1.Function
An expansion valve injects the high-temperature and high-pressure liquid refrigerant, which has passed through the receiver, from the small hole to cause the refrigerant to expand suddenly and to change it into the low-temperature and low-pressure mist refrigerant.
According to the cooling load, the expansion valve adjusts the refrigerant amount to supply to the evaporator.
2.Construction
The valve directly detects the refrigerant temperature (cooling load) around the outlet of the evaporator by the heat-sensing rod and transmits it to the gas inside the diaphragm. The change of the pressure of the gas due to the temperature change and the balance between the pressure of the outlet of the evaporator and that of the pressure spring moves the needle valve to adjust the amount of the refrigerant flow.
3.Operation
The temperature around the outlet of the evaporator changes according to the cooling load.
When the cooling load is small, the temperature around the outlet of the evaporator goes down, and the temperature transmitted from the heat-sensing rod to the gas inside the diaphragm also goes down, which makes the gas contract. As a result, the needle valve is pressed by the outlet refrigerant pressure of the evaporator and the pressure spring pressure, and moves to right. Closing the valve decreases the amount of the refrigerant flow and lowers the cooling capability.
When the cooling load is large, the temperature around the outlet of the evaporator increases and the gas expands. As a result, the needle valve moves to left, pushing the pressure spring. Opening the valve increases the amount of the refrigerant circulating in the cycle and makes the cooling capability higher.

Expansion Valve

1.Construction
The temperature sensing part of the expansion valve is attached to the outside of the outlet of the evaporator. At the top of the diaphragm that leads to the heat sensing tube, refrigerant gas is contained and the pressure of the gas changes depending on the temperature at the outlet of the evaporator.
The refrigerant pressure at the outlet of the evaporator is applied at the bottom of the diaphragm.
The balance between the force to press the diaphragm up (refrigerant pressure at the outlet of the evaporator + spring force) and the refrigerant pressure of the heat sensing tube moves the needle valve to adjust the refrigerant flow.
2.Function, Operation
The function and operation of this type are same as that of the box type.

Evaporator

1.Function
An evaporator evaporates the mist refrigerant, which is made low-temperature and low-pressure at the expansion valve, and cools the air around the evaporator.
2.Construction
This consists of a tank, tubes and cooling fins. The tubes penetrate through a number of cooling fins and form minute passages for good conductivity.
3.Operation
A blower motor fan forces air to the evaporator. The refrigerant removes the heat of evaporation from the air and is heated into a gas.
When the air that has passed the evaporator is cooled, the moisture in the air condenses and attaches to the cooling fin. The moisture becomes droplets and is stored in the drain pan to be drained out of the vehicle through the drain hose.

Why the cause of white smoke can be determined by oil loss via the valve guides
(1) The negative pressure of the intake manifold is high when the engine is idle, so oil is sucked into the combustion chamber from the valve stem. However, the temperature in the combustion chamber is low, so the oil attaches to the carbon, etc. and accumulates on the valve or combustion chamber, decreasing the amount of white smoke.
(2) When racing the engine from the above state (1), the temperature of the combustion chamber increases, instantly burning the accumulated oil, causing a great deal of white smoke to discharge. When the oil is completely burnt, the amount of white smoke decreases.
(3) If the engine is continuously raced, the temperature in the combustion chamber rises, so even if the oil is sucked in, it is burnt before accumulating, therefore decreasing the amount of white smoke.

Engine disassembly inspection
• With oil loss via the piston rings
A lot of carbon attaches to the outer circumference at the top of the piston.
• With oil loss via the valve guides
A lot of carbon attaches to the intake valve face, at the top of the piston, or to the exhaust valve stem. In addition, oil can also attach to these parts, making them wet.
When oil loss via the valve guides is discovered, remove the intake and exhaust valves and inspect the conditions at the face and stem.

When the fuel pressure of the commonrail becomes higher than the target injection pressure, the pressure discharge valve receives a signal from engine ECU, in order to open the valve and send fuel back to the fuel tank so that the fuel pressure can return to the target injection pressure.

1. At target fuel pressure (common-rail or injection pressure)

2. Over target fuel pressure (commonrail or injection pressure)

HINT:

The fuel pressure regulator of 1NDTV E/G has a different appearance, but functions the same.

1ND-TV Engine

The fuel pressure regulator receives the signal from engine ECU and adjusts the fuel pressure inside the common-rail.

REFERENCE

Operation of Pressure Discharge Valve/Pressure Regulator

When the fuel pressure of the commonrail becomes higher than the target injection pressure, the pressure discharge valve receives a signal from engine ECU, in order to open the valve and send fuel back to the fuel tank so that the fuel pressure can return to the target injection pressure.

1. At target fuel pressure (common-rail or injection pressure)

2. Over target fuel pressure (commonrail or injection pressure)

HINT:

The fuel pressure regulator of 1NDTV E/G has a different appearance, but functions the same.

Injection Volume Outline of SPV

There are two types of SPV (Spill Control Valve) that control the injection volume.

Conventional type SPV

(used in axial plunger type pump)

Direct-acting type SPV

(used in the radial plunger type pump for high-pressure applications)

Conventional Type SPV

1. Construction

The conventional type SPV consists of two valves: main valve and pilot valve.

2. Operation

At normal condition

The pilot valve of the SPV is normally closed, as electricity runs through the coil. The fuel pressure and the spring force causes the main valve to close passage “A” as well, due to the pressure from the inside of the valve being greater than that of the outside of the valve.

When the signal from the engine ECU is turned off

When the signal from the ECU turns off, causing the current applied to the coil to turn off, the pilot valve moves upward by the force of the pilot spring, causing passage “B” to open.

When the pilot valve is opened

Then, the pressure that is applied above the main valve decreases. As a result, the main valve ascends, causing passage “A” to open.

Direct-acting Type SPV

1. Construction

In contrast to the conventional type SPV, the direct-acting type SPV, which is fitted in a pump with a higher fuel pressure, achieves high levels of response and spill characteristics. Furthermore, the signals from the ECU are amplified by the EDU to operate the valve at a high voltage of approximately 150V when closing the valve. Thereafter, the valve remains closed at a low voltage.

2. Operation

At normal condition

The spool valve is pulled downward to close the passage because the coil is energized.

When the current does not flow into the coil

When the current to the coil is turned off, the pressure of the fuel pushes the spool valve upward to open the passage.

Starting Voltage of Direct-acting SPV

When the direct-acting type SPV starts to operate, approximately 150V are applied to the coil. Thereafter, duty-cycle control is effected at a lower voltage.

Operation of Pump and SPV

There are two types of plungers:

Axial plunger type pump

Radial plunger type pump

Axial plunger Type Pump and SPV

Operation

Intake stroke

SPV closes.

Plunger moves left.

Fuel is drawn into chamber.

Injection

SPV closes.

Plunger moves right.

Fuel pressure rises and fuel is pumped.

Injection ends

SPV opens.

Due to fuel relief, pressure decreases.

Injection ends.

When the conditions for fuel cut-off have been met, the pressure does not increase because the SPV remains constantly open.

Radial Plunger Type Pump and SPV

Operation

Intake stroke

SPV opens.

Rollers and plungers expand outward, drawing fuel into the chamber.

Pressure rises

SPV closes.

Rollers and plungers contract, causing pressure to rise.

Injection

SPV closes.

Rotor rotates and connects the rotor’s pumping port and distribution port, allowing the fuel to be pumped.

Injection ends

SPV opens.

Due to fuel relief, pressure decreases.

Injection ends.

When the conditions for fuel cut-off have been met, the pressure does not increase because the SPV remains constantly open.

The VVTL-i system is based on the VVT-i system and employs a cam changeover mechanism to change the amount of the intake and exhaust valve lift. This makes it possible to attain high power without affecting the fuel economy or emissions performance. The basic construction and operation of the VVT-i mechanism is the same as that of the VVT-i system. Switching between two cams with different lift amounts is used to change the amount of the valve lift. For the cam changeover mechanism, the engine ECU switches between two cams using the oil control valve for VVTL based on the signals from the water temperature sensor and the crankshaft position sensor.`12Q

Construction
The VVTL-i system configuration components are nearly the same as those of the VVT-i system. The special components for the VVTL-i system are the oil control valve for VVTL and the camshafts and rocker arms.
1. Oil control valve for VVTL
The oil control valve for VVTL controls the oil pressure applied to the high-speed cam side of the cam changeover mechanism using the spool valve position control conducted by the engine ECU.
2. Camshafts and rocker arms
To change the amount of the valve lift, the camshaft has two types of cams, a low- and medium-speed cam and a high-speed cam, for each cylinder. The cam changeover mechanism is built into the rocker arm between the valves and cams. The oil pressure from the oil control valve for VVTL reaches the oil hole in the rocker arm, and this oil pressure pushes the lock pin below the pad. This fixes the pad and engages the high-speed cam. When the oil pressure is not being applied, the lock pin is returned by the spring force and the pad is freed. This makes the pad able to move freely in the vertical direction and disables the high-speed cam.
Operation
The intake and exhaust camshafts have cams with two different lift amounts for each cylinder, and the engine ECU switches these cams to the operating cam by oil pressure.
1. Low- and medium-speed (engine speed: below 6000 rpm)
As shown in the illustration at the top, the oil control valve opens the drain side. Therefore, the oil pressure does not act on the cam changeover mechanism. As shown in the illustration at the bottom, the oil pressure is not acting on the lock pin. Therefore, the lock pin is pushed by the spring in the lock release direction. In this manner, the pad repeats a disabling reciprocal movement. Therefore this lifts the valves by the low- and medium-speed cam.
2. High-speed (engine speed: over 6,000 rpm/coolant temp.: higher than 60°C)
As shown in the illustration at the top, the drain side of oil control valve is closed so that the oil pressure is acting on the high-speed cam of the cam changeover mechanism. At this time, as shown in the illustration at the bottom, inside the rocker arm, the oil pressure is pushing the lock pin below the pad to secure the pad in the rocker arm. Therefore, the high-speed cam pushes down the rocker arm before the low- and medium-speed cam contacts the roller. This lifts the valves by the highspeed cam. At this time, the engine ECU simultaneously detects that the cam has changed over to the high-speed cam based on the signal from the oil pressure switch.

Generally, the valve timing is fixed, but the VVT-i system uses the hydraulic pressure to shift the intake camshaft rotation and vary the valve timing. This makes it possible to increase output, improve fuel efficiency, and lower emissions.  this system is designed to control the valve timing by shifting the intake camshaft rotation within an approximate 40°range of the crankshaft angle to attain a valve timing that is optimum for the engine conditions based on the signals from the sensors. The valve timing is controlled as explained below.
During low temperature, during low speed at light
load, or during light load
The intake valve timing is retarded and the valve overlap is reduced to reduce the exhaust gas blowback to the intake side. This stabilizes idling and improves fuel efficiency and startability.
During medium load, or during low and medium

speed at heavy load
The intake valve timing is advanced and the valve overlap is increased to increase the internal EGR and reduce the pumping loss. This improves emission control and fuel efficiency. In addition, at the same time the intake valve’s closing timing is advanced to reduce intake blowback to the intake side and improve the volumetric efficiency.
During high speed at heavy load
The intake valve timing is advanced and the valve overlap is increased to increase the internal EGR and reduce the pumping loss. This improves emission control and fuel efficiency. In addition, at the same time the intake valve’s closing timing is advanced to reduce intake blowback to the intake side and improve the volumetric efficiency. In addition, feedback control is used to keep the actual intake valve timing at the target valve timing using the camshaft position sensor.
Construction
The VVT-i system actuator consists of a VVT-i controller that shifts the intake camshaft, oil pressure that is the motive force of the VVT-i controller, and a camshaft timing oil control valve that controls the oil passage.
1. VVT-i controller
The controller consists of a housing that is driven by a timing chain and vanes that are fixed on the intake camshaft. The oil pressure sent from the intake camshaft advance or retard side passage rotates the VVT-i controller vanes in the circumferential direction to continuously change the intake valve timing. When the engine is stopped, the intake camshaft moves to the maximum retard state to maintain startability. When the oil pressure does not reach the VVTi controller immediately after engine start, the lock pin locks the VVT-i controller operation mechanism to prevent knocking noise.
REFERENCE:
In addition to the above, there is a type where the piston moves in the axial direction between the helical splines of the outer gear (corresponds to the housing) and inner gear (directly attached to the camshaft) to shift the camshaft phase.
2. Camshaft timing oil control valve
The camshaft timing oil control valve follows the duty control from the engine ECU to control the spool valve position and distribute the oil pressure applied to the VVT-i controller to the advance side or retard side. When the engine is stopped, the intake valve timing is at the maximum retard angle.
Operation
The camshaft timing oil control valve selects the passage to the VVT-i controller in accordance with the amount of current from the engine ECU. The VVT-i controller rotates the intake camshaft in accordance to the position to which the oil pressure is applied, to advance, retard, or keep the valve timing. The engine ECU calculates the optimum valve timing under the various operating conditions in accordance with the engine speed, intake air volume, throttle position, and coolant temperature to control the camshaft timing oil control valve. In addition, the engine ECU uses the signals from the camshaft position sensor and crankshaft position sensor to calculate the actual valve timing, and executes feedback control to attain the target valve timing.
1. Advance
When the camshaft timing oil control valve is placed in the state shown in the illustration by the engine ECU, the oil pressure acts on the timing advance side vane chamber to turn the intake camshaft in the valve timing advance direction.
2. Retard
When the camshaft timing oil control valve is placed in the state shown in the illustration by the engine ECU, the oil pressure acts on the timing retard side vane chamber to turn the intake camshaft in the direction of the valve timing retard direction.
3. Hold
The engine ECU calculates the target valve timing angle in accordance with the operating conditions. After setting to the target valve timing, the camshaft timing oil control valve keeps the oil passage closed as shown in the illustration, to keep the current valve timing.

1. Feed pump

The vane type feed pump consists of four blades and a rotor. The rotor is driven by the drive shaft, and the blades push against the inner wall of the pressure chamber due to centrifugal force. As the center of this rotor is eccentric to the center of the pressure chamber, the fuel between the blades is compressed and pushed outward.

2. Regulating valve

The regulating valve adjusts the discharge pressure of the feed pump according to the pump speed. The fuel injection timing is controlled by the timer which responds to the pressure inside the pump housing.

Fuel Diesel Engine Delivery and Injection System

1. The feed pump, cam plate and plunger are driven by the drive shaft and rotate at the rate of half the engine speed.

2. Two plunger springs push the plunger and cam plate against the rollers.

3. The cam plate has the same number of the face cam as that of the cylinder. (Four-cylinder engine has four face cams.) The cam plate pushes the plunger in and out rotating on the fixed roller. Therefore, the plunger follows the face cam movement, and reciprocates in sync with the face cam with rotating. With one turn of the cam plate, the plunger makes one complete turn and reciprocates four times.

4. Fuel for one cylinder is delivered with each 1/4 turn and one reciprocating motion of the plunger (Four-cylinder engine).

5. The plunger has four suction grooves, a distribution port, a spill port and a pressure equalizing groove. The spill port and distribution port are aligned with the access hole of the plunger center.

6. The fuel is drawn from the suction groove of the plunger. Then the highly compressed fuel is sent through the delivery valve from the distribution port, and pumped into the injection nozzle.

1. Suction

When the plunger goes down (moves to the left), one of four suction grooves in the pump plunger will be aligned with the suction port in the distributive head. Thus, the fuel is drawn into the pressure chamber and from there into the interior of the plunger.

2. Delivery

As the cam plate and plunger rotate, the suction port of the distributive head is closed off and the distribution port of the plunger will be aligned with the distribution passage. As the cam plate rides onto the rollers, the plunger goes up (moves to the right) and compresses the fuel. When the fuel pressure reaches the predetermined value, the fuel is injected from the injection nozzle.

3. Termination

When the cam plate rotates further and the plunger goes up (moves to the right), two spill ports of the plunger are pushed out from end of the spill ring. Then, the highly pressurized fuel is returned back to the pump housing through the spill ports. As a result, the fuel pressure drops suddenly and the fuel injection is terminated.

Effective stroke

The effective stroke is the distance that the plunger moves from the start of the fuel compression till the end. As full pump strokes are constant, the spill ring location is changed to increase or decrease the injection volume by the change of the effective stroke. When the effective stroke becomes longer, the compression ends later and the injection volume will be increased. Conversely the compression ends earlier and the injection volume will be decreased when the effective stroke becomes shorter.

1. Construction

The delivery valve is mounted on the distributive head of injection pump. The valve spring and delivery valve are mounted in the delivery valve holder. The surface of the delivery valve seat is made with high precision.

2. Operation

The delivery valve closes the fuel line quickly at the end of fuel injection in order to keep the residual pressure inside the injection pipe. At the same time, the fuel is drawn back in allowing the injection nozzle to snap shut, thus preventing fuel dribble (dripping).

(1) Start of fuel injection

<1> The highly pressurized fuel from the injection pump is sent to the delivery valve before injection.

<2> The highly pressurized fuel pushes the delivery valve to open the fuel line.

<3> The highly pressurized fuel is sent into the injection nozzle.

(2) End of fuel injection

<1> Pumping from the injection pump ends, and the fuel pressure lowers.

<2> The delivery valve is pushed back by the valve spring.

<3> The delivery valve returns until the valve face adheres the valve seat.

<4> The above process ensure a sudden drop in pressure inside the injection pipe. The nozzle needle then draws back the fuel, which would otherwise be fuel dribble. (3) Keeping airtightness (keeping residual pressure and preventing reverse flow) Airtightness (for keeping residual pressure and preventing reverse flow) is maintained by the valve seat and the surface of the delivery valve. If the pressure inside the injection pipe after the fuel injection is low, the fuel volume is decreased. Because the injection pressure does not reach quickly if the pressure inside the pipe is low. Therefore, it is necessary to keep the pressure constant inside the injection pipe all the times.

1. Four-valve mechanism

The valve mechanism of the diesel engine is basically the same as the one on the gasoline engine. However, some valve mechanisms are distinctive to the engine. The four-valve mechanism consists of the valve rocker arm and valve bridge. When the rocker arm is pushed up by the camshaft, the valve bridge slides along the guide pin and pushes down the two valves simultaneously to open them. In this way, a single camshaft is able to operate four valves per cylinder. Through the use of four valves, not only is the intake and exhaust effectiveness improved, but also the injection nozzle can be placed in the center of the combustion chamber.

HINT:

Valve clearance is adjusted using two adjusting screws, (1) and (2).

2. Replacement interval of timing belt

The timing belt of the diesel engine must be replaced every 100,00km (60,00miles) or 150,00km (90,00miles), depending on the engine models. In some diesel engine vehicles, a timing belt replacement warning light is provided. This light will come on at the specified timing belt replacement intervals. The timing belt warning light must be reset after replacing the timing belt. The method for resetting varies by the model.

Example 1:

Remove the grommet under the speedometer and push the warning light reset knob with a thin rod.

Example 2:

Remove the cancel switch screw and reinstall it in the other installation hole.

1. Necessity

The Exhaust Gas Recirculation (EGR) System recirculates some of the exhaust gases to the intake air system. The flame propagation becomes slow during the combustion when the exhaust gases are mixed with the air-fuel mixture because most of them are the inert (incombustible) gases. Also the combustion temperature drops to reduce the NOx generation because the inert (incombustible) gas absorbs the heat generated by burning.

2. Operation

When the vacuum is applied to the EGR valve, the valve opens and the exhaust gas recirculates.

The vacuum, which operates on the EGR valve, is controlled in accordance with the engine coolant temperature or throttle valve opening to control the ratio of the EGR.

Engine cold The BVSV opens toward the atmosphere side while the engine is cold. Therefore the exhaust gas does not recirculate because a vacuum is not applied to EGR valve.

Idling A vacuum is not applied to the EGR port. Therefore the exhaust gas does not recirculate.

Throttle valve between EGR&EGR R port The vacuum of the EGR port is applied to the EGR valve to open the valve. The vacuum is controlled by the modulator and recirculates a constant ratio of the exhaust gas. EGR port Throttle valve EGR valve Exhaust gas EGR vacuum modulator BVSV EGR Rport EGR port Throttle valve EGR valve Exhaust gas EGR vacuum modulator BVSV Air EGR Rport

Throttle valve opening above EGR R port The vacuum of the EGR port is applied to the EGR valve to open the valve. As the vacuum of R port is applied to the modulator, the vacuum applied to the EGR valve becomes larger so that the EGR opening becomes greater. Throttle valve fully open The exhaust gas is not recirculated because the vacuum applied to the EGR valve with full load is less than the vacuum required to operate the valve.

3. Internal EGR effect of VVT-i (Variable Valve Timing-

intelligent) System

Part of the exhaust gas is drawn in during the intake stroke by overlapping of the intake valve and exhaust valve. The VVT-i system controls the valve timing to control the internal EGR actively. The VVT-i system opens the intake valve quickly and lets some of the exhaust gas flow backwards to the intake side when the end of the exhaust stroke overlaps. The EGR effect is attained by drawing the back-flowing gas and the air-fuel mixture into the cylinder at the same time during the intake stroke. The VVT-i system changes the timing of the valve opening by the engine ECU. Refer to the engine control system for more details.