1UZ-FE Non VVT-i 4L V8
Lexus 1UZ-FE non VVT-i 4L V8
The 1UZ–FE engine is a V–8, 4.0–liter, 32–valve DOHC engine designed exclusively for the luxury LS400 sedan.
This Engine incorporates start of the art technology, High speed Performance and Reliabilty at a very high level. Resulting in a smooth powerful motor.
The cylinder heads are of a cross-flow design and are made of aluminium. The intake ports are on the inside and the exhaust ports are on the outside. The cylinder heads although they are a DOHC (Double Overhead Cam) Design are extremely compact. This is achieved through the pitch on the inlet and exhaust camshafts being shortened and the valve angle being narrowed. A pentroof type combustion chamber with four valves is utilised. The air fuel mixture is guided to the centre of the combustion chamber by the squish area to increase combustion speed and maintain stable engine operation. Plastic region tightening bolts are used for securing the cylinder heads to the block due to their good axial tension stability.
The cylinder block is compact in it’s length and width for it’s displacement due to a bank angle of 90, a bank offset of 0.827 in. (21 mm) and a bore pitch of 4.15 in. (105.5mm). Lightweight Aluminium alloy is used for the construction of the cylinder block. The engine uses a thin cast-iron liner that is press fit into the sleeves to ensure added reliability. Hint: Never try to machine the Cylinder as it only has a very thin 2 mm liner. To help shorten the engine length part of the volute chamber of the water pump and the water by-pass passage are built into the cylinder block. The two knock sensors are located in the inner side of the left and right banks. The starter motor is located inside the V-Bank.
To control thermal expansion Steel struts are used. To maintain proper lubrication and reduce friction loss the skirt of each piston is striation finished (finely grooved). To minimize fluctuation of weight among pistons and balance the engine assembly the piston has a weight–adjusting boss. Piston pins are the full–floating type and are
held in place with snap rings.
Each surface of the compression ring No. 1 and the oil ring side rail is nitrified to prevent an
increase of oil consumption and blow–by gas as the time elapses.
A weight–adjusting boss is provided at the big end to reduce fluctuation of weight and balance the engine assembly. The sintered and forged connecting rod is very rigid and has little weight fluctuation. The connecting rods for the right and left banks are placed in opposite directions with the outer marks facing the crankshaft. The connecting rod cap is held by plastic region tightening bolts.
Note: If you re-use the connecting rod cap bolts, if the diameter at the thread is less than
0.275 in. (7.0 mm), it is necessary to replace them with new ones.
Crankshaft and Crankshaft Bearings
The crankshaft is forged with five main journals, four connecting rod pins and eight balance weights is used. The Bearings are made of Kelmet. The connecting rod pins and the journals are induction–hardened to ensure an added reliability. The crankshaft bearings are carefully selected according to the measured diameters of the cylinder block journal holes and the crank.
Every cylinder has 2 intake valves and 2 exhaust valves. They are directly opened and closed by 4 camshafts. The intake camshafts are driven by a belt while the exhaust camshafts are driven by gears on the camshafts. They use outer shim type valve lifters so they can be adjusted without the need to remove the camshafts.
The exhaust camshafts are driven by gears from the intake camshafts. Lexus used a scissor gear mechanism to reduce backlash and gear noise. The camshaft journals and driven gears are lubricated by oil supplied to the camshaft through an oil passage in the center of the camshafts and the oil supply from the heads to the camshafts is continuous to prevent fluctuations in the oil pressure.The camshafts are cast iron and the nose is chill treated. “T” type oil seals are used.
Valve Lifter and Valve Adjusting Shims
The valve adjusting shims are located on top of the lifters and are outer shim type this means that camshaft removal is not required to adjust the shims. Aluminium valve lifters are used.
Timing Pulleys and Belt
The auto-tensioner is made up of a spring and an oil damper and it maintains proper timing belt tension at all times. The tensioner also suppresses noise made by the timing belt. The tension belt is highly durable and has a high heat resistance.
The lubrication system is fully pressurised and all the oil passes through an oil filter. The oil pump is driven directly by the crankshaft and is a trochiod gear type.
The oil pan is made up of 2 pieces. The top piece is made from cast aluminium and the bottom part is made from steel. The top piece is secured to both the block and the torque converter housing increasing rigidity. The splash plate controls the flow of oil between the two parts when the vehicle is turning or on bumpy roads. An oil level sensor is located in the Sump to provide you with a warning of low oil level.
The cooling system is a force circulation pressurised system. A thermostat with a bypass valve is located on the water pump inlet side. As the coolant temperature rises the thermostat opens and the bypass valve closes ensuring that the temperature is controlled in the cylinder head. A gauge coolant temperature sender, coolant temperature sensor, start injector time switch for the EFI (Electronic Fuel Injection) and BVSV (Bimetal Vacuum Switching Valve) for charcoal canister control are fitted to the front water joint. The rear water joint has a bypass port for heating the throttle body and cooling the EGR valve and for the vehicles heater.
The water pump is driven by the back of the timing belt and has two volute chambers to evenly circulate coolant to the right and left banks of the cylinder head. The water pumps rotor is made from resin.
Intake and Exhaust System
Intake Air Chamber
The EGR valve and the Idle Speed Control passages are attached to the air intake chamber. There is a start injector located in the centre of the air intake chamber to evenly disperse fuel into all 8 cylinders.
The ports are crossed to increase their length and inertia effects of the air entering the ports.
Both of the exhaust manifolds are made of stainless steel and are covered with heat shields to protect the surrounding components against exhaust heat.
Serpentine Belt Drive System
The Serpentine belt drive system is used to power all the engines accessory components. It is a V-Type ribbed belt and reduces the overall length, weight and number of engine parts. There is an automatic tensioner eliminating the need for tension adjustment.
The started motor has a 2KW output and is located in the centre of the V-Bank of the cylinder block.
The alternator has a large output of 1200 watts to supply enough power for the electric load. The alternator is fitted directly to the block without brackets.
Engine Control System (ECU)
Engine control system uses an ECU (Electronic Control Unit) with a built–in microprocessor. Stored inside the ECU is the data for fuel injection duration, ignition timing and idling speed, etc. which are matched with the various engine conditions as well as programs for calculation. The ECU utilizes these data and signals from the various sensors in the vehicle and makes calculations with the stored programs to determine fuel injection duration, ignition timing and idling speed, etc., and outputs control signals to the respective actuators which control operation. The engine ECU and transmission ECU are integrated into one and the ECU is called the engine and transmission ECU. The engine control system for the 1UZ–FE engine has the following functions:
- EFI (Electronic Fuel Injection)
The ECU determines the fuel injection duration according to intake air volume, engine speed, coolant temperature and other signals and sends control signals to the fuel injectors. Also, this fuel injection duration is the basis for deciding the fuel injection timing. The fuel injection system in the 1UZ–FE engine is a four group injection system which injects fuel simultaneously into two cylinders once every two engine revolutions.
- ESA (Electronic Spark Advance)
The ECU determines the amount of ignition advance over the initial set timing of the distributor by the intake air volume, engine speed, coolant temperature and other signal and sends control signals to the igniters. Also, based on signals from the knock sensors, the ECU controls the ignition timing at the optimum in accordance with the petrol’s octane value.
- ISC (Idle Speed Control)
By means of engine speed signals and coolant temperature signals, the ECU sends control signals to the ISC valve so that the actual idling speed becomes the same as the target idling speed stored in the ECU. Also, while the engine is warming up, the ECU, based on coolant temperature signals, sends controls signals to the ISC value to control engine speed to fast idle.
- EGR (Exhaust Gas Recirculation) CUT CONTROL
The ECU sends signals to the EGR VSV to cut the EGR based on coolant temperature, engine speed, neutral start switch or intake air volume signals. This system maintains drivability at low coolant temperature, under light or heavy load conditions, or at high engine speed, etc.
- FUEL PRESSURE CONTROL
The ECU sends signals to the pressure regulator VSV based on coolant temperature, intake air temperature, vehicle speed and engine start signals, and increases the fuel pressure. This system maintains restartability and idling stability when the engine is hot.
- FUEL PUMP SPEED CONTROL
The ECU, based on fuel injection duration, sends control signals to the fuel pump control relay to control the fuel pump speed. That is, when the engine requires a large volume of fuel, the fuel pump turns at high speeds and when only a small volume of fuel is required, the pump turns at low speeds.
EFI (Electronic Fuel Injection)
The EFI system consists of 3 main systems.
1) Fuel System 2) Air Induction System and 3) Electronic Control System
Fuel is pumped by the electric fuel pump from the fuel tank through a fuel filter to the injectors and the cold start injector. The fuel pressure regulator controls the amount of fuel being returned to the fuel tank through the return pipe thereby adjusting the pressure of fuel to the injectors. The pulsation damper absorbs the fluctuations in fuel pressure due to injection of fuel. The injectors inject fuel into the intake port in accordance with injection duration signals from the ECU. The cold start injector injects fuel into the air intake chamber when the coolant temperature is low, improving start-ability in cold weather.
The Lexus uses an in-tank style fuel pump. It is a turbine pump with little discharge pulsation of the fuel inside the pump. The pump consists of the motor portion and the pump portion. It has a check valve a relief valve and a filter incorporated into the unit. The turbine pump has an impellar that is driven by the motor. The turbine pulls fuel from the inlet port to the outlet port. The fuel is then discharged through the motor to the check valve.
The relief valve is designed to open when the pressure reaches 71.192.3 lb/in.2 (5.06.5
kg/cm2) therefore insuring that the fuel pressure does not go beyond that level.
Residual Pressure Check Valve
This valve closes when the fuel pump motor stops to maintain pressure in the fuel line which makes re starting the engine easier.
The pressure regulator regulates the fuel pressure that is supplied to the injectors. The fuel injection quantity is regulated by the ECU and constant fuel pressure must be applied to the injectors at all times. However as the fuel is injected into the motor and the manifold vacuum varies there will be slight variance in the fuel quantity injected even though the signal to the injectors and the fuel pressure is constant. Therefore, to acquire an accurate
injection quantity, the sum of the fuel pressure A and intake manifold vacuum B must be
maintained at 41 lb/in.2 (2.9 kg/cm2).
There are two holes at the tip of the injector. The fuel is injected into the intake port via these two holes and is controlled by the engines ECU. It has a light and small plunger which responds quickly to signals from the ECU. When the signal is recieved from the ECU by the solenoid coil the plunger is pulled back against the spring, and since the valve needle and the plunger are a single unit it is also unseated to allow fuel to be injected. The volume of fuel is controlled by the duration of the signal.
Cold Start Injector
The cold start injector is located in the air intake chamber and injects fuel into the chamber on start-up to help with start-ability. When starting the engine with the coolant below 71.6F (22C) the cold start injectors operation time is controlled by the start injector time switch. When the coolant is below 140F (60C) the operation time is controlled by the ECU. Therefore under 71.6F (22C) it is controlled via both the start injector time switch and the ECU.
Air Flow Meter
The Lexus uses an optical Karman-Vortex type air flow meter. It measure the airflow coming into the engine electronically meaning it’s very precise. They simplified the construction of the air passage to aid with air flow.
The throttle body is made up of the throttle valve that controls the amount of air intake, the TPS (Throttle Position Sensor) that detects the opening od the throttle valve and the dash pot that reduces the rate at which the throttle valve closes. The TPS detects the angle of the throttle valve and converts it to a voltage that is sent to the ECU. The engine coolant also passes through the throttle body to maintain warmth in cold conditions.
Throttle Position Sensor (TPS)
It is mounted on the throttle body as per above and converts the opening angle of the throttle valve to a voltage and submits it to the ECU as the throttle position signal. A constant 5V is supplied to the Vcc terminal from the ECU. As the contact slides along a resistor in the TPS in accordance with the opening angle of the throttle valve a voltage is supplied to the Vta terminal.
The tables below show the variations that were done during the lifetime of the production of this motor.