2 stroke, 4 stroke

2279 Views 20 Replies 5 Participants Last post by ghbzorro, Jan 10, 2010

Drama

Discussion Starter · Jan 8, 2010

ok so i got into a discussion the other day with a friend of mine about 2 stroke and 4 stroke engines, i understand the concept between the two, 4 stroke = suck, squeeze, bang, blow... 2 stroke = same thing but half the steps, he told me there was such a thing as a 4 sroke 2 cycle? i really wasnt following what he was trying to say he made a referance to a later 80's model motor cycle, i belive he said it was a 3 cylinder engine, any help would be appreciated

1 - 20 of 21 Posts

denzee

· #2 · Jan 8, 2010

Since the basic difference between 2 and 4 stroke (or cycle) is the idea that a 2 stroke engine fires every revolution of the crankshaft whereas a 4 stroke fires every other revolution, you can't have both.

2 stroke engines have transfer ports in the cylinder walls for intake and exhaust instead of valves. Their cyl head is basically a cover. Their oil and gas mixture travels through a closed crankcase for lubrication and that is also part of the process. However Detroit Diesel has 2 stroke diesel engines (fires every rotation) that also have 4 exhaust valves in the head like conventional. The intake is through ports in the cyl wall but has a regular lubrication system like a 4 stroke engine.

Maybe something like that but I haven't heard of any other.

bladeracer

· #3 · Jan 8, 2010

There's also a six-stroke engine but I've never heard anything called a four-stroke, two-stroke.
Can you find out what he's talking about?

Drama

Discussion Starter · #4 · Jan 8, 2010

with the way he was describing it to me as your standard 4 stroke, and 2 stroke as described earlier, 2 stroke running mixed gas and 4 stroke running straight gas, but the 4 stroke 2 cycle he said is the same thing as the standard 4 stroke but runs on mixed gas making it a 4 stroke 2 cycle, the discussion got pretty heated because it just didnt sound right to me but i didnt want to shoot my mouth off not knowing exactly what i was talking about

bladeracer

· #5 · Jan 8, 2010

Drama said:
with the way he was describing it to me as your standard 4 stroke, and 2 stroke as described earlier, 2 stroke running mixed gas and 4 stroke running straight gas, but the 4 stroke 2 cycle he said is the same thing as the standard 4 stroke but runs on mixed gas making it a 4 stroke 2 cycle, the discussion got pretty heated because it just didnt sound right to me but i didnt want to shoot my mouth off not knowing exactly what i was talking about

Running a four-stroke on mixed fuel doesn't make it a two-stroke. You can run mixed fuel in any four-stroke but it doesn't make it any less of a four-stroke engine.
Two or four strokes is defined by how many strokes are required for each power stroke.

Drama

Discussion Starter · #6 · Jan 8, 2010

thats what i thought and was the point i was trying to make but he didnt bite so i wasnt sure if i was missing something or not, ill have to talk to him later and get back to you with what he says

bladeracer said:
There's also a six-stroke engine but I've never heard anything called a four-stroke, two-stroke.
Can you find out what he's talking about?

so now i am curious, can i get a little info on the six stroke engine, ive never heard of such a thing nor am i able to piece it together in my head of how it would work

bladeracer

· #7 · Jan 8, 2010

Drama said:
thats what i thought and was the point i was trying to make but he didnt bite so i wasnt sure if i was missing something or not, ill have to talk to him later and get back to you with what he says

so now i am curious, can i get a little info on the six stroke engine, ive never heard of such a thing nor am i able to piece it together in my head of how it would work

Try here as it's fairly involved

Internal combustion engine - Wikipedia, the free encyclopedia
My guess is he has heard something very vague and then made a bunch of assumptions without foundation.
Engine design is very interesting and there have been some really odd designs as well as some brilliant ones that never went anywhere.
Basically, the modern four and two stroke designs haven't evolved significantly since the late nineteenth century so something new would have to be _hugely_ better to go anywhere.

Drama

Discussion Starter · #8 · Jan 8, 2010

speaking of odd engine designs, i have attempted to look up and locate things i have heard on the net to find verification on things but i dont remember exactly what type of block it was but it was used in ww1 ww2 era army jeeps where the intake valves are in the head but the exaughst valves were located on the side of the cylinder wall towards the bottom

bladeracer

· #9 · Jan 8, 2010

Drama said:
speaking of odd engine designs, i have attempted to look up and locate things i have heard on the net to find verification on things but i dont remember exactly what type of block it was but it was used in ww1 ww2 era army jeeps where the intake valves are in the head but the exaughst valves were located on the side of the cylinder wall towards the bottom

Side-valve or flathead maybe?

Willys MB - Wikipedia, the free encyclopedia
Side-valve 2200cc

Drama

Discussion Starter · #10 · Jan 8, 2010

its possible im not sure im not much of a motor head just know the baisics, that link helped alot and gave me a better idea of how they work or what the steps are but what applications were they used for, my assumption of the material would be a locomotive, ship of large size, but other than that i cant think of anything

bladeracer

· #11 · Jan 8, 2010

Drama said:
its possible im not sure im not much of a motor head just know the baisics, that link helped alot and gave me a better idea of how they work or what the steps are but what applications were they used for, my assumption of the material would be a locomotive, ship of large size, but other than that i cant think of anything

Not sure what you mean by applications.
Two-stroke designs are good for small, light vehicles as they don't make much torque and they're significantly lighter and smaller than four-strokes. Being very simple with fewer moving parts also makes them good for aircraft. They don't make twice the power but they do make their power twice as often as four strokes so they can be very potent. Modern 1000cc four-stroke Superbikes are now making roughly the same power as 500cc two-stroke race bikes were ten-fifteen years ago.
Nearly all cars are four-strokes with a handful of two-strokes. Which reminds me, deisel engines are compression engines (no ignition system) and I have heard people call them two-stroke so perhaps that's what's confused your friend.
Other than the rotary (which I have seen any point to) I think all of the other designs are more aimed at stationary engines.
Ships I think use fairly standard four-stroke engines just on a massive scale (as big as houses).
Not sure about train engines but I think they're usually deisel and other than their size not siginificantly different from what you'd find in big haulage trucks.

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Drama

Discussion Starter · #12 · Jan 8, 2010

as far as applications go just reffering to what the motor was used in, as example a guy is talking about a 250 2 stroke but you dont know specifics dirt bike, sport bike, go kart, to have an idea of what exactly they are talking about if that makes any sense, i guess what im asking is where would a 6 stroke engine be used or is that something that was used a while back but no longer is

bladeracer

· #13 · Jan 8, 2010

Drama said:
as far as applications go just reffering to what the motor was used in, as example a guy is talking about a 250 2 stroke but you dont know specifics dirt bike, sport bike, go kart, to have an idea of what exactly they are talking about if that makes any sense, i guess what im asking is where would a 6 stroke engine be used or is that something that was used a while back but no longer is

As far as I know six-stroke designs are newer and not used in anything other than patent prototypes to show that they do work. I'd be amazed if they ever actually got used for anything.

Scruffy

· #14 · Jan 8, 2010

Locomotives use v16 diesels.

bladeracer

· #15 · Jan 8, 2010

bladeracer said:
Two-stroke designs are good for small, light vehicles as they don't make much torque and they're significantly lighter and smaller than four-strokes.

I'll clarify this.
I don't know that two-strokes aren't able to make the required torque but their design limits their power output to a very narrow range which gets narrower with increasing revs.
The piston itself is acting as the intake and exhaust valves by allowing the ports to open and close as it passes them, as revs increase the ports are open for much shorter periods of time.
The ports have to be fairly low in the cylinder so there is sufficient room left after the piston passes for the mixture to be compressed. This means the ports have to open fairly late and close fairly early in the cycle which limits the efficiency of the combustion.
On a four-stroke you can design the camshaft to open and close the ports at any point in the cycle to produce a power curve optimal for the job. The designs of a CBR1000RR engine and a sixteen-litre truck engine are essentially the same - they're just designed to produce power differently.

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bladeracer

· #16 · Jan 8, 2010

Scruffy said:
Locomotives use v16 diesels.

All of them don't I'm sure and some are electric.

denzee

· #17 · Jan 8, 2010

Maybe you guys are not familiar with 2 stroke diesels. Detroit Diesel which was a division of General Motors still make a whole line of them. Incredible power to weight ratio. Several series of engines based on individual cylinder displacement. 53 ci/cyl, 71, 92, 110 and 149. All those were put into different configurations like in 6 cyl was a 6-71, V8 8V-71, 8V-92 and so on right up to 12V-149 used in Marine application. They all had superchargers and some had turbos as well. Here is a sample. Pretty cool engines.

http://www.youtube.com/watch?v=19eQBQep-sc&feature=related

Drama

Discussion Starter · #18 · Jan 8, 2010

hey thanks guys i think i have learned more from this thread than anyother one ive dealt with, but here is my favorite motor, it allmost sounds real, might be a repost but oh well

http://www.youtube.com/watch?v=JMwm3wwqtwc&feature=related

ghbzorro

· #19 · Jan 8, 2010

denzee said:
They all had superchargers and some had turbos as well.

Yes, they all have blowers because without it they would not be able to breath. After all, they have "standard" intake and exhaust valves in the head. With no induction into the crankcase and crankcase compression to charge the cylinder, they need the blower.

denzee

· #20 · Jan 8, 2010

ghbzorro said:
Yes, they all have blowers because without it they would not be able to breath. After all, they have "standard" intake and exhaust valves in the head. With no induction into the crankcase and crankcase compression to charge the cylinder, they need the blower.

All correct gh except instead on intake valves, the charge comes in via cylinder liner ports much like a 2 stroke. The pistons on the way down uncovers the ports and a rush of pressurized air rushes in thanks to the blower and simultaneously is pushing out the spent combustion through 4 open exhaust valves in the head. As the piston rises it has a fresh pressurized air charge to compress and waits for the moment the injector fires in the fuel just BTDC. The 20:1 or more comp ratio then ignites the fuel with no spark.

It's quite a unique system.

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