If anyone using the 4 pin HEI modules on a rotary could comment
that would be great. Do you experience breakup above 5 or 6K?
Would after market modules work better?

as such, i can use the trailing pickup to send signals to fire my leading only coils
- principally to use the trailing boost retard pot
its further sweeping in its range of movement than the leading pot
( i have more vac advance, and more boost retard )
and best of all, i can adjust the timing by pulling on the trailing pot !!!
( the old split adjuster )
bloody handy when FC and Dizzy with PS bracket making dizzy base hard to change !

my tip to one and all, particularly if confronted with s1 dizzy
ALWAYS check connection trigger polarity with a timing light
( simply redo the timing to be sure any inadvertent change in falling to rising edge signal has altered timing )
simply swap wires 6 ( sometimes 3 ) and 7 to re- reverse the signal

specifically check for a crossfire inducing the trailing to spark with the leading
( the dizzy button will only line it to the right chamber fortunately )
if you cant set the trailing timing
- and it appears to shift with the leading , its cross-firing
- the fix is usually swapping ( on s1 dizzy at least ) the trailing igniters 6 ( 3 ) and 7 wire

( but be aware the strong spark is prone to making inductive timing lights also pick up false signals, spread your leads , and get good ones )

in comparison the bosch BIM024 DFI for leading mod on a dizzy
has a lower than optimum fixed dwell for some of the rpm range
-to allow the dwell to be time optimised for the 4000- 9000 rpm range
( where the rotary really needs it to be at its best for power, not like OEM is down low for emissions )
at 9000 rpm the internal igniters fixed dwell period is about 80- 90% of the period between triggers
( investigation shows a 2.9 - 3.1 ms period is typical of that igniter )
the bosch BIM024 igniter loses out on the shorter average charge period at lower rpm
( to an ECU with a 3.25 fixed period, or to a duty dwell igniter or ECU )
but they begin to win when the available period time drops lower
and are ranged well for 4000 - 9000 rpm on a wastespark 4 cyl/ rotary
( and they win cause not many J109's are actually working like they where made 30 years ago )

the low down loss is not so bad as you think---
introducing wastespark has much reduced the low down unburnt hydrocarbons
and much improved many driving characteristics
- and they are better gains that a single long charge spark can bring
if you have bosch BIM 024 and HEI HEC coil in DFI mode
- MEC will outperform the HEC above 8500 rpm ( but not below it )
[ stephen you have dual MEC for leading coil ]


-------------------
the important point -

if ringing out a bridge past 9000 rpm on an ECU or with a J109 igniter type DFI mod
( wastespark leading application )
- you need the MEC, as it outperforms the HEC in any wastespark application above 8500 - 9000 rpm

any ECU running fixed dwell period should be brought below 3.0 ms above 9000 rpm
( or you may need to impose a 9000 rpm limit )
or retain the HEC coil combo, and revert to full sequential ignition
( reverting to duty dwell will optimise some of the losses down low when taking away the wastespark )

if wastesparking, be aware whats going on at 9000 rpm in the ignition !

Info from Bosch, raped from net
the details are not easy to find on the HEC C core coils or BIM024 !

peak primary voltage V rise times typical of a HEC coil
( time needed at that voltage to achieve maximum saturation for peak spark )
10.5 V =3.1 ms
12.0 V =2.6 ms
13.0 V =2.3 ms
13.5 V =2.2 ms
14.0 V =2.1 ms
14.2 V =2.0 ms
16.0 V = 1.7 ms

some more important BIM024 considerations when used with reluctor dizzy =
the BIM024 fire the coil on a 0.7 V zero crossing from a positive to negative trigger
( a falling reluctor pulse )
this is important to note, as incorrect phase polarity will shift the timing significantly at low rpm
ie
triggering on the rise will be dependent on the voltage raised
( and that is RPM related in a reluctor system )
so incorrect polarity will not only mean a significant timing shift
( which can be corrected with a timing light )
but also makes for an erratic trigger that moves with rpm at low dizzy speeds

- the HEI BIM024 module ( when its polarity is correct )
is intended to shift timing with decreasing dwell time and rising voltage ( RPM )
this is to maximise the dwell period at higher RPM
( its a angle based dwell system )
getting the signal polarity thing wrong will make for a system that shortens the dwell at higher RPM , and retards timing


what does that mean??
incorrectly polarised from the reluctor for its trigger signal
the BIM024 will have a timing shift at low RPM that requires the dizzy be reset to relocate the timing to the mark
also the timing point will drift as a result of
1: the air reluctor gap ( the volts generated by the reluctor )
2: also with the input voltage ( cranking )
3 :also the dizzy rpm ! ( irrespective of the centrifugal and vacuum advances )

when revved hard, its spark volts will drop away as the dwell period shortens
and it will pull timing at revs

- 1 degree every 1000 rpm

if, for example
i am trying things on my extend port LPG 13b
- currently modified , the dizzy has 40% of its curve trimmed
this allows me to work things thus ( mech numbers only )

40% x 25 = 10 degrees removed = 15 degree curve

set at 10 BTC degrees idle , my max timing without vac input would be 25 BTDC
( about what most mad extend port petrol engines would enjoy )

i think i want more boost
and knowing LPG likes high initial advance, but same or similar endpoints to petrol for optimum power
( rather than ping limited )

i would like to try things with 22- 23 degree endpoint
( allowing another 2 to 4 psi safety ceiling )
BUT without dropping my aggressive initial timing

- so
50% x25 = 12.5 degrees advance
so, 10 idle, 22.5 max

here-


the dizzy


a pile of indiscriminate screws, actually they all have a place, remember what they are
everything comes out, a screwdriver is all you need
( don't forget the one down centre of shaft , that ones hard )
the trailing pot arm is also fixed in by screw type fitting
remove the pots and the igniter modules
( mine are dummies for bridging through the BIM igniters )





its the weights that are the magic
bending in those spring posts has altered the spring rate, speeding it up
( you can get at them with thin screwdriver via top of assembled dizzy to adjust later )

the little nubs on top ride in our advance slots

- it really is very simple under there



our old advance slots, you can see i had previously altered them permanently, i wanna try a little more
( if you just use a washer cut into moons, it will be easily reversed on the belt sander )



OK, things at 50 % now, using the washer moon method


touch her up on the belt sander , you don't have much room to leave any tac weld high
touch her up more, and i can undo my move !



slam it together
( if gumby, mark things first before disassemble , but you find things more or less line up without much thought )

The Mopar system uses the positive temperature coefficient of the ballast resistor to regulate the primary coil current with changes in duty cycle (engine rpm). A simple, relatively reliable system for most daily drivers. The disadvantage with the ballast resistor is the slow response time of the resistor resulting in the field of the coil not being fully charged during sudden acceleration ie, a spark that may not be as hot as is possible with more modern systems. The GM HEI module is typically based upon a Motorola (now Freescale) MC3334 IC or equivalent. The MC3334 regulates coil current using an internal variable voltage reference. This internal variable voltage reference is able to respond much faster to changes in duty cycle resulting in a much hotter spark durring times of sudden acceleration and less destructive heating to the coil during low rpm operation. The MC3334 also imposes a 1 msec off time to ensure complete discharge of the coil field during a spark event. At very high rpms coil current is limited due to the slope of the coil's primary charging ramp time which is determined by VBatt and the primary impedance of the coil itself. Some good OEM coils are the Ford "E" core coils and the remote GM coil which is also an "E" core design. The MSD Blaster line of aftermarket coils are also very good coils. Don't be fooled by claims of HIGH VOLTAGE from the perveyors of coils. The voltage developed by the coil will only be as high as the break-over voltage of the plug firing, typically only a few thousand volts. When shopping for coils it is important to look for a coil with a high Joules rating and match the rpm range to your needs. If the coil manufacturer does not publish the joules rating of the coil, walk away and buy somewhere else. Don't use a race only coil on the street. It will just overheat and fail.