"Name That Outboard"

[RogerH]

Tim,
I'm still very curious about your very innovative ignition. I recently got the Wilbur Weeks dual plug heads firing on the Johnson RS by using one trigger firing the two CD modules, but used the dual coils, wired in series, per cylinder. Your approach is different as you have dual modules and coils per cylinder, and they are not wired in series as a result. Each module charges two coils, but split between the two dual coils. Is that correct? Thus the two modules charge all four coils (per cyl). This maximizes the spark energy by maintaining the energy (saturation) to the coil that the system was designed to deliver. With a new trigger system, you could "offset" the trigger to one module slightly to get more dwell, but that might be problematic to do within the confines of the flywheel. I still am "nervious" about the "alternator" type of CD system, but they seem to work very well.
If you are doing what I think you are, this shows the flywheel magnetics are able to trigger two CD modules in parallel. The way I did the RS shows the CD module is able to charge two coils in series. Your solution is electrically superior as the energy delivered to the sparkplug is maximized. I really need to test my system at max. RPM to know I have enough saturation in the coil to produce enough spark. Wilbur ran this system with good results, so will give it a try. Otherwise I've got to invest in two more CD modules and do what you have done. Don't have pictures I can access now, but can add them when I get home tomorrow if interested.
Bill, you have a lot of experience with ignitions, what's your take? Another great project Tim!
Roger

[Tim Kurcz]

Hi Roger,

In this case, there are two fully independent OMC CD2 ignition systems mounted under the flywheel 180 degrees apart - as close as tolerances permit. As each CD2 primary is capable of firing only one paired coil, the Piranha relies on the two systems firing two plugs each phased 180 degrees apart. This provides simultaneous spark for all four plugs.

My guess is your twin plug six can use the same method with split primaries to 12 individual or 6 paired coils. Good luck!

Tim

[RogerH]

Tim, I want to understand your terminology "split primary". I see that the dual coils are bolted (grounded) to a mounting bar. By split primary, are you attaching each primary wire to two coils, with one connection to each of the two dual coils per cylinder? If so, this puts those two coils in series with each other. I did the effectively the same thing by useing a nylon bolt to isolate one of the coils from the other in the dual coil package.
Isn't terminology great!!! Makes it hard to explain.

[Tim Kurcz]

Piranha coils are fired in parallel by a split (spliced) primary lead. The only trick for this application is using two fully independent CD2's 180 degrees apart to fire four plugs at once.

Your six should be easy by comparison; simply split the primary and feed both coils.

[Powerabout]

Interestingly one system halves the pak to coil resistance and the other doubles it.
I wonder which one the pak prefers?

[Tim Kurcz]

For Roger, Powerabout, et al.

Easy tests are to use an inductive timing light on each spark plug lead while the engine is running; this proves function and timing. You cross check with an inductive tach to confirm each system is delivering the same rpm.
These tests will tell you if you're actually firing 2 (or 4) plugs and at the correct time.

[Tim Kurcz]

Here are a few views of the Piranha rigged for testing - if only the weather would cooperate. It looks small for the boat!

[RogerH]

Interestingly one system halves the pak to coil resistance and the other doubles it.
I wonder which one the pak prefers?

Tim & others,
This is exactly what's been bugging me. With the coils in series, they both see the same amount of current. This provides the same maximum current to both coils that the CD is able to provide (given the combined resistance of both coils). With the coils in parallel each coil gets half of the available current from the CD. That current may be larger, as the coils in parallel will have half the resistance of the coils in series. This may be a wash as magnetic flux is directly proportional to the current, not the voltage. I thingkthat Powerabout is asking a good question. What does the power-pac "like". Neither application is what it was designed to do. The corresponding question is which wiring (series / parallel) provides the best spark at RPM. All I know is that Freddy Webb told me that Wilbur Weeks definitley advised that the coils should be wired in series for the dual plug heads on the RS. Hey Bill, can you provide some advice on this???

[RogerH]

Here are a few views of the Piranha rigged for testing - if only the weather would cooperate. It looks small for the boat!

Tim, Very impressive!!! Why am I not surprised, everything you do is excellent and full of detail! Let me know when you will be racing this, I'll try to get there.

[Tim Kurcz]

Hi Roger,

I understand your concern and need clarification. How exactly are you wiring the coils in series?