Cooling

Kinetic energy
Explain the terms ( Kinetic energy) Conduction,convection and radiation? Conduction is heat energy moving through a solid e.g. steel. Convection is the cycle ov heat through a liquid as the hot liquid rises the cold falls. Radiation is heat being transfered to the air from a hot object e.g. the engine


Indirect cooling
The coolant is in a closed cycle but still uses the raw water to cool the coolant further, this is a effective way of heat control because it works the same way as a car engine on a thermostat which means less corrosion and a faster warm up.

Direct cooling
The direct cooling method is to pump raw water up and through the water jacket then back out with the exhause fumes, this isnt as effective or practicle as indirect because of the corrosion and how long it takes for the engine to heat up - costing you more fuel.


Indirect and direct cooling propblems
What are the the problems you get with indect and direct cooling? Corrosion is the biggest problem because the raw water is so destructive, maintanance on the indirect cooling can be a mission - depending on how easy it is to get to the heat exchanger. You also have to regularly check the inlet valves because the can get blocked - causing over heating.

What is the puppose of a thermostate
To allow the engine to heat up to optimum running temp before letting the coolant pass through to be kept constant so the engine is always at the right temp.

Pressure cap? The pressure cap is a release valve for when/if the pressure in the radiator becomes to high for the specifications, it is also the way to top up the coolant.

Why is engines fitted with a core plug, and what is the purpose of a core plug? The manufacturors put them in so when they are moulded the can shake out all the core moulding sand. another reason for the core plugs is so if the water in the water jacket freezes it won't crack the block or head it will push out the frost plug instead.

What is the purpose of a heat exchanger? A heat exchanger is the equivelant to a radiator on a car except instead of cooling the coolant with air you cool it with raw water from the ocean which is also cycled to keep cold. It works by raw water circulating through pipes next to the circulating hot coolant the heat is transfered to the raw water leaving the coolant colder.

Fuel injection

Eletronic control unit
The ECU is the brians of the motor and controls everything. it controls how much fuel can enter the motor, when the spark plugs spark, it dose this by reading the multidimen sional preformace maps. it uses engine sensors to control this.

Mass air flow sensor
A mass air flow sensor is used to find out how much air is entering the the fuel injetion system. The air mass in need so the computer can work out how mcuh fuel is need to be injected into the system so it has the wright balance of air/fuel mixture.

Air Temp sensor
The air temp sensor is used for two diffrent purposes. One is a warning system to warn the ECU if the air is to hot.There other purpose is to monitor catalyst functioning. they normally have have two sensors one befor the catalyti and one after to monater the temp after passing the catalytic core.

TPS throttle position sensor
A TPS is a sensor used to monitor the postion of the throttle in a internal combustion engine. The sensor is normally located on the buterfly so it an directly monitor the position of the buterfly.


Throttle body
In fuel injected motors the thrttle body is part of the air intake system. The throttle body is in respons with the accelaraotor pedal. The throtle body is normaly mounted in between the air fitter box and intake manafold. The biggest part on the throttle body is the throttle plate.

Carburators

 2 stroke Carburetors works the same way as  4 stroke carburbtors do. There are fuel lines that go into the float bowl,  the float valve inside the float bowl controls how much fuel that can go into the float bowl. The fuel then enters a jet that jet sprays the fuel into a venturi which adds pressure so the fuel and air mixes together. Above the jet is the air intake, The  air/fuel mixture then passes though the throttle plate. When the throttle plate is fully open it lets as much fuel as it can pass though. The throttle plate is never fully closed because if it was the motor would not iddle witch means it will not run. After that the muxture goes down the carb throat and into the combustionchamber.



Emulsion TubesThe air from the air bleeds enters the main circuit through the emulsion tube. The emulsion tube has a series of small holes from top to bottom, and it is through these holes that air enters the main circuit. At low engine speeds, when fuel demand is low, these holes are submerged in fuel, and so no air can flow through them. As engine speed increases, the fuel level in the float bowl drops, uncovering these holes, and allowing air from the bleeds to enter the main circuit, thus leaning the mixture. As the engine speed increases further, the fuel level in the float bowl continues to drop. This uncovers even more of the holes in the emulsion tube, which makes the air bleed have a greater effect on the mixture


Manual and automatic choke
A manual choke is opparate manualy by pulling a lever that closes the choke buterfly that is at the beggeing of a carburtor. A automatic choke is controled by a thremostic coil which the buterfly sharft is attcaed to. When the heat for the motor running the coil releases and the choke is then opened.

Float valve
The float valve is there to control the amount of fuel that can enter the venturi. As fuel getts used the level of fuel in the float boul drops causing the float to drop and open the needle valve letting more fuel into to the float boul.
Float valve

Mechanice lift pump
A mechanide lift pump is used to pump fuel into the carburtor. A mechanice lift pump is bolted to the head or to the block. This is because the camshaft has an extra lobe on it witch pushes on the lift pump rocker arm. When the pistons travel down to bottom dead centre it sucks fuel into the mechanice lift pump. When the pistons travel to top dead centre the fuel is forced out of the lift pump into the carburtor.


Vacuum fuel pump
The carburtor is not strong enoff to suck fuel into the carburtor so there is a vacuum pump just befor the carb to pump the fuel into the carb. The vacuum pump work by diaphrame.  The diaphrame works on piston strokes. There is also a one way valve in the pump witch make sure the fuel can only go one way and allows no air in the system.
What presure did you get from these pumps?? you gett around 2 - 4 PSI


Diffrents between diesel and petrol
Diesel runs on C.I compression igintion, this is compression to heat, there is enough heat and compreesion to cause an explotion forcing the pistons down.
Petrol runs on S.I spark igintion, petrol is highly flamable so with a small spark it will egint easly. forcing the pistol down.

Fuel cut off switch
The fuel cut off switch works on a copper coil causing a magntice force controling the swith.

What is the four stroke cycle
Intake,
compreesion,
power,
exhaust,

what dose S.I mean?
spark igintion

What dose C.I mean?
cpmpreesion igintion

When taking a carb apart what should you be really carefully with?
You have to be extra carefully and not turn the arb upside down. when turning it upside down the float needle valve can come out and wont go back in propally

When dismantling a carb what precaution should you take? do not turn it upside down because the small springs and valves will change position/alinement.
How does a bimetallic spring work in a automatic choke work? A bimetallic spring that helps with cold starting.when the engine is cold the sping holds the butterfly valve closed, as the engin heats up it slowly opens the valve producing a progressivly leaner fuel mixture. At the same time the high idle gradulay drops back to normal, when the engin is warm the butterfly valve will be fully open, ( standing up) producing the right mixture of air and fuel for the warm engine.

What is the purpose of the venturi and how does it work? it works on the same principles as a aeroplane wing - so it bottlenecks to make the air presure rise and flow faster and the fuel an air to mix more effectively