GDI - The Future is Already Here

8/3/2019 GDI - The Future is Already Here.

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UNDERSTANDING GDI GASOLINE DIRECT INJECTION.

The future of Gasoline Engines lies in the Gasoline Direct Injection (GDI).Couple the consumer demands for Cheaper Prices

,

Better Performance and GreaterFuel Economy together with World Wide legislation on Exhaust Emission Outputs

and you can see the vehicle manufacturers have a very tough task ahead of them in

the next decade.

To meet these demands, the Vehicle Manufacturers are switching to Direct Fuel

Injection, be it Diesel or Gasoline Fuel, Direct Injection is their only way forward.Direct Injection is the Future for the Gasoline Engine and the Future is already here.The abbreviation GDI (with a capitalised letter "I") is a registered trademark of

Mitsubishi Motors. Other companies have developed other names for what is

Gasoline Direct Injection (GDI) engines but have had to change their brand name of

their system, VW/Audi have branded their system

(Fuel Stratified Injection) Alfa Romeo JTS,

Renault HPI and so on, the fact is they are all

Gasoline Fuel fired directly into the combustion chamber.On a direct injection engine, a very

fine mist of Fuel is

injected directly in to the combustion chamber at a

pressure of between 50 120 Bar, depending on the type

of system. During idle and light throttle, the metered fuel

is injected at microscopic milli second (mS) durations at

a pressure of approximately 50 bar.This design enables the engine to operate a stratified charge combustion, described

by most of the vehicle manufacturers as an Ultra Lean Burnmode, giving a muchimproved fuel efficiency, great engine torque and reduced exhaust emission levels at

low load.
http://en.wikipedia.org/wiki/Lean_burnhttp://en.wikipedia.org/wiki/Lean_burnhttp://en.wikipedia.org/wiki/Lean_burnhttp://en.wikipedia.org/wiki/Lean_burnhttp://en.wikipedia.org/wiki/Lean_burnhttp://en.wikipedia.org/wiki/Lean_burnhttp://en.wikipedia.org/wiki/Lean_burnhttp://en.wikipedia.org/wiki/Lean_burnhttp://en.wikipedia.org/wiki/Fuel_efficiencyhttp://en.wikipedia.org/wiki/Fuel_efficiencyhttp://en.wikipedia.org/wiki/Fuel_efficiencyhttp://en.wikipedia.org/wiki/Lean_burn


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To achieve these pressures, the gasoline is pressurized by a

high-pressure pump that is a combination of mechanically

driven and electronically controlled and mounted on the engine.

This pump compresses the fuel to the pressure level required in the

fuel rail.

As the vehicle accelerates and the load increases, in a normal simultaneous gasoline

injection engine, the injector will open for longer mS periods to allow more fuel in to

the manifold to meet the demands of the engine.With the sequential firing GDI systems, the injector only opens to a maximum of

5mS.As the fuel requirement increases, the injector remains at 5mS and the pumppressure increases to meet the demand, allowing the injector to open and close

quickly and efficiently. No more Duty Cycle as we have known it.These engines use a very high specification

injector,Hitachi, Bosch, Denso and Siemensbeing the major suppliers.This design of injector requires a greater

current supply to open them against the

50 bar fuel pressure, some having a very

low resistance of 0.7 OHMS, which allows

them to operate under extreme conditions.With these type of GDI systems, the ECU would supply a Fast On voltage of up to

90v for approximately 150 S, them drop down to a Peak Current for 350 S ,

dropping down again to the Hold Current for another 3500 S before the injectoris closed by the Fast Turn Off that aides the energy dissipation of the injector.

BOSCH DENSOBOSCH DENSOBOSCH DENSOBOSCH DENSO

This graph shows the

Driver ControlUsed in an ASNU GDI

Adapter Box,

show the speed and

efficiency in which

the injector operates in

opening and

closing in a five mS pulse

width.


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The FUEL QUANTITY and FUEL SPRAY and DISTRIBUTION and ATOMISATION

from these injectors is far more critical than ever before for the engines correctrunning, performance, fuel economy and exhaust emissions.During a StratifiedCombustion Mode, the Air/Fuel ration on some system can be as fine as 65:1,

this means that the FUEL represents approximately 1.5% of the total mass

during the combustion stroke.This style of injector can have varying types of spray patterns, depending on

the engine requirements, but all of them will be atomising a much smaller fuel

droplet size. To explain the difference, a conventional injector would have a fuel

droplet size, as an example, of 165 micron, some GDI injectors would produce a

fuel droplet of say, only 65 micron.

Although the spray pattern shape may look the same, the size of the droplet is

much finer and the higher the pressure, the finer the droplet size. Smaller fuel

droplets will burn quicker and a give cleaner, more efficient combustion stroke,

improving performance, economy and reduce exhaust emissions.Even the slightest loss of the fuel delivery will have an adverse effect on the

engines Drivability, Power Output, Fuel Economy and Exhaust Emissions.Carbon can build up on the tip of the injector

and interfere with the distribution and

atomisation of the fuel.

The GDI systems operate in SEQUENTIAL

mode,firing each injector in turn as opposed to theconventionalSIMULTANEOUSmodeas used in most conventional manifold injectionsystems.


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Sealing the injector against compression loss is critical, the Mitsubishi

injectors use a copper compression washer, this must be replaced every time

the injector is removed.

The Bosch injectors use a Teflon seal thatalso needs replacing every time the injector

is removed. Special tools are required to

replace these seals.

The major problem for repair workshops is the diagnosing problems with the

injectors, ASNU M.D Phil Ellisdon, claims that less than 5% of workshops,

including main dealerships, have the training or equipment to diagnose

problems with manifold injection systems, when it comes to GDI, then its less

that 1%.Removing the injectors is a very time consuming task, when Phil Ellisdon asks

workshops what they do when they have injector problems, often the reply

from main dealerships is to replace them with new.

At over 150.00 each, plus over 4 hours labourmeans a very large invoice, but Ellisdon asks, do

you check them first? What happens if you put

the new ones in and the engine still has a problem?

Fitting new injectors on a GDI engine without testing

the injectors is a bit like Russian Roulete.To assist these workshops in their diagnosis, ASNU

have developed a GDI Adapter Box, a system built

and designed to Test & Service all GDI Injectors.ASNU have been working with GDI injectors all over

the world since 1997, when Mitsubishi first

introduced their GDI Injection on their Charisma,


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ASNU service over 60,000 injectors per month around the world, Phil Ellisdon

said that as soon as the Charisma came out, ASNU saw the problems with

carbon on the tips, all of a sudden the phone started ringing from various

parts of the world, asking about the problems with these new injectors.

Fortunately for ASNU Shell Fuels had one of thefirst one in the market and found carbon build up

on the injectors, after only 1500 miles.

Shell already having an ASNU sent Phil Ellisdon a

set for him to decide best how they should be tested

and serviced, the rest as they say, is history.Now 10 years later, GDI injectors have advanced,

Bosch now have 5 generations of GDI injectors,

soon there will be a PiePiePiePiezozozozo gasoline injector, already

being used in the Diesel Common Rail injectors.Gasoline Direction Injection is the future and

the Future is already here.

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GDI - The Future is Already Here