does the ECU control the ignition in any way?

[newaccorddriver]

i was wondering if the ECU in our cars control the ignition system in any way. this is mainly for the fact that when i install megasquirt, i dont want to do anything spark related, and i dont want to keep the stock ECU for anything since it wont be useful to me. since the distributor is vacuum advanced, would i be able to ditch the ECU right away?

[Vanilla Sky]

no, it doesn't touch the ignition timing. this is one of the reasons for going to OBD1.

[newaccorddriver]

so it is all independent and the ignitor and such isnt controlled at all?

[bobafett]

the car has a TDC sensor and cylinder sensor, which is used in the ignition system, but there are no maps on the ECU that will control timing. there is a base timing that happens (i assume) with the assistance of the TDC and CYL sensors, but vaccum controls the rest.

i would not reccomend ditching the ECU altogether, but you may be intercepting these signals in order to allow mega squirt to do it's thing.

[newaccorddriver]

isnt the TDC/CYL sensor for fueling purposes since the distributor is in a locked position and run through engine vacuum? i thought the only thing the ECU does to it was open vacuum sources up for AC and stuff like that which in my case, really doesnt matter.

so, when i go to megasquirt for fueling, what purpose does the ECU still serve when i have nothing much for it to control(fueling wise)?

[bobafett]

honestly i am not sure... you may be right about the ecu not really doing too much. you will be one of the first, if not THE first to actually try MS on the pj0 though...

[newaccorddriver]

honestly i am not sure... you may be right about the ecu not really doing too much. you will be one of the first, if not THE first to actually try MS on the pj0 though...

come spring, or summer, this year, it WILL happen. if it wont, you can kick me in the right nut to your hearts content. being one of the few makes me feel a bit more special though

[shepherd79]

ECU uses TDC and crank censors for ignition triger.
Vacuum is used to advance the timing.
if you are going with megasquard you have to use diff distributor.

[newaccorddriver]

the ECU doesnt have any pinouts to the ignitor or anything

[shepherd79]

ignitor is not part of ECU. it is a part of distributor.

i want to correct myself. Stock 3G distributor has TDC and cylinder sensors.
Cyl sensor detects position of #1 piston as the base for sequential injection, whereas the TDC sensor serves to determine the injection timing for each cylinder.

the one you are missing for stand alone system would be crankshaft sensor. the crank Sensor determines timing for fuel injection and ignition of each cylinder a d also detects engine speed.

So if you convert to OBD1 distributor or use some other crank sensor you should be fine.

[newaccorddriver]

by technicality, megasquirt would actually run with the current distributor i have now since all it needs is a toothed wheel, and a VR sensor. that point aside, if the TDC/CYL sensors are for fueling purposes, then would i be able to ditch the ECU entirely? is there a thorough write-up on how the ignitors on our cars work?

[shepherd79]

i think you need to read up on how ignition works.
http://www.tegger.com/hondafaq/ignit...ion/index.html
http://www.hondaprelude.to/articles/...l/haltech.html
and this one
http://www.msefi.com/viewtopic.php?t...tributor+dizzy
the problem with using stock distirbutor is that it is setup to use vacuum advance. I would switch to diff distributor if i was you.

[POS carb]

here's how it works on my LX (no sensors on the crank, flywheel, etc), i doubt the LXi is any different. The TDC and CYL sensor are probably just for fuel injection control.

There is an ignition coil to raise the voltage high enough to spark in the engine.

There is a distributor that takes the high voltage from the ignition coil and splits it to the four spark plug wires as it rotates. It has a vacuum advance that causes the spark to occur earlier when the engine is idling, it also has a centrifugal advance for compensating for RPM.
There is an ignitor on the distributor that takes a ground (Blk), 12v+ switched (Blk/Yel), and a coil trigger output (Blu). The blue wire hooks up to the (-) post of the coil. The coil receives (+) from the Blk/Yel and also on the Blue wire until it is time to fire, then Blue switches to negative and allows the current to flow. The high voltage winding grounds through the spark plugs to the cylinder head.

So the Blk/Yel wire powers the system, the Blue triggers it. The blue wire is also used to control the tachometer, cruise control, fuel cutoff relay, it gives an RPM reference to the emmission control unit.

The distributor has a pickup coil inside of it that gives a reference to the ignitor

So in actuality the distributor has an internal cylinder position reference and it uses an ignitor to trigger the coil. It relies on mechanical ignition control (centrifugal and vacuum advance)

[lostforawhile]

wanted to update this, has anyone gotten rid of the single coil yet and gone to coil on plug ignition? with the two sensors aleady in the FI dizzy, and adding a crank wheel, couldn't a coil on plug system be added? the dizzy could be locked out of advance, and a cap put over it, it becoming just a sensor, When I was looking for a particular GM coil for it's bracket at the yard, I saw so many 4 cyl engines with this setup, I'm really suprised no one has done it yet.