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Can anyone explain the workings of a 4 stroke motor vs a 2 stroke motor...More than just you mix oil w/the gas in a 2 stroke!

Thanks!
 

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On a 4 stroke, the piston goes down on intake, up on compression, down on fire or explosion and back up for exhaust. It works in conjunction with the vales to achieve this.
Two stroke uses reeds on some and it performs the same action in 2 strokes rather than four. It is supposed to be omre evvicient, and save weight.
But today, even outboards are moving to 4 stroke to cut down on emissions.
 

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What Kinney said and a little more.
here's a link to the four stroke:click


And here's the two stroke:
click
 

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Those links will show the "how", now here's the "why":

2 stroke pros:
  • fewer parts
  • cheaper to build
  • reliable
  • no oil changes
  • good power at high RPM
  • light weight
2stroke cons:
  • noisy
  • messy exhaust
  • in-efficient (lousy MPG)
  • poor low RPM power
  • can't meet emmissions regs
  • limited service life
Four stroke pros:
  • reliable
  • efficient
  • good low end power
  • good high end power
  • quiet
  • clean exhaust (relatively)
  • very good really low end power
  • Potential for "puhTAHta-puTAHta sound"

    Four stroke cons:
    • lots more parts
    • lots more expensive to build
    • somewhat RPM limited
    • heavy
    • really heavy
That'll give you a starting point.
 

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The operational difference: How does the design get the fuel/air into the engine, compress it, burn it, get rid of it?
Four stroke uses valves to control how the mix goes in and out and needs four 'strokes' (two full crankshaft revolutions) to get it done. This means that the four stroke produces power on one 'stroke' or every other revolution. A one-cylinder four stroke engine running 1000 RPM "goes bang" and makes power 500 times per minute.

A two-stroke uses ports that the piston movement opens/closes to control how the mix moves thru the engine. This moves the mix thru the bottom end which cools and lubes the engine also. This process takes two 'strokes' or ONE crankshaft revolution to occur. This also means that it "goes Bang" every revolution. A two-stroke one-cylinder engine running 1000 RPM is going Bang and making power 1000 times per minute!

Now, it would seem that the two-stroke has all the advantages here and obviously makes TWICE as much power, right? Well, no.

Remember that bit about piston ports and such? The port method has some serious drawbacks in relation to cylinder filling and reversion issues. The net result is that individual power strokes are much less powerful (efficient) compared to each power stroke of an equal displacement four stroke. So the two stroke makes a lot less power per "Bang" than a four stroke....but it goes "Bang" twice as much which sort of makes up for its reduced power.
 

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In simple terms, a 2 stroke fires a spark and detonates the fuel every time the piston is at the top of the stroke. A 4 stroke fires off every other stroke and uses the non firing stroke to scavenge the exhaust gases via an exhaust valve and then introduce fuel into the combustion chamber via an intake valve.

06 FXDBI
 

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killer sperm
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Modern direct injection 2 strokes are efficient and clean. Mercury Marine's Optimax and Evinrude's E-TEC engines match 4 stroke engine economy and emmisions.
 
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