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| How Does the 2.8L Ignition Sytem Know Where Cylinder 1 is? (Page 1/2) |
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Romsk
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JUN 29, 05:55 PM
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I understand mechanical and electronic ignition systems. In have been studying various Fiero Ignition System diagrams and I understand it all including how the ECM and ICM control spark timing for advance, except...
What I can't determine is:
How does the Ignition System know when the distributor is at Cylinder 1? The ECM must need to know this for reference, to know which injectors to fire, correct?
The Pick-up Coil only has two wires and it makes a timing pulse for each of the 6 Cylinders, but I see nowhere in any diagram for a sensor (hall effect, coil, or otherwise) that is active only when Cylinder 1 is at TDC of its Compression Stroke.
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pmbrunelle
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JUN 29, 05:59 PM
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It doesn't know.
Injectors (all together simultaneously) fire once per crankshaft revolution.
Sometimes, injector phasing may be related to 1/4 TDC, other times 2/5 TDC, or else 3/6 TDC.
The stock fuel injection is crude.
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Spark is mechanically directed to the correct cylinder via the rotor in the distributor.
The ECM doesn't know which cylinder it is firing.
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Vintage-Nut
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JUN 29, 06:04 PM
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sleek fiero
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JUN 29, 06:22 PM
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It's pretty simple .you find compression stroke on #1 and set your timing from there. compression stoke find the timing mark and and your rotor will be pointing at #1 spark plug position.. If you had your distributor out same thing find #1compression stroke and install the distributor so the rotor ends up pointing at #1 spark plug wire position. then you should be able to set the timing from there .hope this helps you..there is one more step in setting the timing and that is there is a brown wire with white stipe near the battery that you need to disconnect before you do the final timing setting and reconnect after.
sleek
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Romsk
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JUN 29, 06:28 PM
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pmbrunelle and Vintage-Nut,
Thanks for the responses. From the wiring diagrams I was surprised to learn the odd injectors are on one ECM control wire, and the even injectors are on another wire. I just assumed it would fire the odd injectors for intake 1, 3, and 5, and the even injectors for 2, 4, and 6 intake. My initial idea was each injector fired independently, but that was until I saw the diagrams. But what you are saying is that both odd and even injectors fire all at the same time. Ok, I can see how that can work, but how does that make any difference (performance wise) than using just one big injector. I guess an injector spraying on its own intake valve helps the valve to stay cool. What else is going on inside the intake manifold, is all that air/fuel mist just swirling around in there waiting for the next intake valve to open? Doesn't sound much like Multi Port Fuel Injection to me [laugh].
The reason I asked is: I am developing an ICM bench test based on the Arduino UNO R3. I don't need to know where Cylinder 1 is to test the ICM on bench, I just wanted to fill in a blank that came up while researching the ICM and Fiero Ignition System.
Paul
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Romsk
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JUN 29, 06:39 PM
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Sleek Fiero.
Yes, I understand how to align a distributor, rotor, and crankshaft to align for cylinder 1 TDC, I have rebuilt several engines. My question is:
How does the ECM know when the distributor/crankshaft is at cylinder 1. There is no sensor or wire for that, the pick-up coil is for 6 cylinders, and according to others, the ECM doesn't need know. The Fiero fires all 6 injectors at the same time for every intake stroke, it is not independent injector firings like I first assumed.
Thanks.
Paul
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Romsk
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JUN 29, 06:43 PM
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Vintage-Nut,
Thanks for the link. In fact I found that same exact same page in a web search and it helped me to understand what is inside tye ICM, and not seeing anything to tell the ECM when at Cylinder 1... but now I know it doesn't need to as it fires all injectors at the same time, not just the odd even sides at different times.
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Patrick
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JUN 29, 06:43 PM
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| quote | Originally posted by sleek fiero:
there is one more step in setting the timing and that is there is a brown wire with white stipe near the battery that you need to disconnect before you do the final timing setting and reconnect after.
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Okay Bill, you've now certainly confused me with that comment!  Are you thinking of a different car? 
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Romsk
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JUN 29, 06:48 PM
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Patrick,
Ignore that response, he was telling me how to align the distributor to crankshaft cylinder 1 TDC. I know that.
My question was how does the *ECM* know when cylinder 1 is firing. It has been answered, it doesnt... all the injectors fire at the same time. Fieros used a very crude method of multi port fuel injection.
Thanks
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armos
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JUN 29, 07:08 PM
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From what I've seen, GM liked to use different decals and advertising terms depending on what type of fuel injection was being used.
Throttle body injection was usually tagged "Electronic Fuel Injection" or "EFI".
Batch fire port injection systems were advertised as "Multi-port" or "MPFI".
Cars with independently controlled injectors were advertised as "Sequential" and tagged with "SFI" or maybe "SPFI" under the hood.
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