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Fuel Injection Systems Overview
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Fuel Injection Systems Overview
Fuel Injection Systems Overview
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1
Question
Why is fuel injection preferred over carburetion?
Answer
Strict emission standards require precise fuel delivery.
2
Question
What does Electronic Fuel Injection (EFI) provide?
Answer
EFI is very precise, reliable, and cost effective because computers are used to calculate fuel needs.
3
Question
How does fuel injection compare to carburetion?
Answer
Fuel injection serves the same purpose as carburetion by atomizing the fuel stream to aid in evaporation, vaporization, and mixing with the airflow to create an air-fuel mixture.
4
Question
What is the purpose of a fuel injector?
Answer
The purpose of a fuel injector is to deliver the correct amount of fuel to an engine for proper combustion.
5
Question
What are the types of fuel injection?
Answer
Types of injection include CIS, TBI, CPI, CFSI, PFI, and GDI.
6
Question
Where can the injector be mounted?
Answer
Injectors can be mounted before the throttle valve, before the intake valve, or after the throttle valve, and after the intake valve facing directly into the combustion chamber.
7
Question
What are the types of injectors based on mechanical operation?
Answer
Mechanical poppet injectors activated by fluid pressure or electromechanical injectors activated by electric current flow.
8
Question
How does fuel enter the injector?
Answer
Fuel enters the injector through the top, side, or near the bottom; note that injectors spray out of the very bottom.
9
Question
What are the different fire sequences for injectors?
Answer
Simultaneously ganged fired, group fired, batch fired, sequentially, and individually according to fire order.
10
Question
What is the range of injection pressure for different types of fuel injection?
Answer
Low pressure: 9-13 psi (TBI) to high pressure: 500-2900 psi (GDI). Older PFI: 35-45 psi, CIS: 75 psi, CPICSFI: 55-64 psi.
11
Question
What is internal winding resistance for fuel injectors?
Answer
Low: 1-3 ohms; Higher: 11-16 ohms.
12
Question
What are the types of control strategies for solenoid injectors?
Answer
Peak and hold, saturated switch.
13
Question
What types of needle ends do injectors have?
Answer
Pintle, disc, ball.
14
Question
What are the types of spray patterns for injectors?
Answer
Single spray narrow, wide cone, dual spray.
15
Question
What are Mechanical Fuel Injectors?
Answer
Mechanical fuel injectors do NOT have a coil winding, are NOT solenoids, are sometimes called poppet valves, and contain a needle with either a pintle or ball end and return spring.
16
Question
How does a Mechanical Poppet Injector operate?
Answer
The valve needle is pushed off the valve seat by fuel pressure, allowing fuel to spray out of the injector.
17
Question
What happens when the solenoid coil winding is energized in a fuel injector?
Answer
The injector valve needle is unseated, allowing fuel to flow out of the injector tip.
18
Question
What is the purpose of the fuel pressure regulator in a TBI unit?
Answer
The tension of the spring in the fuel-pressure regulator determines the operating pressure.
19
Question
What is CPI and its introduction?
Answer
Central Port Injection (CPI) was introduced in the early 90s by GM on their Vortex engines in their vans, trucks, SUVs.
20
Question
What does PFI stand for?
Answer
Port Fuel Injection.
21
Question
What are the operating pressures for older and newer PFI systems?
Answer
Older systems: 35-45 psi; newer systems: 50-60 psi.
22
Question
What are the modes of operation for GDI?
Answer
Stratified mode and homogeneous mode.
23
Question
What should be taken care of when servicing GDI systems?
Answer
Care should be taken to depressurize the system correctly before opening or servicing to avoid any injection injuries.
24
Question
What is the relationship between manifold pressure and fuel pressure in PFI systems?
Answer
The fuel pressure changes according to manifold pressure conditions, maintaining a constant net fuel pressure across the injector.
25
Question
What is the function of the control plunger in a CIS system?
Answer
The control plunger regulates the amount of fuel sent to each injector based on load conditions.
26
Question
What does the term 'homogeneous mode' mean in GDI operation?
Answer
Homogeneous mode refers to an air-fuel mixture that is the same throughout the cylinder.
27
Question
What is the significance of the injector solenoid in GDI systems?
Answer
The injector solenoid controls the timing and duration of the fuel injection process.
28
Question
What are some examples of vehicles that used the CIS system?
Answer
BMW, Lamborghini, Ferrari, Mercedes-Benz, Volkswagen, Ford, Porsche, Audi, Saab, Delorean, and Volvo.
29
Question
What are the risks associated with high-pressure fuel delivery systems like GDI?
Answer
High-pressure systems can pose injection injuries if not properly depressurized before servicing.
30
Question
How does injected fuel mix with air in a TBI system?
Answer
Airflow is pulled around the injector inside the throttle body, helping to atomize the fuel mixture.