Friday, July 8, 2011

2 stroke engines

2 stroke Engines
Explain how a two stroke engine works?

The spark plug fires, pushing the piston down. Towards the end of the down stroke, the intake valve opens, pulling in new fuel & air. The piston hits the bottom of the stroke & starts back up, compressing the air-fuel mixture, until it hits the top of the stroke & the plug fires.

What is happening below and above the piston?

Above the piston we have Compression, Ignition and Transfer/Exhaust of the fuel.
Below the piston we have Intake, Pre-compression and Tranfer.

Note - As the Fuel/Air/Oil mixture is compressed it lubricates the system.

Explain what is meant, by scavenging when applied to 2 stroke SI engines?

This is the proccess of pushs the exhaust gases out and drawing the new mixture in.

Why must roller and ball race bearings be used on 2 stroke SI engine crankshafts?

2 Stroke engines are lubricated using oil in the fuel. If a sealed type bearing was used then the oil would not enter the bearing when compressed.

Why are rollers caged in crankshaft bearings?

The roller cylinders are all linked to stop uneven spread of the rollers, they are caged to that the rollers all stay in the right place and so that there is not uneven wear on the bearing
Why must ‘split’ type bearings be used on one piece crankshafts?

Why do we have pins between the piston ring gaps on a 2 stroke?
How does a reed valve work on a two stroke?

How do you check a reed valve?

The reed valve can be checked in the sunlight the valve must be closed with no gaps showing.

Explain the term ovality and taper and how are they formed?

How does the piston rings seal in the bore?
What is meant by the terms groove depth, side clearance and end gap on the pistons rings?
Explain the difference between a 2 stroke and a 4 stroke engine?
What is meant by each of the following terms:
(a) Mechanical Efficiency(b) Thermal Efficiency(c) Volumetric Efficiency?
List 2 methods of lubricating the internal parts of 2 stroke S.I. engines?

Reference
http://en.wikipedia.org/wiki/Two-stroke_engine

http://science.howstuffworks.com/transport/engines-equipment/two-stroke.htm

Tuesday, June 21, 2011

Cooling

Convection-The way that heat is transferred from one place to another is convection. Convection takes place when heated molecules move from one place to another, taking the heat with them.

Radiation- In physics, radiation is a process in which energetic particles or energy or waves travel through a medium or space.

Conduction-Heat can also be transferred from one object to another, or from one molecule to another through the process of conduction.

Indirect cooling- This means that there is a small tank on the top of the engine that uses a both fresh water and coolant.

Direct cooling- It makes no difference whether it is salt or fresh, both are used to cool the engine.

What is the puppose of a thermostat- Thermostats are in cooling systems to bring them up to operating temp. quicker for better engine operations and better gas mileage.

Pressure cap- this releases the pressure off the radiator to the reserve tank.

Why is engines fitted with a core plug, and what is the purpose of a core plug -sometimes called freeze plugs, they are used to remove sand from the casting when the engine block is cast.

What is the purpose of a heat exchanger?

How does the heat exchanger work?
What is the core of the heat exchanger made of- The heat exchanger is made with various materials such as steel, copper, bronze.

How does the centrifugal circulating water pump work?
How does a raw water pump work- A raw water pump works the same as a centrifugal circulating pump. It has a central driven impellor, this pump often works via a belt or gear.

Why is it important to lubicate the impellor when fitting from new?
When fitting a impellor what should you check before refitting the housing and why?

What is the purpose of a oil cooler and how does it work- Vehicles are fitted with an engine oil cooling system that attempts to keep the lubricating oil within its optimum operating temperature range.

What is the process of a intercooler/aftercooler how does it work?
Why do we have Inhibitors & antifreeze?
How do you test Antifreeze-

What is cavitation corrosion?
What is galvanic corrosion?
Describle the terms
Stray corrosion?
Stress corrosion
Corrosion Fatigue?
Crevice corrosion?
What is Electrolysis?
How do you prevent corrosion?
Why and what is bonding in the marine industry?
What are sacrifical anode made off?
Where would you place them in the marine industry?

Saturday, June 4, 2011

Diesel Pump

Who invented the diesel engine and when?

Dr. Rudolf Diesel invented the diesel engine in the year 1893. He was mechanical engineer by profession and belonged to Germany. The diesel engine is a compressed–ignition engine that works with a piston which compresses air and injects oil-based fuel into the superheated air, causing spontaneous combustion of the fuel. The main advantage of this engine is that instead of using expensive petrol it makes use of cheap heavy oil and is fuel efficient.

How does the diesel pump work and why do we need to time the pump?

Diesel fuel pumps are designed to inject a specific amount of fuel at a very specific time. They are usually linked to the crankshaft or the camshaft through a series of gears. These gears allow the fuel pump to be driven directly by the crankshaft of the engine.

What is the knock sensor for and where is it situated?

The knock sensor is generally screwed into the engine block for all cars.

How does the diesel injectors work?

The fuel injector is attached to a small pump, which forces air into the injector and pressurizes the diesel fuel. The injector then sprays the diesel fuel through a small nozzle into the cylinder's combustion chamber.

Why do you need to bleed a diesel engine after replacing a fuel filter or removing the pump? How do you bleed the system?

The easiest way to bleed a diesil fuel system is to crack open the fuel line to the number one injector. crank engine , allowing air and fuel to escape from loosened fuel line. once sufficient air has been bled from system, the engine will start.

How does a turbo work?

2 turbine blades one for exhaust one for the intake. They are linked by a shaft. The exhaust turbine is spun by the engine's exhaust output. Since it is linked to the intake turbine the intake turbine pumps more air into the engine, allowing it to burn more fuel.

What is a supercharger?

A supercharger is a device driven by a belt, chain or gears that increases engine power by pumping air into the combustion chambers.

Whats the difference between a turbo and supercharger?

Difference between a turbocharger and a supercharger is itspower supply. A supercharger, there is a belt that connects directly to the engine. It gets its power the same way that the water pump or alternator does. A turbocharger, on the other hand, gets its power from the exhaust stream. The exhaust runs through a turbine, which in turn spins the compressor.

Why do we need a inter-cooler fitted to a diesel engine?

An intercooler is a simply a heat exchanger mounted between the turbo-charger, or super-charger and the inlet side of the engine. Cold air is blown through it to cool down the hot, compressed air inside.

What the difference between in a direct-injection ( DI,) an indirect-injection ( IDI)?

A direct-injection, or DI, system the fuel is sprayed directly into the main combustion chamber and ignites. By contrast, an indirect-injection, or IDI, system sprays the fuel first into a pre-combustion chamber, where ignition occurs before spreading into the main combustion chamber.

What is the difference between a diesel and a common rail diesel?
Basically, fuel is pumped from your tank to the rail, where another pump puts the fuel rail under tremendous (100+psi) pressure. Then when your cars ECU wants a certain injector to fire, a small electric pulse is sent to that injector.

reference

http://en.wikipedia.org/wiki/Rudolf_Diesel

http://whoinvented.org/who-invented-diesel-engine/

http://answers.yahoo.com/question/index?qid=20080328085330AAJd3TP

http://saeforum.net/14/what-does-a-diesel-injection-pump-do-and-how-to-maintain-it.html

http://autorepair.about.com/cs/generalinfo/a/aa102001a_2.htm

http://ask.cars.com/2009/04/what-is-a-supercharger.html

http://autospeed.com/cms/A_108104/article.html

http://wiki.answers.com/Q/How_do_you_bleed_a_diesel_fuel_system

Tuesday, May 31, 2011

Fuel Injection

Fuel injection

ECU- Electronic control unit?

ECU or Engine Control Unit on cars controls the engine on computer controlled cars. It uses a closed-loop control that monitors outputs of a system to control the inputs to a system, managing the emissions and fuel economy of the engine. It also gathers data from the various sensors ranging from coolant temperature to O2 volume in your exhaust (which explains the number of codes which vary from one car make to the other). From the data gathered, it performs somewhat an analysis to determine what is wrong with your car. So its the main brain off the car.

Mass air flow sensor?

A Mass airflow sensor is a device used by the engine control computer to measure the amount of air entering the engine through its air intake system.

Air Temp sensor?

The purpose of an air temperature sensor is to help the computer calculate air density. A change in temperature changes the resistance in the sensor.

TPS throttle position sensor?

The TPS (throttle position sensor) does exactly what the name implies. It looks at how hard your are stepping on the throttle so that it knows how hard the engine is working

Throttle body?

The throttle body controls how much air gets to the engine.

Temp sensor?

A temperature sensor is located in the engine block and is used by the ECU to regulate the radiator cooling system cycle and to turn the electric radiator fans on or off.

fuel rail?

A fuel rail is normally found on EFI engines and is used to distribute fuel to the injectors.

Fuel pressure regulator?

A Fuel Pressure Regulators' sole purpose is to maintain fuel pressure at a constant differential to manifold vacuum under all engine load conditions. The fuel pressure regulator is responsible for controlling the set fuel pressure of the system.

Injectors?

The injectors are supplied with fuel via the fuel rail, which is then sprayed at high pressure into the cylinder head.

O2 sensor ( lambda sensor)?

An oxygen sensor on a car reads how much oxygen in the fuel system at any given time. If it senses too much oxygen it cuts back the air coming in. If it finds too little oxygen it opens the intake and mixes more air with the fuel.

Map sensor?

A map sensor is a Manifold Absolute Pressure sensor. It measures the pressure in the manifold and send that signal to the computer to let the computer know what kind of load is on the engine.

What does EFI stand for

Electronic Fuel Injection.

Reference

http://en.wikipedia.org/wiki/Fuel_injection

http://www.efihardware.com/about_us.php

http://www.ehow.com/how_4478865_troubleshoot-map-sensor.html

Saturday, May 28, 2011

Fuels Systems

How does the carb work?

A carburetor draws air into the throat and mixes fuel with the air as it passes through the carburetor venturies. A cold carburetor will usually have a choke system that will enrichen the air fuel mixture as it warms up to operating temperature. A good carburetor will have good suction and pass the air fuel mixture into the intake manifold to be distributed equally to each cylinder to provide power and economy upon demand.

Indentifly the components?

The main components in most carbureted systems are, float chamber, a venturi, the throttle, idle circuit, main circuit, a choke and an accelerator pump.

What are the holes in the emulsion tube for and how does it work?

The Emulsion Tube mixes air from the air corrector jet with fuel from the main jet, and controls the mixture from the discharge nozzle at all engine speeds that the main jet is working! Basically, the Emulsion Tube changes the diameter and location of small holes in it's body.

How does the manual choke and automatic choke work?

Automotic choke - work on a spring mechanism housed in a plastic cover located on the side of the carburetor. These chokes are electrically heated to promote expansion and contraction. When the engine is cold the spring contracts, coiling more tightly. When the engine is started, the closed choke creates more vacuum in the engine, pulling in more fuel. As the engine continues to warm up, the electrical choke responds to the heater inside and begins to expand and as it does, it begins to push the choke open.

Manual choke - It is a valve that opens and closes to restrict air flow, the restriction riches the fuel/air mixture to aid in the initial startup of the vehicle. The choke creates a stronger vacuum to pull more fuel from the jets and into the air/fuel mixture. When the engine warms up the choke slowly releases and stays in the wide open position.

What is the purpose of the float in the carb?

To ensure a ready mixture, the carburetor has a float chamber that contains a quantity of fuel at near to the atmospheric pressure, ready for use. This reservoir is constantly replenished with fuel supplied by a fuel pump.

What is the purpose and how does mechanical lift pump work?

The mechanical fuel pump for the carburetor system is usually mounted on the cylinder head or the engine block.

It has a flexible diaphragm. That’s a flexible piece of neoprene rubber separating 2 chambers. This diaphragm is operated by an eccentric on the camshaft. It rotates, making the rocker arm move. This movement is transferred to the diaphragm, pulling it down. That draws fuel into the pumping chamber, above the diaphragm. When the engine needs more fuel, the diaphragm moves through a long stroke to pump a lot of fuel.

What the difference between petrol and diesel fuel?

petrol is thinner than diesel and requires more electrics to make it work and deisel needs compression to fire and petrol needs an ignition spark to fire

How does the fuel shut off solenoid work?

A soleniod is a device that produces mechanical motion by electrical induction. They are a coil of wire with either a plunger which is drawn into the coil or a plate that is drawn to a metal core.

What is the four stroke cycle?

intake Stroke-This is the first movement of the piston. This is a downward motion of the piston that develops a vacuum in the cylinder. This vacuum pulls the air and fuel mixture into the cylinder through the open intake valve.
Compression Stroke-During this second stroke, all valves are closed. This allows all of the piston's force to be used to compress the air and fuel mixture. As it is compressed, the mixture becomes more dense creating a more potent mixture for detonation.
Power Stroke-Just before the piston reaches top dead center, the mixture is ignited by a spark plug. The third stroke, the power stroke harnesses the energy of the explosion by allowing the piston to be forced downward from top dead center.
Exhaust Stroke
The last stroke is the exhaust stroke. During this last upward movement of the piston the exhaust valve is open. The piston forces all of the burned gasses from the previous explosion out of the cylinder. The cycle is completed and can begin again.

What does S.I mean?

Comparison of Spark Ignition (SI)

What does C.I mean?

Compression Ignition (CI) Engines

What are some of the causes of high fuel consumption?
Power valve stuck open
Fuel leaks from filter or hose.

An engine lacks power. What is likely to cause this problem?

Restrictions in air intake.

Lack off fuel flow.
Restrictions in air intake, intake air too hot or cold.

Reference

http://www.914world.com/bbs2/index.php?showtopic=105251

http://www.ehow.com/how-does_5011204_how-stroke-carburetor-works.html

http://faculty.sdmiramar.edu/wnorth/249/249five.pdf
http://en.wikipedia.org/wiki/Carburetor

Wednesday, April 6, 2011

Trailers

Single Axle

For small boats, these trailers are most common used.

Double Axle

double axle trailers, these provide better weight distribution on the trailer and tires. One axle can be fitted with brakes, or both of them, to provide safe handling while towing your boat .

Triple Axle

These are the heaviest duty boat trailers. They generally require a heavy duty tow vehicle and have heavy duty brake systems.

Different boat hull shapes

Flat bottom boat - These boats are generally less expensive to build and have a shallow draft. They also tend to be less stable and require careful balancing of cargo and crew.

The "V"-bottom boat is probably the most common hull design. Most manufacturers of boats built today use modifications of this design. This design offers a good ride in rough water as the pointed bow slices forward and the "V"-shaped bottom softens the up-and-down movement of the boat. The degree of the angle of the "V" is called "Deadrise’’.

Round bottom boat - These move easily through the water, especially at slow speeds.

Multi-hull boat - The wide stance provides greater stability. Each of the hulls may carry any of the above bottom designs.

Bunk trailer

Usually have pivoting carpeted bunks connected to the frame with bunk or bolster brackets for adjustment and keel rollers up the centre. Bunks can be replaced with roller bunks for easy launching and retrieving. Less expensive than roller trailers

Roller trailer

Roller Type trailers use rubber faced or plastic rollers. They make boat loading, launching and retrieval easier.

Trailer Materials

Galvanized boat trailers have galvanized tubular box frames. They are the most solid boat trailers. They offer the best protection in the brake lines and the wiring system.

Aluminum I-bean boat trailers are made of high quality aluminum. They are generally lightweight and strong. However, they offer little protection from shocks and mild damage.

C-channel boat trailers are ideal for carrying lightweight boats. They are the least expensive type of boat trailer.

Small boats trailers are designed to carry small boats, usually measuring 12 to 15 feet.
They are usually made of galvanized steel or aluminum, each offering durability and strength

Large boat trailers can carry boats measuring up to 19 feet in length. They commonly have a rectangular tube frame showen above.

Trailer dimension limits

The maximum width for a light simple trailer (including its load) is 2.5 metres.

Maximum length

The maximum length for a light simple trailer (including drawbar and load) is 12.5 metres (previously 11.5 metres). For a towing vehicle and simple trailer combination (including load, but excluding collapsible mirrors), the maximum overall length is 22.0 metres (previously 20.0 metres).

Maximum height

The maximum height for a light simple trailer (including load) is 4.25 metres. All vehicles must be loaded in a safe manner, with a height appropriate to the type of load.

Maximum forward distance

For a simple trailer, forward distance means the distance from the rear axis of the trailer to the centre of the point of attachment on the towing vehicle.

The maximum forward distance is 8.5 metres.

In the diagram above, the boat is the load on the trailer. It has a raised outboard motor that projects more than 1 metre behind the rear of the trailer.

Suspension Types

Leaf spring suspension is the most widely used and available type of trailer suspension. One of the most common styles of leaf spring suspension is the slipper style.

Rubber Torsion

In general, rubber torsion suspension is used for small trailers that are not carrying a heavy or difficult load. operate.

Wheels and Tyres

Don’t underest imate the importance of quality when shopping for boat trailer tires. You’re going to be towing your boat, possibly over very long distances. So you want to get tires from a reliable company that is known for making quality trailer tires.

Brakes:

The trailer brakes out there that have brakes will be drum brakes, activated by a surge unit. The surge brakes are applied by the forward movement of the trailer, when you apply the brakes of the towing vehicle. The trailer "surges" forward activating the master cylinder in the surge unit.

Disc (or caliper) brakes are starting to show on the larger type trailers. The braking methods can be the same as surge drum brakes or a electric unit, activated automatically when the towing vehicle's brakes are applied