Honda K24W9 Specifications
| Engine Model: Honda K24W9 |
| Engine Type: 4-cycle inline 4-cylinder DOHC 16-valve i-VTEC liquid-cooled gasoline |
| Total Displacement: 144 cu.in (2.35 L) |
| Rated Engine Power: 201 Hp (150 kW) at 6800 rpm |
| Fuel System Type: Gasoline direct injection |
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The Honda K24W9 is a 2.4-liter naturally aspirated
inline-four engine developed under the Earth Dreams Technology family. It
represents a high-output variant within the K24W series, engineered specifically
to deliver enhanced performance for sport-oriented applications. Unlike the
broader-use variants found in mainstream sedans, the K24W9 was calibrated for a
more aggressive driving experience, serving as the exclusive powertrain for the
Acura ILX in its final generation.
The engine combines the direct injection foundation of the K24W series with a
raised compression ratio, a unique valvetrain configuration, and a higher
redline. This configuration prioritizes linear power delivery up to a 7,100 rpm
cut-off, distinguishing it from the more efficiency-focused versions of the
platform. By utilizing premium-grade fuel and advanced friction reduction
technologies, the K24W9 achieves a balance of spirited performance and
reasonable efficiency within a compact transverse package.
The engine follows a transverse inline-four layout, optimized for
front-wheel-drive vehicle architectures. The valvetrain is a double overhead
camshaft (DOHC) design incorporating 16 valves and Honda’s intelligent Variable
Valve Timing and Lift Electronic Control (i-VTEC) system, which in this
application is active on the intake side.
Displacement measures 2,356 cc (144 cu.in), achieved through a bore of 87.0 mm
(3.43 in) and a stroke of 99.1 mm (3.90 in), establishing a classic undersquare
architecture that favors low-end torque production relative to engine speed. The
compression ratio is set at 11.6:1, which represents an increase over related
K24W variants.
Maximum power output is 201 hp (150 kW) at 6,800 rpm, with peak torque of 180
lb-ft (244 Nm) delivered at 3,600 rpm. The engine redline is 7,100 rpm, with the
i-VTEC system engaging at 5,000 rpm to alter valve lift and duration for
sustained high-rpm power. The fuel system employs direct injection (DI),
spraying fuel directly into the combustion chamber to improve thermal efficiency
and charge cooling.
The cylinder head is arranged in a reverse-flow configuration, positioning the
intake manifold at the rear of the engine bay and the exhaust manifold at the
front, a layout intended to optimize airflow dynamics and reduce intake air
temperature.
The cylinder block is constructed from high-pressure
die-cast aluminum to reduce overall engine mass while maintaining structural
rigidity. Cast-iron cylinder liners are used to provide a durable wear surface
for the piston rings. The block features an open-deck design, where the
cylinders are not fully supported by the upper deck surface, aiding in cooling
efficiency and weight reduction. Bore spacing is standardized within the K24
family to accommodate the 87.0 mm (3.43 in) bore diameter.
Offset cylinder placement is employed, where the cylinder bore axis is slightly
offset from the crankshaft centerline. This configuration reduces frictional
losses between the pistons and cylinder walls during the power stroke. The
engine utilizes a structural aluminum oil pan that contributes to overall
powertrain rigidity and noise reduction. Four-bolt main bearing caps secure the
crankshaft, providing adequate support for the engine’s power output and
operational speeds.
The cylinder head is a cross-flow, aluminum alloy
casting with a pent-roof combustion chamber design, which facilitates high
compression ratios and efficient flame propagation. The DOHC arrangement uses a
silent-type timing chain on the intake side to drive the camshafts, which are
supported by low-friction roller bearings in the camshaft carriers. The i-VTEC
system on the intake camshaft utilizes a hydraulically actuated locking pin
mechanism to switch between low-lift and high-lift cam profiles.
Intake valves measure 35.0 mm (1.38 in) in diameter, while exhaust valves are
30.0 mm (1.18 in). The valve stems are finished with a polished surface to
minimize friction within the guides. Valve actuation is managed by roller rocker
arms that incorporate needle bearings to reduce sliding friction.
The valve clearance requires manual adjustment and is specified for cold engine
conditions. Intake valve clearance is set between 0.21 mm and 0.25 mm (0.0083 in
and 0.0098 in). Exhaust valve clearance is set between 0.25 mm and 0.29 mm
(0.0098 in and 0.0114 in). The cylinder head gasket is a multi-layer steel (MLS)
design, providing a robust seal under high cylinder pressures generated by the
elevated compression ratio.
The fuel system operates as a direct injection setup
with a high-pressure fuel pump mounted to the cylinder head, driven by a
dedicated cam lobe on the exhaust camshaft. The system generates fuel pressure
up to 3,000 psi (20.7 MPa) to ensure proper atomization directly into the
combustion chamber. Fuel injectors are positioned centrally within the cylinder
head, allowing for targeted spray patterns that promote mixture homogeneity and
combustion stability.
The direct injection architecture eliminates fuel flow over the intake valves,
which has implications for long-term maintenance. The engine management system
utilizes a wideband oxygen sensor to precisely control the air-fuel ratio across
the operating range.
For maximum performance output, premium fuel with an octane rating of 91 or
higher is recommended. The higher compression ratio and aggressive ignition
timing rely on the knock resistance of higher-octane fuel to achieve the rated
power and torque figures without premature detonation.
The lubrication system employs a gear-type oil pump
mounted to the crankshaft, delivering pressurized oil to the crankshaft main
bearings, connecting rod bearings, camshaft journals, and the i-VTEC actuation
system. The oil pump features a variable displacement design in some iterations,
though the K24W9 prioritizes consistent flow for high-rpm operation. Oil
capacity for the system is 4.5 US quarts (4.3 L) including the oil filter.
The recommended oil grade is 0W-20, fully synthetic, selected for its
low-temperature flow characteristics and high-temperature stability. The system
incorporates a piston cooling oil jet, which directs oil to the underside of the
piston crowns to manage combustion temperatures. Ion-plated piston rings are
utilized to reduce frictional losses between the piston and cylinder wall. The
oil pan is baffled to maintain oil pickup during cornering loads, supporting the
engine’s application in sport-oriented vehicles.
The cooling system uses a cross-flow radiator with an
electric cooling fan controlled by the engine control unit. Coolant circulation
is driven by a water pump mounted to the engine block, operated by the timing
chain. The thermostat regulates coolant temperature to maintain optimal
operating conditions, with a rated opening temperature of 180°F (82°C). The
reverse-flow cylinder head configuration allows for efficient coolant routing,
directing flow to the hottest areas of the combustion chamber first.
System capacity is approximately 6.4 US quarts (6.0 L) of a high-quality
ethylene-glycol based coolant, a Type 2 long-life formulation. The cooling
system is designed to manage the thermal load generated by the 11.6:1
compression ratio and sustained high-rpm operation. An integrated oil-to-coolant
heat exchanger is mounted to the oil filter base, allowing the engine oil to
reach operating temperature quickly while preventing oil overheating under
sustained load.
| Intake and Exhaust Systems |
The intake system incorporates a high-flow intake
manifold constructed from composite material to reduce heat soak. A
larger-diameter throttle body, measuring 64 mm (2.52 in), supports the higher
redline and increased airflow requirements compared to standard K24W engines.
The exhaust manifold is integrated into the cylinder head in a 4-2-1
configuration, reducing weight and improving warm-up time for the catalytic
converter.
The ignition system utilizes iridium-tipped spark plugs
with a fine center electrode, specified as NGK DILKAR7G11GS. These plugs are
designed for extended service intervals and reliable ignition under high
cylinder pressures.
The engine management system uses a 32-bit
processor to manage direct injection timing, i-VTEC engagement, ignition
advance, and electronic throttle control. The timing chain system
incorporates a hydraulic tensioner that maintains constant chain tension
across the engine’s operating temperature range. Chain guides are coated
with a low-friction material to reduce parasitic losses.
Height from the bottom of the oil pan to the top of the
intake manifold is 26.5 in (673 mm). Width across the valve cover is roughly
25.0 in (635 mm). Depth from the accessory drive belt to the transmission mating
face is 27.0 in (686 mm). Engine weight, fully dressed with all accessories and
fluids, is 310 lb (141 kg).
Engine oil and filter change intervals are recommended
every 7,500 miles (12,000 km) under normal driving conditions, with shorter
intervals for severe duty. The cooling system requires inspection at 60,000
miles (96,000 km), with coolant replacement specified at 120,000 miles (193,000
km). Spark plug replacement interval is 100,000 miles (160,000 km) due to the
iridium construction. The drive belt is inspected for wear and tension at
regular service intervals.
Valve clearance inspection is recommended at 100,000 miles (160,000 km), with
adjustment performed as necessary using the manual adjustment method on a cold
engine. Due to the direct injection system, intake valve carbon accumulation is
a known operational consideration.
Periodic intake valve cleaning via walnut blasting or chemical induction is
recommended to maintain performance and prevent drivability concerns, as fuel
does not wash over the back of the intake valves. The timing chain is designed
for the life of the engine under normal conditions but should be inspected if
timing-related noises occur.
0Cylinder head bolts follow a torque-to-yield
procedure. Initial torque is applied to 22 lb-ft (30 Nm) in sequence, followed
by a 90-degree turn, then an additional 90-degree turn. Main bearing cap bolts
are torqued to 45 lb-ft (61 Nm) plus a 90-degree turn. Connecting rod cap bolts
receive 20 lb-ft (27 Nm) plus a 90-degree turn. Camshaft carrier bolts are
tightened to 16 lb-ft (22 Nm) in a specified sequence.
The spark plugs are torqued to 18 lb-ft (25 Nm). The oil drain plug requires 30
lb-ft (41 Nm). The high-pressure fuel pump mounting bolts are set to 14 lb-ft
(19 Nm). The water pump mounting bolts are tightened to 9 lb-ft (12 Nm). Intake
manifold bolts receive 16 lb-ft (22 Nm). Exhaust manifold nuts are torqued to 28
lb-ft (38 Nm). All torque specifications assume clean, lightly lubricated
threads unless otherwise specified in the service procedure.
The K24W9 engine was utilized primarily in the Acura
ILX for the 2016 through 2022 model years, where it was paired exclusively with
an 8-speed dual-clutch transmission (DCT) featuring a torque converter for
low-speed refinement. This application represented the final use of a naturally
aspirated engine in the ILX before the model’s discontinuation.
The engine was also applied in the Honda Spirior for the Chinese market between
2015 and 2019, a vehicle positioned as a sport-oriented sedan equivalent to the
Acura TLX and ILX platforms. In all applications, the K24W9 was calibrated for
premium fuel and designed to provide a higher specific output relative to other
K24W series engines used in mainstream Honda Accord and CR-V models.
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