To control the EPHH valve in carbureted engines cars VAZ 2108 - 2110 is used EPHX control unit 50.3761. As a throttle position sensor, a screw sensor is used, which is a plastic screw with a metal tip, screwed into a bracket mounted on the carburetor. 
When opening throttle the tip of the screw, with the wire attached to it, does not rest against the throttle lever. This leads to an open circuit of output 5 of the control unit with ground. This closes the transistor VT7, and the transistor VT5 opens, opening in turn the transistor VT8. The VT8 transistor supplies power to the solenoid valve, regardless of the crankshaft speed.
A wire is connected to terminal 3 of the control unit, connecting it to the terminal of the primary ignition coil, transmitting pulses that are fed to terminal 4 of the A1 microcircuit. At pin 3 of the microcircuit, pulses of constant duration are formed, the repetition of which corresponds to pulses from the distributor. Transistors VT1 and VT2 discharge the timing capacitor C1. If the crankshaft speed is less than 1100 rpm, then the voltage on the capacitor does not rise, with an increase in the number of revolutions, the voltage increases and when it exceeds 8 V, the transistors VT3 and VT4 open, which through the A2 microcircuit open the transistor VT6 and, accordingly, VT8.
EPHH control unit 25.3761
Scheme of the EPHX control unit 25.3761 differs mainly only in operation at revolutions crankshaft over 1100 rpm This is due to the use of a microswitch as a throttle position sensor that supplies power to the electro-pneumatic valve when the throttle is open. The operation of the control unit at idle is identical to block 50.3761.
Block EPHH 1402.3733.
Block EPHH 1402.3733 is installed on cars of the GAZ and UAZ families. The principle of its operation is the same as that of block 50.3761. The difference between the blocks is only in the scheme.
Malfunction of the EPHX control unit.
If the EPHX unit malfunctions, the engine will not idle or when the gas pedal is released, the revolutions will jump from 900 to 1200. To troubleshoot, simply remove the core on the valve or connect the tubes on the carburetor in addition to the “canister”.
What a half-forgotten, and for some even unfamiliar word - economizer! Carburettors, which have been working properly on a car for many years, gradually gave way various systems injection. But the automotive age is long, and sometimes someone has to deal with cars that still have room for a carburetor. Well, his normal work provided near additional devices, among them it is impossible not to mention the fuel saver.
What is an economizer in a car?
The work of the internal combustion engine is based on combustion air-fuel mixture(TVS). Its composition depends on the load of the motor, and should be different when it changes. This means changing the ratio between oxygen (air) and gasoline as driving conditions change. The necessary proportions are provided by the carburetor, or in modern machines- injection controller. Therefore, before talking about the economizer, it is necessary to consider the work of the carburetor.
How does a carburetor work
The following figure will help to understand its principle of operation.
This is the simplest version of the carburetor, one might say, only explaining its structure and the main idea. Gasoline is in the float chamber at constant level, which is supported by the operation of the needle valve. Through air filter air is sucked into the engine cylinders. It passes the mixing chamber, due to the narrowing there, a vacuum is created in this place in relation to the float chamber, in which the level of atmospheric pressure is maintained.
Due to the resulting pressure difference, fuel enters the mixing chamber. Passing through the jet, it breaks into small droplets, evaporates and mixes with air, resulting in the formation of fuel assemblies entering the engine cylinders. The ratio between these components depends on the position of the carburetor flap associated with the position of the accelerator pedal. The more it is pressed on the car, the more the damper is open, the higher the degree of vacuum and more gasoline enters the mixture.
Purpose of the economizer
At the moment when the damper is almost completely open, car motor experiencing maximum loads, which means that to overcome them, he needs more gasoline than during normal operation. At the same time, the economizer begins to work, more fuel is supplied to the formation of the mixture, and the mixture becomes enriched. Its purpose and device, as well as why an economizer is needed, becomes clear from the figure:
The throttle valve of the carburetor is connected to a special valve through the rods and levers. When it is fully open, it causes it to operate, and an additional amount of gasoline, passing through the economizer jet, goes to the formation of fuel assemblies. Such a supply of fuel causes an enrichment of the mixture and ensures the operation of the engine at increased load. When the gas pedal is released, the damper is closed, the spring closes the valve and the economizer operation stops.
Structurally, the economizer device can be made different ways, we will not touch on their specific implementation, since for the carburetor, after the advent of injection controllers, the history of development ended.
Forced idle economizer (EPKhH)
Considering a car economizer, one cannot ignore such a device as the EPHX. It has a completely different purpose than a conventional economizer. If the latter, as we have just considered, enriches the fuel mixture at significant loads, then EPHH, on the contrary, provides fuel economy. forced mode idle move- a special movement option.
This is usually due to engine braking when driving downhill or coasting when the speed is on and the throttle is off. EPHH complements the idle system in the carburetor. It supplies fuel to the engine with the throttle closed. In this case, due to the vacuum created under it, the fuel passes through the jet through a special idle channel and enters the engine, which ensures its operation in this mode.
However, if at the same time the car is coasting or moving downhill, then crankshaft rotates at a higher speed than normal idle, which causes increased consumption of gasoline and reduces the effectiveness of engine braking. To exclude this, the EPHH is activated, and the fuel supply is stopped. In forced idle mode, the flow of gasoline is interrupted by a solenoid valve controlled by a fairly simple electronic unit.
The initial data for the operation of the EPHH (solenoid valve) are the sensor signal about the closed damper and the increased number of revolutions of the crankshaft. EPHH supports this mode so far:
- the speed of movement with the throttle released will not decrease;
- the gear will not be disengaged and the car will start to move in the normal idle mode;
- the driver will not press the gas pedal and the movement will continue at an increased speed, the economizer will turn off by the position of the damper.
The work of the economizer as part of the carburetor ensures the enrichment of fuel assemblies at increased load, as well as fuel economy and better engine braking efficiency in forced idle mode.
Oh, it's been a long time since I've seen a car with a carburetor! I even forgot that there is such a detail in the car. However, cars still drive where combustible mixture, which burns in the engine cylinders, is prepared in a special device, a carburetor. The name of this device comes from the French word "carburant" - "fuel". in the carburetor with special device, jet, small drops of gasoline are sprayed into the air stream that is sucked into the cylinder. The droplets immediately evaporate, forming a highly flammable gasoline- air mixture. Which, in accordance with the name, ignites easily in the engine cylinder after a fraction of a second.
Engine power depends on the concentration of gasoline in the gasoline-air mixture. In turn, this concentration increases if the amount of air entering the carburetor is reduced. The increase or decrease in air flow is regulated by a throttle valve installed in the duct. Turning around its axis, it closes or opens the duct. When the damper is closed, the air becomes less, and the concentration of gasoline increases. The mixture richer in gasoline burns in the cylinder, releasing more energy, the engine runs on increased speed. When the damper is opened, the amount of air in the mixture becomes larger, and accordingly the engine starts to work less vigorously. Throttle rotation is determined by pressing the gas pedal. The harder you press the pedal, the more the damper closes, the richer the gasoline mixture flies out of the carburetor, the harder the engine works. The driver and passengers hear it.
The engine has two modes when it works in a special way. The first is called idle. While idling, the engine runs but the vehicle is stationary. The gas pedal is released, the throttle is almost closed. At the same time, a very small amount of gasoline must be supplied to form a gasoline-air mixture, such that it does not allow the car to stall. This concentration of gasoline in the combustible mixture (from 1: 12 to 1: 14.5) provides special system idle move.
The second special mode of engine operation is the forced idle mode (PHX). This is sometimes referred to as engine braking mode. For example, a car is going down a hill high speed. A running engine will only accelerate the car. In this case, the car's gear is left engaged, and the gas pedal is released. What is happening? The wheels, rotating, turn the engine through the included gear. It is not the engine that turns the wheels, but vice versa, the energy of a moving car, through the wheels and the gearbox, is spent on cranking all the details of the engine. When the gas pedal is released, the throttle valve of the carburetor is closed, providing a minimum supply of fuel to the engine cylinders.
But in forced idle mode, gasoline should not be supplied to the cylinders at all. Why should we overclock an already rapidly spinning engine? In order to stop the fuel supply in the PXX mode, a forced idle economizer (EPKhH).
The economizer consists of a solenoid valve that shuts off the fuel supply to the air duct, a sensor extreme position throttle valve and valve control unit.
The throttle position sensor is a contact screw. When the throttle valve of the carburetor reaches its extreme position (the gas pedal is released, as in idling), the sensor turns off.
The sensor is connected to the valve control unit. The control unit receives a signal from the ignition coil and from the throttle end position sensor. The frequency of the signal from the ignition coil is proportional to the engine speed.
The control unit sends a signal to the solenoid valve when the engine speed is increased and the throttle is closed. Upon receiving a signal, the valve shuts off the supply of gasoline to air flow. The engine, rotating, “grinds” the air, in which there are no gasoline vapors, and which therefore does not explode from a spark flashing “idle”.
When the engine speed drops below a certain limit, the control unit gives a signal that opens the solenoid valve. Now the fuel is supplied to the air mixture, as at idle.
If the accelerator pedal is depressed, the throttle is slightly open and the throttle limit switch is on. In this case, the control unit will never give a signal to close the solenoid valve. At any crankshaft speed, gasoline will flow into the air mixture and the engine will work.
The forced idle economizer (EPKhK) saves fuel. Depending on driving style, this savings can be in the range of 0.2 to 0.5 liters per 100 kilometers. But most importantly, it reduces the likelihood of detonation during engine braking. As a result, the efficiency of engine braking increases, and the amount of products of incomplete combustion of fuel in the exhaust gases decreases to zero. In fact, when braking the engine, nothing burns in it!
This whole system is quite outdated. Since the 1980s, an injection system for injecting fuel into the engine cylinders has been introduced on cars. In this case, the carburetor becomes unnecessary. The gas distribution system, although becoming more complex, is easily automated and controlled using on-board computer. The computer also monitors compliance with the economic regime and, by the way, saves much more fuel than an electro-mechanical economizer.
So, if you don't ride a Lada, forget everything I just told you!
When driving in a city, the engine runs about 25% of the time at forced idle, when the engine crankshaft rotates due to the kinetic energy of the car and it moves with the gear engaged and the throttle pedal released. In these modes, the engine is controlled by a forced idle economizer.
UAZ forced idle economizer control system, control unit, valve, microswitch.
At forced idle, the engine consumes fuel without performing useful work, as a result of the rapid closing of the throttle valve, the combustible mixture is re-enriched and the toxicity of the exhaust gases increases. To reduce fuel consumption and exhaust gas toxicity on UAZ vehicles, a electrical system forced idle economizer control (EPKhH).
The control system and electrical equipment of the forced idle economizer on UAZ vehicles with UMP engines includes control unit 1422.3733, solenoid valve 1902.3741 and carburettor limit switch (microswitch) 421.3709.
The principle of operation of the forced idle economizer control system on UAZ vehicles.
The forced idle mode is characterized by two signs: the engine speed is greater than the idle speed and the carburetor throttle is closed. Information about the frequency of rotation of the crankshaft of the engine enters the EPHX control unit from a sensor, which is used as the primary winding of the ignition coil, and information about closing the throttle valve - from limit switch, microswitch or screw sensor .
When the accelerator pedal is released, as a result of switching the contacts of the carburetor limit switch, the EPHX control unit generates control signals for the electromagnetic (electro-pneumatic) fuel supply valve, depending on the engine crankshaft speed. If the crankshaft speed is higher than the idle speed, then the control unit removes voltage from the solenoid valve and the fuel supply to the engine stops.
At the same time, the crankshaft speed decreases, and when it becomes less than the idle speed, the control unit will turn on the voltage onboard network to the solenoid valve. The fuel supply will resume and the engine speed will increase.
When the crankshaft speed is again greater than the idle speed, the control unit will again turn off the solenoid valve. The process is repeated. Periodic shutdown of the fuel supply in this mode reduces gasoline consumption by 2-3%, and the toxicity of exhaust gases decreases by 15-30%.
When you press the accelerator pedal, the contacts of the limit switch switch in such a way that the voltage of the on-board network is constantly supplied to the solenoid valve. In this case, fuel will be supplied regardless of the engine speed.
Control unit 1422.3733 of forced idle economizer on UAZ vehicles, principle of operation.
On UAZ vehicles with UMZ engines, four-pin economizer control units 1422.3733 are used. Microswitch 421.3709 is used as throttle position sensor. When the throttle is closed, voltage pulses proportional to the speed of the crankshaft come from the primary winding of the ignition coil 1 to the input of a semiconductor switch assembled on a transistor VT1.
During the action of the pulse, the key opens and the capacitor C3 is discharged. In the pauses between pulses, the capacitor C3 is charged. The charge time, and hence the voltage on the SZ, increases with a decrease in the crankshaft speed. At a frequency greater than the idle frequency, the voltage on the SZ is small, the transistors VT2, VT4, VT5, VT6 close. The solenoid (electro-pneumatic) valve is not energized.
The valve closes and the fuel supply stops. The crankshaft speed drops. At a frequency less than the idle frequency, the capacitor C3, during the pause between pulses, has time to charge up to a voltage exceeding reference voltage threshold element assembled on transistors VT2, VT4. Transistors VT2 and VT4 open at the same time, which ensures the opening of transistors VT5 and VT6. At the same time, voltage is applied to the electropneumatic valve.
The valve activates and turns on the fuel supply. When the throttle is opened, the contacts of the microswitch S1 are closed and the voltage of the on-board network is constantly supplied to the electro-pneumatic valve. The valve is constantly open, regardless of the signals of the control unit 1422.3733 of the forced idle economizer.
The EPHH system (forced idle economizer control) is used to reduce fuel consumption and exhaust emissions. The system consists of an electro-pneumatic valve, a control unit and a microswitch. The side fitting of the electro-pneumatic valve is connected by a tube to the pneumatic valve of the forced idle economizer in the carburetor, and the central fitting is connected to the inlet pipe branch pipe. The micro switch is mounted on the carburetor bracket, the electro-pneumatic valve and the control unit are on the motor shield.
The EPHH systems on vehicles with UMPO-331 and VAZ-2106 engines are structurally the same and differ only in the arrangement of carburetor economizers and the type of control units (block 252.3761 is used on the UMPO-331 engine, block 25.3761 or 2533.3761 on the VAZ-2106 engine).
The system works like this. The control unit continuously monitors the engine speed. At a rotation speed of 1500 min -1 ± 5% and a closed throttle (forced idle mode), the control unit turns off the electro-pneumatic valve, its internal cavity communicates with the atmosphere, and the carburetor economizer pneumatic valve associated with it shuts off the fuel supply to the idle system. When the engine crankshaft speed drops to 1245 min -1 ± 5%, the control unit turns on the electro-pneumatic valve, and the fuel supply to the idle system is resumed. When the throttle is open, the voltage supply to the electro-pneumatic valve is provided by a microswitch, the lever of which is actuated by the arm of the throttle actuator lever.
A malfunction of the EPHH system manifests itself in car jerks when driving with low speed, engine stops at idle or flashes in the engine cylinders after the ignition is turned off. Checking the performance of the EPHX system and dismantling its elements on vehicles with UMPO-331 and VAZ-2106 engines are carried out in almost the same way.
Forced idle economizer system diagram
stroke (EPHH): 1 - electropneumatic valve; 2 - microswitch; 3- mounting block; 4 - ignition coil; 5 - control unit.
To check the control unit EPHH system at idle, increase the crankshaft speed to 1500 min -1 and remove the drive from one of the microswitch leads. At serviceable block control, the crankshaft speed will begin to "float" within 1200-1500 min -1, if it is faulty, it will remain stable. To check the pneumatic valve of the carburetor economizer, when the engine is idling, we disconnect the tube from its fitting - the engine should stop. We replace the defective pneumatic valve (see "Carburetor").
To check the solenoid valve with the engine running, disconnect the wire from one of its contacts. With a working pneumatic valve of the carburetor economizer, the engine should stop within 1-2 s. If the engine continues to run, the solenoid valve must be replaced.
