Total Loss Ignition for Racing

Looks like batteries dedicated for total loss racing are up to 16v now. That's two extra cells. It probably starts off at a voltage near 17. Summit has some in their catalog, but I'm not sure if they have motorcycle size batteries. Since you will need a special charger anyway, you may want to go lithium to save some weight. There's a company called Antigravity batteries that may have something you could use. But I don't think it's going to be cheap.

Coils heat up with use, and that increases their resistance significantly. This reduces the current they draw. A 3 ohm coil will likely be wel over 4 ohms at race temperatures. Also, ignitions have around a 1 volt drop from the input to output when they are conducting. And let's not forget that there will typically be about .5v to 1v drop in the rest of the system for fuses, wires, and connections. So let's say the coils are around 4 ohms. The voltage, not running, is 12v. A dyna S draws current just about all the time from both coils. So for one coil you have 10v/4ohm = 2.5amp. For two coils you should be around 5 amps.

When you start running, the coils will eventually get hotter from the engine, and the dwell will not be 100% anymore, so the current may go down further at idle. If the engine is revved up, the voltage will go up, and so will the current. But ignitions use less current when the engine is revved because the percentage of time the coils spend at current-saturation reduces.

So in general, I would plan on about 3 to 5 amps average for a Dyna S running 3-ohm coils. And probably about 1/2 that for points running the stock 4-ohm coils. The precise amount will depend on how long the race is, how big the battery is etc. etc.

Here's a bunch of crap about coils if you need something to put you to sleep.
C:\60546active\VehicleTech\GPZweb\Ignition\IgnitionCoils\IgnitionCoils.html

loudhvx wrote: If the engine is revved up, the voltage will go up, and so will the current.

Is this true even without a charging system? If so, I don't get it...

loudhvx wrote: But ignitions use less current when the engine is revved because the percentage of time the coils spend at current-saturation reduces.

Good info, thanks. Back to thinking I need to run ammeter tests without charging system at various RPMs with both stock ignition and Dyna-S ignition (need to get the coils still, though).

loudhvx wrote: So in general, I would plan on about 3 to 5 amps average for a Dyna S running 3-ohm coils. And probably about 1/2 that for points running the stock 4-ohm coils

So the Dyna runs about double the draw - is there really any benefit to running it in a total loss system? It seems like the "hassle" of points (I find them easy to work with/adjust) is the only reason to go to the Dyna. That said, I could see the advantages in the Dyna-2000 or higher ignition (rev limiter, shift light, etc).

DoubleDub wrote:

loudhvx wrote: If the engine is revved up, the voltage will go up, and so will the current.

Is this true even without a charging system? If so, I don't get it...

Sorry, I should have said "with a charging system".

DoubleDub wrote:

loudhvx wrote: But ignitions use less current when the engine is revved because the percentage of time the coils spend at current-saturation reduces.

Good info, thanks. Back to thinking I need to run ammeter tests without charging system at various RPMs with both stock ignition and Dyna-S ignition (need to get the coils still, though).

And you have to do it while actually riding as intended because heat and time will play a factor. Also, the size of the battery will play a role since the voltage sag will affect the current. It's really one of those things where you make a first guess, set it up, measure it and make a correction, then do it over again until it's right.

The easy way is to just err on the safe side and get a little larger battery. Since it will be a deep cycle, and thus expensive, you want it to last for more than one race.

DoubleDub wrote:

loudhvx wrote: So in general, I would plan on about 3 to 5 amps average for a Dyna S running 3-ohm coils. And probably about 1/2 that for points running the stock 4-ohm coils

So the Dyna runs about double the draw - is there really any benefit to running it in a total loss system? It seems like the "hassle" of points (I find them easy to work with/adjust) is the only reason to go to the Dyna. That said, I could see the advantages in the Dyna-2000 or higher ignition (rev limiter, shift light, etc).

The advantages of the Dyna S are more about more powerful spark and consistent timing. There is not really an advantage or disadvantage of it over points relating to power use. Both use a fixed dwell angle, so both are about the same in that regard.

Points and Dyna S are actually both wasteful since they don't vary the dwell angle. Too long of dwell is where you waste all of your power in an ignition. The long dwell happens at lower RPMs, so if you don't idle the bike for very long, it's not much of a problem. At higher RPMs, the extra dwell angle is needed to charge the coils fully. If you think the bike will be idling for a while, you may want to consider the factory electronic ignition. It's marginally more efficient because it reduces dwell angle at lower RPMs and reduces waste. The Dyna 2000 also does this, but much better, however I don't know how much current it uses to run the box... probably not significant.

Each of the different systems really require different coils for optimum performance.

A poor man's method of saving power, in case you find yourself idling somewhere with points or Dyna S, would be to use a ballast with a switch that you can control.

To give you an idea of the numbers (rough idea), here are some hypothetical examples at an idle of about 1500 RPM. Pull up a chair and have some coffee ready.

Dyna S :
Using the above estimate, was about 5 amps at 12v. (10v on the coil).

A well designed electronic ignition using the same coils:
The coils charge in about .01 second. At 1500 RPM, that is 90 degrees. Because the dwell is short, to the point of just letting the coil get to the correct amount of charge, the signal shape can roughly be approximated to be a triangle. That would make it about 1.25 amps average for the dwell period. But it's actually a little higher, so lets round all the way up to 2 amps. Then let's take into account that the dwell is only 90 degrees, or a 25% duty cycle. So that means the average current for one coil will be somewhere below .5 amp. So for two coils, the total comes to 1 amp at 12v. (10v on the coil).

So as you can see, the difference is pretty huge at idle between the two ignitions.

The latter ignition would have to be able to increase it's dwell angle to nearly 360, at higher RPMs, though, to have the same performance as the Dyna S, with the coils chosen. The factory ignition is not that variable. But using faster coils reduces the need for such a wide range of dwell angle (360-90 is a 270 degree change). Using much faster coils, like the .5 ohm mini coils reduces the amount of dwell range, but requires a lot more precision in the dwell control.

Lets look at that, but at 14v. It should be rather interesting.

The coils (Dyna .5 ohm mini coils) need about .002 seconds to get to 4.5 amps. At 1500 RPM, that is 18 degrees. At 10,000 RPM, that is 120 degrees. So the ignition needs only to have a 102 degree change in dwell.

Now let's look at the amperage. The average amperage is 2.25 amps for the dwell period (using the triangle approximation, which in this case is much closer to a triangle). At 10,000 RPM, it's 120/360 duty gives .75 amp for one coil, that's 1.5 amps for both coils. Now let's look at idle. At idle, the dwell is only 18/360, so it's .1125 amps for one coil at idle. That means at idle, it's using a total of .22 amps for both coils.

Now that is a far cry from 5 amps, but that type of system requires a some decent circuitry to precisely control that dwell. I've been toying with that setup for a few years, using factory pickups/rotor and HEI module. It's close, but not complete, yet.

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There's a lot of calcs on this page, subject to review, so I may be editing this later.

So the benefit of the Dyna-S is then... ?

The only reason I'm considering one at this moment is that I have one. I still have to purchase coils for it (or even for the points ignition).

I would love to run something like the Dyna 2000, but that won't happen my first year out, and may not depending on what the benefits end up being. This is vintage racing, after all. The idea is to keep the cost down and have fun. I'm just trying to learn in the process.

Thanks for all the info Loudhvx!

You weren't kidding about those 16v batteries being expensive!

p10.secure.hostingprod.com/@www.voltphre...1_31&products_id=114

I think I'll probably start out with something like this guy: www.odysseybatteries.com/battery/pc545mj.htm

It claims to have an 18 minute reserve capacity with a 25amp load which should provide plenty for me for a 30 minute race and is even spec'd for a Kz1000-P.

The Dyna S can handle more current than the points, so you can get a more powerful spark. This does mean using more power, though.

DoubleDub wrote: You weren't kidding about those 16v batteries being expensive!

p10.secure.hostingprod.com/@www.voltphre...1_31&products_id=114

Yikes! I thought I saw some in the $250 range, but even that is not easy to swallow.

I think I would just stick with 12v, Dyna S, and 3-ohm coils for now. At least until you get a better idea of what you need.