger rotors.
This separate circuit utilizes its own electric coolant pump to circulate
coolant through the supercharger and a dedicated low-temperature radiator at the
front of the vehicle, ensuring consistent intake air temperature control
regardless of engine thermal state. The specified coolant is G13 (pink/purple),
a silicate-free, long-life formula.
The ignition system consists of six individual
direct-acting coil-on-plug (COP) ignition coils. The specified spark plugs are
NGK PFR8S8EG or equivalent, with a pre-set electrode gap of 0.7-0.8 mm
(0.028-0.031 in). The firing order is 1-4-3-6-2-5.
The engine’s supercharger is an Eaton TVS R1320
Roots-type unit. It is located within the engine’s V-valley and driven by a
multi-ribbed belt from the crankshaft. An electronically controlled bypass valve
integrated into the supercharger housing manages boost pressure. During low-load
conditions, the valve opens to recirculate intake air, reducing parasitic drag
from the supercharger and improving fuel economy.
The engine management system controls all engine functions, including knock
control, which allows the engine to adapt to varying fuel qualities, and a
sophisticated torque monitoring interface with the transmission control unit and
electronic stability control system.
The engine’s external dimensions are compact for its
displacement. Length, inclusive of accessories, is 610 mm (24.0 in). Width is
520 mm (20.5 in), and height is 740 mm (29.1 in). The total dry weight of the
engine, without fluids and including the supercharger and standard accessories,
is 185 kg (408 lb).
The engine oil capacity, including the filter, is 6.8
liters (7.2 qt). The oil change interval is dictated by the vehicle’s service
indicator system, with a maximum of 15,000 km (9,300 mi) or 12 months under
flexible service conditions. The coolant system capacity is 11.0 liters (11.6
qt), with a recommended replacement interval of every 5 years.
Spark plug replacement is specified every 60,000 km (37,300 mi). The drive belt
for ancillary components should be inspected at regular intervals, with
replacement recommended at 120,000 km (74,600 mi). The timing chain is designed
for the life of the engine under normal operating conditions but may require
inspection if abnormal noise develops, particularly at the rear of the engine.
Cylinder head bolts: stage 1 at 40 Nm (30 lb-ft),
followed by a 90-deg turn, final 90-deg turn.
Main bearing cap bolts: 65 Nm (48 lb-ft) plus a 90-deg turn.
Connecting rod cap bolts: 50 Nm (37 lb-ft) plus a 90-deg turn.
Supercharger mounting bolts: 20 Nm (15 lb-ft).
Camshaft bearing cap bolts: 10 Nm (7 lb-ft) plus a 90-deg turn.
Intake manifold bolts: 20 Nm (15 lb-ft).
Spark plugs: 30 Nm (22 lb-ft).
Exhaust manifold nuts: 28 Nm (21 lb-ft).
Engine mount bracket bolts: 40 Nm (30 lb-ft) plus a 90-deg turn.
Front crankshaft pulley bolt: 150 Nm (111 lb-ft) plus a 180-deg turn (use a new
bolt).
Valve cover bolts: 12 Nm (9 lb-ft).
The Audi CTUB engine
served as the standard power unit for specific high-performance models within
the Audi lineup:
Audi S4 (B8.5 Facelift): Production years 2012 to 2016. This model succeeded the
B8 generation S4, incorporating the CTUB as its exclusive engine.
Audi S5 (8T Facelift): Production years 2012 to
2017. This includes the coupe and cabriolet variants, where the CTUB
replaced the earlier 4.2-liter V8 in certain markets for this
generation.
Audi SQ5 (8R): Production years 2013 to 2017.
This model marked the first performance-oriented variant of the Q5 SUV,
utilizing the CTUB to create a distinct high-performance utility
vehicle.
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