Hi guys, I can't seem to get my head around this If I have a basic 6-in-line engine with a distributor and an ecu, what exactly does the ecu do on the ignition side of things? The way I understand it, the rotor/distributor makes the spark go to the right spark plug. The rotor spinning also sorta takes care of the timing? If not, how exactly does it work? Thinking of running a 2jz-ge on lpg only, so ditching the ecu alltogether if possible.
ON the GE the ECU will take care of the injector mapping, O2 sensors, the air con, knock control, auto box but the distributor doesn't have vacuum advance if I remember correctly, so it will take care of that.
"so it will take care of that" is not an explanation I want to know HOW an ecu changes the timing, because in my mind the timing is sorta set with rotor speed etc.
Ignition timing is 2 things. It is sparking the right cylinder at the right time to actually make the engine run on all cylinders- The distributor does that. But what the ECU does, and and what ignition timing is from a tuning/performance point of view, is advancing and retarding the timing within that correct period where the cylinder needs the spark. Advancing or retarding for maximum power/reliabilty. The ECU does that, regardless of the car having a distributor. The only way a distributor does the above is if its got mechanical or vacumn advance, or indeed boost retard, which is a crude way of automatically doing it on a car without an ECU. Basically, having a distributor doesn't affect ECU functions in any way and isn't a disadvantage.
Hi Stavros, yes, those were the things I knew, I just don't get HOW the ecu does that! The ecu advances or retards the timing, but HOW does it do that with a "rigid" distributor, I mean, the rotor only has 6 positions in which it can be? Or are the "contact patches" of the distributor in such a way, that you have like +20 and -20 degrees of advance possible while the coil is "connected" to the right spark plug?
The ECU controls when the coil fires. That is advanced and retarded within the range required. No movement in the distributor.
So simple, didn't even realise that's how it done it... Is there a gwneral maximum distance between the rotor and point that needs to fire? Thanks
Depends on the car, but .100" is fairly normal. No setting it really, just buy the right rotor arm and dizzy cap, job done. They wear after a while, so the gap gets bigger, so makes it too easy to misfire, so you change for a new one.
Ah, ofcourse, the coil is connected to the ecu, not a continues power But since you are using a distributor, I guess there is a maximum amount of retarding or advancing right ? Because the rotor will not be "connected" to the spark plug outside of that range?
