Honda K24Z7 Specifications
| Engine Model: Honda K24Z7 |
| Engine Type: 4-cycle inline 4-cylinder DOHC 16-valve i-VTEC liquid-cooled gasoline |
| Total Displacement: 143.6 cu.in (2.35 L) |
| Rated Engine Power: 201 Hp (150 kW) at 7000 rpm |
| Fuel System Type: Multi-point electronic fuel injection |
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The Honda K24Z7 is a 2.4-liter naturally aspirated
inline-four engine, representing a high-performance evolution within the
K-series family. Specifically engineered for the 9th-generation Civic Si and the
Acura ILX, this powerplant was designed to bridge the gap between the
high-revving character of the K20Z3 and the substantial low-end torque of
larger-displacement economy engines.
The K24Z7 combines the dual-overhead-camshaft (DOHC) architecture of the
performance-oriented K-series with the integrated exhaust manifold design
characteristic of the "Z" variant. Its configuration focuses on delivering a
broad, accessible powerband. The engine employs a high-compression ratio and a
performance-focused i-VTEC system that actuates on both the intake and exhaust
camshafts, a departure from the economy-tuned variants that primarily utilized
VTEC for fuel efficiency.
This specific tuning yields a responsive, sporty character, providing robust
mid-range torque for daily driving while retaining a free-revving top end up to
a 7,100 rpm redline. The engine is renowned for its reliability, compact
packaging due to the integrated manifold, and its role in maintaining the
spirited driving dynamics of the sport compact segment during its production
run.
The engine operates on a four-stroke combustion cycle with a transverse mounting
orientation, standard for front-wheel-drive applications. Its cylinder
configuration is an inline-four, utilizing a cast iron cylinder sleeve within an
aluminum alloy block to balance weight with durability.
The valvetrain is a DOHC design operating 16 valves, with i-VTEC (Intelligent
Variable Valve Timing and Lift Electronic Control) present on both the intake
and exhaust sides. This system allows for distinct low-rpm and high-rpm cam
profiles, optimizing idle stability, fuel economy, and peak power output.
Total displacement is 2,354 cc (2.4 L, 143.7 cu.in), achieved through a bore and
stroke of 87.0 mm (3.43 in) x 99.0 mm (3.90 in). This under-square design, with
a stroke longer than the bore, prioritizes piston speed and torque production.
The compression ratio is set at 11.0:1, a high value necessitating premium-grade
fuel to prevent knock under high-load conditions.
The ignition system is fully electronic, utilizing a direct coil-on-plug design
with an individual ignition coil for each cylinder, managed by the engine
control unit (ECU). The firing order is the standard 1-3-4-2.
Power output is rated at a maximum of 201 hp (150 kW) achieved at 7,000 rpm.
Peak torque is 170 lb-ft (230 Nm) produced at 4,400 rpm. The engine’s redline is
established at 7,100 rpm, with a fuel cut-off intervention occurring at 7,200
rpm to protect rotating assembly integrity. The performance i-VTEC engagement
point is calibrated to occur at 5,000 rpm, transitioning the camshaft profiles
to the high-lift, long-duration lobes for maximum volumetric efficiency in the
upper rev range.
The cylinder block is constructed from high-pressure
die-cast aluminum alloy to minimize overall engine weight, a critical factor for
vehicle dynamics and fuel efficiency. Cast-iron cylinder liners are integrally
cast into the aluminum bores to provide a robust, low-friction wear surface for
the piston rings. The open-deck design, where the water jacket is fully exposed
at the top of the block, enhances cooling efficiency around the cylinders.
The block features a deep-skirt design for increased rigidity and reduced
vibration. A chain-driven balance shaft assembly is housed within a cassette
mounted in the lower crankcase or oil pan region. This dual-balancer system
rotates at twice the engine speed to counteract the secondary vibrations
inherent in a large-stroke inline-four engine, ensuring smooth operation across
the rev range.
The cylinder head is a cast-aluminum component
featuring a DOHC arrangement with four valves per cylinder. A defining
characteristic of the K24Z7 is the integration of the exhaust manifold into the
cylinder head casting. This design eliminates a conventional separate exhaust
manifold, reduces weight, shortens the exhaust path to the catalytic converter
for faster light-off, and contributes to a more compact engine bay. The i-VTEC
system on this head is a dual-profile system. For the intake and exhaust
camshafts, each cylinder utilizes two distinct lobe profiles per valve.
At low engine speeds, the system operates on a low-lift, short-duration profile.
Upon reaching the engagement threshold (5,000 rpm), oil pressure actuates
locking pins within the VTEC rocker arms, coupling them to the high-lift,
long-duration cam profile. This allows for significantly increased valve lift
and timing, maximizing airflow and power output at high RPM. Valve actuation is
facilitated by roller rocker arms to reduce friction. The valve stems are sealed
with positive-type oil seals to control lubrication.
The fuel system employs Honda’s PGM-FI (Programmed Fuel
Injection), a multi-point, sequential fuel injection system. In this
configuration, a fuel injector is positioned in the intake port for each
cylinder. The ECU controls the timing and duration of each injector pulse
independently, delivering fuel in precise synchronization with the engine’s
valve events. This system is supplied by an in-tank electric fuel pump that
maintains a constant pressure to the injector rail.
The system is designed for closed-loop operation, utilizing a wideband oxygen
sensor in the exhaust stream to constantly adjust the air-fuel ratio for optimal
combustion efficiency, emissions control, and power delivery. It is calibrated
to operate on premium unleaded fuel with an octane rating of 91 or higher.
The lubrication system is a fully pressurized, wet-sump
design. A high-volume, gear-type oil pump is driven directly by the crankshaft,
providing consistent oil pressure to all critical engine components. The system
is engineered to use 0W-20 fully synthetic engine oil, a low-viscosity fluid
chosen to reduce internal friction for improved fuel economy and cold-start
protection. The total oil capacity, including the filter, is 4.4 US qt (4.2 L,
3.7 Imp qt).
A spin-on, full-flow oil filter is mounted externally to the block for easy
maintenance. The system incorporates piston cooling oil jets (oil squirters)
directed at the underside of the piston crowns to manage the high thermal load
associated with the 11.0:1 compression ratio and high-rpm operation. The engine
is also equipped with a water-cooled oil cooler integrated into the oil filter
housing to stabilize oil temperature under sustained high-performance driving.
The cooling system is a pressurized, forced-circulation
setup utilizing a centrifugal water pump driven by the engine’s serpentine belt.
The system uses a cross-flow radiator with an electric cooling fan controlled by
the ECU based on coolant temperature and air conditioning demand. The thermostat
is a wax-pellet type with a bypass circuit to ensure rapid engine warm-up and
consistent operating temperature. The integrated exhaust manifold in the
cylinder head necessitates a sophisticated cooling jacket design to manage heat
concentration around the exhaust ports.
A coolant temperature sensor provides data to the ECU for fuel enrichment and
ignition timing adjustments during warm-up. The system is designed to maintain
the engine within its optimal operating temperature range for performance,
efficiency, and durability under various driving conditions. The total coolant
capacity is approximately 5.8 US qt (5.5 L, 4.8 Imp qt).
The engine incorporates a positive crankcase
ventilation (PCV) system to vent blow-by gases from the crankcase back into the
intake manifold for combustion, reducing emissions and preventing sludge
buildup. The timing drive is a high-strength, silent-type chain that operates
the camshafts, balance shafts, and oil pump. The chain system is
maintenance-free under normal operating conditions, though the hydraulic chain
tensioner may require inspection for cold-start noise over extended mileage.
The intake manifold is a dual-stage design with a variable length intake
manifold (VLIM) system, utilizing a set of intake air control valves to alter
the intake runner length based on engine speed and load. This enhances low-end
torque by increasing air velocity while allowing for higher flow at high rpm.
The engine management system (ECU) is a sophisticated unit controlling fuel
delivery, ignition timing, VTEC engagement, VLIM operation, electronic throttle
control (drive-by-wire), and all emissions-related systems.
The total engine length (including accessories) is 26.8
in (680 mm). Width is 26.0 in (660 mm), and height is roughly 26.4 in (670 mm).
The overall dry weight of the engine, without fluids but including the intake
manifold and standard accessories, is 335 lb (152 kg).
Maintenance intervals are defined by the vehicle
manufacturer based on the onboard maintenance minder system. A critical
maintenance task is the manual adjustment of valve clearances. The clearance
specifications, measured with the engine cold, are 0.008-0.010 in (0.21-0.25 mm)
for the intake valves and 0.010-0.011 in (0.25-0.29 mm) for the exhaust valves.
The specified spark plug is an NGK ILZKR7B-11S, a long-life iridium unit with a
gap of 0.044 in (1.1 mm). The ignition system requires no timing adjustment, as
it is fully controlled by the ECU. The engine oil and filter should be replaced
according to the maintenance minder, using 0W-20 fully synthetic oil.
The engine coolant is a specific Honda long-life antifreeze, with initial
replacement typically recommended at 10 years or 120,000 miles (193,000 km),
then every 5 years or 60,000 miles (96,000 km) thereafter. The serpentine
accessory drive belt requires periodic inspection for wear and tension. The
timing chain does not have a specified replacement interval but should be
inspected for stretch or tensioner failure if timing-related noises or codes
occur.
Critical fasteners require precise torque application.
The cylinder head bolts follow a multi-step torque sequence: a preliminary
torque of 30 lb-ft (40 Nm), followed by a final torque of 180 degrees (two
90-degree turns). The main bearing cap bolts are torqued to 30 lb-ft (40 Nm)
plus an additional 90 degrees. The connecting rod cap nuts are tightened to 23
lb-ft (31 Nm) plus an additional 90 degrees.
The camshaft bearing cap bolts are torqued to 14 lb-ft (19 Nm) in a specified
sequence. The flywheel or drive plate mounting bolts are secured to 76 lb-ft
(103 Nm). The spark plugs are torqued to 13 lb-ft (18 Nm). All tightening
torques assume clean, lubricated threads where specified and are critical for
maintaining the structural integrity and sealing of the engine assembly.
The K24Z7 engine served as the exclusive
high-performance powerplant for specific sport compact models in the North
American market.
2012-2015 Honda Civic Si: This engine was installed in both the Coupe and Sedan
body styles for the 9th generation. It was paired exclusively with a 6-speed
manual transmission and a helical limited-slip differential.
2013-2015 Acura ILX: The K24Z7 was utilized in the ILX 2.4L Premium and
Technology trims. Like the Civic Si, its application was mated solely to a
6-speed manual transmission, distinguishing it as the performance-oriented
variant within the ILX lineup.
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