Dual ignition on auto engines without dual plugs
Quite often, one hears people discuss ways of converting auto engine cylinder heads
so that dual plugs can be installed, totally disregarding the fact that these auto engine
heads were never designed with plugs in weird locations. Improper fuel burn, heat buildups,
and more misery is lurking around the corner. And why go through that trouble
when there are easier and probably much more reliable ways to do
things? Drilling new holes and covering up old ones doesn't make me feel
warm and fuzzy about reliablility, to be honest.
When looking at an ignition system, consider what parts are reliable and
which ones aren't:
Basically, we have the following parts:
So in the total picrure, you'd be looking at ways to double the pickup and
coil, and the electrical system if you'd like.
There is a way to do this:
- Open the distributor and mount a second pickup 180 degrees from the first
one. You might need to construct a new base plate to mount these pickups to.
When doing so, make sure it is made of non magnetic material such as
aluminum. Since the reluctor has four equal sides, both pickups will now
fire at the same time.
- Each pickup feeds its own coil. If you really wanted to, you could feed
one coil through a backup battery that is topped off through a diode. Another
way would be to imitate the Potez setup (one side is fed by the battery,
the other by the alternator, and can be separated by a switch). Look at
the Potez coil ignition text for more on this.
- You can't simply tie the outputs of both coils together, as the
destruction of one of them would probably bring the other down as well.
Luckily, racing experience in the US has produced an item called a "coil
joiner". Basically this is two series of high voltage diodes that allow two
coils to be joined to a single distributor. NAPA sells them for around
$100(?) (they are on the web). The package looks like a disc with three
ignition "towers" on top of it, one for a ignition lead to the distributor,
two for two coils. Failure of one side will keep the other side running.
- From the distributor, one rotor will feed single plugs per cylinder.
Simple, foolproof, tried and true and probably covering 95% of all ignition