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| fang |
 Posted: Mon May 29, 2006 5:44 am |
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Junior member
Joined: 19 Oct 2005
Posts: 23
Location: Austin, Texas, USA
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I have been building a nice motor. It is supposed to be well balanced, stronger, lighter and faster. Lots of nice race bits from the likes of R.C., etc. I am almost done building it.
I have been wondering a lot about ignition issues. I want to get away from the points, but I ma not too sure how far I need/want to go. It seems to me that a n especially high revving, high powered motor would not want to have the spark plug fire once per stroke (twice per ignition cycle – as our bikes do when stock). It is my understanding that even the nice Dyna setups still fire every cylinder once every stroke.
So I have been looking into some of these old ARD Magnetos and the R.C. Engineering Power Pack Ignition System. You know, the ones that basically have some fancy belt-driven distributor instead of points (or whatever). They all seem to use just one coil. I have never seen one of these in person, and I don't really know exactly how they work, but they seem to address this concern of mine.
Can anyone tell me a little bit about them? Are they electric ignitions? Are they still points driven? Do they eliminate the battery? Are they worth the big $$ if I can land one? You get he idea.
Thanks for your help – I have my eye on a R.C. Engineering Power Pack Ignition System on evilBay right now. See it HERE. and I am trying to decide if I would be better off buying something like this or maybe a more traditional Dyna setup. Thanks for the input!
-fang |
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| Satanic Mechanic |
| Posted: Wed May 31, 2006 5:53 am |
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Moderator
Joined: 04 Sep 2005
Posts: 309
Location: Munich, Germany
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It is good to hear your motor is almost finished - congratulations! Let us know how it comes out.
Getting rid of the points is a good idea for any motor. What I would do is drop in a Dyna S and probably add a pair of Dyna coils as well. They will still have the lost spark, as they do not change the basic setup of two dual outlet coils, but basically there is nothing wrong with that.
If you are concerned about the spark energy, look at that: It is correct that each of the sparks get half the energy which is loaded into the coil. How much energy gets into the coil depends on the electromagnetic properties of the coil itself and the time the coil is charged. Charge time depends on the dwell and the RPMs, it goes up with more dwell and down with rising RPMs. (Spark energy stays at a more or less constant level from low RPMs up to a certain limit, because the coil is charged up to it's saturation at lower and mid RPMs - the coil cannot store more energy once it's saturated, the excess power is dissipated as heat)
I found the Dyna S tohether with Dyna coils are good for at least 11,000 RPM - they still deliver a good fat spark.
A magneto has two advantages: Spark energy on a battery powered system goes down with rising RPMs as charge time decreases. A magneto will generate more energy with rising RPMs, because the higher RPMs also induce more energy in the magneto.
On the down side, IIRC, these old magneto systems also use points, as do the distributor systems (RC used a VW Beetle distributor AFAIK).
The distributor system has another disadvantage: As it uses a single coil to generate all four sparks, the charge time for the coil is shorter than with the dual coil setup. I personally never quite got the idea behind these systems other that they look cool.
Again, what I would do is drop in a Dyna S and Dyna coils, and decent (copper) wires. That should be well enough, and hassle free as well. |
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| fang |
| Posted: Wed May 31, 2006 6:56 pm |
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Junior member
Joined: 19 Oct 2005
Posts: 23
Location: Austin, Texas, USA
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Thanks for your thoughts. Like I said, I really don't know much about the magneto systems.... except they certainly look neat!
Peace and grease
-fang |
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| Satanic Mechanic |
| Posted: Fri Jun 09, 2006 2:09 pm |
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Moderator
Joined: 04 Sep 2005
Posts: 309
Location: Munich, Germany
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Here's a nice article by Tony Foale on ignition systems:
http://www.tonyfoale.com/Articles/Ignition/Ignition.htm
The megnato systems look cool (which by itself maybe reason enough to get one), they eliminate the need for a battery and charging system (which is nice for racing).
But, above all, since the energy inducted goes up with the speed the magnetic field changes, the spark energy rises with the speed of the engine. |
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