Engine Variable valve Actuating Mechanisms | Valve Train System and Components | Variable Valve Timing Technologies

Valve Actuating Mechanisms:

Each valve must open at the proper time, stay open for the required length of time and close at the proper time. Hence the timing of the valves are controlled by valve actuating mechanisms. Intake valves are just open before the piston reaches the Top Dead Centre (TDC), and exhaust valve remain open after TDC. At this particular instant both valves are open at the same time. This overlap results in better volumetric efficiency and lower operating temperatures.

• Mechanisms with side camshaft
• Double row side valve (T-Head) type
• Single row side valve (L-Head) type
• Overhead inlet and side exhaust valve (F-Head) type
• Single row overhead valve (I-Head) type

• Mechanisms with overhead camshaft
• With inverted bucket type follower operated by single camshaft
• With end-pivoted rocker arm operated by single camshaft
• Inlet valve operated by inverted bucket type follower and exhaust valve by pivoted rocker arm (Double camshaft)
• Double overhead camshaft with inverted bucket type followers
• Double overhead camshaft with separate rocker arms

Valve Train Components:

• Camshaft
• Camshaft drive
• Chain drive
• Gear drive
• Toothed belt
• Valve tappet
• Solid Lifters
• Roller lifters
• Hydraulic lifters
• Followers
• Push rod
• Rocker arm and rocker shaft

Camshaft:

A Shaft with a cam for each intake and exhaust valve. Each cam has a high spot called cam-lobe which controls the valve opening. Camshaft actually controls rotary motion to reciprocating motion.

Camshaft drive:

Cam gear is twice as large as crank gear. This makes the cam turn at 1/2 the speed of the crank

Valve Tappets:

The tappet follows the cam lobe and pushes the push rod. Solid and Roller lifts require adjustable rocker arm. Hydraulic Tappet requires oil to control.

Push Rods:

Metal rod which transfers force from the lifter to the rocker arm

Rocker Arm:

Rocker arm transmit the forces of the pushrod to the valve

Variable Valve Timing (VVT) technologies:

VVT is an engine technology which allows the lift or duration or timing (some or all) of the intake or exhaust valves to be changed during the engine operation

• Phase changing systems
• Profile switching systems
• Variable event timing systems
• Variable lift systems
• Electronic valve actuating systems

VVTi Engines:

VVTi system is a cam phasing system that can be applied on both inlet and exhaust cam shafts. This movement is controlled by engine management system according to need and actuated by hydraulic valve gears.

VTEC Engines:

VTEC stands for Valve Timing Electronic Control, where the system set the optimum valve timing by continuous changing of timing to open or close in Intake and Exhaust valves in response to the engine load, rotation and other operating conditions. This system controls the emission of NOx and HC and the fuel economy is increased.

i-VTEC:

iVTEC stands for Intelligent VTEC. Honda implement this most successful valve actuation system by continuously variable intake valve timing and computer controlled management for optimized torque output and fuel efficiency.

AVTEC:

AVTEC stands for Advanced VTEC. Honda implement this continuously variable phase control system to respond to the drivers power needs independent of engine speed. This system presents 13% better fuel economy and 75% lower emissions than iVTEC.

FIAT Multi - Air Technology:

A new engine air management technology introduced by FIAT which is much better than any VVT technology

Valve Troubles:

• Burning of valve face
• Necking of valve stem
• Valve face wear
• Valve stem and guide wear
• Valve cracking or Breakage
• Noisy valve operation

Technorati Tags: how fiat multiair technology works,overhead camshaft engine,side camshaft engine,the valve train and how it works,valve train system and components,variable valve timing problems,what are the valves in an engine,what do camshafts do,what do pushrods do in an engine,what is an ivtec engine,what is continuously variable valve timing control system,what is the meaning of VVT engine,what is variable valve lift systems,which engine is better DOHC or SOHC

What are the Main Parts of an Engine | What is the Function of the Piston in an Engine | What does the Camshaft do

Main Engine Parts:

• Cylinder Block and Crank case
• Cylinder Head
• Sump or Oil Pan
• Manifolds – Inlet and Exhaust
• Gaskets
• Cylinders and Liners (Dry and Wet)
• Pistons
• Piston Rings
• Connecting Rods
• Piston pins
• Crankshaft
• Main Bearings
• Valves and Valve – actuating mechanisms
• Catalytic converter, Muffler and Tail pipe

Functions of Piston:

• To transmit the force of explosion to the crankshaft
• To form a seal so that high pressure gases in the combustion chamber do not leak into the crankcase
• To serve as a guide and a bearing for small end of the connecting rod.

Piston Requirements:

• Should be silent in operation both during warming up and the normal running
• Design should be such that the seizure does not occur
• Should offer sufficient resistance to corrosion
• Shortest possible length
• Light in weight
• High thermal conductivity
• Long life

Methods to avoid Piston Slap:

• Use of Horizontal / Inclined slots
• Use of vertical or T-Slots
• Taper pistons
• Oval pistons
• Use of Special alloys
• Wire-wound pistons
• Autothermic pistons
• Bi-metal pistons
• Offset piston

Special Pistons:

• Pistons with inserted ring carrier
• Cast steel pistons
• Anodized pistons
• Tinned Pistons
• Oil-Cooled pistons
• Two-piece Pistons
• Composite insulated (heat shielded) pistons
• Squeeze cast pistons
• Aeconoguide pistons

Types of Piston Failure:

• Piston scuffing
• Burnt piston
• Damage to ring land
• Damaged piston boss and circlip groove

Functions of Piston rings:

• To form a seal for the high pressure gases from the combustion chamber against leak into the crankcase
• To provide easy passage for heat flow from the piston crown to the cylinder walls
• To maintain sufficient lubricating oil on cylinder walls throughout the entire length of piston travel

Types of Rings:

• Compression Rings
• Plain
• Taper face
• Torsional wrist
• Scraper type torsional twist
• Taper face torsional twist
• Keystone type
• Oil control Rings:
• Bevelled
• Stepped Scraper
• Slotted scraper
• Delayed action scraper
• Double action scraper
• Composite rail scraper

Cause of Ring Failure:

• Rapid Wear
• Scuffing
• Ring Breakage

Connecting Rod:

It’s function is to convert the reciprocating motion of the piston into rotary motion of the crankshaft

Piston Pin:

It connects the piston and the connecting rod. It also called as “Gudgeon pin”.

Crankshaft:

It is the engine component from which power is taken

Crankshaft assembly:

Includes the crankshaft and Bearings, flywheel, vibration damper, sprocket or gear to drive camshaft and oil seals at front and rear

Main parts of Crankshaft:

• Main Journals
• Crank Pins
• Crank Webs
• Counter Weights
• Oil Holes

Technorati Tags: What are the main parts of an engine,How many parts are there in engine,car engine parts and function diagram,all the piston parts explained,how does the piston work,what is the function of the piston in an engine,what is the function of piston rings,what does the camshaft do,piston function requirements and types

Which Types of Engine are used in Car | How Does a Boxer Engine Works | What is the Miller Cycle Engine

Classification of Engines:

• Engine cycle

• Otto cycle Engine
• Diesel cycle Engine

• Number of Strokes

• Two stroke
• Four stroke

• Fuel used

• Petrol Engine
• Diesel Engine

• Types of Ignition

• Spark ignition
• Compression Ignition

• Number of arrangement of Cylinders

• Single Cylinder Engines
• Two Cylinder Engines
• In-Line Vertical type
• V-type
• Opposed type
• Three cylinder Engines
• Four Cylinder Engines
• In-line Vertical type
• V-Type
• Opposed type
• Six and Eight cylinder Engines
• Radial Engines

Square Engine:

An engine having Stroke equal to Bore. If Stroke / Bore ratio is more than 1, it called “under-square”, while if it is less than 1, it is called “over-square”.

Boxer Engine:

Horizontally opposed engine, where opposing pistons are attached to different crank pins

Wankel Engine:

Engine working on Otto cycle, but the piston having rotary motion. Notable cars which used are Mazda RX-7 and Mazda R-8. Advantages are compact, simpler construction due to far less number of working parts compared to conventional engines, very smooth running, balancing is easier, higher volumetric efficiency, lesser wear of the rotor and better reliability due to lessor speeds of the rotor, low NOx emissions and lower octane fuel can be used. Disadvantages are less torque produced at lower speeds, lower thermal efficiency resulting in higher fuel consumption and higher production cost due to smaller quantity.

Atkinson cycle Engine:

Engine developed by James Atkinson, working on modified Otto cycle, called Atkinson cycle, wherein the compression stroke is shorter than the expansion stroke. Used in “Toyota Prius”.

Miller cycle Engine:

Atkinson cycle engine with a supercharger. An example is the “Mazda Eunos 800 M” Engine

HCCI Engine:

An IC engine in which well mixed fuel and air mixture is compressed to the point of auto-ignition. It has the characteristics of both S.I as well as C.I. engines. Advantages are, higher efficiency and lower emissions compared to conventional engines. Disadvantages are high peak pressures and heat release rates, difficulty to control and higher pre-catalyst emissions of HC and CO, due to which it has not been used so far in any production vehicle.

Electric Vehicle:

Advantages are quick acceleration, noise free operation, no emission, high reliability, easy maintenance, regenerative braking, no loss of power in idling and easy to drive. Disadvantage are limited range, low top speed, limited life of batteries, and substantial cost of replacement of batteries.

Hybrid Systems:

Main components are Heat engine, Fuel tank, Electric Motor, Generator, Batteries and Transmission systems. Types of systems are Series type, Parallel type and Series-Parallel types. Recent examples are Honda "Insight” and Toyota “Prius”. Battery for these should be able to provide high power in short pulses from 1 – 1.5 KWh. I.e. should be able to provide many shallow charging cycles.

Plug-In Hybrid (PHEV):

A hybrid vehicle with batteries which can be recharged from ordinary household electric plug. At present, PHEVs are not yet in production. Operating modes of PHEV are Charge-depleting mode, Charge-sustaining mode, Blended mode and Mixed mode. These need a large battery to provide energy in charge-depleting mode for a defined distance, say 10 KWh for 64 kms or 5 KWh for 16 kms range.

Fuel Cell:

A power source for the future automobiles. Fuel cells produce electricity through chemical reaction with no harmful exhaust emissions. Recent examples are GMs “Hy-Wire” and “Sequel” and Honda’s “FCX”.

Technorati Tags: what are the different types of engine,which types of engine are used in car,what are the some other types of internal combustion engines,what is engine and what are the main types of engine,automobile engines classification in depth tutorials,classification of engine according to valve arrangement,classification of engine according to cylinder arrangement,square under square over square engines,how does a boxer engine works,what is the miller cycle engine,how does the new skyactiv engine work,how does a hybrid car works

Effect of Engine Size, Flywheel Size and Firing order of Car Engines | Which Engine Size is Best | Does Engine Size Effect Performance

Firing order:

In 4 – cylinder Engines:1-3-4-2 or 1-4-3-2

In 6 Cylinder Engines: 1-5-3-6-2-4

In 8 Cylinder Engines: 1-5-4-2-6-3-7-8

In V-8 Engines : 1-8-4-3-6-5-7-2

Effect of Engine Size:

• Doubling cylinder diameter would increase the power to four times
• Doubling the stroke length would double the power
• Doubling stroke length would double the piston speed. If piston speed should not change, crankshaft speed would need to be halved when stroke length id doubled
• Doubling both the cylinder diameter and stroke length would increase torque to eight times

Effect of Flywheel Size:

• Size of the flywheel determines the energy absorbed during the power stroke and released during other three strokes. Thus it would determine the amount of speed fluctuation during a cycle
• A larger flywheel would have higher inertia, which would mean sluggish response; in other words, the acceleration or deceleration of engine would be slow

Use of Multi-cylinder Engine:

• In a multi-cylinder with staggered power stroke, ratio of maximum to mean torques is greatly reduced, reducing the size of the flywheel required, leading to higher response which makes it suitable for automotive application

Technorati Tags: What does size of engine mean,Which engine size is best,Engine Size explained,Does engine size effect performance,Firing order of 4 cylinder engine,firing order of 6 cylinder engine,firing order of 8 cylinder engine,firing order of V8 engine,Why there is a firing order,Engine firing order explained,what is a flywheel in a car and what does it do,what is the purpose of flywheel in an engine