Multispark stuff and other thoughts

[Edward Hernandez R]

Several OEMs are doing this or designing engines that do this, namely,
 one coil per spark plug. Where's the beef?

1) No plug wires. Like someone correctly guessed in their post, if you
 have no plug wires, you don't have to contend with RFI and losses
across the wires. You still have to contend with RFI and losses within
the coil itself, but that's an existing problem. You also eliminate 
one connection when you eliminate the plug wires. That's one less 
thing to breakdown and leave you stranded. Sure, you just added a 
bunch of 12 volt wires to the each coil, but it's much easier to deal
 with 12V than 12kV-45kV.

2) Spark energy. Firing once every two revs means you can charge 
longer and deliver more energy per spark than firing three or four 
times each rev.

3) Multistrike/multiple spark. You can extend the multistrike rpm 
range all the way to redline instead of have to go single strike at 
3000-4000rpm.

Now it gets really interesting...

4) Combustion sensing. You can read the resistance across the gap 
after firing the plug and determine if you misfired or if it the flame
went out. You can then strike the plug again until you are satisfied 
that you've burnt everything! Jacob's Electronics claim they can do 
this with one coil firing many cylinders, but imagine how much better 
you can do it if you have an independant circuit for each cylinder. 
This is literally on demand multistrike capability and can extend your
 lean limits and/or reduce feedgas emissions.

5) Independant cylinder knock control. With two knock sensors, you can
determine which cylinder is knocking and alter that cylinder's spark 
advance without screwing with the remaining cylinders' spark advance.

So, the beef is, with coil per plug, you are one step closer to 
controlling several one cylinder engines instead of controlling a V6 
or V8 or I4. There are tradeoffs, but if you really need some of these
things(especially extending the lean limits and reducing emissions), 
you will pay for them.

Ed Hernandez
Ford Motor Company
ehernan3 at ed8719.pto.ford.com