Cat C11 ACERT Specifications
| Engine Model: Caterpillar C11 ACERT |
| Engine Type: 4-stroke in-line 6-cylinder turbocharged liquid-cooled diesel |
| Total Displacement: 677 cu.in (11.1 L) |
| Rated Engine Power: 325-450 Hp (242-336 kW) at 2100 rpm |
| Fuel System Type: Unit Injection |
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The Caterpillar C11 ACERT represents a
significant chapter in Caterpillar’s evolution of medium-duty diesel
power, designed to bridge the gap between the 9.3-liter and 11.9-liter
offerings. Introduced in the mid-2000s, this engine was part of
Caterpillar’s Advanced Combustion Emissions Reduction Technology (ACERT)
strategy, which sought to meet stringent Tier 3 and Interim Tier 4
emissions standards through sophisticated fuel and air management rather
than solely relying on aftertreatment.
The C11 ACERT is an in-line 6-cylinder, 11.1-liter powerplant renowned
for its robust construction, high-pressure fuel system, and durable core
architecture. While its complexity increased compared to mechanically
governed predecessors, it delivered a balance of performance and
reliability that made it a favored choice for vocational trucks,
industrial equipment, and construction machinery. The engine’s design
emphasizes low-end torque and a compact footprint, providing operators
with responsive power in demanding applications such as concrete mixing,
rock crushing, and heavy hauling.
The Caterpillar C11 ACERT is a 4-cycle, in-line, 6-cylinder diesel
engine with a displacement of 11.1 Liters (677 cubic inches). It
utilizes a bore and stroke measuring 130 mm x 140 mm (5.12 in x 5.51
in). The aspiration system is a turbocharged and aftercooled (TA)
configuration, employing a cross-flow cylinder head to optimize air
induction and exhaust flow. The combustion system is direct injection
with a compression ratio of 17.0:1. Engine rotation is counterclockwise
when viewed from the flywheel end, and the firing order is 1-5-3-6-2-4.
Performance data for the C11 ACERT spans a power range from 242 kW to
336 kW (325 HP to 450 HP) depending on the specific industrial or
on-highway configuration. The rated speed is variable between 1800 and
2100 RPM. The engine produces maximum torque figures between 1,695 Nm
and 1,966 Nm (1,250 lb-ft to 1,450 lb-ft) at 1200 RPM, underscoring its
capability for high-load applications at low engine speeds. The governed
speed is set at 2100 RPM.
0The cylinder block of the C11 ACERT is constructed from cast iron,
providing a rigid foundation that minimizes vibration and ensures
long-term alignment of internal components. It is a deep-skirt design,
meaning the block walls extend below the crankshaft centerline, offering
superior support for the main bearing caps. This architecture enhances
structural rigidity and reduces noise, vibration, and harshness (NVH).
The block incorporates replaceable cylinder liners, which are wet-type
sleeves. Wet liners allow for efficient heat transfer directly from the
liner wall to the surrounding coolant, facilitating consistent cylinder
temperatures. The liner protrusion above the block deck is precisely
controlled to ensure a proper seal when the cylinder head is installed.
The design prioritizes durability for high-cycle applications such as
on-highway trucking and continuous industrial operation.
The cylinder head is a cast iron, cross-flow design where intake air
enters from one side and exhaust gases exit from the opposite side. This
configuration maximizes air density and improves volumetric efficiency
by keeping the intake charge cool and separate from the hot exhaust
manifold. The head houses four valves per cylinder - two intake and two
exhaust - which centralizes the fuel injector nozzle for optimal fuel
atomization and combustion efficiency.
The valves are actuated via a single overhead camshaft (OHC)
arrangement, which uses hardened steel pushrods, roller followers, and
rocker arms. The OHC design reduces the number of moving parts compared
to a traditional in-block camshaft, allowing for more precise valve
timing and improved high-speed performance. The valve stem seals are
integral to the engine’s ACERT strategy, contributing to oil consumption
control and emissions management.
The fuel system on the C11 ACERT is a MEUI (Mechanically Actuated
Electronically Controlled Unit Injection) system. This system combines
the high-pressure generation of a mechanical unit injector with the
precision of electronic control. Each cylinder has its own unit
injector, which is actuated by the engine’s camshaft to generate
injection pressures exceeding 1,600 bar (23,200 psi). The injection
timing, duration, and quantity are governed by the ADEM A4 Electronic
Control Module (ECM).
The ADEM A4 ECM processes inputs from sensors monitoring boost pressure,
coolant temperature, engine speed, and throttle position to optimize
combustion for power output and emissions control. This system
eliminates the need for a high-pressure common rail pump, simplifying
the high-pressure circuit while delivering precise multiple injection
events, which are critical for reducing combustion noise and achieving
ACERT emissions targets.
The lubrication system is a forced-feed, full-flow filtration design. A
gear-driven pump draws oil from the sump and circulates it through the
system. The total oil capacity is 34.1 Liters (9.0 U.S. Gallons).
Filtration is handled by a spin-on, full-flow oil filter, which ensures
that all oil entering the engine’s critical galleries is filtered before
reaching bearings, the camshaft, and the valve train.
The system also typically includes an oil cooler mounted to the engine
block, which uses engine coolant to regulate oil temperature.
Maintaining proper oil viscosity and pressure is critical for the MEUI
system, as the injectors rely on engine oil for both lubrication and
hydraulic actuation. The lubrication circuit includes a bypass valve to
protect the engine in the event of a clogged filter, ensuring continuous
oil flow under all operating conditions.
The cooling system is designed for high heat rejection, a necessity for
an engine with high cylinder pressures and a turbocharger. The
engine-mounted centrifugal water pump circulates coolant through the
cylinder block, cylinder head, and the aftercooler (air-to-water). The
coolant capacity for the engine alone (without the radiator or external
lines) is 11.7 Liters (3.1 U.S. Gal).
Temperature regulation is controlled by a thermostatically controlled
housing that maintains coolant temperature between 82°C and 92°C (180°F
to 197°F). The system is pressurized to raise the boiling point of the
coolant and prevent cavitation, a critical factor in protecting the wet
cylinder liners from erosion. A gear-driven fan, often equipped with a
viscous clutch, provides air flow for the radiator and aftercooler, with
the clutch engagement modulated by the ECM to optimize cooling and
reduce parasitic power loss.
The C11 ACERT is configurable with either 12-volt or 24-volt electrical
systems to suit diverse applications, from on-highway trucks to heavy
industrial machinery. The electrical architecture is centered around the
ADEM A4 ECM, which integrates engine control with vehicle or equipment
interfaces. The system includes a high-output alternator, electric
starting motor, and wiring harnesses designed to withstand high
vibration and thermal cycling.
Air Management: The engine utilizes a wastegated turbocharger to manage
boost pressure across the RPM range. The wastegate allows exhaust gas to
bypass the turbine wheel at high engine speeds, preventing over-boosting
and controlling cylinder pressure. This is coupled with a cross-flow
cylinder head and a jacket water aftercooler (JWA), which cools the
compressed intake air using engine coolant to increase air density
before it enters the combustion chamber.
Crankcase Ventilation (CCV): To meet emissions standards, many
configurations of the C11 ACERT incorporate a closed crankcase
ventilation system. This system routes blow-by gases from the crankcase
back into the intake system, preventing them from being vented to the
atmosphere.
The dry weight is 930 kg (2,050 lbs). The overall length measures 1,202
mm (47.3 in), the width is 1,057 mm (41.6 in), and the height is 1,175
mm (46.3 in). These dimensions are critical for original equipment
manufacturers integrating the engine into tight engine compartments in
vocational trucks or industrial equipment chassis.
Maintenance schedules for the C11 ACERT are interval-based, driven by
engine operating hours or fuel consumption. Oil and filter change
intervals are typically specified at 500 hours or 16,000 km (10,000
miles) for on-highway applications, though this varies based on
application severity and oil analysis results. Fuel system maintenance
focuses on primary and secondary filter changes, with the secondary
filter (located on the engine) typically replaced at the same interval
as the oil change.
The engine coolant requires periodic testing for nitrite levels, which
protect the wet cylinder liners from cavitation erosion; the coolant
conditioner or extended life coolant (ELC) should be serviced according
to Caterpillar’s S-O-S (Scheduled Oil Sampling) Services protocols.
Valve lash adjustments are critical for performance and emissions
compliance, typically required every 2,000 to 4,000 hours, depending on
the application.
The cylinder head bolts utilize a multi-stage torque-to-yield process:
initially 150 Nm (110 lb-ft), followed by a second pass of 150 Nm (110
lb-ft), and finally a 90-degree angular turn.
The connecting rod bolts are tightened to 90 Nm (66 lb-ft) plus a
90-degree angular turn, ensuring proper clamp load on the rod cap. The
main bearing caps are secured with bolts torqued to 260 Nm (190 lb-ft)
followed by a 120-degree angular turn.
The flywheel bolts typically require a torque of 300 Nm (221 lb-ft).
These torque specifications are critical due to the high cylinder
pressures generated by the MEUI system and must be adhered to with
calibrated tools to prevent component failure.
The C11 ACERT was utilized across a broad spectrum of Caterpillar and
third-party machinery. In the on-highway sector, it was commonly found
in vocational trucks, particularly the Cat CT660 and CT680 series, where
it powered day cabs, dump trucks, and concrete mixers. Its high torque
at low RPM made it ideal for stop-and-start operations and heavy
payloads.
In industrial applications, the engine served as the prime mover for
agricultural tractors, rock crushers, and large industrial air
compressors, valued for its durability in stationary and semi-stationary
roles. Within the construction sector, the C11 ACERT was used to power
various Caterpillar excavators, such as the 336E, and wheel loaders like
the 966H, where its compact dimensions and responsive power curve
provided the necessary hydraulic flow and traction force for earthmoving
operations.
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