Re: [Amc-list] TBI fuel injection tuning...

[Frank Swygert <farna@xxxxxxx>]

So I may be wrong on the insulating qualities or whatever -- but I do know that all the bikes use is a coil with two wires, and both fire at the same time. I was told that the cylinder on the exhaust stroke would have a weaker spark than the one under compression. I don't know the physics, was just taking a semi-educated guess, but that's definitely the way it works! 

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Date: Mon, 24 Nov 2008 11:14:10 -0500 (EST)
From: adh@xxxxxxxxxxxxxxxxx (Sandwich Maker)

" From: Frank Swygert <farna@xxxxxxx>
" 
" "Lost spark" systems are typically used on motorcycles. My 1980 Suzuki
" GS1000G has two coils, two plug wires each. The cylinder with the
" compression and mixture hogs the fire, just as you surmised, and the
" one on the exhaust stroke gets a weak fire. If the carb is really out
" of adjustment, has a stuck float or something in that order, it makes
" for a great back fire though! That seldom happens, as there is rarely
" enough oxygen left in the exhaust to allow an explosion. 

those plugs must effectively be in series though.  as tom says, one
would hog the spark if they were in parallel.

if the fuel/air mix is insulating, spark voltage would climb along
with compression.  conversely, if the hot exhaust is at all conductive
spark voltage there would drop.  i don't know if either conjecture is
true, but if they are the exhaust plug would always fire first and hog
the spark if in parallel but present only a minor additional voltage
to the coil if in series.

i vaguely recall that the first dis setup for saab had only 2 coils
for 4 cylinders.

-- 
Frank Swygert
Publisher, "American Motors Cars" 
Magazine (AMC)
For all AMC enthusiasts
http://farna.home.att.net/AMC.html
(free download available!)

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