Engines

GASOLINE DIRECT INJECTION

THEORY 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 the 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 carbureted engine, which greatly improves efficiency, and reduces 'pumping losses' in engines without a throttle plate. Engine speed is controlled by the engine control unit/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/driveability.

The engine management system continually chooses among three combustion modes: ultra lean burn, stoichiometric, and full power output. Each mode is characterized by the air-fuel ratio. The stoichiometric air-fuel ratio for petrol (gasoline) is 14.7:1 by weight, but ultra lean mode can involve ratios as high as 65:1 (or even higher in some engines, for very limited periods). These mixtures are much leaner than in a conventional engine and reduce fuel consumption considerably.

Ultra lean burn mode is used for light-load running conditions, at constant or reducing road speeds, where no acceleration is required. The fuel is not injected at the intake stroke but rather at the latter stages of the compression stroke, so that the small amount of air-fuel mixture is optimally placed near the spark plug. This stratified charge is surrounded mostly by air which keeps the fuel and the flame away from the cylinder walls for lowest emissions and heat losses. The combustion takes place in a toroidal (donut-shaped) cavity on the piston's surface.[citation needed] This technique enables the use of ultra-lean mixtures impossible with carburetors or conventional fuel injection.

Stoichiometric mode is used for moderate load conditions. Fuel is injected during the intake stroke, creating a homogenous fuel-air mixture in the cylinder. From the stoichiometric ratio, an optimum burn results in a clean exhaust emission, further cleaned by the catalytic converter.

Full power mode is used for rapid acceleration and heavy loads (as when climbing a hill). The air-fuel mixture is homogenous and the ratio is slightly richer than stoichiometric, which helps prevent knock (pinging). The fuel is injected during the intake stroke.

IN TWO STROKE ENGINES Two types of GDi are used in two-strokes:

low-pressure air-assisted, and high pressure. The former, developed by Orbital Engine Corporation of Australia (now Orbital Corporation) injects a mixture of fuel and compressed air into the combustion chamber. When the air expands it atomizes the fuel into 8-micrometre droplets, very small relative to the 20 to 30-micrometre fuel droplets in other direct injection systems. The Orbital system is used in motor scooters manufactured by Aprilia, Piaggio, Peugeot and Kymco, in outboard motors manufactured by Mercury and Tohatsu, and in personal watercraft manufactured by Bombardier Recreational Products (BRP).

In the early 1990s, Ficht GmbH of Kirchseeon, Germany developed a high-pressure direct injector for use with two stroke engines. This injector was unique in that it did not require a high pressure pump but was still capable of generating enough pressure to inject into a closed combustion chamber. Outboard Marine Corporation (OMC) licensed the technology in 1995 and introduced it on a production outboard engine in 1996. OMC purchased a controlling interest in Ficht in 1998.Beset by extensive warranty claims for its Ficht outboards and prior and concurrent management-financial problems, OMC declared bankruptcy in December 2000 and the engine manufacturing portion and brands (Evinrude Outboard Motors and Johnson Outboards), including the Ficht technology, were purchased by BRP in 2001.

FUTURETwin-fuel engine

Code named Bobcat the new twin-fuel engine from Ford. It is based on a 5.0L V8 engine block, but it uses E85 cylinder injection and gasoline port injection. The engine was co-developed with Ethanol Boosting Systems, LLC of Cambridge, Massachusetts, which calls its trademarked process DI Octane Boost. The direct injection of ethanol increases the octane of regular gasoline from 88-91 octane to more than 150 octane. The Bobcat project was unveiled in Department of Energy and Society of Automotive Engineers in April 2009.

CRDI• The common rail system was developed in the late 1960s by Robert Huber

of Switzerland. After that, the technology was further developed by Dr. Marco Ganser at the Swiss Federal Institute of Technology in Zurich, later of Ganser-Hydromag AG (estb. 1995) in Ober geri. In the mid-nineties, �Dr. Shohei Itoh and Masahiko Miyaki, of the Denso Corporation, a Japanese automotive parts manufacturer, developed the Common Rail Fuel System for Heavy Duty Vehicles and finally turned into its first practical use on their ECD-U2 Common Rail system, which was mounted on the

Hino Rising Ranger truck and sold for general use in 1995

PRINCIPLESolenoid or piezoelectric valves make possible fine electronic control over the fuel injection time and quantity, and the higher pressure that

the common rail technology makes available provides better fuel atomisation. In order to lower engine noise the engine's

electronic control unit can inject a small amount of diesel just before the main injection event ("pilot" injection), thus reducing its explosiveness

and vibration, as well as optimising injection timing and quantity for variations in fuel quality, cold starting, and so on. Some advanced

common rail fuel systems perform as many as five injections per stroke.Common rail engines require no heating up time and produce lower

engine noise and emissions than older systems.Diesel engines have historically used various forms of fuel injection.

Two common types include the unit injection system and the distributor/inline pump systems. While these older systems provided

accurate fuel quantity and injection timing control they were limited by several factors:

PRINCIPLE & WORKING

Modern common rail systems, whilst working on the same principle, are governed by an engine control unit (ECU) which opens each injector electronically rather than mechanically. This was extensively prototyped in the 1990s, with collaboration between Magneti Marelli, Centro Ricerche Fiat and Elasis. After research and development by the Fiat Group, the design was acquired by the German company Robert Bosch GmbH for completion of development and making suitable for mass-production. In 1997 they extended its use for passenger cars. The first passenger car that used the common rail system was the 1997 model Alfa Romeo 156 1.9 JTD and later on that same year Mercedes-Benz E 320 CDI.

• They were cam driven and injection pressure was proportional to engine speed. This typically meant that the highest injection pressure could only be achieved at the highest engine speed and the maximum achievable injection pressure decreased as engine speed decreased. This relationship is true with all pumps, even those used on common rail systems; with the unit or distributor systems, however, the injection pressure is tied to the instantaneous pressure of a single pumping event with no accumulator and thus the relationship is more prominent and troublesome.

• They were limited on the number of and timing of injection events that could be commanded during a single combustion event. While multiple injection events are possible with these older systems, it is much more difficult and costly to achieve.

• For the typical distributor/inline system the start of injection occurred at a pre-determined pressure (often referred to as: pop pressure) and ended at a pre-determined pressure. This characteristic results from "dummy" injectors in the cylinder head which opened and closed at pressures determined by the spring preload applied to the plunger in the injector. Once the pressure in the injector reached a pre-determined level, the plunger would lift and injection would start.

In common rail systems a high pressure pump stores a reservoir of fuel at high pressure — up to and above 2,000 bars (29,000 psi). The term "common rail" refers to the fact that all of the fuel injectors are supplied by a common fuel rail which is nothing more than a pressure accumulator where the fuel is stored at high pressure. This accumulator supplies multiple fuel injectors with high pressure fuel. This simplifies the purpose of the high pressure pump in that it only has to maintain a commanded pressure at a target (either mechanically or electronically controlled). The fuel injectors are typically ECU-controlled. When the fuel injectors are electrically activated a hydraulic valve (consisting of a nozzle and plunger) is mechanically or hydraulically opened and fuel is sprayed into the cylinders at the desired pressure. Since the fuel pressure energy is stored remotely and the injectors are electrically actuated the injection pressure at the start and end of injection is very near the pressure in the accumulator (rail), thus producing a square injection rate. If the accumulator, pump, and plumbing are sized properly, the injection pressure and rate will be the same for each of the multiple injection events.

Common rail engines have been used in marine and locomotive applications for some time. The Cooper-Bessemer GN-8 (circa 1942) is an example of a hydraulically operated common rail diesel engine, also

known as a modified common rail.Vickers used common rail systems in submarine engines circa 1916.

Doxford Engines Ltd.[5] (opposed piston heavy marine engines) used a common rail system (from 1921 to 1980) whereby a multi-cylinder

reciprocating fuel pump generated a pressure of approximately 600bar with the fuel being stored in accumulator bottles. Pressure control was achieved by means of an adjustable pump discharge stroke and a "spill

valve". Camshaft operated mechanical timing valves were used to supply the spring loaded Brice/CAV/Lucas injectors which injected

through the side of the cylinder into the chamber formed between the pistons. Early engines had a pair of timing cams, one for ahead running and one for astern. Later engines had two injectors per cylinder and the final series of constant pressure turbocharged engines were fitted with

four injectors per cylinder. This system was used for the injection of both diesel oil and heavy fuel oil (600cSt heated to a temperature of

approximately 130°C).

Close up on the "common rail" fuel injection system on Volvo's D7E 7.2L diesel engine

ADVANTAGES

1. Low Fuel Consumption2. Lower pollutants in Exhaust gas.3. Quiet Running of the Engine.4. Improved Engine Performance. 5. Battery economy6. Smooth drive7. More power

DISADVANTAGES

This engine also have few disadvantages. The key disadvantage of the CRDi engine is that it is costly than the conventional engine. The list also includes high degree of engine maintenance and costly spare parts.

COMMON RAIL TODAY Today the common rail system has brought about a

revolution in diesel engine technology. Robert Bosch GmbH, Delphi Automotive Systems,Denso Corporation, and Siemens VDO (now owned by Continental AG) are the main suppliers of modern common rail systems. The car makers refer to their common rail engines by their own brand names:

• BMW's D-engines (also used in the Land Rover Freelander TD4)• Cummins and Scania's XPI (Developed under joint venture)• Cummins CCR (Cummins pump with Bosch Injectors)• Daimler's CDI (and on Chrysler's Jeep vehicles simply as CRD)• Fiat Group's (Fiat, Alfa Romeo and Lancia) JTD (also branded as MultiJet, JTDm, Ecotec

CDTi, TiD, TTiD , DDiS, Quadra-Jet)• Ford Motor Company's TDCi Duratorq and Powerstroke• General Motors Opel/Vauxhall CDTi (manufactured by Fiat and GM Daewoo) and DTi (Isuzu)• General Motors Daewoo/Chevrolet VCDi (licensed from VM Motori; also branded as Ecotec CDTi)• Honda's i-CTDi• Hyundai-Kia's CRDi• Land Rover's "Storm" TD5 derived from the Rover L-Series engine• Mahindra's CRDe• Mazda's MZR-CD (1.4 MZ-CD, 1.6 MZ-CD manufactured by joint venture Ford/PSA Peugeot

Citroën)• Mitsubishi's DI-D (recently developed 4N1 engine family uses next generation 200 MPa (2000 bar)

injection system))• Nissan's dCi• PSA Peugeot Citroën's HDI or HDi (1.4HDI, 1.6 HDI, 2.0 HDI, 2.2 HDI and V6 HDI developed

under joint venture with Ford)• Renault's 'dCi• SsangYong's XDi (most of these engines are manufactured by Daimler AG)• Subaru's Legacy TD (as of Jan 2008)• Tata's DICOR• Toyota's D-4D• Volkswagen Group: The 4.2 V8 TDI and the latest 2.7 and 3.0 TDI (V6) engines featured on

current Audi models use common rail, as opposed to the earlier unit injector engines. The 2.0 TDI in the Volkswagen Tiguan SUV uses common rail, as does the 2008 model Audi A4. Volkswagen Group has announced that the 2.0 TDI (common rail) engine will be available for Volkswagen Passat as well as the 2009Volkswagen Jetta

• Volvo 2.4D and D5 engines (1.6D, 2.0D manufactured by Ford and PSA Peugeot Citroen)

MPFI ENGINE

MPFI

M.P.F.I. means Multi Point Fuel Injection system. In this system each cylinder has number of injectors to supply/spray fuel in the cylinders as compared to one injector located

ADVANTAGES OF MPFI:

1) More uniform A/F mixture will be supplied to each cylinder, hence the difference in power developed in each cylinder is minimum. Vibration from the engine equipped with this system is less, due to this the life of engine components is improved.

(2) No need to crank the engine twice or thrice in case of cold starting as happens in the carburetor system.

(3) Immediate response, in case of sudden acceleration / deceleration.

(4) Since the engine is controlled by ECM* (Engine Control Module), more accurate amount of A/F mixture will be supplied and as a result complete combustion will take place. This leads to effective utilization of fuel supplied and hence low emission level.

(5) The mileage of the vehicle will be improved.

ECM ( Engine Control Module) and its function

The function of ECM is to receive signal from various sensors, manipulate the signals and send control signals to the actuators.

Sensors; Sensing different parameters (Temperature, Pressure, Engine Speed etc.) of the engine and send signal to ECM.

Actuators; Receives control signal from ECM and does function accordingly (ISCA, PCSV, Injectors, Power Transistor etc.)

Case I: If ECM fails to send control signal to all actuators then the engine won't get started.

Case II: If ECM fails to service from all sensors then also the engine won't get started. 

VEHICLES with MPFi ➲ chrysler K engine➲ saturn I4 ➲ chevrolet cavelior➲ opel vectra➲ GM 60 degree V6 ➲ suzuki G➲ dodgespirit➲ audi 80➲ buick V6➲ nissan VQ➲ tata indica

MPFi V/S CRDi

V/S

MPFI : mean multi point fuel injection system ie. in petrol engine for gaining more uniform Air Fuel blending fuel is injected at various point in the path of air. this tech is used in light weight car running on petrol. there is also milage improvement due to this.

but in case of DTSI(digital twin spark ignition) : theengine cylinder consist of two no of spark plug for proper combustion of charge.

DTSI : It is the DIGITAL TWIN SPARK IGNITION system.

The principle of operation is that, there is an additional SPARK PLUG introduced at the other end of the combustion chamber along with the usual spark plug with the the traditional placement at the top centre.

The idea was introduced considering the SLOWER Flame Propogation with only one Spark Plug as in traditional engine design.

Also due to the rectangular shape of the Combustion Chamber the Flame could not reach all the sides and corners regions of the Combustion Chamber, thus leaving some amount of the A/F mixture UNBURNT.

Both the above points were a drawback resulting in :

Slower and Incomplete burnig of the A/F mixture thus Producing LESSER POWER, LOWER FUEL EFFICIENCY and HIGHER HC EMISSIONS.

By introducing the DTSI, due to Two Spark Plugs at two opposite ends of the Combustion chamber, there is:

Faster and More Precise Flame Propogation and,

Better reach of the Flame covering more chamber space resulting in Greater amount of mixture burned in a more even manner.

There is also Swirl Induction incorporated at times for bettermixing inside the combustion Chamber and give better Burning of the fuel.

Both these Improvisations lead to Higher Fuel Efficiency and Higher Power and Torque Developed.This considerably Improves the Engine Performance, than the traditional FI systems.

The Engine Power and Torque is believed to improve by nearly 8% by using DTSI

Also the DTSI is combined with the COMPUTERISED DIRECT IGNITION or CDI which is an eight bit microprocessor chip with preprogrammed maps of Ignition Timings for various engine rpms and engine loads.The CDI works along with the THROTTLE RESPONSIVE IGNITION CONTROL SYSTEM. This TRICS controls the Ignition based upon the Amount of Throttle Opening.Thus when the rider Accelerates suddenly or goes on a smooth uniform drive mode, the Ignition requirement varies acccordingly Hence the Throttle openig also changes, this is sensed by the TRICS which accordingly opens and closes the Reed Switch operated magnetically. This TRICS is connected to the CDI which inturn controls the IGNITION SPARK ADVANCE AND TIMING thus giving a much efficient SPARK ADVANCE for every engine rpm and load conditions.

This eventually increases the Engine Performance and Fuel Efficiency of the vehicle and reduces the HC Emissions.

MPFI : It is the MULTIPORT FUEL IGNITION system.

In this there is at least ONE INDIVIDUAL FUEL INJECTION NOZZLE/PORT for EVERY INDIVIDUAL CYLINDER of the Engine as opposed to the ONE CENTRAL FUEL PORT in the traditional Engine design.

The basic idea is to provide better ratio of A/F mixture in every cylinder nearing the Stoichiometric Value of 14.7 : 1 as far as possible for all various speeds (rpm) and acceleration demands. This was not so much achievable with the single central fuel port system.

This system allows to have a desired A/F ratio for demand condition, thus almost eliminating the A/F distribution issues.

The MPFI includes intake runner length adjustments, MAF ( Mass Air Flow) sensors, coupled to the ECM ( Electronic Control Module ).

The Longer intake runners are for Low Torque Demand in normal road driving, amd Shrter Intake runner for Sudden High Rpms and Acceleration requirements.

The MAF sensors are situated between the Air Filter and the Throttle body in the Intake Manifold. This sensor accurately measures the Air Flow Rates into the engine ( which is an indication of the engine rpm) and sends the feedback to the ECM which inturn does the PROPER FUEL METERING .

Thus a correct A/F ratio can be achieved in each cylinder. This inturn assuresa better fuel Efficiency,greater power output for same mixture ratio,a much better control over the A/F ratio as per te instanteneous speed demand.Overall better performance.

A PROJECT BY

ABHILASH N CABIN M PADARSH BADARSH B ADIL MOHAMMEDAJESH A