Mazda F6A Specifications
| Engine Model: Mazda F6A |
| Engine Type: 4-cycle inline 3-cylinder SOHC or DOHC liquid-cooled gasoline |
| Total Displacement: 40.1 cu.in (0.65 L) |
| Rated Engine Power: 35-63 Hp (26-47 kW) at 6500 rpm |
| Fuel System Type: Carburetor (SOHC) or Multi-point fuel injection (DOHC) |
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The Mazda F6A is a 657 cc, three-cylinder engine
sourced from Suzuki as part of a technical partnership during the Kei car era of
the late 1980s through the 1990s. It was primarily utilized in Mazda’s Kei car
lineup sold under the Autozam brand, most notably the mid-engined Autozam AZ-1
sports car.
This engine family represented a significant collaboration between the two
manufacturers, allowing Mazda to offer a range of compact, efficient powerplants
compliant with Japanese Kei car regulations. The F6A architecture encompassed
numerous variants, from economical single overhead camshaft (SOHC) units to
high-performance dual overhead camshaft (DOHC) turbocharged versions that
defined the spirited driving characteristics of the AZ-1.
The F6A engine is recognized for its robust construction and adaptability across
a wide spectrum of Kei car applications. Its cast-iron cylinder block provides
durability suitable for forced induction, while the aluminum cylinder head
offers weight reduction. The engine’s compact dimensions allowed for transverse
mounting in front-engine vehicles and longitudinal mid-engine placement in the
AZ-1.
The DOHC turbocharged variant, with a redline reaching 9,000 rpm, became
legendary among enthusiasts for its responsive power delivery and distinctive
induction sound. However, the engine’s interference design in later production
iterations made precise timing belt maintenance mandatory to avoid catastrophic
valve-to-piston contact. The evolution from carburetion to electronic fuel
injection improved reliability and cold-start performance across the model
range.
Engine Type: Inline 3-cylinder, 4-cycle, water-cooled gasoline engine.
Displacement: 657 cc (40.1 cu.in).
Bore: 65.0 mm (2.56 in).
Stroke: 66.0 mm (2.60 in).
Compression Ratio: 8.0:1 for turbocharged variants.
Compression Ratio: 9.5:1 for naturally aspirated variants.
Firing Order: 1-2-3.
Maximum Power (Naturally Aspirated SOHC): 26-40 kW (35-54 hp).
Maximum Torque (Naturally Aspirated SOHC): 50-62 Nm (37-46 lb-ft).
Maximum Power (Turbocharged DOHC - Autozam AZ-1): 47 kW (63 hp) @ 6,500 rpm.
Maximum Torque (Turbocharged DOHC): 85-90 Nm (63-66 lb-ft) @ 3,500-4,000 rpm.
Redline: 8,500 rpm for naturally aspirated variants.
Redline: Up to 9,000 rpm for DOHC turbocharged performance versions.
Valvetrain Configurations
SOHC, 6-valve (2 valves per cylinder).
SOHC, 12-valve (4 valves per cylinder).
DOHC, 12-valve (4 valves per cylinder) for high-performance versions
The cylinder block is constructed from cast iron,
providing exceptional rigidity and resistance to the thermal and mechanical
stresses associated with forced induction. This material choice contributed to
the engine’s durability in turbocharged applications. The block features a
closed-deck design with integrated coolant passages surrounding each of the
three cylinder bores.
The deep-skirt configuration extends below the crankshaft centerline, enhancing
structural integrity and minimizing vibration inherent to three-cylinder engine
layouts. The block incorporates the necessary mounting points for both
transverse front-engine applications and the longitudinal mid-engine
configuration found in the Autozam AZ-1.
The cylinder head is manufactured from aluminum alloy
to reduce overall engine weight and improve heat dissipation. Valve
configuration varies by variant. In SOHC 6-valve forms, a single camshaft
operates two valves per cylinder through rocker arms. In SOHC 12-valve forms,
the single camshaft actuates four valves per cylinder using a combination of
direct-acting and rocker-arm mechanisms.
The DOHC variant features two camshafts operating four valves per cylinder
through bucket-type tappets. Valve diameters vary by configuration, with intake
valves measuring approximately 28.0 mm (1.10 in) and exhaust valves 24.0 mm
(0.94 in) in DOHC performance versions. The valvetrain in middle and late
production F6A engines operates with interference geometry, meaning piston
crowns occupy the same space as open valves if timing belt failure occurs.
The fuel system evolved throughout the F6A production
lifespan. Early SOHC variants utilized a carburetor system with a mechanically
operated fuel pump mounted to the cylinder head. These carbureted versions
employed either a two-barrel downdraft or side-draft configuration depending on
the vehicle application. Later naturally aspirated and all turbocharged variants
transitioned to a Multi-Point Fuel Injection (MPFI) system.
This electronically controlled system utilized four-hole injectors positioned in
the intake ports, delivering fuel directly toward the intake valves. The intake
manifold was constructed from aluminum for naturally aspirated versions and from
cast aluminum with integrated mounting points for the top-mount intercooler in
turbocharged applications.
The lubrication system is a forced-feed, wet-sump type
utilizing a rotor-type oil pump mounted to the front of the crankshaft and
driven directly by the crankshaft nose. Oil is drawn from a stamped steel oil
pan through a pick-up strainer before pressurization. A full-flow spin-on oil
filter is mounted externally on the cylinder block.
The system supplies lubricant to the crankshaft main bearings, connecting rod
bearings, camshaft journals, and valve actuation components. In turbocharged
variants, an additional oil feed line supplies the turbocharger center bearing
with pressurized oil, while a return line drains oil back to the sump through
gravity.
The cooling system is a pressurized, water-cooled setup
utilizing a centrifugal water pump driven by the engine’s timing belt or
accessory drive belt, depending on the variant. A wax-type thermostat regulates
engine operating temperature, with opening temperatures varying between 82°C
(180°F) for naturally aspirated versions and 88°C (190°F) for turbocharged
versions.
Coolant circulates through the cast-iron cylinder block and aluminum cylinder
head before passing through a cross-flow radiator. An electric cooling fan,
controlled by a thermoswitch or the Engine Control Unit (ECU) in fuel-injected
variants, provides supplemental airflow. Turbocharged models incorporate an
additional coolant line to the turbocharger bearing housing for post-shutdown
heat soak protection.
Ignition System: Early carbureted SOHC variants
employed a distributor-based ignition system with mechanical advance. Later SOHC
fuel-injected and all DOHC variants utilized a distributorless ignition system
with individual ignition coils or a single coil pack delivering spark through
high-tension leads.
Timing System: The camshaft is driven by a rubber-toothed timing belt. The belt
drives the camshaft sprocket from the crankshaft sprocket, with an automatic
tensioner maintaining correct belt tension. The interference design of middle
and late production engines mandates strict adherence to replacement intervals
to prevent valve-to-piston contact upon belt failure.
Turbocharging (High-Performance Variants): Forced induction is provided by a
small IHI turbocharger, specifically the RHB3B or RHB31 model. The turbocharger
is mounted on the exhaust manifold and features a wastegate to regulate boost
pressure. A top-mount intercooler, positioned above the engine, reduces intake
air temperature before delivery to the throttle body. Boost pressure is
regulated between 0.6 and 0.8 bar (8.7-11.6 psi) in factory configurations.
Exhaust System: A cast-iron exhaust manifold collects gases from the three
cylinders. In turbocharged variants, the manifold integrates the turbocharger
mounting flange. The system includes a catalytic converter and a single muffler
outlet.
Overall Engine Length: 480 mm (18.90 in).
Overall Engine Width: 550 mm (21.65 in).
Overall Engine Height: 580 mm (22.83 in).
Dry Weight (SOHC Naturally Aspirated): 85 kg (187 lb).
Dry Weight (DOHC Turbocharged): 98 kg (216 lb), including the turbocharger and
intercooler assembly.
Engine Oil Capacity (with Filter): 2.8 liters (3.0 qt)
for naturally aspirated variants; 3.0 liters (3.2 qt) for turbocharged variants.
Engine Oil Specification: SAE 10W-30 or 5W-30 meeting API SG or higher
classification. Turbocharged variants require higher-quality oils meeting API SH
or SJ standards. Coolant Capacity: 3.2 liters (3.4 qt) for naturally aspirated
variants; 3.5 liters (3.7 qt) for turbocharged variants.
Spark Plug Type: NGK BPR5ES or equivalent for naturally aspirated variants; NGK
BPR6ES or equivalent for turbocharged variants. Spark Plug Gap: 0.8-1.0 mm
(0.031-0.039 in). Timing Belt Replacement Interval: 60,000 km (37,000 mi) for
interference-type engines; failure to adhere to this interval risks valve
damage.
Valve Clearance (SOHC with Rocker Arms): Intake: 0.13-0.18 mm (0.005-0.007 in);
Exhaust: 0.18-0.23 mm (0.007-0.009 in) measured with engine cold. Adjustment is
performed using adjustment screws or shims depending on the variant.
Valve Clearance (DOHC with Bucket Tappets): Intake: 0.13-0.18 mm (0.005-0.007
in); Exhaust: 0.18-0.23 mm (0.007-0.009 in) measured with engine cold.
Adjustment requires replacement of the appropriate shim.
Cylinder Head Bolts: 54.0-60.0 Nm (5.5-6.1 kgf-m, 40-44
lb-ft).
Main Bearing Cap Bolts: 42.0-48.0 Nm (4.3-4.9 kgf-m, 31-35 lb-ft).
Connecting Rod Cap Bolts: 30.0-35.0 Nm (3.1-3.6 kgf-m, 22-26 lb-ft).
Camshaft Bearing Cap Bolts (DOHC): 12.0-15.0 Nm (1.2-1.5 kgf-m, 9-11 lb-ft).
Intake Manifold Bolts: 18.0-22.0 Nm (1.8-2.2 kgf-m, 13-16 lb-ft).
Exhaust Manifold Nuts: 28.0-33.0 Nm (2.9-3.4 kgf-m, 21-24 lb-ft).
Crankshaft Pulley Bolt: 110.0-130.0 Nm (11.2-13.3 kgf-m, 81-96 lb-ft).
Spark Plugs: 18.0-25.0 Nm (1.8-2.5 kgf-m, 13-18 lb-ft).
Oil Filter: 12.0-14.0 Nm (1.2-1.4 kgf-m, 9-10 lb-ft).
Flywheel Bolts: 65.0-70.0 Nm (6.6-7.1 kgf-m, 48-52 lb-ft).
Turbocharger Mounting Nuts (if equipped): 35.0-40.0 Nm (3.6-4.1 kgf-m, 26-30
lb-ft).
The Mazda F6A engine was utilized across the Mazda and
Autozam Kei car lineup from 1990 through 2000.
Applications include:
Autozam AZ-1: PG6SA (1992-1994) with DOHC turbocharged configuration in
mid-engine layout.
Autozam Carol / Mazda Carol: 1990-2000 with SOHC naturally aspirated and SOHC
turbocharged variants in front-engine, front-wheel-drive layout.
Mazda Laputa: 1999-2000 with SOHC naturally aspirated configuration.
Mazda Scrum: Sourced from Suzuki Carry / Every, utilizing SOHC naturally
aspirated and turbocharged variants in commercial vehicle applications.
Autozam Revue: Early production models (1990-1992) equipped with SOHC naturally
aspirated F6A engines before transition to larger displacement units.
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