How The ECU Works | Jaguar Land Rover ECU | BMW ECU

UCU Control of Air/Fuel Mixture Ratio

Modern engines such as BMW, Jaguar Land Rover, Discovery and Range Rover Sport use a similar type of fuel injection system to deliver fuel to its cylinders. The Engine Control Module or ECU determines this amount of fuel to inject based on a number of readings supplied by the sensors. Oxygen sensors tell the ECU whether the engine is running rich or running too lean. The throttle position sensor is responsible for telling the ECU how far the throttle plate (butterfly) is opened when the accelerator is pressed which opens the butterfly. The mass air flow sensor or air flow valve measures the amount of air flowing into the cylinders through the throttle plate or throttle body. The engines coolant temperature sensor measures whether the engine is warmed up, hot or still cool. If the engine is cool then additional fuel will be injected into the respective cylinders.

ECU Ignition Timing

A coil pack spark is required to initiate combustion in the combustion chamber. The ECU has the ability to adjust the exact timing of the spark which is called ignition timing. This deliberation of spark to crankshaft/camshaft timing will provide better power and economy of the engine. If the ECU detects knock via the knock sensors and determines it to be the result of the ignition timing occurring too early in the compression stroke, it will retard the timing of the spark to prevent this from happening. Knock tends to occur more easily at lower rpm and should this be the case the ECU may send a signal for the automatic transmission to downshift as a first attempt to alleviate knock within the engine.

ECU Control of Idle Speed

Most UCU’s have an idle speed control facility built into the system. The speed of the engine RPM is monitored by the crankshaft position sensor which plays a primary role in the engine timing functions which includes the valve timing, fuel injection and the exact delivery of the spark. Idle speed is controlled by a throttle stop or an idle air bypass control stepper motor. Idle speed control must anticipate the engine load at idle speed of the engine.

UCU Control of Variable Valve Timing

Most modern engines have Variable Valve Timing and in such engines the ECU determines the exact time in the engine cycle at which the valves open and close. Intake and exhaust valves are usually opened earlier at higher speeds than at lower speeds and this can optimize the flow of air into the cylinder thereby increasing the power and fuel economy of an engine.

ECU Electronic Valve Control

Experimental engines such as used in Formula One Racing engines have been made and tested that have no camshaft, but have full electronic control of the intake and exhaust valve opening, valve closing and area of the valve opening. The first production engine of this type was developed in 2000 and introduced in 2008/09 by Italian automaker Fiat. Their Multiair engines use electronic valve control which dramatically improve torque and horsepower, while reducing fuel consumption as much as 15%. The valves are opened by hydraulic pumps, which are operated by the ECU and the valves can open and close several times per intake stroke, based on engine load.

Under a sudden increase in throttle position, the valve opens in the same intake stroke and a greater amount of fuel is injected into the respective cylinders, which allows more response in acceleration. In time for the next stroke, the ECU calculates engine load at the eventual higher RPM and decides how to open the valve, either earlier or later or wide open or partially open. The optimal opening and timing are always reached and combustion is as precise as possible. This cannot be achieved with a standard or ‘normal’ camshaft which opens the valve for the whole intake period to full lobe lift.

The elimination of cams, lifters, rockers, and timing set reduces not only weight and bulk, but also friction which is responsible for heat gains within any engine. Cylinder deactivation, for instance, could be made much more fuel efficient if the intake valve could be opened on every down-stroke and the exhaust valve opened on every up-stroke of the deactivated cylinder. Another even more significant advancement will be the elimination of the convention throttle. With electronic valve operation, it is possible to control the engines speed by regulating the valve lift. At part throttle, when less air and gas are needed, the valve lift would not be as great. Full throttle is achieved when the gas pedal is depressed, sending an electronic signal to the ECU, which in turn regulates the lift of each valve event, and opens it all the way up by means of a third camshaft or intermediated camshaft which is motivated by actuators.

Programmable ECU’s

Programmable ECUs are required where significant aftermarket modifications have been made to a vehicle's engine which includes the addition or changing of a turbo or supercharger, intercooler, exhaust system or a conversion enabling the engine to run on alternative fuel.

The programmable ECU may control the amount of fuel to be injected into each cylinder. This varies depending on the engine's RPM and the position of the accelerator pedal or the manifold air pressure.

By modifying these values while monitoring the exhausts using a wide band lambda probe to see if the engine runs rich or lean, the tuner can find the optimal amount of fuel to inject to the engine at different RPM and throttle positions which is better carried out on a dynamometer.

V8 ENGINE is your one stop V8 engine reconditioning shop for V8 engines on exchange

CLICK HERE for more information on a BMW ECU | Jaguar Land Rover ECU | Jaguar Land Rover ECU | V8 Engines.