Honda H22A4 Specifications
| Engine Model: Honda H22A4 |
| Engine Type: 4-cycle inline 4-cylinder DOHC 16-valve VTEC liquid-cooled gasoline |
| Total Displacement: 131.6 cu.in (2.16 L) |
| Rated Engine Power: 200 Hp (149 kW) at 7000 rpm |
| Fuel System Type: Multi-point electronic fuel injection |
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The Honda H22A4 represents the culmination of the
H-series engine lineage, serving as the final and most sophisticated iteration
of the 2.2-liter powerplant. Produced from 1997 through 2001, this engine was
the exclusive power unit for the fifth-generation Honda Prelude in the North
American and Australian markets. Distinguished from its predecessors, such as
the H22A1, the A4 variant was engineered with a focus on enhanced durability,
refined emissions compliance, and a broader, more accessible power band.
While retaining the fundamental architecture of the H-series - a
transverse-mounted inline-four with Honda’s signature DOHC VTEC system - the
H22A4 incorporated critical internal revisions. The most notable change was an
increase in main bearing diameter, a modification that significantly bolstered
bottom-end strength for sustained high-rpm operation. It retained the complex
cylinder head design that made the H22 legendary, combining high specific output
with the dual-character personality of VTEC: docile efficiency below the
engagement threshold and aggressive power delivery beyond it.
The engine’s application was diverse within the Prelude chassis, being offered
in both base form and the Type SH variant, where it was paired with Honda’s
innovative Active Torque Transfer System (ATTS) to manage torque steer and
enhance cornering dynamics. This engine remains a benchmark for naturally
aspirated four-cylinder engineering, celebrated for its high-revving nature,
robust construction when properly maintained, and the distinctive mechanical
symphony of its VTEC crossover.
Engine Type: 4-stroke, water-cooled, DOHC, inline-4, gasoline.
Displacement: 2,157 cc (2.2 L / 131.6 cu.in).
Bore: 87.0 mm (3.43 in).
Stroke: 90.7 mm (3.57 in).
Compression Ratio: 10.0:1.
Firing Order: 1-3-4-2.
Maximum Power (1999-2001 models): 149 kW (200 hp) at 7,000 rpm.
Maximum Torque: 212 Nm (156 lb-ft) at 5,250 rpm.
VTEC Engagement Point: 5,200 rpm.
Engine Redline: 7,400 rpm.
Rev Limiter: 8,000 rpm.
The cylinder block of the H22A4 is constructed from
high-pressure die-cast aluminum to reduce overall engine weight. It retains the
open-deck design, where the cylinder bores are not supported by the full height
of the block casting at their tops. This configuration promotes superior coolant
flow around the cylinder walls, ensuring consistent thermal management under
high-load conditions, though it offers less structural rigidity than a
closed-deck design for extreme forced induction applications.
A defining characteristic of this block is the use of Fiber Reinforced Metal
(FRM) cylinder liners. These liners are a composite material integrating
aluminum oxide and carbon fibers, creating a hard, wear-resistant surface that
is lighter than traditional cast-iron sleeves. This technology mandates strict
adherence to piston selection; only pistons specifically designed for FRM
compatibility, such as those manufactured by Mahle for OEM applications, can be
used. The use of standard forged aluminum pistons will result in rapid cylinder
wall scoring and engine failure.
A significant evolutionary change for the H22A4 is found in the main bearing
journals. Unlike earlier H22 variants (H22A1, H22A2) which utilized 50 mm (1.97
in) main bearings, the H22A4 was upgraded to 55 mm (2.17 in) main bearing
journals. This increase in diameter enhances the rigidity of the
crankshaft-to-block interface, providing a more stable foundation for the
rotating assembly at high engine speeds and improving overall durability. The
cylinder block also features a shallow-sump design with a reshaped oil pan to
accommodate the chassis bracing and subframe changes of the fifth-generation
Prelude.
The cylinder head is a dual-overhead camshaft (DOHC)
design, constructed from aluminum alloy. It houses 16 valves (4 per cylinder)
actuated by a combination of roller rocker arms and the VTEC (Variable Valve
Timing and Lift Electronic Control) system. The VTEC system utilizes two
distinct cam profiles for the intake valves: a low-lobe profile for fuel
efficiency and stability at low rpm, and a high-lobe profile that engages at
5,200 rpm to provide increased valve lift and duration for maximum power output.
Valve Configuration: DOHC, 4 valves per cylinder.
Intake Valve Diameter: 35.0 mm (1.38 in).
Exhaust Valve Diameter: 30.0 mm (1.18 in).
Valve Stem Diameter (Intake and Exhaust): 5.5 mm (0.22 in).
Camshaft Drive: Timing belt.
The valvetrain is designed for high-rpm durability. The roller rocker arms
reduce friction between the cam lobes and the valve train, while the VTEC rocker
arm assembly uses a hydraulic locking pin to engage the high-lobe profile. The
cylinder head also utilizes a cross-flow design, with the intake manifold on the
front side and the exhaust manifold on the rear side, optimizing airflow
dynamics.
The H22A4 employs a PGM-FI (Programmed Fuel Injection)
system, specifically a multi-point, sequential fuel injection setup. In this
system, each cylinder is provided with its own fuel injector located in the
intake manifold runner, which sprays fuel directly onto the back of the intake
valves. The injection timing is synchronized with the engine’s firing order,
allowing for precise fuel delivery tailored to individual cylinder events.
This system is managed by the engine control unit (ECU), which utilizes data
from sensors such as the mass airflow (MAF) sensor, throttle position sensor
(TPS), and oxygen sensors to maintain an optimal air-fuel ratio (approximately
14.7:1 under cruise conditions). The system is calibrated for emissions
compliance and driveability, providing crisp throttle response across the rev
range.
The lubrication system is a full-flow, trochoid-type
oil pump driven directly by the crankshaft. The system is engineered to maintain
stable oil pressure across the high-rpm range for which the engine is known. The
oil pan features a revised baffle design to prevent oil starvation during
high-cornering loads, a critical consideration given the Prelude’s
performance-oriented chassis.
Oil Capacity (with filter): 4.8 L (5.1 qt).
Oil Pressure (at 3,000 rpm, warm): 3.5 bar (51 psi).
Recommended Oil Viscosity: 5W-30 or 10W-30.
Oil Pump Type: Trochoid gear pump.
A critical component of the lubrication system is the VTEC oil pressure circuit.
The system includes a dedicated oil pressure switch that must register
sufficient pressure (approximately 0.8 bar or 12 psi) to allow the VTEC system
to engage. Low oil level or pressure will deactivate the VTEC mechanism, serving
as a protective measure for the valvetrain.
The cooling system is a pressurized, water-cooled setup
designed to maintain stable operating temperatures under demanding conditions.
The water pump is a centrifugal type, driven by the timing belt. The system
employs a thermostatically controlled bypass circuit to allow the engine to
reach operating temperature quickly.
Coolant Capacity: 6.2 L (6.6 qt).
Thermostat Opening Temperature: 78°C (172°F).
Radiator Cap Pressure: 1.1 bar (16 psi).
Water Pump Drive: Timing belt.
The open-deck design of the cylinder block facilitates superior coolant
circulation around the cylinder bores, mitigating the formation of hot spots.
This is particularly important for an engine that operates at high rpm and
utilizes FRM cylinder liners, which have different thermal expansion properties
compared to cast iron.
Direct ignition system with a distributor-less design.
Each cylinder has its own ignition coil and spark plug. The system uses a
crankshaft position sensor (CKP) and camshaft position sensor (CMP) to determine
ignition timing with high precision. The timing is managed by the ECU, with a
base ignition timing of 15° BTDC.
Emissions Control: The engine is equipped with an
exhaust gas recirculation (EGR) system to reduce nitrogen oxide (NOx) emissions.
It also utilizes a three-way catalytic converter and a secondary oxygen sensor
downstream of the catalyst to monitor converter efficiency.
Intake System: A variable-length intake manifold (IMRC - Intake Manifold Runner
Control) is utilized to optimize airflow. The system uses butterfly valves
within the intake runners that open at higher rpm to shorten the effective
runner length, enhancing top-end power while maintaining low-end torque.
Active Torque Transfer System (Type SH only): In the Prelude Type SH, the H22A4
is mated to an ATTS unit housed within the transaxle. This electromechanical
differential uses hydraulic clutches to actively distribute torque between the
front wheels during cornering, applying more torque to the outside wheel to
reduce understeer and improve turn-in response.
Dry Engine Weight (complete, with manifolds): 147 kg
(324 lb).
Overall Length: 580 mm (22.8 in).
Overall Width: 640 mm (25.2 in).
Overall Height: 650 mm (25.6 in).
Valve Clearance (Intake, cold): 0.21-0.25 mm
(0.008-0.010 in).
Valve Clearance (Exhaust, cold): 0.25-0.29 mm (0.010-0.011 in).
Timing Belt Replacement Interval: 96,000 km (60,000 miles).
Spark Plug Type: NGK PFR7G-11S or DENSO PKJ20CR-L11.
Spark Plug Gap: 1.1 mm (0.043 in).
Engine Oil Change Interval: 8,000 km (5,000 miles) under normal conditions.
Coolant Replacement Interval: 96,000 km (60,000 miles) or 5 years.
Cylinder Head Bolts (Step 1): 29 Nm (21 lb-ft).
Cylinder Head Bolts (Step 2, angle): 90° rotation.
Connecting Rod Cap Bolts (Step 1): 20 Nm (14 lb-ft).
Connecting Rod Cap Bolts (Step 2, angle): 90° rotation.
Main Bearing Cap Bolts (Step 1): 49 Nm (36 lb-ft).
Main Bearing Cap Bolts (Step 2, angle): 45° rotation.
Camshaft Bearing Cap Bolts: 21 Nm (15 lb-ft).
Flywheel / Drive Plate Bolts: 101 Nm (74 lb-ft).
Intake Manifold Nuts: 23 Nm (17 lb-ft).
Exhaust Manifold Nuts: 32 Nm (24 lb-ft).
Spark Plugs: 18 Nm (13 lb-ft).
Oil Drain Plug: 39 Nm (29 lb-ft).
1997-2001 Honda Prelude (Base Model) - North America
and Australia: The H22A4 was the sole engine offering for the fifth-generation
Prelude in these markets. In the base configuration, it was paired with either a
5-speed manual transmission or a 4-speed automatic transmission.
1997-2001 Honda Prelude Type SH (Super Handling) - North America: This variant
utilized the H22A4 in conjunction with Honda’s ATTS (Active Torque Transfer
System). The ATTS unit was integrated into the transmission assembly and
replaced the standard open differential. This application featured revised
engine mounts and a unique oil pan to accommodate the ATTS hardware, but the
engine’s power output and internal specifications remained identical to the base
model.
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