I will continue to try to carry the basics of chip tuning to the masses. Today I will try to talk about the key parameter maps. However, understanding the purpose of the key maps requires knowledge of the general principles of engine control and the role of the main sensors in the system. Therefore, for starters, I will give brief information from the engine manual (JSC "ZMZ". "Diesel engine model ZMZ-51432 CRS for UAZ vehicles of environmental class 4. Design, operation, maintenance and repair."), While I strongly recommend to everyone this book for reading.
The Bosch EDC16 system implements a diesel engine torque control. The data on the required torque entering the EDC16 system control unit is systematized, processed and used to adjust the fuel supply.
Fuel supply regulation The most important parameters of the engine directly depend on the amount of injected fuel: torque, fuel consumption, emission of harmful substances, as well as its mechanical and thermal load. The regulation of the cyclic dose of the injected fuel allows the combustion process to be optimized in all operating modes of the engine. The torque required is the sum of the torque required to overcome internal losses and the torque required to drive the vehicle. Each torque value corresponds to a certain dose of fuel injected into the cylinders.
The engine control unit calculates the injected fuel dose taking into account the following factors:
• the position of the accelerator pedal,
• the engine speed,
• the mass of air entering the cylinders,
• the coolant temperature,
• the fuel temperature.
The maximum dose of injected fuel should be limited based on the mechanical strength of the engine parts and smokeless combustion. Therefore, the control unit calculates the maximum permissible injection dose.
The maximum cycle fuel dose depends on:
• the crankshaft speed,
• the air mass entering the cylinders.
As you already understood, torque is the main characteristic that the engine controller operates, and fuel delivery is secondary to torque and depends on many factors. For example, in EDC15 blocks (installed in cars produced in the early 2000s), everything danced precisely from the fuel supply.
Thus, in a very simplified way, the control scheme looks like this - the driver, pressing the gas pedal, asks for a certain amount of torque. The engine, in accordance with the parameters sewn into it, gives out a certain amount of torque, but not immediately (the anti-smoke system works to ensure smokeless combustion of fuel) and, possibly, not all (the mechanical protection systems of the engine are working).
List of key cards (as an example, I will give addresses and pictures of cards from Fiat, which was discussed in the previous part):
DRIVER WISH
The map determines the torque requested by the driver (Nm) depending on the degree of pressing the accelerator pedal and the current engine speed. There can be several of these cards, for example, for "normal" and "sport" modes. In fact, the map determines the responsiveness of the car to the gas pedal, but does not affect the operation of the engine itself. Moreover, if you look at the moments written in this map, for example, for 100% pressing the accelerator pedal, you can see that they overlap with a margin the maximum capabilities of the engine. For example, in the standard firmware from ZMZ, the requested torque of 355 Nm is indicated when the gas is fully pressed for revolutions from 600 to 2800 rpm, although it is obvious that such a torque value will never be reached. Thus, it is possible for a sports car and it makes sense to edit this map,
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DRIVER WISH (1C1662, 1C18A6, 1C1D2E) |
EGR
The map determines the desired mass air flow (air mass / cylinder) depending on the fuel cycle (injection volume / cycle) and the current engine speed. Based on this card, the recirculation valve is controlled. Let's say in the EGR card that at 2000 rpm and a cycle filling of 20 mm ^ 3 / cycle, 460 mg / cylinder of fresh air is required, while let's say that the maximum cylinder filling for a given engine with a given turbine is 900 mg / cylinder. Then the remaining part (900-460 = 440 mg / cylinder) can be filled with conditionally inert gas taken from the engine outlet. One of the ways to disable EGR is to fill this map with values corresponding to the maximum filling of the cylinders with gas, however, in this method, the controller can ignite an error. There is a more progressive way for EDC16 (more on that in the next part).
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EGR (1C356C) |
SMOKE LIMIT
The map determines the cycle fuel consumption limit (injection volume / cycle, or lambda coefficient) for a given mass air flow and engine speed. It is with the help of this card that smokeless combustion of fuel is realized (anti-smoke system). The card works as follows: let's say the driver pressed the gas pedal. The controller knows how much fuel needs to be injected to provide the requested torque, but limits the fuel injection until the turbine spins up and the desired air flow occurs. Therefore, there is a "dull" response to pressing the gas. As the turbine spins up, the air consumption increases, and the restriction on fuel injection is gradually removed. At high speeds, the turbine creates constant pressure, while the air flow will stop changing, therefore, for high speeds, when the turbine has already started spinning, there is no point in editing the map. The values in the map are selected in such a way that the required mass air flow exceeds the optimal one by 10-20% - this ensures completely smokeless fuel combustion. Thus, by reducing the required air consumption in this map, we will increase the amount of smoke during fuel combustion, but we will sharpen the reaction rate to the gas pedal. It is not worth getting carried away here too much - anyway, without air, the engine will not be able to provide confident traction, but the catalytic converter can suffer greatly from an excess of unburned fuel. There can be several cards, for example, for a ZMZ diesel engine - its own card for each gear, only 5 cards. Thus, by reducing the required air consumption in this map, we will increase the amount of smoke during fuel combustion, but we will sharpen the reaction rate to the gas pedal. It is not worth getting carried away here too much - anyway, without air, the engine will not be able to provide confident traction, but the catalytic converter can suffer greatly from an excess of unburned fuel. There can be several cards, for example, for a ZMZ diesel engine - its own card for each gear, only 5 cards. Thus, by reducing the required air consumption in this map, we will increase the amount of smoke during fuel combustion, but we will sharpen the reaction rate to the gas pedal. It is not worth getting carried away here too much - anyway, without air, the engine will not be able to provide confident traction, but the catalytic converter can suffer greatly from an excess of unburned fuel. There can be several cards, for example, for a ZMZ diesel engine - its own card for each gear, only 5 cards.
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SMOKE LIMIT (1CD144, 1CD388) |
TORQUE LIMIT
The map determines the maximum torque (Nm), depending on the engine speed. In fact, this is the map that is usually given as the BCX characteristics of the engine. The main purpose of this card is mechanical protection of the engine. Sometimes the map is set for several values of atmospheric pressure - normal, and low, as, for example, in the mountains. In rarefied air, the torque (and, therefore, the cycle fuel consumption) must be reduced so as not to exceed the turbine speed and not to disrupt its operation into an unstable mode (surge). By editing this map, it is possible (within certain, small limits) to increase the torque and maximum engine power, but in an amicable way, this requires the presence of a motor stand, and, at least, reconfiguring the operation of the turbine (without increasing the boost pressure, the torque will not increase).
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TORQUE LIMIT (1CBD4A) |
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