Honda H22A2 Specifications
| Engine Model: Honda H22A2 |
| Engine Type: 4-cycle inline 4-cylinder DOHC 16-valve VTEC liquid-cooled gasoline |
| Total Displacement: 134 cu.in (2.15 L) |
| Rated Engine Power: 182 Hp (136 kW) at 6800 rpm |
| Fuel System Type: Multi-point electronic fuel injection |
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The Honda H22A2 represents a significant chapter in the
high-performance, naturally aspirated four-cylinder lineage from Honda’s golden
era. As part of the H-series, often referred to as the “big block” relative to
the B-series, this 2.2-liter engine was engineered to deliver a blend of robust
low-end torque and exhilarating top-end power. Its primary application was in
the European market, serving as the flagship powertrain for the
fourth-generation Honda Prelude.
The engine’s defining characteristic is its implementation of the VTEC (Variable
Valve Timing and Lift Electronic Control) system on the dual overhead camshaft
layout, allowing for a dual personality: civilized efficiency during daily
driving and aggressive, high-rpm power delivery upon engagement. The H22A2 is
distinguished by its use of a Fiber Reinforced Metal (FRM) cylinder bore, a
lightweight aluminum block, and a sophisticated balance shaft system, making it
a technologically dense and highly desirable engine for enthusiasts who
prioritize a high-revving, naturally aspirated experience.
The Honda H22A2 is a water-cooled, four-stroke, spark-ignition internal
combustion engine. Its architecture is defined by a transversely mounted,
inline-four-cylinder configuration. The valvetrain operates with a dual overhead
camshaft (DOHC) design, actuating four valves per cylinder for a total of
sixteen valves. The combustion chamber efficiency is optimized through the VTEC
system, which utilizes three different cam profiles per pair of cylinders -
low-rpm, mid-range, and high-rpm - to optimize volumetric efficiency across the
entire power band.
Total displacement is calculated at 2,157 cc (2.2 L), achieved through a bore
and stroke measuring 87.0 mm x 90.7 mm (3.43 in x 3.57 in). This under-square
ratio (bore smaller than stroke) contributes to the engine’s favorable torque
characteristics at lower engine speeds. The compression ratio is set at 10.0:1,
a figure calibrated for the European market’s fuel quality and emissions
standards.
Maximum power output is achieved at 6,800 rpm, delivering 136 kW (182 hp). Peak
torque is rated at 212 Nm (156 lb-ft), occurring at 5,300 rpm. The VTEC
engagement point is calibrated to 5,200 rpm, providing a distinct surge in power
delivery. The engine’s operational limits are defined by a redline of 7,200 rpm,
with a fuel cut-off (rev limit) intervention occurring at 7,600 rpm to prevent
mechanical over-rev. The firing order follows the common inline-four pattern of
1-3-4-2.
The cylinder block is constructed from cast aluminum, a
design choice aimed at reducing overall engine weight and improving thermal
conductivity. Unlike many aluminum blocks of the era, the H22A2 does not utilize
cast iron cylinder liners. Instead, the bores are coated with a proprietary
Fiber Reinforced Metal (FRM) material. This composite consists of aluminum alloy
impregnated with ceramic and carbon fibers, creating a bore surface that is
exceptionally hard, lightweight, and provides superior heat dissipation. The FRM
liners allow for tighter piston-to-wall clearances and reduce frictional losses.
However, this material requires the use of specific piston rings with a hard
coating to prevent accelerated wear. The block architecture incorporates a
deep-skirt design for increased rigidity and houses a forged steel crankshaft
supported by five main bearings. Integral to the lower block assembly are dual
internal balance shafts, driven by a gear system off the crankshaft. These
shafts rotate in opposite directions to counteract the secondary vibrations
inherent in a large-displacement inline-four engine, ensuring smooth operation
up to the redline.
The cylinder head is a cross-flow design cast from
aluminum, featuring dual overhead camshafts. The DOHC configuration allows for a
pent-roof combustion chamber shape, optimizing flame propagation and
accommodating the four-valve-per-cylinder arrangement. The valves are arranged
in a narrow angle to reduce combustion chamber surface area.
The VTEC system is integrated into the cylinder
head, utilizing a complex rocker arm assembly. For each pair of valves,
there are three rocker arms: two primary rockers driven by low-lift,
low-duration cam lobes, and a central secondary rocker driven by a
high-lift, long-duration cam lobe.
At low engine speeds, the primary rockers actuate the valves
independently, while the secondary rocker moves freely without
contacting the valves. Upon VTEC engagement at 5,200 rpm, engine oil
pressure drives a locking pin that connects the secondary rocker to the
primary rockers, forcing them to follow the higher-performance cam
profile.
This system effectively changes the valve lift
and timing. The intake valves are larger in diameter than the exhaust
valves to facilitate optimal cylinder filling, with specifications
including a 35 mm (1.38 in) intake valve and a 30 mm (1.18 in) exhaust
valve. Valve stem seals are precision-engineered to manage oil
consumption under the high cylinder pressures generated during VTEC
operation.
The fuel system is managed by Honda’s PGM-FI
(Programmed Fuel Injection) system, a fully electronic multi-point fuel
injection setup. This system utilizes a sequential injection strategy, where
fuel injectors fire individually in time with each cylinder’s intake stroke,
rather than batch-firing. This precise delivery improves fuel atomization,
throttle response, and emissions control.
The system is comprised of an in-tank fuel pump, a fuel pressure regulator
maintaining consistent pressure to the injector rail, and four high-impedance
injectors located in the intake manifold runners, directing fuel just ahead of
the intake valves.
The engine control unit (ECU) utilizes inputs
from a mass airflow sensor, throttle position sensor, engine coolant
temperature sensor, and a knock sensor to calculate the optimal air-fuel
ratio, targeting a stoichiometric mixture of 14.7:1 under cruising
conditions and enriching the mixture under high-load, high-rpm operation
to suppress detonation and maintain power.
The lubrication system is a wet-sump type, designed to
provide consistent oil pressure under high lateral loads and high-rpm operation.
Oil is drawn from a pressed steel oil pan by a gear-type oil pump, which is
driven directly by the crankshaft. The system capacity is 4.8 liters (5.1 US
qt). A key feature of the lubrication system is its role in actuating the VTEC
mechanism. The system must generate sufficient oil pressure to overcome the
spring tension of the VTEC locking pins; a dedicated oil pressure switch
confirms engagement.
The oil pump also supplies pressure to the dual balance shafts. To ensure
longevity under high-rpm stress, the engine utilizes a piston cooling oil jet
system. These oil jets, or squirters, are mounted in the crankcase and direct a
continuous spray of oil to the underside of the pistons, dissipating heat and
ensuring thermal stability of the FRM cylinder bores and piston rings.
The cooling system is a pressurized, thermosiphon-type
with a centrifugal water pump driven by the timing belt. The system circulates
coolant through the aluminum cylinder block and cylinder head to manage the
significant thermal load generated by high specific output. The thermostat,
rated at 78 °C (172 °F), regulates coolant flow to maintain optimal operating
temperature for combustion efficiency and emissions control.
A notable aspect of the H22A2’s cooling architecture is the coolant bypass
system, which allows circulation through the block and heater core during
warm-up to promote rapid engine warm-up and ensure consistent VTEC oil pressure.
The system utilizes a cross-flow aluminum radiator with dual electric cooling
fans, controlled by the ECU based on coolant temperature and vehicle speed
sensors.
The ignition system is a distributor-based, electronic
spark advance system. The distributor houses a camshaft position sensor and a
cylinder position sensor, providing the ECU with precise timing data. The spark
is delivered via a high-output ignition coil to spark plugs with a specific heat
range designed for the high combustion chamber temperatures encountered during
VTEC operation.
The induction system features a two-stage intake manifold designed to enhance
torque characteristics. It utilizes a variable length intake manifold (VLIM)
system, where butterfly valves within the manifold change the intake runner
length. At lower engine speeds, the runners are long to increase air velocity
and torque; above approximately 4,800 rpm, the runners are shortened to allow
higher airflow for peak horsepower.
The exhaust system incorporates a tubular stainless steel header designed to
reduce exhaust pulse interference, improving scavenging efficiency. The engine
management system is calibrated to work with a closed-loop lambda (oxygen)
sensor for emissions compliance, adjusting fuel trims in real-time based on
exhaust gas composition.
The engine, fully dressed with the intake manifold,
exhaust manifold, and all ancillary components, measures 670 mm (26.4 in) in
length, 650 mm (25.6 in) in width, and 680 mm (26.8 in) in height. The complete
engine weight, including the alternator, starter motor, and power steering pump,
is 185 kg (408 lb). The long block assembly - comprising the cylinder block,
crankshaft, pistons, cylinder head, and camshafts - has a weight of roughly 145
kg (320 lb).
Engine oil must adhere to a viscosity grade of 10W-30
or 10W-40 for most ambient temperatures, with a recommended API service grade of
SG or higher. The oil and filter replacement interval is specified at 7,500 km
(4,660 mi) under normal operating conditions. The timing belt is a critical
maintenance component; replacement is mandatory every 96,000 km (60,000 mi) or
every 72 months, as failure results in valve-to-piston contact due to the
interference design of the engine.
The spark plug replacement interval is 48,000 km (30,000 mi), with a specified
spark plug type of NGK PFR6G-11 or equivalent platinum-tipped plug. Coolant
capacity is 6.4 liters (6.8 US qt), requiring a 50/50 mixture of Honda Long Life
Antifreeze and distilled water, with replacement every 48,000 km (30,000 mi) or
24 months.
Critical fasteners require precise torque application
to ensure integrity under high stress. The cylinder head bolts utilize a
multi-stage torque sequence: initially tightened to 29 Nm (21 lb-ft), then to 49
Nm (36 lb-ft), followed by a 90-degree angular rotation, and finally a second
90-degree angular rotation. Main bearing cap bolts are tightened to 54 Nm (40
lb-ft). Connecting rod cap nuts require 44 Nm (32 lb-ft).
The flywheel or flexplate bolts are torqued to 93 Nm (69 lb-ft). Camshaft
bearing cap bolts are set to 22 Nm (16 lb-ft). The spark plugs are installed to
18 Nm (13 lb-ft). The oil drain plug is secured at 39 Nm (29 lb-ft). All torque
specifications are critical for maintaining clamping force and preventing gasket
failure or component distortion under the engine’s operational stresses.
The H22A2 was designated specifically for the European
automotive market, with its primary application being the fourth-generation
Honda Prelude. From 1992 to 1996, it was installed in the Honda Prelude 2.2i
VTEC, chassis code BB1. This model represented the top-tier performance trim
level for the Prelude in Europe.
The engine was paired exclusively with a close-ratio manual transmission - the
Honda M2A4 or M2F4 five-speed unit - featuring a helical limited-slip
differential in certain variants to manage torque steer and maximize traction
under hard acceleration.
The H22A2 was not offered in the Japanese Domestic Market (JDM), where the
higher-compression H22A was utilized, nor was it offered in the North American
market, which received the H22A1 variant with different emission control
calibrations.
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