Stock ignitor operation:
-IGT is the signal from the ecu telling the ignitor to fire the coil at a precise crank angle. This is the trigger for the ignition event and is the timing angle control signal from the ecu to the ignition coils. If the ecu calls for 30 degrees of timing, this signal is sent to the ignitor before the crank reaches this point. The signal goes high (+5v) and is held high until 30 degrees BTDC is reached. At 30 degrees the signal is pulled low (0v) and the ignition event/coil is triggered to spark. So.. square wave, 0-5v, triggers ignition on the negative slope.
-IGA/IGB are the ‘data’ signals that tell the ignitor which coil is to be fired. Simple truth table with four possibilities bouncing through these two wires. Jetjock has explained this in depth before and the toyo tech papers explain it well enough in the tsrm. Main thing to remember is they are 0-5v square waves. A binary 1 = 5v, 0 = 0v. Input from both signals is needed to properly select each coil. They change state at the triggering of each ignition event (the falling edge of IGT).
View attachment NewFile6.bmp
IGA/B signals
-3 transistors in parallel handle the high current. 1 per coil. Coils are charged until 7-7.5amps and then current limited until IGT triggers the ignition event. The dwell time that the coil is allowed to charge for varies between 3.5-6+ ms depending on rpm. Rarely is more than 4ms available though. Some form of built in rpm vs dwell is calculated in the ignitor. Assuming this is calculated based on the previous IGT or IGA/IGB signals.
View attachment NewFile2.bmp
Stock coil.
Blue is coil voltage showing dwell, current limiting and ignition event/burn time.
Yellow is current ramp, 100mv=1amp
-IGF appears to be triggered by an avalanche diode, once the coil voltage spikes above 50v or so, IGF goes high (+5v). Interestingly the Tach signal triggers at the same time. Probably why you see the tach jump around when there is a misfire.
View attachment NewFile7.bmp
Tach signal
Blue is Tach signal
Yellow is IGT signal
View attachment NewFile8.bmp
IGF signal
Blue is IGF signal
Yellow is IGT signal
Most ecu’s control the ignition coil dwell directly through the IGT signal. As the IGT signal goes high (+5v, turns on), coil charging begins. This is not the case at any point in the 7mgte ecu. IGT has no direct effect on coil dwell. The coils are allowed to charge before IGT is ever received. Even at idle, the longest possible duration for the dwell period, IGT is several 100uS late to the prom..
View attachment cccccccc.bmp
IGT and Coil signal
Blue is IGT
Yellow is coil
So the whole cycle looks like this:
IGA/IGB select coil to be fired - Coil begins to charge – IGT turns on – coil reaches 7amps and is held there – IGT turns off, ignition event triggered – IGA/IGB select next coil- etc..
The short story, its an integral part of the ignition system. Removal requires some rather simple Boolean algebra but potentially complicated dwell calculator. I haven’t spent time studying the transient events to see how dwell is handled. Once that’s understood a way to replicate it shouldn’t be to hard. My goal is true Coil on Plug with smart coils, 1zz or VAG style.
Next up, is300/ford/stock coil comparisons..
-IGT is the signal from the ecu telling the ignitor to fire the coil at a precise crank angle. This is the trigger for the ignition event and is the timing angle control signal from the ecu to the ignition coils. If the ecu calls for 30 degrees of timing, this signal is sent to the ignitor before the crank reaches this point. The signal goes high (+5v) and is held high until 30 degrees BTDC is reached. At 30 degrees the signal is pulled low (0v) and the ignition event/coil is triggered to spark. So.. square wave, 0-5v, triggers ignition on the negative slope.
-IGA/IGB are the ‘data’ signals that tell the ignitor which coil is to be fired. Simple truth table with four possibilities bouncing through these two wires. Jetjock has explained this in depth before and the toyo tech papers explain it well enough in the tsrm. Main thing to remember is they are 0-5v square waves. A binary 1 = 5v, 0 = 0v. Input from both signals is needed to properly select each coil. They change state at the triggering of each ignition event (the falling edge of IGT).
View attachment NewFile6.bmp
IGA/B signals
-3 transistors in parallel handle the high current. 1 per coil. Coils are charged until 7-7.5amps and then current limited until IGT triggers the ignition event. The dwell time that the coil is allowed to charge for varies between 3.5-6+ ms depending on rpm. Rarely is more than 4ms available though. Some form of built in rpm vs dwell is calculated in the ignitor. Assuming this is calculated based on the previous IGT or IGA/IGB signals.
View attachment NewFile2.bmp
Stock coil.
Blue is coil voltage showing dwell, current limiting and ignition event/burn time.
Yellow is current ramp, 100mv=1amp
-IGF appears to be triggered by an avalanche diode, once the coil voltage spikes above 50v or so, IGF goes high (+5v). Interestingly the Tach signal triggers at the same time. Probably why you see the tach jump around when there is a misfire.
View attachment NewFile7.bmp
Tach signal
Blue is Tach signal
Yellow is IGT signal
View attachment NewFile8.bmp
IGF signal
Blue is IGF signal
Yellow is IGT signal
Most ecu’s control the ignition coil dwell directly through the IGT signal. As the IGT signal goes high (+5v, turns on), coil charging begins. This is not the case at any point in the 7mgte ecu. IGT has no direct effect on coil dwell. The coils are allowed to charge before IGT is ever received. Even at idle, the longest possible duration for the dwell period, IGT is several 100uS late to the prom..
View attachment cccccccc.bmp
IGT and Coil signal
Blue is IGT
Yellow is coil
So the whole cycle looks like this:
IGA/IGB select coil to be fired - Coil begins to charge – IGT turns on – coil reaches 7amps and is held there – IGT turns off, ignition event triggered – IGA/IGB select next coil- etc..
The short story, its an integral part of the ignition system. Removal requires some rather simple Boolean algebra but potentially complicated dwell calculator. I haven’t spent time studying the transient events to see how dwell is handled. Once that’s understood a way to replicate it shouldn’t be to hard. My goal is true Coil on Plug with smart coils, 1zz or VAG style.
Next up, is300/ford/stock coil comparisons..
. Very well done sir.
