Originally Posted by winders (Post 11202307)

It's not that simple.

Here is an interesting read:

Ignition Systems - Basics to High Performance

Inductive Discharge vs Capacitive Discharge Ignition (CD)

All of the above descriptions are examples of Inductive Discharge type ignition systems. The first high performance ignition system design was the Capacitive Discharge Ignition which uses high voltage stored in a capacitor to induce the few hundred volt pulse into the secondary instead of generating it in the primary as with an inductive system. In a CD system a high voltage oscillator circuit charges a capacitor. When it is time for a spark, another circuit discharges the capacitor into the coil primary. The voltage produced from the secondary is in the same proportion as with an inductive system. For example if the capacitor is charged to 400 volts, a 100:1 coil will produce 40,000 volts (or there abouts). CD ignitions have certain limitations depending on design. As an example if the oscillator is not powerful enough, the capacitor will not recharge quick enough and the ignition will have an RPM limitation. As you engineer more powerful oscillators, power consumption also increases. As the size of the capacitor is increased, the output of the ignition also increases, however the oscillator must be made more powerful. Certain tradeoffs must be made in design for a particular application.

Compared to inductive systems of the day, CD systems were more powerful since higher primary voltages could be discharged into the coils. One inherent limitation to a CD system is that the spark duration is short due to small capacitors used. As mentioned earlier, spark duration does the actual work burning an air fuel mixture, the voltage is used to initialize current flow across a spark plug gap. Due to the high primary currents of an inductive system, spark duration is naturally longer. Some Manufacturers of CD ignition systems provide multiple sparks to increase overall spark duration. Of course, as mentioned before, capacitors take time to charge up so there are limitations as to what RPM levels a CD system can maintain multiple sparks.

Today with improvements in technology, inductive ignition systems can be made more powerful with special transistors (Mosfets) switching the coil. These devices have higher breakdown/clamping voltages which allow the primary voltage to increase ( 550+ volts) resulting in higher secondary voltages. This coupled with the inherent long duration makes for a powerful ignition which has the capability of also going multi spark. Inductive ignition systems are emerging as the new high power ignition systems.

Originally Posted by Neil Harvey (Post 11890689)

I'm going to throw my oar in the water again.

It was never about which was the better system, in theory. For me, its all about which one is better in these large hemispherical chambers with domed pistons and offset plug(s).

Pent roofed chambers with volumes down in the 40's, with centralized plugs built for cars that have to comply with emission requirements need a long duration. And the fuel today does not burn as quickly as fuel from a few years ago.

Its all about the application, for me. Nothing else. I read where the discussions get heated over which ignition is better, but I have not yet read anything where the application was included in the argument.

We can disagree on anything. Simply, as a business building some Porsche 2V high performance engines, I choose what I feel is better, based on testing done, back to back. If others have found differing results, then that's ok too.