diffrence between 2 stroke and 4 stroke? for science project

[boatman03]

hey, i am doing a science project and i need to compare the diffrences and simalarities of a 2 stroke outboard to a 4 stroke outboard. any info will be very appreciated.

 

[roscoe]

Re: diffrence between 2 stroke and 4 stroke? for science project

Way to many things to list here. May I suggest you go to local library and ask librarian for the technical service manuals.<br />Look for general repair manuals. They will have a section in the front that describes the operation of the engines.<br /><br />I would suggest the Seloc or Clymer manual for Force engines, that will cover the 2 strokes.<br /> <br />And the manual for either Mercury or Yamaha to get info on the 4 strokes.<br /><br />p.s. and stop fishing at petco !

 

[JB]

Re: diffrence between 2 stroke and 4 stroke? for science project

Howdy, boatman03.<br /><br />Wow! I could write a book on this one, but let me give you a few basics and then you can ask questions.<br /><br />Similarities: <br />* They all mount to the transom of a boat, "outboard" of the hull.<br />* They all drive a propeller or "jet" pump which is submerged in the water.<br />* There are a very few that burn Diesel fuel or Jet fuel, but the rest all burn gasoline.<br />* They are mostly self contained. Most require seperate fuel tanks and external batteries and controls, but some include their own fuel tanks and starting mechanism and require no external controls at all.<br /><br />Two stroke engines: There is not just one type of 2 stroke engine, there are several and they differ from each other in performance and efficiency as much as they differ from 4 stroke engines.<br />* A few are air cooled, the rest are water cooled.<br />* Many use carburetors and fuel that is mixed with oil. Some use carburetors and supply the fuel and oil seperately. These "carbureted" engines are the lightest and least expensive for their power of all outboards. They are also the noisyest, least efficient, simplest to service and the worst polluters.<br />* Some inject fuel and oil into the crankcase.<br />* Some inject oil into the crankcase but inject fuel under computer control directly into the cylinders. These are called DFI (Direct Fuel Injection) engines, and they are the most efficient, quietest and cleanest burning 2 stroke engines in the world.<br /><br />Four stroke engines:<br />* Because they require a camshaft and a valve train, as well as an oil sump and pump, 4 stroke engines are typically bigger and heavier than similar power 2 strokes.<br />* Some 4 strokes use carburetors to supply fuel to the engine. <br />* Most of the larger 4 stroke outboards use computer controlled electronic fuel injection (EFI) and ignition. One even uses a supercharger.<br />* In weight, efficiency, noise and cost EFI 4 strokes compare favorably with DFI 2 strokes, but are more complex, usually heavier and more expensive than the carbed 2 strokes.<br /><br />You are unlikely to find two knowledgable people that agree with me or each other about everything above, but if you have questions, ask away.

 

[Laddies]

Re: diffrence between 2 stroke and 4 stroke? for science project

My God JB, thats about two days typing for me Bob

 

[boatman03]

Re: diffrence between 2 stroke and 4 stroke? for science project

thank you all for the input especially you JB it was very informing. is a quick summery that a 2 stroke takes two rotations of the camshaft to make one rotation of the prop and on a 4 stroke it is 4 rotations of the camshaft for one "power stroke" making the 2 stroke faster but less powerfull?<br /><br />JB, what would be the diffrence of burning jet fuel compared to regular gasoline? Does one run cleaner or faster?<br /><br />Thanks again for all the info.<br /><br />ps. ok i will stop fishing at petco but i will tell you, you are garantied to catch a fish. but no boating allowed!!!

 

[JB]

Re: diffrence between 2 stroke and 4 stroke? for science project

The descriptions of 2 and 4 strokes refer to how many strokes of the piston are required to complete one cycle. . .intake, compression, combustion (power), and exhaust, boatman03.<br /><br />The complete terms are two stroke cycle and four stroke cycle. Two strokes do it in two strokes, one revolution of the crankshaft and four strokes take four strokes or two revolutions of the crankshaft.<br /><br />Two strokes have no camshaft. They use the underside of the piston as a pump that draws the charge into the crankcase, then pumps it into the cylinder (called acavenging). Reed valves and piston ports that are opened and closed by the pistons act as the "valving" for 2 strokes. You can get a much more detailed and illustrated explanation from a good encyclopedia.<br /><br />The propellor is usually geared to turn a bit slower than the engine crankshaft. Two strokes and four strokes use similar gearing.<br /><br />One would expect 2 stroke engines to make twice the power of same size 4 strokes at the same speed, but that is not the case. Two strokes only make full use of about 50% of their displacement to make power because the piston uses around half of its travel to pump, when it isn't making power.<br /><br />Jet fuel, kerosene and Diesel fuel have higher energy content than gasoline but are much harder to pump and ignite. They usually also burn less completely in 2 strokes, making a lot more smoke and pollution. The 2 strokes that I know about that use these safer and more available fuels are specially modified for use by the military (fuels more available to the military, that is).<br /><br />Good luck with the project.

 

[dustydiesel]

Re: diffrence between 2 stroke and 4 stroke? for science project

2 stroke is one turn of the crankshaft one stroke up second stroke down 4 stroke is two turns of the crankshaft 1st intake 2nd compression 3rd power 4th exhaust two strokes do not use cam shafts detroit diesel two stroke has oil pan oil pump cam shaft valve train used on older trucks generators and in some marine engines

 

[rogerwa]

Re: diffrence between 2 stroke and 4 stroke? for science project

Check out this site for pictoral explanation..<br /><br /> http://science.howstuffworks.com/two-stroke2.htm

 

[boatman03]

Re: diffrence between 2 stroke and 4 stroke? for science project

thank you for all the great info it will help so much on my project. i will tell you how i did when it is done. we have to have it finshed by some time in juneany other infot that you happen to come across will be appreciated.<br /><br />Hey roscoe, i live in like the smallest town and i don't think my libray wil help bu ti will look around.

 

[rwise]

Re: diffrence between 2 stroke and 4 stroke? for science project

2 stroke gets (somewhat) cleaner with age (less polution) due to advanced oils, 4 strokes are as clean as there going to be the first time you start them and get worse with age due to useing more oil. just a thought.

 

[retnug]

Re: diffrence between 2 stroke and 4 stroke? for science project

Try here.<br /><br /><br /> http://science.howstuffworks.com/two-stroke1.htm <br /><br /> http://auto.howstuffworks.com/engine.htm

 

[boatman03]

Re: diffrence between 2 stroke and 4 stroke? for science project

one more quick question can you run a two stroke on just pure oil if you were to get stuck out of gas and if so how would it work ? would the combustion be the same?

 

[Paul Moir]

Re: diffrence between 2 stroke and 4 stroke? for science project

Practically and theoretically, no you can't for engines that normally run on gasoline. Oil is too heavy to burn effectively at spark-ignition engine compression levels. Not to mention that the oil would not work properly with the fuel induction system, be it an injector or a carburetor.

 

[beniam]

Re: diffrence between 2 stroke and 4 stroke? for science project

Really good summary, JB! Batavier

 

[Stratosfied]

Re: diffrence between 2 stroke and 4 stroke? for science project

Yeah, what JB said!

 

[boatman03]

Re: diffrence between 2 stroke and 4 stroke? for science project

thanks you all for the great info i have a feeling that i will ace this one for sure.<br />me and my partners are greatful

 

[LubeDude]

Re: diffrence between 2 stroke and 4 stroke? for science project

You will also find that 2 cycles are generally not near as efficient as four strokes as they will push more unburned fuel out the exhaust, However, the new Evenrude Etechs seem to have solved some of this in there new engines. 2 strokes will generally have more power at the high end though, but less torque at the low end.

 

[Ross J]

Re: diffrence between 2 stroke and 4 stroke? for science project

One other point for you to consider, a lot of countries are banning two stroke outboards and insisting on 4 stroke. Some even ban any commercial operation from running on petrol totally and insist they run on diesel (Australia).<br />You could add to the project by a small item on local fuel laws.<br />Ross

 

[boatman03]

Re: diffrence between 2 stroke and 4 stroke? for science project

hey all, i passed with a 92 so i thank you all for your help me and my parters really appreciate it.

 

[JB]

Re: diffrence between 2 stroke and 4 stroke? for science project

That's good news, indeed, boatman03.