Gasoline direct-injection (GDI) engines directly inject fuel into the combustion chamber, achieving lower fuel consumption than diesel engines while providing more power than conventional port fuel injection engines. GDI engines allow for ultra-lean air-fuel mixtures as late direct injection provides stratified charging. This stable combustion of extremely lean mixtures at ratios of 40:1 reduces fuel consumption by 40% during idling compared to conventional engines. GDI engines also improve volumetric efficiency through upright intake ports and vaporized fuel cooling the air charge, allowing increased compression ratios of 12 for better combustion efficiency and output superior to conventional port fuel injection engines.

2. • Gasoline direct-injection engines generate
the air/fuel mixture in the combustion
chamber.
• During the induction stroke, only the
combustion air flows through the open intake
valve.
• The fuel is injected directly into the
combustion chamber by special fuel
injectors.

3. Major Objectives of the GDI engine
Ultra-low fuel consumption that betters that
of even diesel engines
Superior power to conventional MPI engines

4. WHY NOT CARBURETTOR?
Carburetor has following disadvantages
 Vapor lock
Perfect air/fuel mixture cannot be obtained
Lack of throttle response
Low volumetric efficiency
Icing – problem in aircraft engines
Mechanical device
Compromises on emission

5. Transition of fuel supply

6. Major characteristics of the GDI engine
1. Lower fuel and higher output consumption
 Optimal fuel spray for two-combustion
mode
 Ultra-lean Combustion Mode
 Superior Output Mode

7. 2. The GDI engines foundation technologies
 In-cylinder Airflow

8. Realization of lower fuel consumption
Basic Concept
• In conventional gasoline engines, dispersion of an
air-fuel mixture with the ideal density around the
spark plug was very difficult. However, this is
possible in the GDI engine. Furthermore,
extremely low fuel consumption is achieved
because ideal stratification enables fuel injected
late in the compression stroke to maintain an
ultra-lean air-fuel mixture.

9. • As a result, extremely stable combustion of ultra-
lean mixture with an air-fuel ratio of 40 (55, EGR
included) is achieved as shown below.

10. Combustion of Ultra-lean Mixture

In conventional MPI engines, there were limits to
the mixtures leanness due to large changes in
combustion characteristics. However, the
stratified mixture of the GDI enabled greatly
decreasing the air-fuel ratio without leading to
poorer combustion. For example, during idling
when combustion is most inactive and unstable,
the GDI engine maintains a stable and fast
combustion even with an extremely lean mixture
of 40 to 1 air-fuel ratio (55 to 1, EGR included)

12. Vehicle Fuel Consumption
Fuel Consumption during Idling
 The GDI engine maintains stable combustion
even at low idle speeds.
 Moreover, it offers greater flexibility in setting
the idle speed.
 Compared to conventional engines, its fuel
consumption during idling is 40% less.

13. Graph

14. Emission control
• However, in the case of GDI engine, 97% NOx
reduction is achieved by utilizing high-rate
EGR (Exhaust Gas Ratio) such as 30% that is
allowed by the stable combustion unique to
the GDI as well as a use of a newly developed
lean-NOx catalyst.

15. Basic concept
 To achieve power superior to conventional
MPI engines, the GDI engine has a high
compression ratio and a highly efficient air
intake system, which result in improved
volumetric efficiency.
Realization of Superior Output

16. Improved Volumetric Efficiency
• Compared to conventional engines, the
Mitsubishi GDI engine provides better volumetric
efficiency.
• The upright straight intake ports enable smoother
air intake.
• And the vaporization of fuel, which occurs in the
cylinder at a late stage of the compression stroke,
cools the air for better volumetric efficiency.

18. Increased Compression Ratio
• The cooling of air inside the cylinder by the
vaporization of fuel has another benefit, to minimize
engine knocking. This allows a high compression
ratio of 12, and thus improved combustion efficiency

19. GDI Vehicles
 BMW
 Ford
 EcoBoost
 General Motors
 2.0L Ecotec
 Hyundai
 Theta
 Lexus
 Mazda Speed
 Direct Injection Spark
Ignition
 Mitsubishi
 Gasoline Direct Injection
 Volkswagen
 FSI Fuel Stratified
Injection