Gasoline Direct Injection (PDF)

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					MIM   Tech Talk in association with

Gasoline Direct Injection:                                                                                                       One
At a time of even greater                                                    GDI designed engines, when     cycles: ultra lean burn,
demand on automotive                                                         compared to a conventional     stoichiometric, and full
manufactures to further                                                      fuel injected or carbureted    power output. Each cycle is
improve emission standards                                                   engine, which greatly          characterised by the air-fuel ratio.
and fuel economy, it’s time to                                               improves efficiency and        The stoichiometric air-fuel ratio
revisit the topic of fuel injection                                          reduces ‘pumping losses’ in    for petrol (gasoline) engines is
systems. But before taking a                                                 engines without a throttle     14.7:1 by weight, but the ultra lean
look at latest advancements,             Basic theory of operation           plate. Engine speed is         cycle can involve ratios as high
let’s remind ourselves of the            The major advantages of a           controlled by the engine       as 35:1 (or even higher in some
history, basic operation and             GDI engine are lower emission       management system which        engines, for very limited periods).
development of GDI.                      levels, increased fuel efficiency   regulates fuel injection and   These mixtures are much leaner
     In internal combustion              and higher engine power             ignition timing parameters,    than in a conventional fuel
engines, Gasoline Direct                 output. In addition, the cooling    instead of having a throttle   injected engine and reduce fuel
Injection (GDI), sometimes               effect of the injected fuel and     plate which restricts the      consumption and certain levels of
known as Fuel Stratified                 the more evenly dispersed           incoming air supply. Adding    exhaust emissions considerably.
Injection (FSI), is an                   combustion mixtures and             this function
increasingly popular type of             temperatures allow for              to the engine
fuel injection system employed           improved ignition timing            management
in modern four and two-stroke            settings which are an equally       system requires
petrol engines. The petrol/              important system requirement.       considerable
gasoline is highly pressurised,              Emissions levels can be         enhancement of
and injected by high voltage             more accurately controlled          its processing
driven injectors via a common            with the GDI system. The            and memory, as
rail fuel line directly into the         lower levels are achieved by        direct injection
combustion chamber of                    the precise control over the        plus other engine
                                         amount of fuel, air and ignition    management systems must             Ultra lean burn cycle is used
                                         settings which are varied           have very precise mapping      for light-load running conditions,
                                         according to the engine load        for good performance and       at constant or reducing road
                                         conditions and ambient air          driveability.                  speeds, where no acceleration
                                         temperatures.                           The engine management      is required. The fuel is not
                                              In addition, there are         system continually chooses     injected at the intake stroke but
                                         no throttling losses in some        among three combustion         rather at the latter stages of the
                                                                                                            compression stroke, so that the
                                                                                                            small amount of air-fuel mixture
each cylinder, as opposed                                                                                   is optimally placed near the spark
to conventional single or                                                                                   plug. This stratified charge is
multi-point fuel injection                                                                                  surrounded mostly by air which
that happens in the intake                                                                                  keeps the fuel and the flame
manifold tract, or cylinder                                                                                 away from the cylinder walls for
port. In some applications,                                                                                 low emissions and heat losses.
gasoline direct injection                                                                                   The combustion of the fuel takes
enables a stratified fuel charge                                                                            place in a toroidal (donut-shaped)
(ultra lean burn) combustion                                                                                cavity on the piston’s surface
for improved fuel efficiency,                                                                               designed to improve air swirl and
and reduced emission levels at                                                                              delivered by a specially designed
low load.                                                                                                   injector nozzle. This allows

40 MOTOR INDUSTRY M A G A Z I N E J U N E 2 0 1 0                                                                       W W W . MOTOR.ORG.UK
successful ignition without         As the RPM increases, the
misfire, even when the air/fuel     time available to inject fuel
mixture is very lean                decreases. Newer GDI systems
     Stoichiometric cycle           have sufficient fuel pressure to
is used for moderate load           inject more than once during a
conditions. Fuel is injected        single cycle. Fuel injection takes
during the intake stroke,           place in two phases. During the
creating a homogenous fuel-air      intake stroke, some amount of
mixture in the cylinder. From the   fuel is “pre-injected” into the          Q: A 2002 Citroen C5 2.0             Q: A 2003 Renault Trafic II
stoichiometric ratio, an optimum    combustion chamber which                 HDI performs poorly. The             2.5 dCi with a G9U engine
burn results in a clean exhaust     cools the incoming air, thus             vehicle is very slow to build        code is producing lots of
emission, further cleaned by the    improving volumetric efficiency          up speed and struggles to            black exhaust smoke and
catalytic converter.                and ensuring an even fuel/air            climb moderately steep hills.        does not generate sufficient
     Full power cycle is            mixture within the combustion            Initial investigation with           power. The engine MIL
used for rapid acceleration         chamber. Main injection takes            the scanner suggests that            light is on and the engine
and heavy loads (as when            place as the piston approaches           both the fuel pressure and           management DTC suggests
climbing a hill). The air-fuel      top dead centre on the                   turbo boost pressure are             an EGR fault. The EGR valve
mixture is homogenous and           compression stroke, shortly              correct and a visual check           is OK. We can clear the DTC
the ratio is slightly richer than   before ignition.                         of the engine management             but as soon as the engine is
stoichiometric, which helps                                                  components reveals nothing           running the MIL illuminates
prevent knock (pinging). The        Two-stroke engines                       wrong. Neither are there any         and the same engine
fuel is injected                                                             fault codes in the system to         management DTC is logged.
during the intake                                                            guide us.                            A: On this engine there
stroke.                                                                      A: The problem may be                is a transfer pipe between
     Direct injection                                                        caused by water from the             the cylinder head and the
is supported by                                                              surrounding atmosphere               EGR valve which is prone to
other engine                                                                 finding its way into the mass        corrosion at the flanges of the
management                                                                   air flow sensor. It collects in      pipe. It is also possible for
systems such                                                                 the bottom of the air filter         this pipe to become blocked
as variable valve                                                            housing and then gets drawn          by carbon. Clean or replace the
timing (VVT)                                                                 up into the mass air flow            transfer pipe as necessary.
with variable                                                                sensor. Locate the air cleaner
length intake manifold              The benefits of direct injection         housing behind the LH front          Q: A 2007 Fiat Scudo 2.0D
(VLIM) or acoustic controlled       are even more pronounced in              wheel arch liner and remove          has a knocking noise that
intake system (ACIS). A high        two-stroke engines, because              the housing complete. Check          only occurs when the steering
performance exhaust gas             it eliminates much of the                that there is a drain hole in        wheel is being turned.
recirculation valve (EGR) will      pollution that their conventional        the bottom. If not, drill a 5mm      Originally, the power steering
almost certainly be required to     design causes. In conventional           hole in the lowest part of the       pump was thought to be
reduce the high nitrogen oxides     two-strokes, the exhaust and             housing. Change the air filter       the cause, but this has been
(NOx) emissions which will          intake ports are both open at            element and refit the air filter     replaced and the problem
result from burning ultra lean      the same time, at the bottom             housing. Ensure that the air         persists.
mixtures.                           of the piston stroke. A large            filter housing will be exposed       A: Remove the engine
     Conventional fuel injection    portion of the fuel/air mixture          to the minimum amount of             undertray and check that all
engines could inject fuel           entering the cylinder from               water by sealing the bodywork        the engine mounts are fitted
throughout the 4 stroke             the crankcase through the                joint inside the wheel arch at       correctly and all the bolts are
sequence, as the injector injects   intake ports goes directly out,          approximately the same level         tight. The engine should not
fuel onto the back of a closed      unburned, through the exhaust            as the top of the bumper.            vibrate against anything when
valve. Earlier direct injection     port. With direct injection, only        Seal all the remaining joints in     the power steering pump load
engines, where the injector         air comes from the crankcase,            the wing liner and road test. If     is applied. Check the power
injects fuel directly into the      and fuel is not injected until the       the performance is still poor,       steering pump low pressure
cylinder, were limited to the       piston rises and all ports are           test the mass air flow sensor,       pipe. If it is too close to the
induction stroke of the piston.     closed.                                  which may need replacing.            chassis leg it will knock when

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    MIM   Tech Talk in association with

           Auto                                History                               combustion), utilising a unique        inline-four unit, under the

                                               The first use of direct gasoline      high pressure pump and direct          product name “Fuel Stratified
                                               injection was on the Hesselman        injectors. The project was cancelled   Injection” (FSI). The technology
                                               engine invented by Swedish            for several reasons: electronic        was adapted from Audi’s Le
                                               engineer Jonas Hesselman in           controls, a key requirement, were      Mans prototype race car R8.
                                               1925. Hesselman engines used          in their early design stage and             In 2001, Ford introduced its
    the steering is in operation.              the ultra lean burn principle and     lacked sufficient processing power;    first European engine to use direct

    If this is the case, check the             injected the fuel in the end of the   pump and injector costs were           injection technology, badged SCi
    condition of the pipe and                  compression stroke and then           also extremely high; and as later      (Smart Charge injection) for Direct-
    replace it if necessary. There             ignited it with a spark plug. It      designers discovered, lean burn        Injection-Spark-Ignition (DISI).
    is a spacer tube available that            was often started on gasoline         combustion mixtures produce                  In 2002, the Alfa Romeo 156
    fits over the low pressure                 and then switched over to run         excessive nitrogen oxides levels.      with a direct-injection engine, the
    pipe to keep it away from the              on diesel or kerosene. The                                                   JTS (Jet Thrust Stoichiometric),
    chassis leg.                               Hesselman engine was a low            Latersystems                           went on sale and today the
                                               compression design constructed        In 1996 gasoline direct injection      technology is used on almost
    Q: A 2006 Citroen C5 2.0                   to run on heavy fuel oils.            reappeared in the automotive           every Alfa Romeo engine.
    HDi, engine code RHR has                        Direct gasoline injection        market. Mitsubishi was the                  In 2003, BMW introduced
    the engine management                      was also used on production           first with a GDI engine in the         a low-pressure gasoline direct
    light on all the time. Using               aircraft in 1937 during WWII,         Japanese market with its               injection N73 V12. This initial
    our scanner, we got DTC                                                          4G93 1.8 L inline-four. It was         BMW setup could not enter lean-
    P1421, DPF temperature                                                           subsequently brought to Europe         burn mode, but the company
    sensor open circuit. The                                                         in 1997.                               introduced its second-generation
    engine management                                                                     In 1998, Toyota’s D4 direct       High Precision Injection (HPI)
    light has been coming on                                                         injection four-stroke system first     system on the updated N52
    intermittently for a short                                                       appeared on various Japanese           straight-6 in 2006 which used
    time but has always gone                                                         vehicles within its home market.       high-pressure injectors.
    out on restart.                                                                  Toyota later introduced its D4              In 2007, Ford introduced
    A: Locate the DPF                                                                system to European markets             its new Ford EcoBoost engine
    temperature sensor in the                                                        with the 1AZ-FSE engine.               technology designed for a range of
    exhaust system. Follow the                 with the German Junkers Jumo          Toyota’s 2GR-FSE V6 uses a             global vehicles (from small cars to
    wiring loom along its length               210, Daimler-Benz DB 601. The         more advanced direct injection         large trucks). The global EcoBoost
    from the sensor and where                  first automotive direct injection     system, which combines both            family of 4-cylinder and 6-cylinder
    the wiring harness is clipped              system used to run on gasoline        direct and indirect injection using    engines features turbo charging
    onto the edge of the exhaust               was developed by Bosch and was        two fuel injectors per cylinder,       and direct injection technology
    heat shield and you will find              introduced by Goliath and Gutbrod     a traditional port fuel injector       (GTDI - Gasoline Turbocharged
    that the clip has chafed                   in 1952. The 1955 Mercedes-           (low pressure) and a direct fuel       Direct Injection).
    against the wiring harness.                Benz 300SL, the first sports car      injector (high pressure) in a               In 2008, Mercedes-Benz
    One of the wires will either               to use fuel injection, used direct    system known as D4-S                   released its direct injection system
    have a cut in the insulation               injection. The Bosch fuel injectors        In 1999, Renault introduced       (Charged Gasoline Injection,
    causing a short circuit or will            were placed into the bores on the     the 2.0 IDE (Injection Direct          or “CGI”) on the CLS 350 CGI
    be completely cut causing                  cylinder wall used by the spark       Essence), which was used first         featuring common rail, piezo-
    an open circuit. Replace                   plugs in other Mercedes-Benz          on the Megane model.                   electric direct fuel injectors.
    the sensor and re-route                    six-cylinder engines (the plugs            In 2000, Volkswagen                     Part 2 of this series will
    the wiring so that it is fixed             were relocated to the cylinder        introduced its gasoline                take a more detailed look at
    securely.                                  head). Later, more mainstream         direct injection engine in the         the components and operation
                                               applications of fuel injection        Volkswagen Lupo, a 1.4 litre           of GDI.
                                               favoured less expensive indirect
                                               injection methods.
                                                                                       These articles are contributed by ProAuto, an automotive technical
          Material supplied by                      During the late 1970s, Ford
                                                                                       training company based in Shrewsbury, Shropshire. The company
                                               Motor Company developed a               runs courses from venues nationally, so a course is never too far
                                               stratified-charge engine they           away. For further details, visit or email
                                               called “ProCo” (programmed     or telephone 01743 762050.

    42 MOTOR INDUSTRY M A G A Z I N E J U N E 1 0 2 0 1 0                                                                               W W W . MOTOR.ORG.UK

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