How does the EZK retard the ignition?
08-11-2010, 02:29 PM
#31
Drifting
Thread Starter
Is the cam timing tied to the ignition timing in any way? In other words, if one uses a VR32 to adjust Cam timing relative to the crank, is the ignition timing also adjusted in the process?
The EZK can use the CPS to know where the crank is located and the Hall to know where the cam is located. The combination of these two would give it all the information needed to know which cylinder to fire and when. Then it adjusts the ‘base map’ according various inputs and conditions (MAF, RPM, Temp, TPS, Knock, Etc.). The base map is programmed in the EPROM and can be adjusted with a ST… as well as ‘other’ maps.
So if the cam is ‘adjusted’ does the Hall have the resolution to read this minute variation? Alternatively, does the CPS provide the precision needed for the ‘base’ signal and the Hall just indicates go/no-go depending on cam/valve phase? I guess what I’m asking is how does the EZK know where the engine is prior to it thinking about and determining how much to retard or not retard?
The EZK can use the CPS to know where the crank is located and the Hall to know where the cam is located. The combination of these two would give it all the information needed to know which cylinder to fire and when. Then it adjusts the ‘base map’ according various inputs and conditions (MAF, RPM, Temp, TPS, Knock, Etc.). The base map is programmed in the EPROM and can be adjusted with a ST… as well as ‘other’ maps.
So if the cam is ‘adjusted’ does the Hall have the resolution to read this minute variation? Alternatively, does the CPS provide the precision needed for the ‘base’ signal and the Hall just indicates go/no-go depending on cam/valve phase? I guess what I’m asking is how does the EZK know where the engine is prior to it thinking about and determining how much to retard or not retard?
08-11-2010, 02:32 PM
#32
Inventor
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08-11-2010, 02:36 PM
#33
Inventor
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08-11-2010, 02:37 PM
#34
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Cam timing does not affect igntion timing at all.
The CPS is the precision timing for the spark timing.
The Hall sensor only needs to give an approx position signal to tell the EZK which pot is firing. The timing slot is quite wide. As you say, a go/no-go on which cylinders are coming up to the firing stroke.
Cam adjustment within normal limits cannot affect igntion timing or render the Hall signal incorrect.
The CPS is the precision timing for the spark timing.
The Hall sensor only needs to give an approx position signal to tell the EZK which pot is firing. The timing slot is quite wide. As you say, a go/no-go on which cylinders are coming up to the firing stroke.
Cam adjustment within normal limits cannot affect igntion timing or render the Hall signal incorrect.
08-12-2010, 11:15 AM
#37
Rennlist Member
Thanks ! Jim Corenman's mails are also very informative, he is very knowledgable about 928s in general, the SharkTuner and of course his SharkPlotter program that complements the ST.
08-12-2010, 12:24 PM
#38
Drifting
Thread Starter
I just started reading Jim's manual on the Shark Plotter and OMG... it's amazing! I can't wait to start logging, plotting, and analysing data, but before I do... I'm trying to get a handle on a few more concepts... Hense this thread: https://rennlist.com/forums/928-foru...ml#post7810001
08-12-2010, 01:19 PM
#39
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A few random points on the discussion...
AFAIK, no 928 ever had breaker points - all were electronic ignition systems.
Electrical flow is generated by relative movement between a conductor and a magnetic field. In an ignition coil, the primary current builds a magnetic field for each spark event in the primary side of the coil - a few hundred turns of medium-sized wire. The field builds slowly enough that there is not much induced voltage in the secondary side of the coil - a few thousand turns of fine wire. When the current flow is cut off, the magnetic field surrounding both the primary and secondary sides of the coil collapses very quickly, inducing a high voltage surge in the secondary side of the coil, which then flows to the distributors and then to the plugs.
The knock sensors are piezoelectric crystals that are tuned to generate a small voltage when they see the precise band of vibration frequencies generated by detonation during the combustion event. The EZK ECU uses time-of-flight from each sensor to calculate which cylinder is detonating, and then retards the spark to that cylinder the next time that it fires.
The EZK ECU can't predict the future, so it can only retard the spark. It starts from the most-advanced time that the spark could ever occur, and retards it to the correct point.
Fun stuff. I wish that the control of the injection was at the same level of sophistication, but it doesn't make nearly as much difference there anyway.
AFAIK, no 928 ever had breaker points - all were electronic ignition systems.
Electrical flow is generated by relative movement between a conductor and a magnetic field. In an ignition coil, the primary current builds a magnetic field for each spark event in the primary side of the coil - a few hundred turns of medium-sized wire. The field builds slowly enough that there is not much induced voltage in the secondary side of the coil - a few thousand turns of fine wire. When the current flow is cut off, the magnetic field surrounding both the primary and secondary sides of the coil collapses very quickly, inducing a high voltage surge in the secondary side of the coil, which then flows to the distributors and then to the plugs.
The knock sensors are piezoelectric crystals that are tuned to generate a small voltage when they see the precise band of vibration frequencies generated by detonation during the combustion event. The EZK ECU uses time-of-flight from each sensor to calculate which cylinder is detonating, and then retards the spark to that cylinder the next time that it fires.
The EZK ECU can't predict the future, so it can only retard the spark. It starts from the most-advanced time that the spark could ever occur, and retards it to the correct point.
Fun stuff. I wish that the control of the injection was at the same level of sophistication, but it doesn't make nearly as much difference there anyway.
08-12-2010, 02:44 PM
#40
Drifting
Thread Starter
Now I'm going to pre date myself, but I've heard of the term points and condensers. I’m guessing that points also know as breaker points, but condensers sound more synonymous to a capacitor… not a coil. These were all the pre electronic days and were phase out about when??? (60’s or early 70’s maybe). I do believe you are correct when saying none of the 928 had points.
Next came the ignition control module which was an electronic device that replaced the points and condensers aspect of the ignition system but retained the distributor. I used to play with these as a toy growing up, but they really didn’t do much. The best I could to was attempt to break one open to get at the jelly inside. Ceramic substrates with screen printed circuits and die bonded ICs, I know… what they do/did I don’t.
Looking at the coil is slow motion…. sounds like it goes like this:
Primary side, which consists of larger wires with fewer turns, is enegergized
This creates a magnetic field which is coupled to the secondary side
The secondary side, which consists of smaller wire and more turns, is therefore energized
Power to the primary is disconnected
The magnetic field collapses causing the pressure (aka voltage) on the secondary side to shoot through the roof (or should I say… spark plug)
Further analysis…
Power is neither created nor destroyed in the process so what ever power is fed to the coil is released by the coil. Except for some losses due to resistance and some other minor jazz, which is released as heat, the majority flow right through.
Voltage is like water pressure and current is like how fast you can fill up a bucket. So in essence you have low pressure water entering in one side through a big pipe and high pressure water exiting out the other side through a tiny pipe, but the amount of water flowing out for most practical purposes is the same as the amount of water flowing in.
Power equals volts time amps. So if you feed in 12 volts and 1 amp of current that’s 12 watts. At the other end, you get about a bazillion volts and next to nothing current… but that bazillion times next to nothing will still basically equal the initial 12 provided.
Never really thought about how a coil actually works, but I think I got most of it now.
Next came the ignition control module which was an electronic device that replaced the points and condensers aspect of the ignition system but retained the distributor. I used to play with these as a toy growing up, but they really didn’t do much. The best I could to was attempt to break one open to get at the jelly inside. Ceramic substrates with screen printed circuits and die bonded ICs, I know… what they do/did I don’t.
Looking at the coil is slow motion…. sounds like it goes like this:
Primary side, which consists of larger wires with fewer turns, is enegergized
This creates a magnetic field which is coupled to the secondary side
The secondary side, which consists of smaller wire and more turns, is therefore energized
Power to the primary is disconnected
The magnetic field collapses causing the pressure (aka voltage) on the secondary side to shoot through the roof (or should I say… spark plug)
Further analysis…
Power is neither created nor destroyed in the process so what ever power is fed to the coil is released by the coil. Except for some losses due to resistance and some other minor jazz, which is released as heat, the majority flow right through.
Voltage is like water pressure and current is like how fast you can fill up a bucket. So in essence you have low pressure water entering in one side through a big pipe and high pressure water exiting out the other side through a tiny pipe, but the amount of water flowing out for most practical purposes is the same as the amount of water flowing in.
Power equals volts time amps. So if you feed in 12 volts and 1 amp of current that’s 12 watts. At the other end, you get about a bazillion volts and next to nothing current… but that bazillion times next to nothing will still basically equal the initial 12 provided.
Never really thought about how a coil actually works, but I think I got most of it now.
08-12-2010, 03:07 PM
#41
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Close, but not exact. The key is that electrical power is generated by relative movement between a conductor and a field. The relative movement in an ignition coil is the very rapid collapse of the primary field when it is switched off. This collapse cuts thru the secondary windings very rapidly, and generates a very high voltage output, and in the case of the later 928, it is a pretty high amperage output as well - enough to do serious damage to your body.
The developed voltage is controlled by the level required to punch a spark across the plug gap, plus the amount required to jump the gap between the rotor and cap, plus the minor amount required to overcome the resistor caps, etc. The voltage required varies with the cylinder filling - more fuel/air mixture (which is an insulator) packed in the plug gap will raise the required voltage from say, 20,000 volts to perhaps 40,000 volts (also affected by sharpness of the plug electrodes, cylinder temp, etc.).
(A top fuel dragster uses a magneto to fire the plugs. The system pops over a hundred amps across the plug gaps at the finish line, since the plug electrodes are burned well back into the insulator tips, and the ground electrode is burned away. The engine actually runs pretty much on auto-ignition the last part of the run, since it is running at the very edge of hydro-locking on the fuel.
Between fuel and normal part replacement, it costs between $5000 and $10,000 every run - if nothing breaks.)
The developed voltage is controlled by the level required to punch a spark across the plug gap, plus the amount required to jump the gap between the rotor and cap, plus the minor amount required to overcome the resistor caps, etc. The voltage required varies with the cylinder filling - more fuel/air mixture (which is an insulator) packed in the plug gap will raise the required voltage from say, 20,000 volts to perhaps 40,000 volts (also affected by sharpness of the plug electrodes, cylinder temp, etc.).
(A top fuel dragster uses a magneto to fire the plugs. The system pops over a hundred amps across the plug gaps at the finish line, since the plug electrodes are burned well back into the insulator tips, and the ground electrode is burned away. The engine actually runs pretty much on auto-ignition the last part of the run, since it is running at the very edge of hydro-locking on the fuel.
Between fuel and normal part replacement, it costs between $5000 and $10,000 every run - if nothing breaks.)
08-12-2010, 03:18 PM
#42
Drifting
Thread Starter
Oh, that's right... good point. An inductor looks like a short circuit to DC power... it's AC power that converts (steps up or down) or should I say flows through transformers.
So in essence, it’s the switching on/off of the DC power that is exhibiting AC characteristics. So that power in versus power out jazz isn’t exactly correct.
The main event that’s of interest is the collapse of the magnetic field (which happens to be at 90 degrees to the wires), as it cut across them.
I’ll have to ponder that thought some more.
So in essence, it’s the switching on/off of the DC power that is exhibiting AC characteristics. So that power in versus power out jazz isn’t exactly correct.
The main event that’s of interest is the collapse of the magnetic field (which happens to be at 90 degrees to the wires), as it cut across them.
I’ll have to ponder that thought some more.
08-14-2010, 06:18 PM
#43
Kurt, the EZF is a simpler ECU and does not have any knock-retard. It also doesn't have the hall-sensor signal, so it fires the spark for each cylinder on each revolution-- both compression and exhaust stroke. (This is a "wasted spark" method and is quite common. Since sparks are "free" there is no real waste).
The EZF also has access to engine vacuum, I don't know if it uses that instead of a MAF-derived load signal (from the LH) or in addition. In theory the MAF's load signal tells the EZK everything it needs to know about engine loading.
The EZF also has access to engine vacuum, I don't know if it uses that instead of a MAF-derived load signal (from the LH) or in addition. In theory the MAF's load signal tells the EZK everything it needs to know about engine loading.
08-15-2010, 08:03 AM
#45
Rennlist Member
The LH derived load signal of the 87> cars has the advantage that is electronically generated and so the load signal can be more accurately mapped for the load signal to the EZK.
