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  1. #1
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    Smile two stroke engine

    Hi , will build a 2 stroke engine, it will be a 119 cc one cilynder engine, with intake by the block, in the future i would like to do a 2 stroke v4 or 4 in line, i want to know how the intake is made in that engines. Another question is the water cooling, how do i do the water circuit arround the cilynder in my engine?

    Thank you

  2. #2
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    hi, i wonder what is the problem.... 153 views, no reply, anyonde to explain this to me?

  3. #3
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    Quote Originally Posted by PoWaKiD42 View Post
    hi, i wonder what is the problem.... 153 views, no reply, anyonde to explain this to me?

    Maybe it's just the fact that the 2 stroke is complex in the area of intake design. The port timing is very critical and most people don't do the design work. I would'nt want to try it. Maybe try a forum with engineers who work in that field.

  4. #4
    Community Moderator svenakela's Avatar
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    It's quite easy actually. By using Reed valves you can have big intakes as the piston is not responsible for closing the intake.
    You should try to have an even amount of water all way around, the biggest problems are how close to the exhaust you can have water, and second to be sure that the head gets enough of water.

  5. #5
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    The problem is with a 2 stroke you lose half the combustion through the exhust which includes half the fuel/air mixture so for emmisions its not too feasable. Thats why they have expansion chambers and secondary power valving if you could figure a way to use that secondary gas for power and cleaner emmissions we could sell 2 stroke across the globe.
    Joe
    another thing I used to have a honda replica gp 500 2 stroke bike(kenny roberts) fast as hell and a cr250 dirt bike all the majors have moved to 4 stroke for emmisions? I now have a crf450 200cc more than the 250 thats all they race anymore? the 450 is fast but 450 2 stroke??? I think a cr 500 will beat it on the straight???

  6. #6
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    Probably the easiest way to build a v 4 two stroke would be to use reed valve induction ,letting the engine dictate when it needs to be fed its airfuel mix.The induction system is only the begining of your adventure into making a two stroke engine ,the exhaust port the transfer ports/ crankcase ratio/combustion chamber shape/piston crown shape/stroke/bore.These really are just a few desighn considerations,remembering to the beauty of this engine is you can make it run in reverse with just a change in ignition.A very basic engine can be made with a reasonable amount of knowledge, however if you plan on getting into something a little more high performance some serious home work will need to be done along with many nights of head scratching.Its a great engine to start playing with and im sure you will have a lots of fun with your project,good luck greg.

  7. #7
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    PoWakiD42, If you are in the design phase of this project I suggest you look into "The Basic Design of the Two Stroke Engine" by GP Blair, Queens University, Belfast. Its published in the US by SAE. My copy has been "borrowed" by a "freindly competitor".
    DZASTR

  8. #8
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    For ideas on how to package cooling water, look for fotos of a 4-71 Detroit Diesel.

    Yes it is a diesel but, but it is a two stroke and it shows how to package coolant around the intake port and other stuff. Asside from compression ratio and spark plug in place of the injector, the "basics" are pretty much the same.

    Whether you use valves-in-head or piston porting to do the exhausting is purely an issue of packaging. The book recommendation by DZASTR is a great starting point for 2 cycle engine studies.

  9. #9
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    PoWaKiD42, Another interesting 2-stroke V-4 is an aircraft engine called the Delta Hawk. They are somewhere on the internet, I'll see if I can find them.

    Add: www.deltahawkengines.com
    DZASTR

  10. #10
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    Thanks a lot for the help! i will post some pictures of my solidworks designs, they are not finished yet. Is it to bad that i make the engine air cooled? Is it possible to make the engine with a manual mill? i have acess to a cnc machine on college but its not working right now, it has some programing problems...

  11. #11
    Community Moderator svenakela's Avatar
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    Everything is possible, you just need patience, time and knowledge (or room for errors... ).

    --S

  12. #12
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    If you have seen the older Detroit series of engines as mentioned you will find they are 2 stroke water cooled. Used in lots of applications including boats and other equipment. Locomotives may still have them also.
    With this series the clyinders are wet sleeve. They are sealed on the top and also near the bottom with most having 3 o ring's which is a press fit for sealing. The water circulates around the sleeve for cooling. The engine is also different and more complicated than normal 2 strokes as it has valves for intake and piston porting for exhaust.
    In there day they where very popular but they also had there problems. I have never seen one that did not leak somewhere and if used as a unattended power plant and if they broke the quill shaft you would understand why they called them screaming jimmies. Almost instant destruction with the block looking like a seive from the rods sticking out.
    Retired mechanic,
    John

  13. #13
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    Here is a decent site for some insight:

    http://macdizzy.com/cyl_primer.htm

    Scott
    Consistency is a good thing....unless you're consistently an idiot.

  14. #14
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    mxtras, Excellent link!!!

    PoWaKid42, There are many fine aircooled 2-strokers. You must be sure to provide adequate cooling fins of material capable of heat transfer at the rate needed to properly cool the engine.

    As far as losing unburned fuel-air out of the exhaust, this is readily controlled. This requires a carefully tuned exhaust and results in a fairly narrow powerband. Usually, the higher the output the narrower the powerband. This now a fairly well developed science but back in the "old days" (when I raced) it was pretty much a black art. The above mentioned book by Blair explains it well enough to be understood.

    Olav Aaen also has a good book on 2-stroke tuning if it's still available.

    Keep working on it and good luck
    DZASTR

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    Thanks a lot for the help =D. Another question is the spark plug timing, i searched and found that the way that motocross bikes do it ,by example, is with a magneto, it provides the power and the timing, i preffer this metod, because i think that it is better that having a battery and a power generator conected to the engine. how do i make this type of ignition?

    I can make the engine water cooled but i will need to conect to the engine a water pump, i will see the best way to do it...

    Thank you

  16. #16
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    i saw this site: http://www.sportdevices.com/ignition/ignition.htm

    Its about a 'cdi programable digital ignition', this sistem has advantages to the magneto system? i think i can make this circuit, how do i programme it?

    Please tell me what you think that is the best solution for my engine.

    Thanks

  17. #17
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    PoWaKiD42, You can make the ignition, fuel input, exhaust system as simple or complicated as your knowledge wiil permit. High output 2-cycle engines are "elegant designs". Far more complicated than apparent.

    You could use the programable electronic ignition, add electronic fuel injection and if you like, adjustable exhaust port timing. Add to that adjustable length tuned exhaust pipes to vary the powerband up and down the rpm range.

    Personally I'd keep it simple on the first one. Reed valve intake, magneto ignition with timing adjustment, tuneable carburetor like Mikuni and an exaust system with a wide powerband rather than high power narrow powerband.

    To repeat myself, try to get a copy of Blairs book (or other competent authority). Re-inventing the wheel is a waste of time and effort. All the port heights, tuned pipe geometry etc. is in there. Also, pay close attention to combustion chamber design (squish band size, clearance to piston dome etc.)

    Basic engine volume ratios (crankcase volume / swept volume etc.).

    Many important details involved. If you already have that knowledge ignore everything I said.

    BTW, that Sportdevices CDI looks good.

    Good Luck,
    DZASTR

  18. #18
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    There are some things that need to be addressed before you start with the ignition and other attachments. Where is this engine going to be installed? If it is a weight problem when mounting in an aircraft then electronic ignition is better. If in a model vehicle or boat then magneto is okay.
    If you go electronic you maybe want to look at an RC model type. They are also programable but do not require the 12 volt battery. They run with a 4.8volt pack which is lighter. Also when you make your board with the PIC chip at first you do not need it. You can install a jumper from your pickup directly(hall sensor or points) to the SCR to trigger the spark. The PIC gives you your auto advance and if you need high rpm then you can install it later otherwise stay with fixed timing to get it running.
    John

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    PoWaKiD42, here is another contact www.aaenperformance.com

    They make and sell V4 2-stroke race engines among other 2-stroke stuff. Olav Aaen authored a couple of good 2-stroke tech books that may still be available.
    DZASTR

  20. #20
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    Designing and literally "bBuilding" an engine from the ground up is a VERY challenging and difficult task. Even noted engine building firms like Ford, GM, DCX, Cosworth, etc are known to farm out the design and construction of various engine components. Even they simply screw the parts together.

    Motec makes and sells an ignition system that "bolts on" to single cyl go-cart and motorcycle engines. Magnetos on race versions of chain and motorcycle engines often have the factory magneto's removed and a CD electronic ignition ala Motec bolted on instead.

    Why?

    Tthey perform better at high rpm and do fit into a smaller package space than the cumbersome magneto - even if/when you add a supplemental battery and/or mini-motorcycle alternator.

    If you are really going to "build" the engine, figure out what you REALLY can build and prepare yourself to designe and build THAT part of the project. However, to start the thread by saying "how do I build a 2 cycle?" which is then followed by " how to I build a magneto?" suggests that you may be trying to reach just a bit beyond your grasp - especially if you don't know how the most basic of ignition systems (magneto) works.

    I assure you that designing and making the mechanical stuff will be challenginge enough. Trying to learn how to generate and control the 30Kv or more worth of volts needed create a properly timed spark can be very difficult. Why? Because you can't see the electrons which is why you can't trust them. Anything you can't see that you have to create in order for the engine to run will cause difficulty. Besides, it is a PITA.

    This is only going to get far worse when the next "how do I do whatever" gets asked. And that will probably occure when it comes time to craft up a carburetor or EFI system. With all sincereity and candor, find and buy one (as in carb or EFI) - there are sites dedicated to those topics in their entirety.

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