Honda J37A4 Specifications
| Engine Model: Honda J37A4 |
| Engine Type: 4-cycle 6-cylinder SOHC 24-valve VTEC liquid-cooled gasoline |
| Total Displacement: 223.6 cu.in (3.66 L) |
| Rated Engine Power: 305 Hp (227 kW) at 6300 rpm |
| Fuel System Type: Multi-point electronic fuel injection |
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The Honda J37A4 represents the apex of the naturally
aspirated J-series V6 engine family, serving as the flagship powerplant for the
fourth-generation Acura TL. It distinguished itself from its contemporaries
within the J-series lineup through a singular focus on high-rpm power delivery,
a characteristic reserved for Honda’s legendary four-cylinder VTEC engines.
The defining feature of the J37A4 is its implementation of Dual VTEC, a system
that engages Variable Valve Timing and Lift Electronic Control on both the
intake and exhaust camshafts. This architecture allowed the engine to combine
strong volumetric efficiency at high engine speeds with a broad torque curve for
daily drivability.
Built upon a 60-degree V6 architecture, displacement was increased to 3.7 liters
through a larger bore and a longer stroke compared to the widely used J35. To
accommodate the larger bore without increasing the engine’s external dimensions,
the J37A4 utilized advanced Metal Matrix Composite (MMC) cylinder liners. These
high-silicon aluminum liners eliminated the need for cast-iron sleeves, allowing
for a greater cylinder bore within the existing block casting.
The engine was exclusively paired with the Super Handling All-Wheel Drive
(SH-AWD) system in the Acura TL, delivering power through a close-ratio
six-speed manual or a six-speed automatic transmission. While praised for its
responsive powerband and distinctive induction sound, the J37A4 gained a
reputation for specific maintenance sensitivities, particularly concerning oil
consumption and the critical nature of its timing belt service intervals.
The Honda J37A4 employs a 60-degree V6 configuration with a transverse mounting
orientation, optimized for front-wheel-drive-based all-wheel-drive platforms.
The valvetrain is a Single Overhead Camshaft (SOHC) design operating 24 valves.
The hallmark of this engine is the Dual VTEC system, where each camshaft is
equipped with VTEC rocker arms that engage a high-lift, long-duration cam lobe
at predetermined engine speeds and load conditions. This setup operates
independently on the intake and exhaust sides to optimize scavenging and
cylinder filling.
Displacement is precisely 3,664 cc (223.6 cu.in), achieved with a bore of 90.0
mm (3.54 in) and a stroke of 96.0 mm (3.78 in). The compression ratio is set at
11.2:1, necessitating premium grade fuel for maximum performance and knock
prevention. The engine management system utilizes Honda’s Programmed Fuel
Injection (PGM-FI), a multi-point sequential fuel injection system.
Maximum power output is rated at 305 hp (227 kW) at 6,300 rpm, with peak torque
of 273 lb-ft (370 Nm) at 5,000 rpm. The engine redline is 6,700 rpm, with the
VTEC engagement point occurring in the upper range to maximize power output
without compromising low-end drivability.
The cylinder block is constructed from high-pressure
die-cast aluminum to reduce overall engine mass. The structural rigidity of the
block is enhanced by a deep-skirt design and a cast aluminum ladder frame that
secures the main bearing caps, contributing to reduced noise, vibration, and
harshness. Unlike conventional aluminum blocks that require cast-iron cylinder
liners, the J37A4 features direct-cylinder liners made from a Metal Matrix
Composite (MMC) or high-silicon aluminum alloy (Alusil). In this process,
silicon particles are uniformly distributed throughout the aluminum liner
material.
After the block is cast, the cylinder bores are etched to expose the hard
silicon crystals, creating an extremely durable, low-friction surface against
which the aluminum piston rings slide directly. This technology permitted the
engine to achieve a 90.0 mm (3.54 in) bore, a dimension that would have been
challenging to accommodate with cast-iron sleeves within the same external block
dimensions.
The cylinder heads are constructed from aluminum alloy
and utilize a cross-flow design to optimize intake and exhaust routing. Each
head houses the single camshaft, which operates four valves per cylinder via
roller rocker arms. The Dual VTEC system is integrated into the rocker arm
assemblies. Each cylinder’s valve pair (intake and exhaust) is equipped with
three rocker arms: a primary, a secondary, and a mid-VTEC rocker arm. During
low-rpm operation, the primary and secondary rocker arms follow low-lift cam
lobes.
When VTEC activates, hydraulic pressure from a spool valve locks the three
rocker arms together, forcing them to follow a larger, high-lift cam lobe
positioned in the center. The valve diameter is optimized for high flow, with
intake valves measuring 35.0 mm (1.38 in) in diameter and exhaust valves
measuring 30.0 mm (1.18 in).
The valves are angled to create a compact
combustion chamber that promotes efficient flame propagation. Valve stem
seals are manufactured from fluoro-rubber for high-temperature
durability. Maintenance requires manual valve clearance adjustments, as
the system does not incorporate hydraulic lash adjusters.
The fuel system is a returnless multi-point port
injection design, managed by the PGM-FI system. Fuel is delivered from an
in-tank pump to individual fuel injectors positioned in the intake ports, just
upstream of the intake valves. The injectors are electronically controlled to
deliver precise fuel amounts based on signals from the Mass Air Flow (MAF)
sensor, oxygen sensors, and engine load calculations.
The intake manifold is constructed from magnesium, a material chosen for its
light weight and high rigidity. It incorporates a dual-stage intake runner
system to enhance torque across the engine speed range. At low engine speeds,
long intake runners increase air velocity to improve cylinder filling. At high
engine speeds, a set of intake manifold valves opens to shorten the runner
length, allowing for higher volumetric flow to support the power output
generated by the VTEC system.
The lubrication system utilizes a gear-driven oil pump
mounted directly to the crankshaft. The pump is designed to provide high flow at
low engine speeds while preventing excessive pressure at high rpm. The system
capacity is approximately 5.6 liters (5.9 qt). A water-cooled oil cooler is
integrated into the system to stabilize oil temperature under severe operating
conditions, such as sustained high-rpm driving. A critical aspect of the J37A4’s
lubrication design is the piston oiler jets.
These jets are mounted in the cylinder block and spray oil onto the undersides
of the pistons to dissipate heat. The MMC cylinder liners, combined with
low-tension piston rings designed to reduce friction, create a susceptibility to
oil consumption. The engine relies on the precise control of oil viscosity and
level; frequent monitoring is a specified operational requirement.
The cooling system is a pressurized, cross-flow design.
Coolant is circulated by a water pump driven by the timing belt, a configuration
that ensures precise pump operation relative to engine speed. The system
incorporates a high-capacity aluminum radiator with a dual-fan assembly to
manage heat rejection, particularly crucial given the engine’s high specific
output and the additional cooling demands of the SH-AWD rear differential unit.
The thermostat is located on the water pump housing and opens at a temperature
of 78°C (172°F) to maintain optimal operating temperatures. A cast aluminum
coolant outlet housing integrates the engine coolant temperature sensor. The
system also includes a heater core bypass circuit to maintain consistent flow
when the cabin heater is not in use.
The ignition system utilizes a direct-fire,
coil-on-plug design, where each cylinder has its own ignition coil mounted
directly over the spark plug. This eliminates the need for spark plug wires and
ensures maximum spark energy delivery. The engine management system is
integrated with the vehicle’s drive-by-wire throttle control, which regulates
the electronically controlled throttle plate based on accelerator pedal position
and stability control logic.
The exhaust system features dual exhaust manifolds with integrated catalytic
converters mounted close to the engine to reduce light-off time for emissions
compliance. The timing system is a belt-driven configuration, requiring a
high-tensile strength belt with automatic tensioner and idler pulleys. This is
an interference engine, meaning valve-to-piston contact occurs if the timing
belt fails.
Overall engine length is 521 mm (20.5 in), width is 775
mm (30.5 in), and height is 724 mm (28.5 in) when fully dressed with intake and
exhaust manifolds. The engine weight, fully dressed and without fluids, is 161
kg (355 lb). The dry weight of the long block assembly alone is 100 kg (220 lb).
Valve clearance inspection and adjustment is required
at intervals of 96,000 to 160,000 km (60,000 to 100,000 miles). The intake valve
clearance specification is 0.21 mm to 0.25 mm (0.0083 in to 0.0098 in) for the
primary and secondary rocker arms, with a specific clearance of 0.22 mm to 0.26
mm (0.0087 in to 0.0102 in) for the VTEC rocker arm.
Exhaust valve clearance is set at 0.25 mm to 0.29 mm (0.0098 in to 0.0114 in)
for primary and secondary rockers, and 0.26 mm to 0.30 mm (0.0102 in to 0.0118
in) for the exhaust VTEC rocker. The timing belt replacement interval is 169,000
km (105,000 miles) or seven years. The spark plug replacement interval is
169,000 km (105,000 miles), using iridium-tipped plugs with a gap of 1.1 mm
(0.043 in).
The engine oil and filter change interval is recommended at 12,000 km (7,500
miles) under normal driving conditions, using SAE 5W-20 viscosity grade meeting
API specifications. The engine oil capacity with filter is 5.6 liters (5.9 qt).
Coolant capacity is 8.1 liters (8.6 qt) for the engine and radiator system. The
automatic tensioner for the accessory drive belt should be inspected during
timing belt replacement.
The cylinder head bolts require a multi-stage torque
sequence. Stage one is 30 Nm (22 lb-ft). Stage two is 90 degrees of angular
rotation. Stage three is an additional 90 degrees of angular rotation. Main
bearing cap bolts are torqued to 43 Nm (32 lb-ft) plus 60 degrees of angular
rotation. Connecting rod cap nuts are torqued to 33 Nm (24 lb-ft) plus 60
degrees of angular rotation.
The camshaft sprocket bolt is torqued to 64 Nm (47 lb-ft). The crankshaft pulley
bolt is torqued to 245 Nm (181 lb-ft). The intake manifold mounting nuts are
torqued to 22 Nm (16 lb-ft). The exhaust manifold mounting nuts are torqued to
31 Nm (23 lb-ft). The spark plugs are torqued to 18 Nm (13 lb-ft). The timing
belt tensioner bolt is torqued to 22 Nm (16 lb-ft). The engine mount
through-bolts are torqued to 64 Nm (47 lb-ft).
The Honda J37A4 engine was utilized exclusively for the
performance-oriented trim of the fourth-generation Acura TL. Its singular
application was the 2009 to 2014 Acura TL SH-AWD (Super Handling All-Wheel
Drive).
In this application, the engine was paired with either a six-speed manual
transmission or a six-speed automatic transmission, both of which were
integrated with the SH-AWD system. No other Honda or Acura models received this
specific engine variant, making its production run synonymous with the lifecycle
of the TL SH-AWD.
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