23 replies to this topic

[me madjoe 90]

arrhhhhhhhh i got so much to do i have to hand write like 500 words and i cant write verry well and i have to include diagrams explaining the fourstroke cycle where apropriate i have to write about main componants of the four stroke cycle and use the heading working principles of the fourstroke cycle and write about that...... and then at some point tomoro i have to fugar out how to get it to the collage witch is nin middel of countryside miles away and im not alowed to drive ma mini not insured and i scared because i wont be able to go to collage next year if i dont get in and i duno what to writed because i can explain it in about four words intake - comprestion - ignition - exhuast i duno what to do.................................................................. other than keep adding stuff to what i already have witch is this............................................... below

The four stroke cycle
A brief history of the four stroke cycle.
The four stroke cycle was patented for the first time in 1854 by Eugenio Barsanti and Felice Matteucci by 1860 two Italians had developed the first prototype. Although a German engineer called Nicolaus Otto was the first to create a functioning four stroke engine that was demonstrated in 1876. This is why they four stroke cycle is often known today as the Otto cycle. Four stroke engines are one of the most common forms of internal combustion engine today.

The four strokes are:
• Intake stroke
• Compression stroke
• Combustion stroke
• Exhaust stroke

The intake stroke - during the intake stroke fuel and air mixture is pulled or (forced) into the cylinder when the intake valve is open. This happens on the downward stroke.

The compression stroke – the intake valve closes and the piston is forced upward by momentum of the fly wheel compressing the fuel and air mixture.

The combustion stroke – the piston reaches the top of the compression stroke the compressed fuel and air mixture is ignited the expansion from the reaction forces the piston down.

The exhaust stroke – the piston reaches the bottom of the combustion stroke the exhaust valve opens and the momentum of the fly wheel pushes the piston upward forcing the exhaust gases and any other deposits out of the cylinder. The piston reaches the top of the exhaust stroke the exhaust valve closes and the cycle can begin all over again.

Meany four stroke engines include more than one cylinder and have different arrangements for the camshaft (duel, overhead, etc.) engines may feature fuel injection systems, turbo chargers and multiple valves any of theses enhancements do- not change the basic operation of the engine using the four stroke cycle or Otto cycle.


The four stroke cycle
A brief history of the four stroke cycle.
The four stroke cycle was patented for the first time in 1854 by Eugenio Barsanti and Felice Matteucci by 1860 two Italians had developed the first prototype. Although a German engineer called Nicolaus Otto was the first to create a functioning four stroke engine that was demonstrated in 1876. This is why they four stroke cycle is often known today as the Otto cycle. Four stroke engines are one of the most common forms of internal combustion engine today.

The four strokes are:
• Intake stroke
• Compression stroke
• Combustion stroke
• Exhaust stroke

The intake stroke - during the intake stroke fuel and air mixture is pulled or (forced) into the cylinder when the intake valve is open. This happens on the downward stroke.

The compression stroke – the intake valve closes and the piston is forced upward by momentum of the fly wheel compressing the fuel and air mixture.

The combustion stroke – the piston reaches the top of the compression stroke the compressed fuel and air mixture is ignited the expansion from the reaction forces the piston down.

The exhaust stroke – the piston reaches the bottom of the combustion stroke the exhaust valve opens and the momentum of the fly wheel pushes the piston upward forcing the exhaust gases and any other deposits out of the cylinder. The piston reaches the top of the exhaust stroke the exhaust valve closes and the cycle can begin all over again.

Meany four stroke engines include more than one cylinder and have different arrangements for the camshaft (duel, overhead, etc.) engines may feature fuel injection systems, turbo chargers and multiple valves any of theses enhancements do- not change the basic operation of the engine using the four stroke cycle or Otto cycle.


The four stroke cycle
A brief history of the four stroke cycle.
The four stroke cycle was patented for the first time in 1854 by Eugenio Barsanti and Felice Matteucci by 1860 two Italians had developed the first prototype. Although a German engineer called Nicolaus Otto was the first to create a functioning four stroke engine that was demonstrated in 1876. This is why they four stroke cycle is often known today as the Otto cycle. Four stroke engines are one of the most common forms of internal combustion engine today.

The four strokes are:
• Intake stroke
• Compression stroke
• Combustion stroke
• Exhaust stroke

The intake stroke - during the intake stroke fuel and air mixture is pulled or (forced) into the cylinder when the intake valve is open. This happens on the downward stroke.

The compression stroke – the intake valve closes and the piston is forced upward by momentum of the fly wheel compressing the fuel and air mixture.

The combustion stroke – the piston reaches the top of the compression stroke the compressed fuel and air mixture is ignited the expansion from the reaction forces the piston down.

The exhaust stroke – the piston reaches the bottom of the combustion stroke the exhaust valve opens and the momentum of the fly wheel pushes the piston upward forcing the exhaust gases and any other deposits out of the cylinder. The piston reaches the top of the exhaust stroke the exhaust valve closes and the cycle can begin all over again.

Meany four stroke engines include more than one cylinder and have different arrangements for the camshaft (duel, overhead, etc.) engines may feature fuel injection systems, turbo chargers and multiple valves any of theses enhancements do- not change the basic operation of the engine using the four stroke cycle or Otto cycle.

Main components of the four stroke cycle
In most internal combustion engines using the four stroke cycle many components are needed to work together in sync for the engine to run properly to understand these components more easily some more information is needed. In a petrol engine exhaust and inlet manifolds (these are like tunnels) and valve ports (inlets and outlets) are needed to provide fuel and air on the intake stroke of the engine, and to expel burned gases on the exhaust stroke. The ports are opened and closed at the proper times by the intake and exhaust valves, which close against the sides of the ports to create a seal. The valves are controlled by the camshaft, a camshaft has lobes on it these lobes are all shaped differently, but resemble an oval on a camshafts lobe sits a lifter. A lifter is cylindrical in shape and pushes up on a push rod, when the lobes are rotating on the camshaft. A push rod is connected to a rocker arm witch then “rocks” down on a spring that is connected to the valve holding it closed when the spring is pushed by the rocker arm the valve opens. This all happens due to the rotation of the camshaft witch is connected via gears to the crankshaft (that the pistons connect to) these are all parts of the four stroke cycle that are needed for the engine to function properly.

[sweetser]

Have fun

[me madjoe 90]

Have fun

oh thank you a definatly am doing i hate the four stroke cycle now have to make everything a big job dont thy and it all has to work in sync sack that im puting a two stroke outbord motor engine in my mini no four stroke for me XD (joke)

[Dan]

First off, start from first principles. A lot of what you've written assumes certain knowledge on the part of the reader such as how a four stroke engine would be laid out and what the components are. Don't be lazy like that, describe an engine briefly. Don't go into too much detail though because you are meant to be talking about the principle that makes the engine work rather than an engine specifically. Point out that the engine you've described is just one type of four stroke engine. Secondly the cam shaft and valve arrangement is the most esential system and pretty much the defining characteristic of a four stroke engine (well, timing is. some four stroke engines don't have either a cam or conventional valves and you should probably mention that) so give them a bit more than half a line of description. You are right to put that the type of valve drive doesn't change the cycle of the engine but you talk about valves a lot without describing what they are and what they do. Don't just limit this to poppet valves either, you can mention sleeve valves and their complexities providing that you point out that however the valving is managed it's still the same four stroke cycle that makes the engine work. You should talk about how the Otto cycle breaks down combustion into four discreet processes that the engine can deal with in different ways and how the different parts of the engine are associated with each process, and that different engine designs use different parts to perform each process with a timing arrangement governing it all. You can contrast this with the two stroke, five stroke or six stroke cycles as evidence that you really understand what makes the four stroke work and what defines it. Just don't go into too much detail on the other systems. You could describe rotary engines and how they differ from reciprocating engines, you could talk about other uses of the four stroke cycle such as Diesel or Napier engines which are four stroke but not technically Otto cycle. You could use that last bit as further evidence that you understand exactly how the process of combustion and power development is broken down into four seperate stages in the four stroke engine. You could show that Otto, by using spark ignition and a fixed cylinder head with valves has only used the very basic principles of the cycle leaving much to be developed by others.

to be honest I'd have trouble limiting myself to just 1500 words on this! Good luck.

Edited by Dan, 14 June 2009 - 07:51 PM.

[me madjoe 90]

First off, start from first principles. A lot of what you've written assumes certain knowledge on the part of the reader such as how a four stroke engine would be laid out and what the components are. Don't be lazy like that, describe the engine briefly. Don't go into too much detail though because you are meant to be talking about the principle that makes the engine work rather than an engine specifically. Secondly the cam shaft and valve arrangement is the most esential system and pretty much the defining characteristic of a four stroke engine so give them a bit more than half a line of description. You are right to put that the type of valve drive doesn't change the cycle of the engine but you talk about valves a lot without describing what they are and what they do. You should talk about how the Otto cycle breaks down combustion into four discreet processes that the engine can deal with in different ways and how the different parts of the engine are associated with each process, with the cam shaft and timing arrangement governing it all.

thanks thats given me more of an idea what to write about because i dident realy know what to put for componets so i just started rambeling on abit about differant parts of the engine thats alot of help thanks and i haven been given an spacific type/ styile of fourstroke engine to write about so its hard to go into alot od detail im doing some more now thanks for your help tho and i apologise for not puting punctuation and cr*p in as im rushing abit ................ thanks for your help tho

[yeti21586]

suck

squeeze

bang

blow


lol how i got taught it at college

[me madjoe 90]

suck

squeeze

bang

blow


lol how i got taught it at college

thats how i know it now i got to write 1500 words about it some how lol

[yeti21586]

hmmm im guesing your not alowed to just repeat that??

[zebidee]

Sounds fun to write! (I'm not joking)

How in depth do you need to go? Are you looking into it simply as a mechanical process or the depth of the physics behind it?

Edited by zebidee, 14 June 2009 - 07:59 PM.

[me madjoe 90]

Sounds fun to write! (I'm not joking)

How in depth do you need to go? Are you looking into it simply as a mechanical process or the depth of the physics behind it?

do you want to do it for me and and recon you would get it done in a night XD
and im jokin but u can if u like and i think just mechanical process as its only a motor sport couse erm id find it fun if i dident have to do it all in one night ............ im stressed
need more caffine........................... going to get realy strong coffee

[zebidee]

I would if i didn't happen to have a thermodynamics exam tomorrow morning . It was weird that this topic was here, because i was just looking over the otto cycle and adiabatic expansion!

[me madjoe 90]

I would if i didn't happen to have a thermodynamics exam tomorrow morning . It was weird that this topic was here, because i was just looking over the otto cycle and adiabatic expansion!

fun good luck in your exam sounds like something intresting unlike most of the crap some people do in collage and uni

[me madjoe 90]

thermodynamics so whats that about then exactly im gusing like explotions and heat and energy un stuff like that........?

[zebidee]

Cheers...its my last one, can't wait to be over for summer

Yep. I actually study physics at Exeter uni. The thermo module is pretty much based around the link between pressure and temperature and the laws of thermodynamics. A couple of months ago i did an experiment into the thermal efficiency of the Otto cycle, comparing it to a highly idealized model. Turned out that the efficiency of most gasoline fueled cycles is around 35%...pretty poor!

[me madjoe 90]

Cheers...its my last one, can't wait to be over for summer

Yep. I actually study physics at Exeter uni. The thermo module is pretty much based around the link between pressure and temperature and the laws of thermodynamics. A couple of months ago i did an experiment into the thermal efficiency of the Otto cycle, comparing it to a highly idealized model. Turned out that the efficiency of most gasoline fueled cycles is around 35%...pretty poor!

hope u tested it against mini engines most of them are prity fuel efficant and that if set up corectly....