engine TOYOTA CAMRY 2000 Service User Guide

CAMRY ± NEW FEATURES36
5S-FNE ENGINE
1. Description
The 5S-FNE engine is a new engine that uses CNG (Compressed Natural Gas) as fuel, which has been devel-
oped based on the 5S-FE gasoline engine.
The main component of natural gas is methane (CH
4), which has fewer carbous (C) than gasoline (mean mo-
lecular formula: C
7.5H13.4). Therefore, the amount of CO2 discharged by this engine is approximately 70%
that of the gasoline engine. Furthermore, this engine achieves low-emission operation by precisely controlled
air-fuel ratio and using special catalysts for the CNG application.
However, because the fuel is in the gaseous form, its volumetric efficiency is low, causing lower power output
if this fuel is used in the base engine.
Therefore, the 5S-FNE engine has adopted the following features: a high compression ratio, the intake valves
with early closed timing, the intake and exhaust valves with increased lift, a low back pressure muffler made
possible by the 2-way exhaust system, injectors for gaseous fuel, and a catalytic converter designed exclu-
sively for CNG application. At the same time, precision air-fuel ratio control is effected through the use of
the air-fuel ratio sensor* and the heater oxygen sensor, thus achieving the level of performance that is equiva-
lent to the base engine. Moreover, this engine realizes extremely low emissions and restoring engine torque.
*: Already adopted on the California specification 5S-FE engine.

Specifications 
Item5S-FNE Engine5S-FE Engine
No. of Cyls. & Arrangement4-Cylinder, In-Line
Valve Mechanism16-Valve DOHC,
Belt & Gear Drive
Combustion CamberPentroof Type
ManifoldsCross-Flow
Fuel SystemSFI
Displacement cm3 (cu.in.)2164 (312.0)
Bore x Stroke mm (in.)87.0 x 91.0 (3.43 x 3.58)
Compression Ratio11.0 : 19.5 : 1
Max. Output [SAE-NET]88 kW @ 5200 rpm
(118 HP @ 5200 rpm)
101 kW @ 5200 rpm
(136 HP @ 5200 rpm)
97 kW @ 5200 rpm*
(133 HP @ 5200 rpm)*
Max. Torque [SAE-NET]178 N.m @ 2400 rpm
(131 ft-lbf @ 2400 rpm)
203 N.m @ 4400 rpm
(150 ft-lbf @ 4400 rpm)
201 N
.m @ 4400 rpm*
(148 ft-lbf @ 4400 rpm)*
IntakeOpen3 BTDC
Valve
IntakeClose38 ABDC43 ABDCValve
Timing
ExhaustOpen45 BBDCExhaustClose3 AT D C
Fuel Octane Number RON13091
Oil GradeAPI SJ EC or ILSAC
*: California Specification Models

3
CAMRY ± NEW FEATURES
167CN20
N.m (ft-lbf)
200
180
160
140
120140
130
120
110
100
90
1000 20003000 4000 5000 6000(HP) kW
130
120
110
100
90
80
70
60
50
40
30
20
10
0100
90
80
70
60
50
40
30
20
10
0
Torque
Output
Engine Speed (rpm)37

Performance Curve 

CAMRY ± NEW FEATURES 38
2. Features of 5S-FNE Engine
Features of the 5S-FNE engine are listed below.
Item
Features
Performance
High compression ratio is used.
High lift camshaft is used.
Low back pressure muffler is used.
Fuel Economy
High compression ratio is used.
Valve spring load has been reduced.
Low-friction. TiN (titanium nitride) coated valve lifters has been adopted.
Low Emission
A fuel injection system containing gas injectors has been adopted.
Because the fuel is in the gaseous state, it does not come in contact with
the wall surface, making optimal air-fuel ratio control possible
immediately after the engine has been started.
Precision air-fuel ratio feedback control that uses an air-fuel ratio sensor
and a heated oxygen sensor has been adopted.
Two catalytic converters designed exclusively for the natural gas engine
have been adopted: the WU-TWC (Warm Up Three-Way Catalytic
Converter) and the TWC (Three-Way Catalytic Converter).
Other Features
Highly rigid pistons have been adopted to accommodate the high
compression ratio.
A CNG (Compressed Natural Gas) pressure regulator that precisely
regulates the CNG has been adopted.
A large-bore delivery pipe and fuel hose with minimal internal conduit
resistance have been adopted.
The electro magnetic fuel shutoff valve is added on the delivery pipe.
A fuel pressure sensor that corrects the fuel injection volume and a fuel
temperature sensor have been provided on the delivery pipe.
The starting performance of the engine at low temperatures has been
ensured by increasing the volume of the airflow of the IAC (Idle Air
Control).
Materials that excel in wear resistance have been adopted on the valves
and valve seats for both the intake and exhaust.
Rust-resistant spark plugs have been adopted.
Aluminum lining and carbon fiber have been adopted in the fuel tank.
For the fuel gauge, a fuel tank fuel temperature sensor and a fuel pipe fuel
pressure sensor have been adopted.

3
CAMRY ± NEW FEATURES
167CN03 167CN02
5S-FNE Engine 5S-FE Engine39
3. Engine Proper
General
The cylinder head and the pistons have been changed for the CNG application.
Cylinder Head
Materials that excel in wear resistance have been adopted on the valve seats for both the intake and exhaust.
The shape of the holes into which the injectors mount has been changed to accommodate the injectors de-
signed exclusively for the CNG application.
The shape of water jacket around plug has been modified to prevent the deformation.
Piston
To achieve a high compression ratio, the shape of the top of the piston has been changed and pin boss hole
with taper has been adopted.
An additional surface treatment has been provided to improve heat resistance.
The material has been changed to increase rigidity.

CAMRY ± NEW FEATURES
167CN04
Valve Lifters
Intake ValveAdjusting Shims
Exhaust Valve 40
4. Valve Mechanism
Camshaft
To recover the reduction of engine performance, the intake valve timing and the amount of lift of the intake
and exhaust valves have been changed from those of the base 5S-FE engine.

Specificaitons 
Valve TimingValve Lift mm (in.)
EngineIntakeExhaustIntakeExhaustg
OpenCloseOpenCloseIntakeExhaust
5S-FNE3 BTDC38 ABDC45 BBDC3 AT D C7.9 (0.311)8.25 (0.325)
5S-FE
43 ABDC

7.7 (0.303)7.7 (0.303)
Intake and Exhaust Valves
To improve their wear resistance, the intake valves have undergone special heat treatment, and the mate-
rial of the exhaust vavles has been changed.
The shape of the stem to which the keepers attach has been changed to accommodate the adoption of the
cam with a high lift and of the inner shim type valve adjusting shims.
Valve Lifter and Adjusting Shims
TiN (titanium nitride) coated valve lifter is used to reduce the friction.
To accommodate the high lift, inner shim type valve adjusting shims are used.
Valve Spring
The valve springs for both the intake and exhaust sides accommodate the adoption of the cam with a high
lift and of the inner shim type valve adjusting shims. In addition, their spring rate has been optimized to
reduce friction.

3
CAMRY ± NEW FEATURES
167CN05
WU-TWC
167CN06
TWCSub MufflerMain Muffler41
5. Intake and Exhaust System
Throttle Body
The throttle body is basically the same as that of the 5S-FE engine. However, to ensure the starting perfor-
mance at low temperatures, the air passage for the IAC (Idle Air Control) has been increased on the 5S-FNE
engine. The IAC valve is a 1-coil type with a built-in driver.
Exhaust Manifold
As in the California specification 5S-FE engine,
the stainless steel exhaust manifold and WU-
TWC (Warm Up Three-Way Catalytic Convert-
er) have been integrated to improve the warm-up
performance of TWC, thus reducing exhaust
emissions.
However, the 5S-FNE engine uses a catalytic
converter that has been designed exclusively for
the CNG application, in which the loading of the
noble metal has been increased.
Exhaust Pipe
1) General
To secure sufficient luggage compartment capacity, the main muffler has been relocated below the rear
seat. Furthermore, the muffler capacity has been increased.
A 2-way exhaust control system has been adopted to improve engine performance and reduce the exhaust
noise.
Similar to the WU-TWC, the TWC (Three-Way Catalytic Converter) has been designed exclusively for
the CNG application, in which the loading of the noble metal has been increased.

CAMRY ± NEW FEATURES
167CN07
Exhaust Gas
Control Valve
Control Valve: Low Engine Speed
: High Engine Speed
42
2) 2-Way Exhaust Control System
a. General
A 2-way exhaust control system reduces the back pressure by opening and closing two control valves
that are enclosed in the main muffler, thus verying the exhaust gas passage.
The valves open steplessly in accordance with the operating condition of the engine, thus enabling
a quieter operation at low engine speeds, and reducing back pressure at high engine speeds.
b. Operation
The control valves are closed at low engine speeds because the pressure in the main muffler is low.
Therefore, the exhaust gas flows as indicated by the black arrow below, thus reducing the exhaust noise.
The control valves open at high engine speeds because the exhaust gas pressure increased. Therefore,
the exhaust gas flows as indicated by the white arrow below to reduce the back pressure, thus improving
the engine's power output.

3
CAMRY ± NEW FEATURES
172CM14
Fuel
Pressure
SensorFuel Temp.
SensorFuel
Pressure
RegulatorFuel Shutoff ValveFuel Tank
Fuel Shutoff ValveRelief Valve
Inlet Check
Valve
Fuel Temp.
Sensor
Coupler
Tank Valve Assembly
Vent Tube Manual
Shutoff
Valve Oil
Separator
Fuel Shutoff Valve Injectors
Delivery Pipe Discharge
ValveFuel
Pressure
SensorFuel
Filter43
6. Fuel System
General
The compressed gas [maximum pressure approximately 250 kg / cm
2 (3600 psi, 24.8 MPa) @ 21C
(70F)] from the CNG fuel tank located in the rear section of the vehicle is routed via a fuel filter to the
engine compartment. The pressure of the fuel is then reduced to 8 kg / cm
2 (114 psi, 785 kPa).
A pressure regulator and injectors designed exclusively for CNG application have been adopted.
A fuel pressure sensor and a fuel temperature sensor that are used for the correction of the fuel injection
volume are located on the delivery pipe.
The fuel tank, pressure regulator, and the delivery pipe are provided with shutoff valves that shut off the
fuel when the ignition switch is turned OFF.
In addition, these valves shut off the fuel when the engine stalls, the SRS airbag is deployed, or the pres-
sure in the main pipe becomes abnormally low.
A fuel temperature sensor for the fuel gauge is mounted on the tank valve assembly, and a fuel pressure
sensor is mounted immediately upstream of the pressure regulator.

Fuel System Diagram 

3
CAMRY ± NEW FEATURES
172CM17
CloseOpen45
2) Fuel Shutoff Valve for Fuel Tank
This valve uses an solenoid valve. The main pipe that supplies compressed gas to the engine is connected
to this valve, which opens when the ignition switch is turned ON. If the engine stalls, this valve automati-
cally shuts off the fuel even if the ignition switch is turned ON. The valve reopens upon restarting the
engine.
Also, this valve shuts off the fuel if the SRS airbag is deployed in a collision or if the pressure in the main
pipe becomes abnormally low.
3) Inlet Check Valve
Connected to a filler pipe that guides the fuel that fills through the coupler, the inlet check valve shuts
off by the force of a spring and by the pressure of the gas in the tank.
During filling, the pressure of the filling gas opens the inlet check valve.
4) Relief Valve
A vent tube is connected to this valve.
If the fuel tank is exposed to an abnormally high temperature, this valve opens (by melting) to discharge
the CNG at a predetermined temperature, thus helping prevent the fuel tank from bursting due to the in-
crease in gas pressure.
The discharged CNG is guided under the floor through a vent tube and is released outside of the vehicle.
Coupler
The coupler allows the fuel to be filled when it is connected with a fuel filling nozzle. The coupler has a
built-in check valve to help prevent the CNG from flowing backward.
Manual Shutoff Valve
This valve is mounted below the vehicle floor.
When servicing the vehicle, this valve can be
manually turned 90 degrees to shut off the main
pipe.

CAMRY ± NEW FEATURES
167CN10
172CM15
Fuel
Shutoff
Valve
Water Passage
Oil SeparatorRelief Valve 46
Fuel Filter
Mounted below the vehicle floor, the fuel filter
removes any moisture or oil from the fuel.
Fuel Pressure Regulator
The fuel pressure regulator regulates the fuel pressure by reducing the pressure of the compressed natural
gas from the fuel tank to the fuel injection pressure, which is 8 kg / cm
2 (114 psi, 785 kPa).
Similar to the fuel shutoff valve for the fuel tank, a fuel shutoff valve is provided on the fuel inlet side
of the fuel pressure regulator to shut off the supply of fuel when the engine is stopped or during abnormal
conditions.
An oil separator that traps the moisture and oil in the fuel is provided on the low pressure side.
A built-in relief valve is provided to protect the parts located on the low pressure side.
While the fuel pressure is being reduced by the fuel pressure regulator, the Joule-Thomson effect
associated with the expansion of the gas causes the fuel pressure regulator to be cooled excessively, exert-
ing unfavorable influence on the rubber parts such as diaphragms and fuel hoses.
Therefore, to raise the gas temperature, a water passage is provided in the fuel pressure regulator to allow
the engine coolant to warm the regulator.