What is Gasoline Direct Ignition (GDI) Engine?

Like other IC engine,like petrol or diesel engine GDI is also an internal combustion engine,but main difference is that in GDI injection occur during the intake stroke or sometimes in compression stroke.
GDI engine has some advantages-
1.GDI has better Anti-knock than other system
2.Better transient Response
3.Better volumetric efficiency

It has also problems-
1.DGI has Greater need of Emission Control
2.C0mbustion .Chamber design and Control
of GDI is complex.
3.There is a Problem of matching with Cat Converter
Design for GDI engine.

 Direct Gasoline Injection was introduced on production
aircraft during WWII, with both German (Daimler Benz) and
Soviet (KB Khimavtomatika) designs. During the
late 1970s, the Ford Motor Company developed
a stratified-charge engine they called
"ProCo" (programmed combustion), utilizing a unique high pressure pump and direct injectors.

It was not until 1996 that gasoline direct injection reappeared in the automotive market. Mitsubishi Motors was the first with a GDI engine in the Japanese market Galant/Legnum's  4G93 1.8 L straight-4, which it subsequently brought to

Europe in 1997 in the Mitsubishi Carisma, and 2.4L GDI for Galant, although Europe's high-sulphur fuel led to emissions problems, and fuel efficiency was less than expected. It also developed the first six cylinder GDI power plant, the 6G74 3.5 L V6, in 1997. Mitsubishi applied this technology widely, producing over one million GDI engines in four families by 2001, PSA Peugeot Citroën and Hyundai Motors both licensed Mitsubishi's GDI technology in 1999, the latter using the first GDI V8. Toyota introduced direct injection engine D4 (Toyota AZ engine) in 2000 Toyota Avensis. Although other companies have since developed gasoline direct injection engines, GDI (with an uppercase final "I") remains a registered trademark of Mitsubishi Motors.

 The major advantages of a GDI engine are increased fuel efficiency and high power
output. In addition, the cooling effect of the injected fuel and the more evenly dispersed
mixtures allow for more aggressive ignition timing curves. Emissions levels can also be
more accurately controlled with the GDI system. The cited gains are achieved by the
precise control over amount of fuel and injection timings which are varied according to the load conditions.

In addition, there are no throttling losses in some GDI engines, when compared to a conventional fuel injected or carburetter engine, which greatly improves efficiency in engines without a throttle plate. Engine speed is controlled by the engine management system (EMS) which regulates fuel injection function and
ignition timing, instead of having a throttle plate which restricts the incoming air supply. Adding this function to the EMS requires considerable enhancement of its processing and memory, as direct injection plus the engine speed management must have very precise algorithms for good performance/drive ability.




Direct injection of gasoline into the cylinder is rarely used because of (a) the difficulty of finding space in the head for an injector,(b) the added cooling and casting complications,(c) the added cost,(d) the refinements that are necessary for idling ,and(e) the problem of exact metering at high loads from cylinder to cylinder owining to the individual plungers.