Geoffrey

Cool, thanks for the info.

125shifter

I didn't notice any ignition problems during dyno tuning, but I do notice some high speed miss ever since a DE. Perhaps this is due to running one Pro-14 with 6 wasted spark coils? What would the symptoms be? Maybe I'll too have a Pro-14 for sale. Or someone could buy schnele's coils and mount and run a Pro-16 and I could buy his Pro-14 for the second.

m42racer

I would huess you may be suffering from a loss of Plug energy. I know you can drive 2 plugs from each CDI leg and 1/2 the energy, but 4 would be too much I fear. Yes, you may need another Pro 14.

DonE

Neil called me today and said a pro-16 is the way to go. You only use one vs two pro-14's for twin plug. Add 6 dual output coils, wire the 6 ignition channels, use the cam position sensor for sync, and away you go.

Geoffrey

Hmm, so that means you are running sequential ignition out of double ended coils, so you are wiring both cylinder's plugs to the same double ended coil. You'll definately get 1/2 the energy wiring it that way. While it may run the engine, double ended coils are not designed to be run that way and you will not have a peak performing ignition system.

DonE

OK - I guess I didn't understand him. Just after I heard the cost, I didn't take it any further. The car runs just fine the way it is.

m42racer

I'm sure you were told to change to the special Bosch Coil that can fire both legs at once. That is what I had to change over to. Like geoffrey stated, some of the Dual post coils need to run 1 leg wasted and the other firing. That special Bosch Coil can be fired at the same time. I believe its a transformer more than an coil. I may have that wrong, but I do know its special.

125shifter

Seems like the easiest way would be to run 3 ignition signals to the A, B, C pins jumpered to the D, E, F pins on the Pro-16b box to drive 6 waste spark coils. No need for a sync signal. Don could you PM the cost?

Geoffrey

Hi Simon, that may be, I don't know, but I'm having a hard time with it because of how the CDI system works. The spark energy in a CDI system is stored in a capaciter within the CDI box, not within the coil, unlike Inductive where the coil also serves as the storage device. In a CDI, the coils simply "step up" the voltage which is why they have very low resistance in their windings. Therefore, I can't see how the energy would not be 1/2 when firing 2 plugs at the same time.

m42racer

You are correct. With 2 plugs per Cylinder everything changes I'm told. The Coil that I had, (used) can be wired 1 per each Cylinder to make the setup alot cleaner. Regardless of the setup, once 2 Plugs are fired with a Dual outlet Coil, the Plug energy is 1/2. The other way with 1 Pro 14, I'm told, the energy is 1/2 again as each output of the CDI is driving 4 plugs instead of 2.

The only way to get max plug energy I'm told with 2 plugs per Cylinder is to run 12 Coils. My black engine ended up with 12 of those Ferrite Coils, but the cost becomes quite high.

The energy at the plug when 1/2 is still far greater than with our level of Inductive. Those Bosch Coils unlike many othe dual outlet Coils can be run both channels at the same time.

Geoffrey

I wonder what Bosch coils they are because for the last 10+ years, Bosch has been using only inductive style components, mainly because their ECUs (including motorsports) have built in ignition drivers for inductive type setups. I am aware of some racing CDI coil on plug units that look nice and I'd like to try them with a pair of pro 16s.

BTW, when running in waste spark mode (4 plugs from 2 coils or 2 plugs from 1 coil) the spark plug on the exhaust cycle consumes minimal ignition energy, somewhere around 10-15%. Remember the spark will take the path of least resistance which will be the spark plug in the air fuel mixture.

schnele

Geoffrey, just to gain some knowledge on the subject, when I was originally setting up my engine build you advised me on the double ended coils with the M&W Pro-14 it is also the same set-up that Stephen uses on his EFI conversions, my intention was to run sequential injection but a wasted spark ignition. For the sake of this discussion are you now stating that this is less than optimal?

Geoffrey

In general I do not like wasted spark ignition systems, however, due to the complexity of the dual plug 911 engine it is a COST EFFECTIVE solution and the M&W Pro 14 ignition boxes (2 of them) and the 6 coils represented the best performing wasted spark ignition system at that time. Since your engine was configured in wasted spark mode, the spark energy is going to the plug on the combustion cycle. It was a fine design and I like it better than the Denso 580 coil near plug (Corvette) inductive system that you are now running even though it is a sequential system.

Ideally, I would like a dual distributor with M&W Pro 10s, or a pair of Pro 16s with CDI coil on plug setup. That would be optimum, but costly.