Week 2 engine questions

The firing order of a 4 cylinder 4 stroke engine is 1-3-2-4

The difference between S.I and C.I is that S.I is spark ignition and requires a spark plug where as a C.I is compression based and uses heat to ignite the fuel through compression.

Examples are the otto cycle(spark ignition) and the diesel cycle

Reference: http://en.wikipedia.org/wiki/Internal_combustion_engine

The diesel engine was invented in 1893 by a german engineer by the name of Rudolf Diesel it was originally a air and oil mix in the first compression ignition.

Reference: http://factbooks.blogspot.com/2007/09/who-invented-diesel-engine_07.html

the purpose of oil jest on the connecting rods is to spray the pumped oil into the bore of the engine it is sprayed on  the thrust side of the bore.

The small end of the conrod is connected to the piston pin (aka gudgeon pin) and the big end of the conrod is connected to the bearing journal on the crankshaft.

With indirect injection on a diesel engine the injector inject's the diesel into what is refered to as a "pre-chamber"  combustion begins here then moves to the main chamber this mean that there can be less pressure used in the injectors and allows for a quiter smoother running engine, unfortunatly this decreases the fuel effiency by 5-10%.

Where as with a direct injection diesel engine the injectors are mounted at the top of the combustion chamber spraying directly into the chamber at a higher pressure however they are noiser than indirect injection but do have 5-10% better fuel effiency.

the term valve timing means the exact time that the valve opens and closes for both inlet and exhaust valves and is usually run by a camshaft on a piston engine.

We have valve clearance in the engine so that when the inlet and exhaust valves are opening they dont hit the piston as that would badly damage the engine.

Engine Tech questions

Taper and ovality refer to the condition of the cylinder bore, Ovality is the difference between the two diameter measurements that are measured at 90 degree angles to each other

Taper is the difference between the largest diameter at the top of the cylinder measurement and the smallest measurement at the bottom of the cylinder.

Ovality is cause by uneven pressure through the piston as it goes u and down in the cylinder.

Taper is caused by the piston ring as they rub against the cylinder wall.

Taper and Ovality are measured using a cylinder bore gauge, for taper you move the gauge up and down slowly and take the measurement at the top, middle and bottom, for ovality measure it just below the piston ring mark move it up and down slowly taking measurements and at 90 degree angles to each other

Piston side clearence is the space between the piston rings and the ring grooves.

The valves.
The difference between the intake and exhaust valves is that the intake valves are bigger to allow for less resistance and easier flow into the engine of the fuel.

The exhaust valves will reach temperatures 900 degrees celcius, the intake valve will reach around 250 degrees celcius .

The pistons in a four stroke engine must be able to with stand 300 degrees and must be able to cope with speeds of 30 meters/second(around 108kp/h) or around 7,500rpm

We have piston ring end gap clearance because the piston moves fast and generates alot of heat so the piston ring needs room to expand.

If the piston ring end gap clearance is too small then there isn't enough room for the the piston ring to expand.

Aluminium cylinder heads usually have a steel shim between the valve spring and cylinder head surface because the valve springs move at such a high speed that the could damage the aluminium cylinder head where as steel is alot stronger and can handle the pressure.

The term S.I means Spark Ignition.
The term C.I means Compression Ignition

The purpose of a core plug is to act as an expansion plug on the side of the block that protects the engine block when the water freeze's as water expands when it freeze's, this usually happens when there isn't enough anti-freeze in the water in a cold enviroment 

Crankshafft run-out is how much the crankshaft itself is bent from when it was originally made we measure the crankshaft run-out with the D.T.I

Four stroke engine

A four stroke engine works by using four cycles: Intake, Compression, Power and Exhaust

Intake: On intake the piston moves from T.D.C(Top Dead Center) to B.D.C to reduce the pressure in the cylinder a mixture of fuel and air is pushed in by the intake valve opening then the intake valve closes completing this stage of the intake stage

Compression: With both the intake and exhaust valves closed in this stage the piston moves back up applying compression to the fuel air mixture, this completes the compression stage

Power: When the piston is close to the T.D.C(Top Dead Center) the compressed mixture of fuel and air is ignited by the spark plug, the resulting pressure from the compression  forces the piston back down to the B.D.C(Bottom Dead Center) with tremendous force, this completes the power stage

Exhaust: On the exhaust stroke the piston again returns to T.D.C only this time the exhaust valve is opened to let the spent air and fuel mixture through to the exhaust system, this completes the four stroke engine cycle

Nikolaus august otto invented the four stroke engine in 1864, the engine was perfected in 1876 however when the first four stroke was built(http://library.thinkquest.org/C006011/english/sites/ottomotor.php3?v=2 , http://inventors.about.com/library/inventors/blotto.htm ).

The purpose of the crankshaft is to turn up and down motion of the pistons to a rotating motion, the bottom of the pistons are connected to the crankshaft with main bearings.

The purpose of the camshaft is to open and close the intake and exhaust valves in the engine.
.
The purpose of the head gasket is to seal the cylinder to ensure maximum compression and avoid the leakage of coolant and/or oil from getting into the pistons

The purpose of the piston is to transfer the force of expanding compressed gas in the cylinder down to the crank shaft via the piston/connecting rod, with some engines the piston also acts as a valve opening and closing ports in the cylinder wall.
The piston ring is an open-ended ring that fits in the grove of a piston in a combustion engine, its purpose is to seal the combustion chamber, it also supports heat transfer from the piston to the cylinder wall, lastly it also regulate engine oil consumption.

The purpose of the cambelt(also known as the timing belt) is to control the timing of the engines valves, it is run around the camshaft gears and the crank pully gear, the teeth on the belt turn the camshafts in-sync with the crankshaft

The purpose of the fly wheel is to steady the rotation of the shaft when we have fluctuating torque put onto the engine from its power source, it uses inertia momentum for rotational energy.

The purpose of the valve keepers is to hold the valve washer in place while connected in to the groves of the valve stem.

The purpose of valve stem seals is to avoid leakage of oil into the internals of the engines and to avoid leakage into the exhaust system.

Stroke and Bore

Bore is the diameter of the cylinder in the engine.

Stroke is the action of the piston traveling the length of the cylinder in one direction inside the engine

The displacement can be calculated as follows:

Reference: http://en.wikipedia.org/wiki/Four-stroke_engine
                 http://www.youtube.com/watch?v=-8cXXjsRg70
                 http://inventors.about.com/library/inventors/blotto.htm
                 http://library.thinkquest.org/C006011/english/sites/ottomotor.php3?v=2
                 http://en.wikipedia.org/wiki/Crankshaft
                 http://en.wikipedia.org/wiki/Piston
                 http://en.wikipedia.org/wiki/Piston_ring
                 http://en.wikipedia.org/wiki/Cambelt