a question from my auto exam

[Landy Smurf]

hey i have just finished my yr 11 exams and one of my exams was automotives and this is one of the questions try and answer it without looking it up anyway this was the question
for a four stroke engine list in order what is each stroke is called and what does it do
ill give you a clue there is 4 of them lol

[haggisbasher]

suck, sqeeze, bang, blow?

is that it?......:wasntme:

Chris

[AKW]

Intake, compression, power, exhaust.....



But suck, squeez, bang, blow, sounds better.

Andrew

'93tdi200 disco
'65 88" s2a

[Blknight.aus]

Starting at TDC (assuming a single cylinder over head valve configuration)

With both valves on the rock, inlet opening exhaust closing the next downward movement of the cylinder is called the induction stroke which is achieved initially via an external force applied to the crankshaft to initiat rotation and once the OTTO cycle is established under inertia gained during the power stroke. The inlet valve opens rapidly and at the bottom of this stroke the inlet valve closes and piston begins to move up the cylinder. At this point a fuel/air charge (in the case of a petrol) has been administered to the cylinder and is ready for compression (in the case of a diesel its only air)

The next stroke is the compression stroke there is no valve movement on this stroke of the cylinder and the piston is forced up via the rotation of the crankshaft via an externally applied force or under the inertia of itself, the flywheel and any other rotating mass attached. Near the top of this stroke the spark plug is fed a high voltage from the ignition system which arcs across the airgap and commences combustion The piston is still moving upwards when this occours. In the case of a Diesel the compression is sufficient to raise the air temperature above the flash point of the fuel that is injected in atomised form into the combustion chamber. This injection occours at about the same timing as the spark in a petrol engine.

Once the crank rotates past TDC with both valves closed the power stroke (assuming the combustion process has occurred and is self sustaining) the power stroke has begun which takes advantage of the adiabatic process where a rise in temperature gives a rise in pressure, The rise in pressure exerts force on the crown of the piston and in following with the isobaric rules for thermal reactions pushes the piston down (AKA nature abhors a vacuum) As the piston approaches bottom dead center the exhuast valve begins to open and the residual energy of the combustion process begins the process of evacuating the combustion area.

Once the cylinder has passed bottom dead center and is rising again the exhaust valve rapidly opens and the piston again under inertia or external force applied to the crank shaft rises and expels the remaining gases. Near the top of this stroke the exhaust valve begins to close and the inlet valve begins to open in preperation for the cycle to begin again. This forth and final stroke is called the exhaust stroke.


Is that close enough or do you want an indepth answer?

[Benny_IIA]

Starting at TDC (assuming a single cylinder over head valve configuration)

With both valves on the rock, inlet opening exhaust closing the next downward movement of the cylinder is called the induction stroke which is achieved initially via an external force applied to the crankshaft to initiat rotation and once the OTTO cycle is established under inertia gained during the power stroke. The inlet valve opens rapidly and at the bottom of this stroke the inlet valve closes and piston begins to move up the cylinder. At this point a fuel/air charge (in the case of a petrol) has been administered to the cylinder and is ready for compression (in the case of a diesel its only air)

The next stroke is the compression stroke there is no valve movement on this stroke of the cylinder and the piston is forced up via the rotation of the crankshaft via an externally applied force or under the inertia of itself, the flywheel and any other rotating mass attached. Near the top of this stroke the spark plug is fed a high voltage from the ignition system which arcs across the airgap and commences combustion The piston is still moving upwards when this occours. In the case of a Diesel the compression is sufficient to raise the air temperature above the flash point of the fuel that is injected in atomised form into the combustion chamber. This injection occours at about the same timing as the spark in a petrol engine.

Once the crank rotates past TDC with both valves closed the power stroke (assuming the combustion process has occurred and is self sustaining) the power stroke has begun which takes advantage of the adiabatic process where a rise in temperature gives a rise in pressure, The rise in pressure exerts force on the crown of the piston and in following with the isobaric rules for thermal reactions pushes the piston down (AKA nature abhors a vacuum) As the piston approaches bottom dead center the exhuast valve begins to open and the residual energy of the combustion process begins the process of evacuating the combustion area.

Once the cylinder has passed bottom dead center and is rising again the exhaust valve rapidly opens and the piston again under inertia or external force applied to the crank shaft rises and expels the remaining gases. Near the top of this stroke the exhaust valve begins to close and the inlet valve begins to open in preperation for the cycle to begin again. This forth and final stroke is called the exhaust stroke.


Is that close enough or do you want an indepth answer?

Dave I think you may have just a little to much spare time:wasntme:.... very good
answer though

Ben.....

[Landy Smurf]

good answers another question was name 2 advantages that a 2-stroke engine has over a 4-stroke engine once u guys tell me your answers ill tell you mine just in case im wrong

[Jock The Rock]

good answers another question was name 2 advantages that a 2-stroke engine has over a 4-stroke engine once u guys tell me your answers ill tell you mine just in case im wrong

No need for a sump or reserve of oil/engine lubricant

Able to run at higher revs

Also, they are lighter due to less moving parts

[JDNSW]

Twice as many power strokes per revolution

Fewer moving parts.

John

[HBWC]

Intake, compression, power, exhaust.....



But suck, squeez, bang, blow, sounds better.

Andrew

'93tdi200 disco
'65 88" s2a


the top one is right
the bottom is wat we use to use ase a description
(tafe courses)

[Landy Smurf]

once agaon good answers i sed they are cheaper to repair and that they have more power for the size of the engine

[d@rk51d3]

2-stroke will generally give you higher torque.

[Blknight.aus]

cheaper to make
higher power to weight ratio
No requirement to have internal lubrication system
less moving parts

[Slunnie]

once agaon good answers i sed they are cheaper to repair and that they have more power for the size of the engine
In racing circles, the 4 strokes are now able to produce more power than a 2 stroke for a given capacity. The problem with a 2-stroke is that even with expansion chambers they are still not an efficient motor. The other limitation is that 2-strokes is that they cant really make peak power happen beyond about 11,000 rpm, though they can make it linger well beyond that rather than falling off. 4-strokes they can make pull for as long as things remain in synch. I think F1 are hitting around 18,000rpm and I'm not sure what the bikes are doing these days.

[CraigE]

2 stroke benefit - no o/h valves, simple power valve set up, no complicated head, no timing chain.

[Blknight.aus]

not always...

Ive seen 2 strokes with timing chains and over head valves.

[Slunnie]

Yep. diesel 2 strokes.

The petrol 2 stroke with rotary/disc valves can also have a timing belt when the intake is aligned with the gap in the crankshaft rather than the normal side entry.

[DeanoH]

Mazda rotarys are effectively a two stroke and had their capacity doubled (on paper) after their first year of racing to make the other cars competitive. Gricey cleaned up that year. You also have two stroke diesels like the twin knocker. You can even have 1 stroke steam engines and the Stirling engine

Deano

[Blknight.aus]

You can even have 1 stroke steam engines

Deano


would that be a steam cannon?

[JDNSW]

2 stroke benefit - no o/h valves, simple power valve set up, no complicated head, no timing chain.

Not necessarily - some two stroke diesels have overhead valves. Some two stroke diesels have no head cylinder head; e.g. Junkers style engines. Simplicity is not necessarily a feature of two strokes.

John

[stig0000]

and i think the exhast on a 2 strok is alot more inportent then a 4 stroke, ;)

[DeanoH]

would that be a steam cannon?

Not really, it was called double reciprocating or something. From memory, single double ended piston with con rods extending through the 'heads', drove the wheels through some crank/slide arangement. Long time since I went to school. Steam was fed into each end of the cylinder by a valve arrangement so that it 'fired' at the end of each stroke. Very powerful for its size.

Deano

[Pedro_The_Swift]

In racing circles, the 4 strokes are now able to produce more power than a 2 stroke for a given capacity. The problem with a 2-stroke is that even with expansion chambers they are still not an efficient motor. The other limitation is that 2-strokes is that they cant really make peak power happen beyond about 11,000 rpm, though they can make it linger well beyond that rather than falling off. 4-strokes they can make pull for as long as things remain in synch. I think F1 are hitting around 18,000rpm and I'm not sure what the bikes are doing these days.

The biggest limiting factor in a modern 2stroke is---

They no longer race them,,,,

yes.
that old chestnut " racing improves the breed" IS true.

[Bigbjorn]

Starting at TDC (assuming a single cylinder over head valve configuration)

With both valves on the rock, inlet opening exhaust closing the next downward movement of the cylinder is called the induction stroke which is achieved initially via an external force applied to the crankshaft to initiat rotation and once the OTTO cycle is established under inertia gained during the power stroke. The inlet valve opens rapidly and at the bottom of this stroke the inlet valve closes and piston begins to move up the cylinder. At this point a fuel/air charge (in the case of a petrol) has been administered to the cylinder and is ready for compression (in the case of a diesel its only air)

The next stroke is the compression stroke there is no valve movement on this stroke of the cylinder and the piston is forced up via the rotation of the crankshaft via an externally applied force or under the inertia of itself, the flywheel and any other rotating mass attached. Near the top of this stroke the spark plug is fed a high voltage from the ignition system which arcs across the airgap and commences combustion The piston is still moving upwards when this occours. In the case of a Diesel the compression is sufficient to raise the air temperature above the flash point of the fuel that is injected in atomised form into the combustion chamber. This injection occours at about the same timing as the spark in a petrol engine.

Once the crank rotates past TDC with both valves closed the power stroke (assuming the combustion process has occurred and is self sustaining) the power stroke has begun which takes advantage of the adiabatic process where a rise in temperature gives a rise in pressure, The rise in pressure exerts force on the crown of the piston and in following with the isobaric rules for thermal reactions pushes the piston down (AKA nature abhors a vacuum) As the piston approaches bottom dead center the exhuast valve begins to open and the residual energy of the combustion process begins the process of evacuating the combustion area.

Once the cylinder has passed bottom dead center and is rising again the exhaust valve rapidly opens and the piston again under inertia or external force applied to the crank shaft rises and expels the remaining gases. Near the top of this stroke the exhaust valve begins to close and the inlet valve begins to open in preperation for the cycle to begin again. This forth and final stroke is called the exhaust stroke.


Is that close enough or do you want an indepth answer?

Dave, have a cup of tea, a Bex, and a nice lie down. Failing that, take a laxative.

[JDNSW]

And if you want some really interesting engines, I seem to remember from the 1920s a marine engine that ran steam below the pistons, and diesel above, with steam being raised by the diesel exhaust.

John

[CraigE]

not always...

Ive seen 2 strokes with timing chains and over head valves.

Yes, you are quite right, I was talking in general in what most of us will see in petrol and generally in motorcycle / buggy type engines. I was not including rotary valves only OH valves. Who could forget the 2 stroke Detroit Diesels, not that many of us will actually see to many close up let alone work on them, but I do love them.:angel::wasntme::angel:
Actually only rebuilt the kids 2 stroke quad this week. What a pleasure and simple task they are to work on. Complete big bore kit installed in 45 minutes. The 4 strokes I am used to would have taken all day or more.
As per another post a Rotary is not a 2 stroke in the true sense as it works in a completely different way and application. My understanding is the Rotary Wankel works a bit more like a 4 stroke than a 2 stroke with Inlet, Compression, Combustion & Exhaust with each task occuring independentlly, but I also dont know too much about these, so I could be way off base. Where as a 2 stroke has two different task occuring at each stroke.

[Benny_IIA]

The biggest limiting factor in a modern 2stroke is---

They no longer race them,,,,

yes.
that old chestnut " racing improves the breed" IS true.


True in the case of Motor-X yes which is very sad but the old 250 2 smokers can not keep up with 450 thumpers (I own a 450 and have ridden many 250 2s).

But in the boating world Evenrude turned the game on its head the E-tec.
Fuel injected 2 stoke outboard.
The two-stroke lives! : Evinrude's E - TEC engines have done the seemingly impossible; saving the air-cooled two-stroke from oblivion | Automotive Design & Production | Find Articles at BNET (http://findarticles.com/p/articles/mi_m0KJI/is_6_115/ai_103990207/)

Ben

[vnx205]

:angel:
Actually only rebuilt the kids 2 stroke quad this week. What a pleasure and simple task they are to work on. Complete big bore kit installed in 45 minutes. The 4 strokes I am used to would have taken all day or more.


I can't accept that unfair criticism of 4 strokes.:p:p

When I used to run my SL125 Honda (bored and stroked to 175cc) on petrol during the week and alcohol when racing on Sundays, it used to take me less than an hour to do the swap.

That included:


removing the fuel tank
removing the head and barrel
removing the piston
fitting the higher (or lower) compression piston.
replacing the barrel, head and fuel tank
remove the bottom of the carby
replace the main jet with on that was 40% bigger (or smaller)
lift the carby slide out and move the circlip down (or up) three notches
drain the petrol (or alcohol) and replace with alcohol (or petrol)

I used to think that was reasonably slick but a friend of mine who was a mechanic and had access to a better range of tools than I did could do that same swap at the start of his lunch break and still have time to ride home across town for a bite to eat and get back in time for the afternoon.

I reckon with the right tools, I could have given you a run for your money with your 45 minute 2 stroke changeover. :p:p:p

[Sleepy]

good answers another question was name 2 advantages that a 2-stroke engine has over a 4-stroke engine once u guys tell me your answers ill tell you mine just in case im wrong


They start easier than a 4 stroke after sitting, neglected, in the shed for a year.
They smell like trailbikes.

[Landy Smurf]

They start easier than a 4 stroke after sitting, neglected, in the shed for a year.
They smell like trailbikes.

we have an old 1980 kv 250 4-stroke that we leave for olng periods of time and it generally starts within the first 5 kicks

[Sleepy]

we have an old 1980 kv 250 4-stroke that we leave for olng periods of time and it generally starts within the first 5 kicks

Oh, just thinking of my brushcutter and my lazy gardening habits. Unfortunately when I do get it out (yearly) it always starts :(.

[Landy Smurf]

:Rolling:

[DeanoH]

As per another post a Rotary is not a 2 stroke in the true sense ................

Exactly right, but 2 stroke in effect in that each rotor fires once for each revolution of the crankshaft.

Deano

[Slunnie]

Exactly right, but 2 stroke in effect in that each rotor fires once for each revolution of the crankshaft.

Deano
A rotary doesn't even stroke. So perhaps its really something along the lines of a 1 revolution. :lol2:

[V8Ian]

A rotary doesn't even stroke. So perhaps its really something along the lines of a 1 revolution. :lol2:
Don't they have two plugs per combustion chamber?

[pop058]

Don't they have two plugs per combustion chamber?

so do a few conventional in line 4-strokes eg. Nissan Z series motors as used in the later Bluebird (and others)

Paul

[DeanoH]

Don't they have two plugs per combustion chamber?

Yes. Anyway SWMBO's early RX3 did when we were young and silly. Also had oil injection same as 2 stroke motor bikes. 10A engine turned into a water pump when the seals failed. . Went like s**t of a shovel but the brakes, scary. The rears were reminiscent of a morris minor and the front discs very small. Definitely a fun car to drive.

Deano

[CraigE]

I can't accept that unfair criticism of 4 strokes.:p:p

When I used to run my SL125 Honda (bored and stroked to 175cc) on petrol during the week and alcohol when racing on Sundays, it used to take me less than an hour to do the swap.

That included:


removing the fuel tank
removing the head and barrel
removing the piston
fitting the higher (or lower) compression piston.
replacing the barrel, head and fuel tank
remove the bottom of the carby
replace the main jet with on that was 40% bigger (or smaller)
lift the carby slide out and move the circlip down (or up) three notches
drain the petrol (or alcohol) and replace with alcohol (or petrol)
I used to think that was reasonably slick but a friend of mine who was a mechanic and had access to a better range of tools than I did could do that same swap at the start of his lunch break and still have time to ride home across town for a bite to eat and get back in time for the afternoon.

I reckon with the right tools, I could have given you a run for your money with your 45 minute 2 stroke changeover. :p:p:p
:D I suppose it depends on the bike and set up. I have generally worked on Honda XL / XR, Yamaha XT, YZF 4 strokes in the past and they would take me a bit, but then I was learning and not in a hurry either.

[ramblingboy42]

I seem to recall an 8 stroke diesel. Cant remember too much about it some nice person donated it to the cause after Cyclone Tracy in Darwin 1974. It ran 4 stroke when under load and off load reverted to a second camshaft which allowed it to fire every 4th revolution. Had huge flywheels and ran a 32 volt generator if I remember correctly, was about 12" bore and 24" stroke. It is probably still sitting in a shed at Batchelor.

[Blknight.aus]

that particular engine was actually a very clever 4 stroke with valve and injection hitnmiss governing.

if power wasnt needed from a particular pot it was allowed to miss a turn and its subsequent strokes just kept on rolling but the valves opend for each turn of the crank the inlet for the downwards stroke and the exhaust for the upward.

it was setup so that each pot would only miss 2 turns before being made to fire again. Stupidly expensive, seriously complicated but very very effective.

Generally it didnt really count as an 8 stroke engine as if you loaded it up it would revert to normal 4 stroke operations.

there was however some serious looksee-ery into 6 stroke petrol engine and for the day (remeber this was before CAD flow dynamics) the engine produced the same amount of power as the same size 4 stroke there was that much extra power to be found by giving the engine an extra intake and exhaust stroke to purge all the burnt gasses out of the combustion chamber.

then someone came up with forced induction. (actually from memory it was the cost of manufacture and unreliable cold running that did it in)

[Slunnie]

Don't they have two plugs per combustion chamber?
Yes, they were paired up.

https://www.aulro.com/afvb/images/imported/2009/09/743.jpg