Suzuki G12B Specifications
| Engine Model: Suzuki G12B |
| Engine Type: 4-cycle inline 4-cylinder SOHC 16-valve liquid-cooled gasoline |
| Total Displacement: 73 cu.in (1.19 L) |
| Rated Engine Power: 72 Hp (54 kW) at 6000 rpm |
| Fuel System Type: Multi-Point Fuel Injection |
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The Suzuki G12B is a 1.2-liter, inline 4-cylinder
petrol engine developed primarily by Maruti Suzuki for the Indian domestic
market. Conceived as a strategic evolution of the larger G13BB engine, its
development was driven by a specific market requirement: to reduce engine
displacement below 1200 cc, thereby qualifying for substantial excise duty
reductions on compact vehicles.
Introduced in 2010, the G12B represents a pragmatic exercise in downsizing,
utilizing the proven architecture of the G-series engine family while
incorporating a smaller bore to achieve a displacement of 1,196 cc. The engine
is notable for its all-aluminum construction - incorporating an aluminum alloy
block, cylinder head, and pistons - which contributes to reduced weight and
improved thermal management.
Fueled by a Multi-Point Fuel Injection (MPFi) system, the G12B delivers a modest
but reliable power output tailored for urban utility and commercial
applications. Its most significant role has been as the powerplant for the
Maruti Suzuki Eeco van and the Super Carry mini-truck, where durability,
serviceability, and low running costs are paramount. The engine is also offered
in a factory-fitted bi-fuel (petrol/CNG) configuration, underscoring its
adaptability to markets with alternative fuel infrastructure.
Engine Code: G12B.
Engine Family: Suzuki G-series.
Configuration: Inline 4-cylinder.
Valvetrain: Single Overhead Camshaft (SOHC), 16 valves (4 per cylinder).
Displacement: 1196 cc (73.0 cu.in).
Bore: 71.0 mm (2.80 in).
Stroke: 75.5 mm (2.97 in).
Compression Ratio: 9.8:1.
Firing Order: 1-3-4-2.
Fuel System: Multi-Point Fuel Injection (MPFi).
Emission Standard: BS6 (Bharat Stage 6).
Maximum Power (Petrol): 73 PS (54 kW; 72 bhp) at 6000 rpm.
Maximum Torque (Petrol): 98 Nm (72 lb-ft) at 3000 rpm.
Maximum Power (CNG): 65 PS (48 kW; 64 bhp) at 6000 rpm.
Maximum Torque (CNG): 85 Nm (63 lb-ft) at 3000 rpm.
The cylinder block is constructed from aluminum alloy,
a departure from the cast iron blocks used in earlier G-series engines. This
material choice substantially reduces overall engine mass, contributing to
improved vehicle fuel economy and handling characteristics, particularly
important in lightweight commercial and passenger applications. The block
features an open-deck design, where the cylinder bores are unsupported at the
top by the coolant jacket.
This configuration enhances cooling efficiency around the upper cylinder region
but requires precise manufacturing to maintain bore roundness under thermal
expansion. The bores are machined directly into the aluminum block without cast
iron liners; instead, a high-silicon aluminum alloy is used for the cylinder
wall surface, with the pistons incorporating iron-coated skirts for wear
compatibility. The crankshaft is supported by five main bearings, and the block
is designed with a structural oil pan mounting face to enhance powertrain
rigidity.
The cylinder head is cast from aluminum alloy and
employs a Single Overhead Camshaft (SOHC) design. The camshaft operates 16
valves - 4 per cylinder - via a system of roller rocker arms. This arrangement
reduces frictional losses compared to direct-acting bucket tappets, contributing
to fuel efficiency and smoother operation. The valves are arranged in a
cross-flow pattern, with intake ports on one side of the head and exhaust ports
on the opposite side, optimizing gas flow through the combustion chamber.
The rocker arms incorporate screw-and-locknut type adjusters for valve lash
setting, requiring periodic manual adjustment. The combustion chambers feature a
pent-roof shape with a centrally located spark plug to promote efficient flame
propagation. The camshaft is driven by a timing belt, a system derived from the
G13 family architecture, which requires scheduled replacement.
The fuel system is a Multi-Point Fuel Injection (MPFi)
design, employing a port-injection strategy where fuel is injected into the
intake port just upstream of each intake valve. The system uses sequentially
fired injectors controlled by the Engine Control Module (ECM), allowing precise
fuel delivery calibrated to engine load, speed, and temperature. A fuel pump
module located within the fuel tank supplies pressurized fuel to the injector
rail.
A fuel pressure regulator, integrated into the fuel pump module in later BS6
variants, maintains a consistent pressure differential across the injectors. For
bi-fuel (CNG) variants, the factory system incorporates a separate set of CNG
injectors mounted on the intake manifold, a vaporizer/regulator that reduces
high-pressure CNG from the storage cylinder to a low-pressure vapor, and an
ECM-calibrated fuel map for alternate fuel operation. The system automatically
switches between petrol and CNG based on driver selection and engine operating
conditions.
The lubrication system is a pressurized, wet-sump
design utilizing a rotor-type oil pump mounted directly to the crankshaft nose.
This location enables rapid oil pressure buildup upon startup. The oil pump
draws lubricant from a pressed-steel oil pan, with a total system capacity of
3.5 liters (3.7 qt) including the filter. A spin-on, full-flow oil filter with
an integral bypass valve is mounted externally to the engine block.
The system incorporates piston cooling jets - oil nozzles that direct a stream
of oil to the underside of each piston crown - to manage piston temperatures
during sustained high-load operation, a feature particularly beneficial in
commercial vehicle applications. The recommended oil viscosity is 5W-30 or
10W-30, conforming to API SG or higher specifications, with the specific grade
selected based on ambient operating temperatures.
The cooling system is a sealed, pressurized arrangement
employing a belt-driven centrifugal water pump. The water pump is mounted to the
cylinder block and driven by the same external serpentine belt that powers the
alternator. Coolant circulates through the aluminum cylinder block and cylinder
head, with flow directed first to the critical upper cylinder and combustion
chamber regions.
A wax-element thermostat, with an opening temperature of 82°C (180°F), regulates
coolant flow between the engine and the front-mounted radiator. A coolant
reservoir tank allows for thermal expansion and serves as a fill point for the
system. The total cooling system capacity, including the radiator, heater core,
and engine passages, is 4.2 liters (4.4 qt). A 1.1-bar (16.0 psi) radiator cap
maintains system pressure, raising the boiling point of the coolant to prevent
localized boiling in high-temperature zones.
Ignition System: The ignition system is a
distributor-less, direct-fire design utilizing individual ignition coils mounted
directly over each spark plug (coil-on-plug). The ECM controls ignition timing
based on inputs from the crankshaft position sensor, camshaft position sensor,
knock sensor, and engine load parameters. This system eliminates high-tension
spark plug wires, reducing electromagnetic interference and improving ignition
reliability.
Intake and Exhaust Systems: The intake system incorporates a plastic composite
intake manifold with long, tuned runners designed to enhance low-end torque
characteristics. An electronically controlled idle air control valve manages
idle speed under varying engine loads. The exhaust manifold is constructed from
cast iron, with a single oxygen sensor mounted upstream of the catalytic
converter for closed-loop fuel control.
Engine Management: The engine is managed by a single Engine Control Module (ECM)
that integrates fuel injection, ignition timing, idle speed control, and
evaporative emission system functions. For bi-fuel variants, the ECM
incorporates dual fuel maps and controls the switching mechanism between petrol
and CNG operation.
Emission Control: The emission control system includes a three-way catalytic
converter, a heated oxygen sensor for closed-loop air-fuel ratio control, a
positive crankcase ventilation (PCV) system, and an evaporative emission control
system with a charcoal canister.
Overall Length: 520 mm (20.5 in)
Overall Width: 550 mm (21.7 in)
Overall Height: 630 mm (24.8 in)
Dry Weight (without ancillaries): 92 kg (203 lb)
Dry Weight (fully dressed with manifolds, alternator, and starter): 105 kg (231
lb)
Engine Oil Capacity (with filter change): 3.5 liters
(3.7 qt).
Engine Oil Capacity (without filter change): 3.3 liters (3.5 qt).
Engine Oil Specification: 5W-30 or 10W-30, API SG or higher.
Oil Change Interval: 10,000 km (6,250 miles) or 1 year.
Coolant Capacity: 4.2 liters (4.4 qt).
Coolant Specification: Ethylene glycol-based, silicate-free long-life coolant.
Timing Belt Replacement Interval: 60,000 km (37,500 miles) for severe duty.
Timing Belt Replacement Interval: 80,000 km (50,000 miles) for normal duty.
Valve Clearance (cold, intake): 0.13-0.17 mm (0.0051-0.0067 in).
Valve Clearance (cold, exhaust): 0.23-0.27 mm (0.0091-0.0106 in).
Valve Clearance Adjustment Interval: Inspect every 40,000 km (25,000 miles);
adjust as required.
Spark Plug Type: NGK BKR5E-11 or equivalent.
Spark Plug Gap: 1.0-1.1 mm (0.039-0.043 in).
Spark Plug Replacement Interval: 20,000 km (12,500 miles) for copper core.
Spark Plug Replacement Interval: 40,000 km (25,000 miles) for platinum.
Drive Belt (serpentine) Tension: Deflection of 10-12 mm (0.39-0.47 in) under 10
kg (22 lb) at midpoint.
Fuel Filter Replacement Interval: 40,000 km (25,000 miles) for earlier variants.
Cylinder Head Bolts: 35 Nm (26 lb-ft)
Main Bearing Cap Bolts: 55 Nm (41 lb-ft)
Connecting Rod Cap Bolts: 35 Nm (26 lb-ft)
Camshaft Sprocket Bolt: 55 Nm (41 lb-ft)
Crankshaft Pulley Bolt: 150 Nm (111 lb-ft)
Flywheel Bolts: 70 Nm (52 lb-ft)
Intake Manifold Bolts: 23 Nm (17 lb-ft)
Exhaust Manifold Nuts: 23 Nm (17 lb-ft)
Spark Plugs: 25 Nm (18 lb-ft)
Oil Pan Bolts: 11 Nm (8 lb-ft)
Rocker Arm Assembly Bolts: 23 Nm (17 lb-ft)
Valve Lash Lock Nut: 18 Nm (13 lb-ft)
Water Pump Bolts: 11 Nm (8 lb-ft)
Maruti Suzuki Eeco (2010-2022): The primary application
for the G12B engine in passenger and cargo van configurations. The engine
replaced the earlier 1.0-liter F10D unit. Available in both 5-seater and
7-seater van variants, as well as cargo versions, with factory-fitted CNG option
introduced in later production years. Production of the G12B in the Eeco ceased
in late 2022 with the transition to the K12N engine.
Maruti Suzuki Super Carry (2016-present): The G12B serves as the powerplant for
this mini-truck and light commercial vehicle platform. Designed for
payload-focused applications, the engine in the Super Carry is tuned for
durability under sustained load cycles. Factory-fitted CNG variants are also
available for commercial operators seeking lower fuel costs. The engine
continues in production for this application.
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