Injection timing is a critical variable in internal combustion engines. From every horsepower that needs tweaking to engineers seeking breakthroughs in fuel efficiency, the adjustments made here affect the entire engine system.
For an engine to receive the correct amount of fuel to function properly, the injection process must be precisely controlled. Nowadays, this is often a digital process, with the engine control unit (ECU) receiving data from a series of sensors and adjusting fuel timing accordingly.
This is an overview of the main types of sensors used in fuel injection systems today.
1. Air mass flow sensor
The mass airflow (MAF) sensor measures the amount of air entering the engine. Air density varies with altitude and ambient temperature. This means that continuous measurement is required to maintain the correct fuel-air ratio in the engine.
There are two types of mass flow sensors – hot-wire sensors and vane flow meters. The former is a newer and better technology. Hot-wire sensors are typically smaller, more sensitive to minute changes, and have lower installation costs.
2. Oxygen (O2) sensor
Most cars manufactured after 1980 are equipped with oxygen sensors. During combustion, the ideal air-to-gas ratio differs for each fuel. The oxygen sensor determines whether that ratio is maintained at any given time.
An oxygen sensor works by monitoring a vehicle's exhaust and measuring the oxygen content. Too little air results in excess fuel; this is called a "rich" mixture. Too much air creates a "lean" mixture.
Both conditions can result in avoidable levels of pollutants, including nitrogen oxides. A lean air-fuel mixture can also impair performance or damage the engine.
3. Throttle position sensor
Drivers introduce many variables while driving, which is why modern cars come standard with throttle position sensors.
These sensors provide direct feedback to the fuel injection system by periodically measuring the degree to which the throttle valve opens or closes and the speed at which these changes are made.
Essentially, the throttle position sensor provides data on how to drive the car and the instantaneous power demands placed on the engine. By using this sensor to "synchronize" throttle behavior with fuel injection timing, the vehicle can idle smoothly and accelerate as needed.
4. Manifold Absolute Pressure (MAP) Sensor
The MAP sensor, located near or inside the vehicle's intake manifold, measures the power load applied to the engine at any given time. The sensor compares these measurements to a vacuum level to ensure consistency.
MAP sensors are important because they report external factors that can lead to higher engine loads and a greater demand for fuel. For example, if a vehicle begins to climb a hill, the MAP sensor should show low vacuum and high engine load. In turn, the MAP sensor sends this data to the ECU, which then requests more fuel.
5. Engine coolant temperature (ECT) sensor
Like other sensor technologies mentioned here, ECT sensors help harmonize conditions inside and outside the engine. In this case, an ECT sensor located next to the car's thermostat determines the effect of ambient temperature on the engine.
If the engine is cold, two things are needed for it to function properly:
Large quantities of fuel.
A higher idle speed makes ignition smoother.
On the other hand, engine warm-up requires self-adjustment. As the engine warms up, the ECT sensor and ECU activate the cooling fan or adjust the ignition timing. When the ignition timing works properly, the engine should not lose power when required. Poor ignition timing can lead to engine knocking, power loss, and engine damage.
Other sensor technologies
This is the most common appearance of a fuel injection timing sensor. There are many other applications under active development, and many of them perform best when used in series.
A scientific study explored a range of non-standard but “quite effective” and “reliable” techniques, including:
Needle lift sensors: These sensors can measure the start and end of fuel injection in real time.
Piezoresistive pressure sensors: These sensors can measure pressure changes within the engine more accurately.
Photoelectric (or optical window) sensor: This type of sensor can quickly measure the onset and duration of combustion.
Smart technology can improve fuel injection
A more detailed study of fuel injection and the integration of sensors to provide real-time data capture has several advantages. Fine-tuning fuel injection can improve engine life, increase engine power when most needed, and reduce fuel consumption.
These smart sensors bring Industry 4.0 principles, such as data mobility, into the inner recesses of some of the most commonly used machines on Earth, such as gasoline engines.
Applying the right technology at this level can make our cars more efficient. This fuel savings also mean a healthier world, thanks to the Zhenggong Chain Industrial Automation Platform.
