Here is a decent site for some insight:
http://macdizzy.com/cyl_primer.htm
Scott
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Here is a decent site for some insight:
http://macdizzy.com/cyl_primer.htm
Scott
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
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
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
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,
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
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.
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.
Aw c'mon NC, why can't PoWaKiD42 suffer like we did? After all, I'm sure he has enough time to waste to say he is learning from his experience (aka failures) and still recover!!
PoWaKi, NC in his wisdom has a good point or two. Before you decide firmly to design from scratch, you might consider combining existing components to produce your target engine.
I see situations where very succesful Sports Car Club of America (SCCA) class C & D Sport race cars are made of combined engine components. For example, a custom do-it-yourself (DIY) engine builder made his own crankcase. He attached (6) cylinders [from (3) 2-cyl. engines] to his crank & crankcase. He also used the pistons & connecting rods from the above cylinders. This combination was (and might still be ) the US points champion in SCCA C & D Sports Racer class.
I myself made such wierdo engines for snowmobile and outboard motor boat racing (thats why I got kicked out of APBA sanctioned STOCK racing and was told to move to NOA where they allowed modifying) Many years ago.
But if you want to suffer like NC & I keep on trying.
Why should a budding tinkerer have to reinvent the wheel and/or re-experience an unmittigated disaster if they don't have to?
Yes, we learn from our mistakes but, BUT if you know that it is a mistake to jump off a bridge, do you still let someone do it to see if they might, just might see a different result from the same bad judgement/decision?
I think not.
Part of the benefit of a free form message board is to share information and knowledge - both good and bad experiences are here to be shared and learned from. Should the member wish to jump off the bridge in spite of admonitions to the contrary, they are free to go ahead and do so - I would tend NOT to however.
THere is one thing worse than being a dreamer. That is to be a dreamer who, in spite of admontions to not do something, they go ahead and do it anyway to "I'll show you" - especiallly something that really shouldn't be attempted by a rank rookie.
I've done that and occasionally have shown that the common thinking may need to be adjusted, just a bit. I've also had the "what the hill were you thinking" realization hit me because I didn't listen to the seasoned veteran. On occasion, however, with the support of sound research and engineering, I've confounded some veterans and moved on at a faster rate.
Dreaming is cool - I did my share. However, I also created some nightmares by NOT buying when I should have and tried to make too much on my own.
Ultimately, caveat emptor. You heard it here first.
I thought I covered that pretty much in #17 above. I think PoWaKiD42 can find his level then ask the right questions. Then the rest of us old farts can help him with our in (un) valuable information gathered over years of experience (self inflicted failures). As above and above that, try Blairs and others books.
PoWaKiD42, It might help us to help you if we would have some idea of your experience / education / knowledge base relative to 2-stroke engines.
Understand that most enthusiastic users of these simple?? machines have a very limited understanding of how they function. This is not an attempt to embarrass or humiliate anybody (myself included).
There are many "racing speed secrets" out there that are clever improvements in engine design. Many have been included in commercially produced products. Examples: 3-port transfers, 5-port transfers, P (power) ports, expansion chamber (tuned) exhaust and intake systems and many more.
When you started this thread, you mentioned starting with a small displacement single cylinder motor. Maybe we should go back to your start point.