Two stroke engines

Introduction

            In two stroke cycle engines, the whole sequence of events i.e., suction, compression, power and exhaust are completed in two strokes of the piston i.e. one revolution of the crankshaft. There is no valve in this type of engine. Gas movement takes place through holes called ports in the cylinder. The crankcase of the engine is air tight in which the crankshaft rotates. 


Upward stroke of the piston (Suction + Compression)

               When the piston moves upward it covers two of the ports, the exhaust port and transfer port, which are normally almost opposite to each other. This traps the charge of air- fuel mixture drawn already in to the cylinder. Further upward movement of the piston compresses the charge and also uncovers the suction port. Now fresh mixture is drawn through this port into the crankcase. Just before the end of this stroke, the mixture in the cylinder is ignited by a spark plug. Thus, during this stroke both suction and compression events are completed.


Downward stroke (Power + Exhaust)

              Burning of the fuel rises the temperature and pressure of the gases which forces the piston to move down the cylinder. When the piston moves down, it closes the suction port, trapping the fresh charge drawn into the crankcase during the previous upward stroke. Further downward movement of the piston uncovers first the exhaust port and then the transfer port. Now fresh charge in the crankcase moves in to the cylinder through the transfer port driving out the burnt gases through the exhaust port. Special shaped piston crown deflect the incoming mixture up around the cylinder so that it can help in driving out the exhaust gases . During the downward stroke of the piston power and exhaust events are completed.  

Application 

• Lawn and garden equipment (chain saws, leaf blowers, trimmers)
• Dirt bikes
• Mopeds
• Jet skis
• Small outboard motors
• Radio-controlled model planes

Reference video : https://youtu.be/EKQprWAHFTk

Four Stroke Cycle Engines

Introduction

              A four-stroke cycle engine is an internal combustion engine that utilizes four distinct piston strokes (intake, compression, power, and exhaust) to complete one operating cycle. The piston make two complete passes in the cylinder to complete one operating cycle. An operating cycle requires two revolutions (720°) of the crankshaft. The four-stroke cycle engine is the most common type of small engine. A four-stroke cycle engine completes five Strokes in one operating cycle, including intake, compression, ignition, power, and exhaust Strokes.

Intake Stroke

         The intake event is when the air-fuel mixture is introduced to fill the combustion chamber. The intake event occurs when the piston moves from TDC (top dead center) to BDC (bottom dead center) and the intake valve is open. The movement of the piston toward BDC creates a low pressure in the cylinder. Ambient atmospheric pressure forces the air-fuel mixture through the open intake valve into the cylinder to fill the low pressure area created by the piston movement. The cylinder continues to fill slightly past BDC as the air-fuel mixture continues to flow by its own inertia while the piston begins to change direction. The intake valve remains open a few degrees of crankshaft rotation after BDC. Depending on engine design. The intake valve then closes and the air-fuel mixture is sealed inside the cylinder.

Compression Stroke

        The compression stroke is when the trapped air-fuel mixture is compressed inside the cylinder. The combustion chamber is sealed to form the charge. The charge is the volume of compressed air-fuel mixture trapped inside the combustion chamber ready for ignition. Compressing the air-fuel mixture allows more energy to be released when the charge is ignited. Intake and exhaust valves must be closed to ensure that the cylinder is sealed to provide compression. Compression is the process of reducing or squeezing a charge from a large volume to a smaller volume in the combustion chamber. The flywheel helps to maintain the momentum necessary to compress the charge.

When the piston of an engine compresses the charge, an increase in compressive force supplied by work being done by the piston causes heat to be generated. The compression and heating of the air-fuel vapor in the charge results in an increase in charge temperature and an increase in fuel vaporization. The increase in charge temperature occurs uniformly throughout the combustion chamber to produce faster combustion (fuel oxidation) after ignition.

           The increase in fuel vaporization occurs as small droplets of fuel become vaporized more completely from the heat generated. The increased droplet surface area exposed to the ignition flame allows more complete burning of the charge in the combustion chamber. Only gasoline vapor ignites. An increase in droplet surface area allows gasoline to release more vapor rather than remaining a liquid.

          The more the charge vapor molecules are compressed, the more energy obtained from the combustion process. The energy needed to compress the charge is substantially less than the gain in force produced during the combustion process. For example, in a typical small engine, energy required to compress the charge is only one-fourth the amount of energy produced during combustion.

          The compression ratio of an engine is a comparison of the volume of the combustion chamber with the piston at BDC to the volume of the combustion chamber with the piston at TDC. This area, combined with the design and style of combustion chamber, determines the compression ratio. Gasoline engines commonly have a compression ratio ranging from 6:1 - 10:1. The higher the compression ratio, the more fuel-efficient the engine. A higher compression ratio normally provides a substantial gain in combustion pressure or force on the piston. However, higher compression ratios increase operator effort required to start the engine. Some small engines feature a system to relieve pressure during the compression stroke to reduce operator effort required when starting the engine.

Ignition Event 

         The ignition (combustion) event occurs when the charge is ignited and rapidly oxidized through a chemical reaction to release heat energy. Combustion is the rapid, oxidizing chemical reaction in which a fuel chemically combines with oxygen in the atmosphere and releases energy in the form of heat.

       Proper combustion involves a short but finite time to spread a flame throughout the combustion chamber. The spark at the spark plug initiates combustion at approximately 20° of crankshaft rotation before TDC (BTDC). The atmospheric oxygen and fuel vapor are consumed by a progressing flame front. A flame front is the boundary wall that separates the charge from the combustion by-products. The flame front progresses across the combustion chamber until the entire charge has burned.

Power Stroke

         The power stroke is an engine operation Stroke in which hot expanding gases force the piston head away from the cylinder head. Piston force and subsequent motion are transferred through the connecting rod to apply torque to the crankshaft. The torque applied initiates crankshaft rotation. The amount of torque produced is determined by the pressure on the piston, the size of the piston, and the throw of the engine. During the power Stroke, both valves are closed.

Exhaust Stroke

       The exhaust stroke occurs when spent gases are expelled from the combustion chamber and released to the atmosphere. The exhaust stroke is the final stroke and occurs when the exhaust valve is open and the intake valve is closed. Piston movement evacuates exhaust gases to the atmosphere.

As the piston reaches BDC during the power stroke combustion is complete and the cylinder is filled with exhaust gases. The exhaust valve opens, and inertia of the flywheel and other moving parts push the piston back to TDC, forcing the exhaust gases out through the open exhaust valve. At the end of the exhaust stroke, the piston is at TDC and one operating cycle has been completed.

Uses in : Bikes, cars, buses, trucks

Reference video : https://youtu.be/OGj8OneMjek 

CRDI (Common Rail Direct Injection)

Introduction

       CRDi stands for Common Rail Direct Injection meaning, direct injection of the fuel into the cylinders of a diesel engine via a single, common line, called the common rail which is connected to all the fuel injectors.

    Whereas ordinary diesel direct fuel-injection systems have to build up pressure anew for each and every injection cycle, the new common rail (line) engines maintain constant pressure regardless of the injection sequence. This pressure then remains permanently available throughout the fuel line. The engine's electronic timing regulates injection pressure according to engine speed and load. The electronic control unit (ECU) modifies injection pressure precisely and as needed, based on data obtained from sensors on the cam and crankshafts. In other words, compression and injection occur independently of each other. This technique allows fuel to be injected as needed, saving fuel and lowering emissions.

     More accurately measured and timed mixture spray in the combustion chamber significantly reducing unburned fuel gives CRDi the potential to meet future emission guidelines such as Euro V. CRDi engines are now being used in almost all Mercedes-Benz, Toyota, Hyundai, Ford and many other diesel automobiles.

History

     The common rail system prototype was developed in the late 1960s by Robert Huber of Switzerland and the technology further developed by Dr. Marco Ganser at the Swiss Federal Institute of Technology in Zurich, later of Ganser-Hydromag AG (est.1995) in Oberägeri. The first successful usage in a production vehicle began in Japan by the mid-1990s. 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. The first passenger car that used the common rail system was the 1997 model Alfa Romeo 156 2.4 JTD, and later on that same year Mercedes-Benz C 220 CDI.

     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. 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). The common rail system is suitable for all types of road cars with diesel engines, ranging from city cars such as the Fiat Nuova Panda to executive cars such as the Audi A6.

Operating Principle

     Solenoid 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 optimizing 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 very short (< 10 second) or no heating-up time at all , dependent on ambient temperature, 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 (See diesel engine and unit injector for more information). While these older systems provided accurate fuel quantity and injection timing control, they were limited by several factors:

• 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 in the number 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 resulted 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 (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.

Advantages

     CRDi engines are advantageous in many ways. Cars fitted with this new engine technology are believed to deliver 25% more power and torque than the normal direct injection engine. It also offers superior pick up, lower levels of noise and vibration, higher mileage, lower emissions, lower fuel consumption, and improved performance.

      In India, diesel is cheaper than petrol and this fact adds to the credibility of the common rail direct injection system.

Disadvantages

    Like all good things have a negative side, 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. Also this technology can’t be employed to ordinary engines.

Applications

     The most common applications of common rail engines are marine and locomotive applications. Also, in the present day they are widely used in a variety of car models ranging from city cars to premium executive cars.

     Some of the Indian car manufacturers who have widely accepted the use of common rail diesel engine in their respective car models are the Hyundai Motors, Maruti Suzuki, Fiat, General Motors, Honda Motors, and the Skoda. In the list of luxury car manufacturers, the Mercedes-Benz and BMW have also adopted this advanced engine technology. All the car manufacturers have given their own unique names to the common CRDi engine system.

     However, most of the car manufacturers have started using the new engine concept and are appreciating the long term benefits of the same. The technology that has revolutionized the diesel engine market is now gaining prominence in the global car industry.

     CRDi technology revolutionized diesel engines and also petrol engines (by introduction of GDI technology).

     By introduction of CRDi a lot of advantages are obtained, some of them are, more power is developed, increased fuel efficiency, reduced noise, more stability, pollutants are reduced, particulates of exhaust are reduced, exhaust gas recirculation is enhanced, precise injection timing is obtained, pilot and post injection increase the combustion quality, more pulverization of fuel is obtained, very high injection pressure can be achieved, the powerful microcomputer make the whole system more perfect, it doubles the torque at lower engine speeds. The main disadvantage is that this technology increase the cost of the engine. Also this technology can’t be employed to ordinary engines

Uses in : Mercedes-Benz, Toyota, Hyundai, Ford

Reference video : https://youtu.be/jDRa1cSJhSQ

                          https://youtu.be/7yy27APhpHA

Anti-Lock Braking System (ABS)

Introduction

                  The ABS (Anti-lock Brake System) monitors the speed of each wheel to detect locking. When it detects sudden braking, it will release braking pressure for a moment and then provide optimum braking pressure to each wheel. By repeating this process in a short period of time, it enhances steering control during sudden stops. As a result, it will also help improve the ability of stopping the vehicle.

                   The role of the ABS is to control the wheel speed in order to prevent the wheels from locking and to assure a maximum braking force. This is of major importance when the runway is slippery or very short. Wheel moment of inertia, Rotational wheel speed, Friction coefficient, Wheel Radius Normal force per wheel Friction force, Aircraft speed are analogous to the above vehicle wheel shown. Forces acting on a braked wheel .The ABS commands the brake pressure as a function of the difference between the measured and the reference wheel speed.

                   The latter is calculated from the measured aircraft speed and the desired wheel slips, using equation. At the moment, when the pilot pushes the brake pedal the brake pressure and the wheel slip increase provoking a ground force between tyre and runway. Assuming the case of full braking, the ABS will control the wheel speed to its reference value. To achieve a maximum braking force the reference slip should be chosen close to the optimum slip. However, when the pressure level in the brakes becomes too high, the wheel slip slides beyond the optimum of the adhesion curve and the system tyre/runway becomes instable. The slope of u (s) being negative, the wheel immediately starts to lock. In this case, the ABS rapidly releases the brake pressure to force the wheel speed back to the stable side of the adhesion curve. In fact, this situation occurs, when either the desired slip s, has been chosen on the instable side of the friction characteristic, or when a sudden change in ground force is encountered (e.g. a transition from a dry to a wet runway surface). The principle problem in ABS design is that the optimum slip and the exact shape of the adhesion characteristic depend on the runway surface and further parameters, which cannot be measured, such as the condition of the tyres or the dynamics of the normal forces. Bearing in mind that the optimum slip value may vary between 3% and 20%, it is clear that the choice of the reference slip value is crucial for a safe and efficient ABS. If it is too small the braking force might become insufficient, if it is too high, wheel lockup occurs.

                 Recently there has been a growing interest in intelligent control techniques for the design of aircraft and road vehicle Antilock Brake Systems (ABS). In particular, rule-based, fuzzy logic controllers have been applied to this problem and successfully tested in simulation. In fact, the use of non-linear, fuzzy control techniques appears to be particularly appropriate for the ABS control problem because of the high non-linearity of the system and the lack of a precise physical model of the friction force between tyre and runway. In addition to that, the controller must operate at an unstable equilibrium point to achieve an optimal braking performance. The most important problem in ABS control design - fuzzy or conventional - is that the optimum adhesion coefficient varies significantly with the surface condition (i.e. dry, wet, icy, etc.) of the runway. Because the latter is unknown, it is extremely difficult to define a controller that guaranties an optimal braking performance for all types of runway conditions.

How Do Wheels Lock?

            During braking, wheels lock if the brake force applied is more than the friction between the road and tyre. This often happens in a panic braking situation, especially on a slippery road. When the front wheels lock, the vehicle slides in direction of motion. When the rear wheels locks, the vehicle swings around. It is impossible to steer around an obstacle with wheels locked. Locked wheels can thus result in accident. Skidding also reduce tyre life.

What Does ABS Do?

             The system detects when the wheel are about to lock and momentarily release the pressure on locking wheel. The brakes are reapplied as soon as the wheels have recovered.

        A toothed wheel (pole wheel) is fitted to the rotating wheel hub. A magnetic sensor mounted on each wheel in close in close proximity to the teeth, generates electrical pulses when the pole wheel rotates. The rate at which the pulses are generated (frequency) is a measure of wheel speed. This signal is read by electronic control unit (ECU). When a wheel is lock, the ECU (electronic control unit) sends an electrical signal to the modulator valve solenoid, which release pressure from the brake chamber. When the wheel recovers sufficiently, the brake pressure is reapplied again by the switch off signal to the modulator valve.

         The modulator valve has an addition ‘hold’ state which maintains pressure. In break in the chamber, thus optimizing the braking process. The cycling of modulator valve (5 to 6 times per second) is continued till the vehicle comes to a controlled stop. With ABS, the vehicle remains completely stable even when the driver continues to press the brake pedal during braking, thus avoiding accidents.

Uses in : Apache RTR , Swift Dzire, BMW

Reference video : https://youtu.be/mKiTAcXK6M4

                          https://youtu.be/12r0wUBhMF4
                                    https://youtu.be/t1JRRywzXPc

Digital Twin Spark Ignition

Introduction

              It is very interesting to know about complete combustion in automobile engineering. Because in actual practice, perfect combustion is not at all possible due to various losses in the combustion chamber as well as design of the internal combustion engine. Moreover the process of burning of the fuel is also not instantaneous. However an alternate solution to it is by making the combustion of fuel as fast as possible. This can be done by using two spark plugs which spark alternatively at a certain time interval so as increase the diameter of the flame & burn the fuel instantaneously. This system is called DTSI (Digital Spark Ignition system). In this system, due to twin sparks, combustion will be complete. This paper represents the working of digital twin spark ignition system, how twin sparks are produced at 20,000 Volts, their timings, efficiency, advantages & disadvantages, diameter of the flame, how complete combustion is possible & how to decrease smoke & exhausts from the exhaust pipe of the bike using Twin Spark System.

DIGITAL TWIN SPARK ignition engine has two Spark plugs located at opposite ends of the combustion chamber and hence fast and efficient combustion is obtained. The benefits of this efficient combustion process can be felt in terms of better fuel efficiency and lower emissions. The, ignition system on the Twin spark is a digital system with static spark advance and no moving parts subject to wear. It is mapped by the integrated digital electronic control box which also handles fuel injection and valve timing. It features two plugs per cylinder.

             This innovative solution, also entailing a special configuration of the hemispherical combustion chambers and piston heads, ensures a fast, wide flame front when the air-fuel mixture is ignited, and therefore less ignition advance, enabling, moreover, relatively lean mixtures to be used. This technology provides a combination of the light weight and twice the power offered by two-stroke engines with a significant power boost, i.e. a considerable"power-to-weight ratio" compared to quite a few four-stroke engines. Fig.1. show the actual picture of Bajaj Pulsar Bike.

                  Moreover, such a system can adjust idling speed & even cuts off fuel feed when the accelerator pedal is released, and meters the enrichment of the air-fuel mixture for cold starting and accelerating purposes; if necessary, it also prevents the upper rev limit from being exceeded. At low revs, the over boost is mostly used when overtaking, and this is why it cuts out automatically. At higher revving speeds the over boost will enhance full power delivery and will stay on as long as the driver exercises maximum pressure on the accelerator.

Construction

             Digital spark technology is currently used in Bajaj motor cycles in India, because they have the patent right. Digital twin spark ignition technology powered engine has two spark plugs. It is located at opposite sides of combustion chamber. This DTS-I technology will have greater combustion rate because of twin spark plug located around it. The engine combust fuel at double rate than normal. This enhances both engine life and fuel efficiency. It is mapped by the digital electronic control box which also handles fuel ignition and valve timing.

A microprocessor continuously senses speed and load of the engine and respond by altering the ignition timing there by optimizing power and fuel economy.

Advantages

• Less vibrations and noise

• Long life of the engine parts such as piston rings and valve stem.

• Decrease in the specific fuel consumption

• No over heating

• Increase the Thermal Efficiency of the Engine & even bear high loads on it.

• Better starting of engine even in winter season & cold climatic conditions or at very low temperatures because of increased Compression ratio.

• Because of twin Sparks the diameter of the flame increases rapidly that would result in instantaneous burning of fuels. Thus force exerted on the piston would increase leading to better work output.

Disadvantages

• There is high NOx emission

• If one spark plug get damaged then we have to replace both

• The cost is relatively more

Applications

It uses in automotive engines. In India Bajaj has patented for dts-i technology. At present platina, xcd125, 135, discover150, pulsar135, 150, 180, 200, 220 etc. are using the dts-i(digital twin spark ignition system). Which means the petrol enters into the cylinder burns more efficiently.

Hence the application of these technologies in the present day automobiles will give the present generation what they want i.e. power bikes with fuel efficiency. Since these technologies also minimize the fuel consumption and harmful emission levels, they can also be considered as one of the solutions for increasing fuel costs and increasing effect of global warming.

The perfect Combustion in Internal Combustion engine is not possible. So for the instantaneous burning of fuels in I.C. engine twin spark system can be used which producing twin sparks at regular interval can help to complete the combustion

Uses in : Bajaj Pulsar, Bajaj Discover

Reference video : https://youtu.be/XF8BtOzppLM

Air Brake System Of Indian Railways

Introduction

The most vital factor in the running and control of any vehicle whether it is a cycle, scooter, car, bus, or train is the breaking system. In order slow down the moving vehicle in a shorter possible time, the energy of motion possessed by vehicle must be converted in to other forms. During break application in any vehicle the energy of motion is converted in to heat. This u might have noticed at the rim when you apply brakes repeatedly at short intervals.

Brake : brake is an arrangement provided in the vehicle for slowing down or bringing to rest a moving vehicle in the shortest possible distance.

Factor affecting the brake: The various factor that governs braking action in any vehicle are :-
1. pressure
2. surface area in contact
3. kind of material
4. heat generation.

Basic Requirements of brake:-

                  Keeping in the view the safety of human life and physical resources the basic requirements of brake are:

1. brake must be strong enough to stop the vehicle during an emergency with in a shorter possible distance.

2. there should be no skidding during brake application &driver must have proper control over the vehicle during the emergency.

3. effectivness of brakes should remain constant even on prolonged application or during descending on a down gradient.

4. brake must keep the vehicle in a stationary position even when the driver is not present.

VACUUM BRAKE-

Brake application takes place when vacuum is destroyed by allowing air to enter to the system. During brake application piston is pushed inward.

LIMITATIONS OF VACCUM BRAKE SYSTEM:-

# Brake cylinder piston takes longer time to release after each application of brakes because single train pipe.

# successive brake application on gradients are not effective as piston takes longer time for release.

# vacuum brakes are not suitable for high speed trains the maximum pressure available for brake application is only atmospheric. Thebrake power is inadequate for higher loads and speed.

# brake power destroyed over the period of time as train run over long period.

AIR BRAKE

1. Brake application is takes place when pressure is dropped in brake pipe

2. during brake application the piston is pushed outward.

GRADUATED RELEASE AIR BRAKE SYSTEM

           Graduated release air brake system is most suitable for Indian railways. Operation of graduated release air brake system consists of following stages:

* Charging
* Graduated Application and Emergency application
* Graduated Release
*For application of brakes pressure in brake pipe is dropped .
* Magnitude of braking force is proportional to reduction in brake pipe pressure.

Various stages of brake application are 

- Minimum application
- Service application
- Full service application
- Emergency application

* As compared to single pipe graduated release air brake system twin pipe graduated release air brake system is more suitable for passenger coaches

Uses in : Railway , buses 

Reference video : https://youtu.be/42u4v-AbWA4

i-VTEC

Introduction

              The most important challenge facing car manufacturers today is to offer vehicles that deliver excellent fuel efficiency and superb performance while maintaining cleaner emissions and driving comfort. This paper deals with i-VTEC (intelligent-Variable valve Timing and lift Electronic Control) engine technology which is one of the advanced technology in the IC engine. i-VTEC is the new trend in Honda's latest large capacity four cylinder petrol engine family. The name is derived from 'intelligent' combThe most important challenge facing car manufacturers today is to offer vehicles that deliver excellent fuel efficiency and superb performance while maintaining cleaner emissions and driving comfort. This paper deals with  i-VTEC(intelligent-Variable valve Timing and lift Electronic Control) engine technology which is one of the advanced technology in the IC engine. i-VTEC is the new trend in Honda's latest large capacity four cylinder petrol engine family. The name is derived from 'intelligent' combustion control technologies that match outstanding fuel economy, cleaner emissions and reduced weight with high output and greatly improved torque characteristics in all speed range. The design cleverly combines the highly renowned VTEC system which varies the timing and amount of lift of the valves with Variable Timing Control.

           VTC (Variable Timing Control) is able to advance and retard inlet valve opening by altering the phasing of the inlet camshaft to best match the engine load at any given moment. The two systems work in concern under the close control of the engine management system delivering improved cylinder charging and combustion efficiency, reduced intake resistance, and improved exhaust gas recirculation among the benefits. i-VTEC technology offers tremendous flexibility since it is able to fully maximize engine potential over its complete range of operation. In short Honda's i-VTEC technology gives us the best in vehicle performance.

        The latest and most sophisticated VTEC development is i-VTEC ("intelligent" VTEC), which combines features of all the various previous VTEC systems for even greater power band width and cleaner emissions. With the latest i-VTEC setup, at low rpm the timing of the intake valves is now staggered and their lift is asymmetric, which creates a swirl effect within the combustion chambers. At high rpm, the VTEC transitions as previously into a high-lift, long-duration cam profile.

               The i-VTEC system utilizes Honda's proprietary VTEC system and adds VTC (Variable Timing Control), which allows for dynamic/continuous intake valve timing and overlap control. The demanding aspects of fuel economy, ample torque, and clean emissions can all be controlled and provided at a higher level with VTEC (intake valve timing and lift control) and VTC (valve overlap control) combinedustion control technologies that match outstanding fuel economy, cleaner emissions and reduced weight with high output and greatly improved torque characteristics in all speed range. The design cleverly combines the highly renowned VTEC system - which varies the timing and amount of lift of the valves - with Variable Timing Control.

             VTC is able to advance and retard inlet valve opening by altering the phasing of the inlet camshaft to best match the engine load at any given moment. The two systems work in concern under the close control of the engine management system delivering improved cylinder charging and combustion efficiency, reduced intake resistance, and improved exhaust gas recirculation among the benefits. i-VTEC technology offers tremendous flexibility since it is able to fully maximize engine potential over its complete range of operation. In short Honda's i-VTEC technology gives us the best in vehicle performance.

The latest and most sophisticated VTEC development is i-VTEC ("intelligent" VTEC), which combines features of all the various previous VTEC systems for even greater power band width and cleaner emissions. With the latest i-VTEC setup, at low rpm the timing of the intake valves is now staggered and their lift is asymmetric, which creates a swirl effect within the combustion chambers. At high rpm, the VTEC transitions as previously into a high-lift, long-duration cam profile.

             The i-VTEC system utilizes Honda's proprietary VTEC system and adds VTC (Variable Timing Control), which allows for dynamic/continuous intake valve timing and overlap control. The demanding aspects of fuel economy, ample torque, and clean  emissions can all be controlled and provided at a higher level with VTEC (intake valve timing and lift control) and VTC (valve overlap control) combined.

            The i stands for intelligent: i-VTEC is intelligent-VTEC. Honda introduced many new innovations in i-VTEC, but the most significant one is the addition of a variable valve opening overlap mechanism to the VTEC system. Named VTC for Variable Timing Control, the current (initial) implementation is on the intake camshaft and allows the valve opening overlap between the intake and exhaust valves to be continuously varied during engine operation. This allows for a further refinement to the power delivery characteristics of VTEC, permitting fine-tuning of the mid-band power delivery of the engine.

Uses in : Honda

Reference video : https://youtu.be/UEtm2y1yXnI