Explain working of Variable Valve Timing and Electronic lift control (VTEC) system. Enlist its advantage and Drawbacks

Explain working of Variable Valve Timing and Electronic lift control (VTEC) system. Enlist its advantage and Drawbacks
by

1 Answer

Answer :

Answer: Working of Variable Valve Timing and Electronic lift control (VTEC) system:- VTEC (which stands for Variable Valve Timing and Lift Electronic Control) is an electronic and mechanical system which effectively has multiple camshafts. As the engine moves into different rpm ranges, the engine's computer can activate alternate lobes on the camshaft and change the cam's timing. In this way, the engine gets the best features of low-speed and highspeed camshafts in the same engine An elegant, simple mechanism Switching between high and low valve lift using two cam profiles and two rocker arms per cylinder. The switch is made using hydraulic pressure to push/release the sliding pin, locking/unlocking the middle rocker arm and the other rocker arm. At low engine speeds, the pin is retracted, disengaging the middle rocker arm. The valves are operated by the two outside, low-profile cams for a low valve lift. At higher engine speeds, increased hydraulic pressure pushes the pin, engaging the middle rocker arm. The valves are operated by the middle, high profile cam for high valve lift.

image

Advantages: 

1) Increased fuel efficiency and

2) High power output.

3) Emissions levels can also be more accurately controlled.

4) Improved Volumetric Efficiency

5) Improve drivability.

Drawbacks: 

1) High initial cost

2) Maintenance cost is high

3) Very complex structure required complicated control system.

by

Related questions

Enlist drawbacks of carbureted (SI) Engine on the basis of emission fuel Consumption, Air fuel ratio and fuel distribution.

Description : Enlist drawbacks of carbureted (SI) Engine on the basis of emission fuel Consumption, Air fuel ratio and fuel distribution.

Last Answer : Drawbacks of carbureted (SI) Engine. Parameter Drawbacks Emission Does not meet emission Norms Fuel consumption Due to absence of throttling specific fuel consumption is ... distribution of charge. Fuel distribution for each cylinder is not equal for multi cylinder engine.

Explain how VTEC is beneficial over VVT.

Description : Explain how VTEC is beneficial over VVT.

Last Answer : VTEC stands for Variable valve timing and electronic lift control. In VTEC, the valve timing and the valve lift is controlled using ECU to provide efficient breathing of engine and efficient performance of ... GDI is capable of using very lean mixture i.e. 65:1 while using VTEC Improve drivability 

What does VTEC stands for? State advantages of it.

Description : What does VTEC stands for? State advantages of it.

Last Answer : VTEC stands for Variable valve timing and electronic lift control. In VTEC, the valve timing and the valve lift is controlled using ECU to provide efficient breathing of engine and efficient performance of ... GDI is capable of using very lean mixture i.e. 65:1 while using VTEC Improve drivability

With neat labeled figure, explain the working of any two position of PCV (positive crank case ventilation) valve.

Description : With neat labeled figure, explain the working of any two position of PCV (positive crank case ventilation) valve.

Last Answer : PCV Valve: It consists of a spring loaded tapered valve for flow control. The crankcase pressure and manifold vacuum act together to close the valve where as the spring pressure tends to keep it open.(Fig a ... back seat sealing the inlet and crankcase is protected from the back fire.(Fig d).

Enlist the measures of control detonation in SI engine.

Description : Enlist the measures of control detonation in SI engine. 

Last Answer : Detonation can be control by any or all of the following techniques: 1) Use of a fuel with high octane rating. 2) Enriching the air-fuel ratio. 3) Reducing peak cylinder pressure. 4) decreasing ... . 8) Retarding spark. 9) Water injection 10) Use of high octane fuel can eliminate detonation.

State four drawbacks of carbureted SI engine

Description : State four drawbacks of carbureted SI engine 

Last Answer : Drawbacks of carbureted SI engine: 1) No altitude compensation. 2) Mal-distribution of charge. 3) Variation in air: fuel ratio. 4) Inaccurate metering of charge. 5) Does not meet emission ... in poor efficiency. 10) Backfiring may take place. 11) Carburetor Icing may take place.

List two drawbacks of carbureted SI engine during fuel distribution and drivability.

Description : List two drawbacks of carbureted SI engine during fuel distribution and drivability.

Last Answer : Fuel distribution : Drawbacks 1. Mal-distribution of charge. 2. Inaccurate metering of charge. 3. Fuel atomization depends upon velocity of air in the venture. Drivability: Drawbacks 1 ... temperature compensation. 4) No compensation of Exhaust gas recirculation. 5) Backfiring may take place.

Discuss the drawbacks of carbureted SI engine on the base of, Air-fuel ratio, fuel consumption, power output, emission.

Description : Discuss the drawbacks of carbureted SI engine on the base of, Air-fuel ratio, fuel consumption, power output, emission. 

Last Answer : 1) Air-fuel ratio: - As in SI engine Air-fuel ratio varies from 8:1 to 18.5:1 i.e. from 8 kg of air/kg of fuel to 18.5 kg of air/kg of fuel. Richer or leaner air-fuel ratio limit causes the engine to ... 8 kg of air/kg of fuel to 18.5 kg of air/kg of fuel. So emission is more in SI engine.

State the drawbacks of carbureted (SI) engines on the basis of fuel distribution, emission, power output and fuel consumption.

Description : State the drawbacks of carbureted (SI) engines on the basis of fuel distribution, emission, power output and fuel consumption.

Last Answer :  Drawbacks of carburetted S.I. engine: 1) Fuel distribution- Mal-distribution of charge. 2) Emission- More emissin 3) Power output- Less 4) Fuel consumption - More

List four drawbacks of carburetted S.I. engine.

Description : List four drawbacks of carburetted S.I. engine. 

Last Answer : Drawbacks of carburetted SI engine: 1) No altitude compensation. 2) Mal-distribution of charge. 3) Variation in air: fuel ratio. 4) Inaccurate metering of charge. 5) Does not meet emission ... parts results in poor efficiency. 10) Backfiring may take place. 11) Carburetor Icing may take place

Describe the working of EGR valve with neat sketch.

Description : Describe the working of EGR valve with neat sketch.

Last Answer : Answer: Exhaust Gas Recirculation Valve (Operation-2 marks, Sketch-2 marks) When the engine is idling, the EGR valve is closed and there is no EGR flow into the manifold. The EGR valve remains closed ... exhaust gas (less than 10% of total) to be supplied into the incoming air: fuel mixture

Describe with neat sketch operation of PCV valve under different engine operating condition to control/ emission

Description : Describe with neat sketch operation of PCV valve under different engine operating condition to control/ emission

Last Answer : PCV Valve: It consists of a spring loaded tapered valve for flow control. The crankcase pressure and manifold vacuum act together to close the valve whereas the spring pressure tends to keep it open.( ... at idle and low speed (c)High speed/Load operation (d)Preventing backfire during cranking  

Differentiate air fuel ratio between carburetted engine and electronic fuel injection engines control system.

Description : Differentiate air fuel ratio between carburetted engine and electronic fuel injection engines control system.

Last Answer : Sr. No. Carburetted engine Electronic Fuel Injection (EFI) engine 1 Fuel atomization depends upon velocity of air in the venturi. Atomization of fuel is independent of cranking ... occurs in carbureted engine. Equal quantity of fuel is supplied to port for each cylinder

With the help of neat sketch, describe block diagram of Electronic Diesel Control Unit (EDC).

Description : With the help of neat sketch, describe block diagram of Electronic Diesel Control Unit (EDC).

Last Answer : EDC: The ECU determines the correct quantity of the fuel to be injected based on the inputs and the data in the look up table. The fuel input depends on the rack position and thus ECU ... ECU can also protect the engine against overheating by regulating the maximum quantity of fuel delivered.

Name the sensors which are placed at intake manifold ,throttle valve, water jacket and exhaust manifold.

Description : Name the sensors which are placed at intake manifold ,throttle valve, water jacket and exhaust manifold. 

Last Answer : Sensors: Intake manifolds:- Mass air flow sensor (MAF), Manifold absolute pressure sensor (MAP) Throttle valve:- Throttle position sensor (TPS) Water jacket:- Engine temperature sensor or coolant temperature sensor Exhaust manifolds: - Exhaust gas temperature sensor, Oxygen sensor (O2)

Describe DTSI system. Write two advantage of it.

Description : Describe DTSI system. Write two advantage of it. 

Last Answer : DTSI 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 considerably high "power-to ... winter season & cold climatic conditions or at very  low temperatures because of increased Compression ratio

Describe any four variable affection detonations.

Description : Describe any four variable affection detonations.

Last Answer : Variable affecting detonations. 1. Temperature : Increasing the temperature of the unburned mixture increase the possibility of knock in the SI engine following are the effect on SI engine ... atmospheric humidity decreases the tendency to knock by decreasing the reaction time of the fuel.

Write advantage of VGT over conventional turbocharger.

Description : Write advantage of VGT over conventional turbocharger.

Last Answer : Advantages: 1. VGT is very effective for improving combustion efficiency. 2. Exhaust smoke decreases and BSFC is improved by about 3 to 10 percent at low engine speed region of 1000 to ... engine emissions. 6. Power output of VGT is higher even at lower speed than conventional turbocharger.

Explain the working computer controlled EGR system.

Description : Explain the working computer controlled EGR system.

Last Answer : Exhaust Gas recirculation: EGR System is control by the ECM. A pressure sensor monitors the exhaust system pressure. The sensor signals this information of pressure to the ECM. The ECM sends the signal ... open and close the EGR valve. Thus it controls the amount of exhaust gas recalculated.

Explain the construction and working of throttle body injection (TBI) system.

Description : Explain the construction and working of throttle body injection (TBI) system. 

Last Answer : The throttle body injection (TBI) system uses one or two injector valves mounted in a throttle body assembly. The injectors spray fuel into the top of the throttle body air horn The TBI fuel ... are then used to calculate the triggering signals for the injectors and other system actuators.  

Explain the working of high pressure accumulator in CRDI system.

Description : Explain the working of high pressure accumulator in CRDI system. 

Last Answer : 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 ... in that it only has to maintain a commanded pressure at a target (either mechanically or electronically controlled). 

Explain working of LPG kit with labeled block diagram.

Description : Explain working of LPG kit with labeled block diagram.

Last Answer : Working of LPG Kit: LPG Tank: It is used to store the LPG at 10 bar Filler Valve: It allows the LPG into the tank while feeling. Pressure Relief Valve: It is used to limit ... regulator Mixer / gas injection which flows the LPG into the combustion chamber  Block diagram:  

Explain the working of series hybrid vehicle.

Description : Explain the working of series hybrid vehicle.

Last Answer : Series-Hybrid vehicle In Series Hybrid vehicles, the Internal Combustion Engine (ICE) drives a generator, which charges the battery and supplies current to the electronically controlled motor. The electric motor ... have to be rated to the maximum power. It has low overall system efficiency.

Explain the working of diesel engine glow plugs with neat sketch

Description : Explain the working of diesel engine glow plugs with neat sketch

Last Answer : Glow plug is an aid for cold starting of a C.I. engine. The self-ignition temperature of diesel is 250°C. For compression ignition, the charge (air + diesel) should reach a temperature of ... plugs is automatically interrupted. But starting may be attempted again as soon as the driver wishes.   

What is hybrid vehicle? Explain working with the help of layout of a series hybrid vehicle.

Description : What is hybrid vehicle? Explain working with the help of layout of a series hybrid vehicle. 

Last Answer : Hybrid Vehicle: A hybrid vehicle is one that uses two different methods to propel the vehicle. A hybrid electric vehicle, abbreviated HEV uses both an internal combustion engine and an electric motor to propel ... have to be rated to the maximum power. It has low overall system efficiency.

Explain Evaporative emission control system.

Description : Explain Evaporative emission control system.

Last Answer : EVAP system Operation: When the engine is running, stored fuel vapours in fuel tank are purged from the canister whenever the throttle has opened past the purge port and coolant temperature is above 54 °C. ... The EVAP system is designed to limit maximum vacuum and pressure in the fuel tank.   

Draw a block diagram of CRDI system and describe its working.

Description : Draw a block diagram of CRDI system and describe its working.

Last Answer : Working of CRDI system: High pressure pump provides high pressure fuel to the common rail. The common rail stores the fuel and maintains a constant pressure in the common rail line (approximately 1500 bars.). ... rate can be modified by controlling the nozzle needle movement. OR

Describe features of Variable Valve Timing Mechanism (VVT)

Description : Describe features of Variable Valve Timing Mechanism (VVT)

Last Answer : Features of VVT: Variable valve timing (VVT) is a system for varying the valve opening of an internal combustion engine. This allows the engine to deliver high power, but also to work tractably ... actually driven by that fast cam. Therefore, fast timing and high lift are obtained in both valves 

List the actuators used in MPFI system and working of any one.

Description : List the actuators used in MPFI system and working of any one. 

Last Answer : Actuators of MPFI 1.Fuel Injector 2. Idle speed control valve. 3. Inlet metering valve. 4. Vacuum solenoid valve 5. Cam actuators. Fuel Injector-In MPFI system, Top feed fuel ... fuel between the Pintle and discharge opening to form a fine spray pattern that has a cone shape.  

Describe construction and working of TBI system with suitable sketch.

Description : Describe construction and working of TBI system with suitable sketch.

Last Answer : Construction and working of TBI system: Throttle Body Injection is an electronically controlled injection system in which an electronic fuel injector injects the fuel intermittently in to the intake manifold ... to calculate the triggering signals for the injectors and other system actuators.

Explain engine design modification parameter to control emissions.

Description : Explain engine design modification parameter to control emissions.

Last Answer : Methods used for improving the exhaust emission under the engine design modification are 1. Use of leaner air-fuel ratios: The carburetor may be modified to provide relatively lean air fuel ... tolerances and using special type of carburetors. This also includes fuel injection in manifold.  

List out the methods for evaporation control and explain any one.

Description : List out the methods for evaporation control and explain any one.

Last Answer : Methods for evaporation control:- 1. Charcoal Canister System (for Fuel tank and carburetor float bowl emissions 2. Positive Crankcase Ventilation (PCV) System (for crankcase ... crankcase ventilation performance is optimized, while engine performance and drivability remains unaffected.

Explain any two engine modifications and two fuel modifications to control emission from gasoline engine.

Description : Explain any two engine modifications and two fuel modifications to control emission from gasoline engine. 

Last Answer : Methods used for improving the exhaust emission under the engine design modification are 1. Use of leaner air-fuel ratios: The carburetor may be modified to provide relatively lean air ... Fuel Volatility: Fuel volatility is compromise of high volatility and low volatility to control the pollution

Draw a labeled block diagram of CNG conversion Kit. Describe it’s working

Description : Draw a labeled block diagram of CNG conversion Kit. Describe it’s working

Last Answer : Working of CNG Kit: The Sequential Injection system still has a high pressure tank, filler, filter and regulator, the regulator is different in that it puts out a steady pressure as opposed ... , natural gas temperature sensor and coolant temperature sensor to operate and control the system.  

Draw a labeled block of LPG conversion kit. Describe its working.

Description : Draw a labeled block of LPG conversion kit. Describe its working.

Last Answer : Working of CNG Kit: The Sequential Injection system still has a high pressure tank, filler, filter and regulator, the regulator is different in that it puts out a steady pressure as opposed ... , natural gas temperature sensor and coolant temperature sensor to operate and control the system.

Describe the working of high pressure fuel pump.

Description : Describe the working of high pressure fuel pump. 

Last Answer : Working: Downward motion of plunger: The safety valve at the inlet opens if the pre-supply pressure of fuel exceeds 1.5 bars and fuel comes and fills the chamber till the plunger moves up to BDC. ... . A constant pressure of about 1400 to 1600 bar is maintained in the common rail. 

With the help of suitable sketch describe the working of pressure regulator.

Description : With the help of suitable sketch describe the working of pressure regulator.

Last Answer : Working of pressure regulator : The fuel pump provides more fuel than the maximum required by the engine. Fuel not used by the engine is returned to the fuel tank. The fuel rail supplies all injectors. The pressure ... between 2.0 and 3.5 bar and allows excess fuel to return to the fuel tank.

Describe the construction and working of D-MPFI and L-MPFI with help of neat sketch.

Description : Describe the construction and working of D-MPFI and L-MPFI with help of neat sketch.

Last Answer : D-LMFI System: It is Manifold fuel injection system.In this type, the vacuum in the intake manifold and volume of air by its density are sensed in this type of MPFI system .As air enters into ... intake manifold , the air flow sensor measures the amount of air and sends information to ECU.

Describe the working of fuel injector with neat sketch

Description : Describe the working of fuel injector with neat sketch

Last Answer : Fuel Injector: The injector assembly consists of - i) a needle valve ii) a compression spring iii) a nozzle iv) an injector body When the fuel is supplied to lift the injection ... spring tension and hence the valve opening pressure is controlled by adjusting the screw provided at the top.

Describe the working of electronically controlled diesel injection pump.

Description : Describe the working of electronically controlled diesel injection pump. 

Last Answer : Answer: Electronically controlled diesel injection pump: This is similar to conventional pumps, but its injection is controlled by Electronic Control Unit (ECU) which control solenoid valve in the injection pump ... modifies the current to the solenoid valve, to supply fuel as per requirement.  

What is diesel smoke? State two methods to control diesel smoke.

Description : What is diesel smoke? State two methods to control diesel smoke.

Last Answer : Diesel smoke: Smoke is defined as visible products of combustion, is due to poor combustion. It originates early in the combustion. Rich fuel-air mixture & at pressures developed in diesel ... manifold. This shortens the delay period- curbs thermal cracking which is responsible for soot format

Illustrate idle speed control as an output control function of ECM.

Description : Illustrate idle speed control as an output control function of ECM.

Last Answer : Idle Speed Control as Output function of a ECM: While the engine is being started, or operated, the logic module of Electronic Control Module (ECM) will signal the Stepper motor of Idle Speed Control ( ... control valve stepper motor allows 125 possible valve opening positions.  OR

Illustrate with neat sketch the process to control production of NOx in combustion chamber.

Description : Illustrate with neat sketch the process to control production of NOx in combustion chamber.

Last Answer : Method to control NOx: The EGR system is used to reduce the amount of NOx in the exhaust. NOx production increases as the temperature inside the combustion chamber rises due to acceleration or heavy engine loads, ... (less than 10% of total) to be supplied into the incoming air: fuel mixture.  

State input and output control functions of ECM. Describe the idle speed control with sketch.

Description : State input and output control functions of ECM. Describe the idle speed control with sketch. 

Last Answer : Inputs and outputs of Electronic Control Module The inputs of ECM 1. The Ignition (Engine Speed Sensor). 2. Temperature Sensor (Coolant Temperature). 3. Throttle Potentiometer (Intake ... through. The Idle speed control valve stepper motor allows 125 possible valve opening positions. 

Write function of canister purge control and idle speed control in S.I. engine.

Description : Write function of canister purge control and idle speed control in S.I. engine.

Last Answer : Function of canister purge control - 1. The purge valve is the part of the vehicle Evaporative Emission Control (EVAP) system. 2. The EVAP system prevents fuel vapors in the fuel tank from escaping ... control is used to prevent engine stall during idle and to allow the engine to run at low RPM.

Explain the methods of fuel injection used EFI system.

Description : Explain the methods of fuel injection used EFI system.

Last Answer : Methods of fuel injection: 1. Sequential fuel injection. (SFI) 2. Grouped fuel injection. 3. Simultaneous fuel injection. 4. Continuous injection. 1. Simultaneous Injection: Injection of fuel ... of the fuel injection is determined by ECU depending upon load and speed. 

List eight ways of reducing pollution. Explain PCV and evaporative emission system with suitable sketch.

Description : List eight ways of reducing pollution. Explain PCV and evaporative emission system with suitable sketch.

Last Answer : Eight ways of reducing pollution:-  1) Optimize Ignition Advance 2) Use unleaded gasoline & Low sulphur diesel 3) Use leaner air fuel ratio 4) Use exhaust gas treatment devices ex Catalytic ... check valve. The EVAP system is designed to limit maximum vacuum and pressure in the fuel tank.

Explain the effect of positive crankcase ventilation (PCV) system on engine emission.

Description : Explain the effect of positive crankcase ventilation (PCV) system on engine emission. 

Last Answer : PCV system: The purpose of PCV system is to remove the harmful gases from the crankcase before damage occurs and combine them with the engine's normal incoming air: fuel mixture. ... is optimized, while engine performance and drivability remains unaffected positive crankcase ventilation

Explain PFI system with neat sketch.

Description : Explain PFI system with neat sketch.

Last Answer : PFI system In the port injection arrangement, the injector is placed on the side of the intake manifold near the intake port. The injector sprays gasoline into the air, inside the intake manifold. The ... of gasoline and air then passes through the intake valve and enters into the cylinder.

Draw the circuit diagram of glow plug and explain its operation.

Description : Draw the circuit diagram of glow plug and explain its operation.

Last Answer : Answer: Operation of glow plug: Glow plug is an aid for cold starting of a C.I. engine. The selfignition temperature of diesel is 250°C. For compression ignition, the charge (air + diesel) ... is automatically interrupted. But starting may be attempted again as soon as the driver wishes.