austinramsay

Can someone explain to me the exact function of the ignitor and the process of how it works? Im still a little confused. A good detailed explanation would be preferred

t_g_farrell

iTrader: (1)

So the ignitor is basically a switch that takes the weak magnetically induced signal from
dizzy as the lobes of the reluctor passes the leading and trailing magnetic pickups. This signal is
used to collapse the field in the coil instantly. This causes current to flow out of the coil through
the spark plug wires as the field collapses in the coil and causes a spark to be
emitted in the plug.

Heres a whole thread on it, did you try a search at all:

https://www.rx7club.com/1st-generati...s-work-203202/

austinramsay

Wow I have no idea how i missed that thread. Sorry about that. That helps out a lot! But I have another question now that I know how they work. Why is the coil's negative side connected to the ignitor? I understand it completes the circuit (kind of like a fast switch), but the igniter has 12v going to it, how does it complete the ground? What does the ignitor do with 12v it has going to it once that magnetic pickup passes it? Sorry if these questions sound dumb i know in my head what im trying to say, just hard to write it haha

j9fd3s

iTrader: (3)

think of the ignitor as a set of solid state points, and you're not far off.

bumpstart

first.. there is two types of igniter...

the igniter used in the FC coils is a "dumb" type.. it is merely a fast acting transister relay


its job ..and the job of all igniters ultimately is to hold the negative wire from that coil to earth
( through the igniter base ) to allow the coil to build a field
on instruction..( from the ecu ) the circuit is broken and the field collaspses and fires the secondary windings, and you get a spark

the time the ecu holds the igniter ( and coil negative ) to earth is called dwell
this ecu controlled igniter gets its trigger signals as square wave 5v signals from the ecu
( called TTL .. transister to transister logic )


in terms of a dizzy igniter,, they are called j105 ( s1 ) and J109 ( s2 and s3 )
.. and similar to inductive igniters made for GM HEI dizzies
then it has an extra role to achieve

it is no longer a simple transister relay switch .. it is much smarter than that


this is why this style of igniter is called a "smart" igniter while the other type is "dumb"

it sees the inductive signal from the pickups .. these signals are known as variable reluctance signals
the voltage of the signal will increase with rpm
.. and the trigger point.. know as the "zero crossing" point.. about 0.7 V will shift slightly with revs

this j105 or j109 ..or bosch BIM024 type igniter .. has to calculate the change in frequency
( rpm )
and the change in signal voltage spike

to gauge the changes in acceleration between previous ignition events .. so as to PREDICT the correct point at which to initiate dwell before the next spark event

ie.. it has to make a smart guess as to when to begin to clamp that coil negative to earth

so that when triggered for a spark ,, it has achieved the full dwell saturation
( the bim024 aims to make 7 amps of current )

this involves some complicated electronics.. and indeed there is a miniature transister brain in there