Multispark

[Edward Hernandez R]

"Of course, most of this started out of a discusion about DIY EFI,
so the 100,000 mile tune up is kind of irrelevant.  But then, you are
not looking at this from a diyers point of view."

Guilty, as charged. I thought someone asked what's the beef with coil
on plugs, and I answered from an OEM's perspective of what's possible.

"What problems would there be in having one TPU channel fire two
coils?"

Okay, now I understand why you(and another poster) want to fire a coil
on plug system as if it was wasted spark. This is DIY, and you're
trying to save channels/outputs. This is starting to get out my
league, so can't comment on how you would do it(latches, AND gates,
other stuff  I've forgotten from college). BUT electrically(as opposed
to electronically), I see only one possible problem: coils made for 
coil per plug systems are designed for certain rise times based on 
firing once every two revs. Fire them more often than that and you 
risk running out of saturation time for the next firing.

Now, I'll put my DIY hat on and guess that you would probably use a 
coil that wasn't made for coil per plug, but instead was designed to 
fire once per rev or more often. No problem! In fact, some of you 
would probably test the coil of choice to determine it's saturation 
time and program yourself some kind of automatic dwell control for the
coils you choose so you don't overheat the coil/waste 
electricity(read, unnecessary alternator load). Certainly it is 
possible.

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