flyback transformer ignition

[NiHaoMike]

Has anyone tried to develop a better ignition system based on flyback transformers? It can be designed for a higher voltage than a standard ignition system. The spark plug gap is then widened, so the voltage and therefore the energy stored in capacitance is increased.

I've heard that someone tried to install high voltage capacitors in parallel with the spark plugs, except the timing got thrown off by the charging delay and the engine ran very poorly. But if a flyback transformer with a higher current output is used and specialized control circuits installed, couldn't that problem be solved?

[wikityler]

Is the goal to try to get a larger spark? What advantage does this have?

[NiHaoMike]

It would become apparent when you do a simple experiment with a flyback transformer and a small high voltage capacitor. Without the capacitor, the spark is weak. With the capacitor, the spark becomes brighter and louder. And the longer the spark, the more energetic the spark becomes provided the flyback transformer can supply enough voltage.

[KitCarlsonEMS]

I built a high energy system with a follow-on energy supplied by a capacitor. The capacitor discharged to prolong the spark, no initial delay. The plug made very loud pops and bright light. The follow-on supply that charged the capacitor to 300V could be switched off to test, with and without. The test car was a VW Beetle air-cooled engine. The stronger spark, resulted in a better idle during warm-up. The negative - plug wear was very significant!

I went on to build an Engine management system and used waste fire for simplicity.

KitCarlsonEMS Homepage

More info another post in this forum.

[KitCarlsonEMS]

Here a picture of the spark system used to test on lawn mower engine. Note HV supply not shown. See small fly-back coil (the type used for flash ignition).

[almightybmw]

Did you consider using platinum plugs to offset the increased plug wear? Many seem to enjoy 100,000 miles without problem.

[KitCarlsonEMS]

A conventional plug lasted about 1K miles. The electrode was rounded and the gap increased about 0.01". I think the energy is sufficient to vaporize a Bosch fine wire platinum in a few sparks. I did this over 10 years ago. This was before other platinum plugs. The spark sounds like a small fire cracker going off. Visually the spark is a white ball of light about 0.25" in diameter. I could have reduced the capacitor value for less energy. The seat of the pants dyno showed slight improvement only under condition such as too rich or lean of fuel mixture. The complexity of the system made me think, reliability could be poor. I also worried about burning a hole in a piston.

[vtec-e]

Try a ball nose on the plug. Plugs seem to to want to wear to this shape so you could just form te tip to that shape.
I wouldn't worry about burning a hole in the piston. Detonation will cause that. You may find yourself having to adjust the timing to take care of the fact that the fuel is igniting that little bit quicker.

ollie

[NiHaoMike]

If the spark sounds like firecrackers, it is probably too powerful.

[KitCarlsonEMS]

I agree, more is not always better. If I ever get a dyno, I will know for sure.