Sequential COP questions & research
#41
And, as to why this is needed, you discharge the coils half as often compared to the present wasted spark setup so:
1) Your coils would last twice as longer (theoretically speaking).
2) You would have a lot more spark energy available and therefore, all of the spark energy available due to capacitive discharge can be exploited. In essence this would mean you can open up that spark plug gap even more.
1) Your coils would last twice as longer (theoretically speaking).
2) You would have a lot more spark energy available and therefore, all of the spark energy available due to capacitive discharge can be exploited. In essence this would mean you can open up that spark plug gap even more.
2) No, it's not gonna be a lot more. The coils charge and discharge. I don't have my books and formulas, but doubling charge time doesn't double spark. If the coil gets 99.5% charged before you spark, and then you give it twice as much time to charge, your working on getting that last 0.5%. Granted as RPM increase the time the coils have to charge decreases, but that doesn't mean spark power drops linearly with time.
But get er dun. I'm MS II so If I ever do COPs I wanna do them sequential, since I already have a crank wheel and plenty of outputs.
#42
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I'll buy the increased longevity concept. Fewer firings, less heat. Maybe.
Not sure about the "Spark Energy" concept, though. That is almost entirely a function of dwell time, and we're not running into a dwell limitation. For an engine turning 8,000 RPM, running wasted spark, there are 133 ignition events per coil per second, or 7.5 milliseconds between each ignition event. With the stock coils, we typically run ~5ms dwell, and with the COPs we run even less (somebody help me out here- 3ms? 3.5? Something like that)
Point is that once the primary winding is fully saturated, increasing the dwell doesn't get you anything except a damaged primary winding. And with wasted-spark, there is more than adequate time to reach full saturation.
Ok- to be purely academic, if the coil fires half as often, then the windings will run *slightly* cooler, the DC resistance on the primary will be *slightly* lower, and therefore the saturated charge current will be *slightly* higher. But you'd need a pretty accurate scope to notice.
Not sure about the "Spark Energy" concept, though. That is almost entirely a function of dwell time, and we're not running into a dwell limitation. For an engine turning 8,000 RPM, running wasted spark, there are 133 ignition events per coil per second, or 7.5 milliseconds between each ignition event. With the stock coils, we typically run ~5ms dwell, and with the COPs we run even less (somebody help me out here- 3ms? 3.5? Something like that)
Point is that once the primary winding is fully saturated, increasing the dwell doesn't get you anything except a damaged primary winding. And with wasted-spark, there is more than adequate time to reach full saturation.
Ok- to be purely academic, if the coil fires half as often, then the windings will run *slightly* cooler, the DC resistance on the primary will be *slightly* lower, and therefore the saturated charge current will be *slightly* higher. But you'd need a pretty accurate scope to notice.
#44
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This is true. The supply wire running to the coils is kinda puny, hence the "Cap mod" that folks are talking about now. Charging one coil vs. two means less drop across the V+ supply wire. Increasing the voltage available at the coil would raise the saturation point.
#45
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OEMs run sequential COP because it extends the lean misfire limit. Guess we dont really need to run that lean, except off-boost.
Anyway, I'm going to compare both and see if there's a difference or not. Sometimes things don't always follow theory.
Couple of quick questions for you guys:
1) If the 94+ CAS is magnetic (VR), then how can it give the same signal as the 90-93 optical (Hall) CAS?
2) The COPs that you guys run now, is it inductive coil or CDI?
Anyway, I'm going to compare both and see if there's a difference or not. Sometimes things don't always follow theory.
Couple of quick questions for you guys:
1) If the 94+ CAS is magnetic (VR), then how can it give the same signal as the 90-93 optical (Hall) CAS?
2) The COPs that you guys run now, is it inductive coil or CDI?
Last edited by The_Pipefather; 04-30-2008 at 12:40 PM.
#46
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The signals are the same between the two CASs because they both contain an active circuit which provides a squarewave output via an open-collector driver (that's why they require an external +12 supply to operate). By contrast, most VR sensors that we see in Ford EDIS applications or DIY crank triggers do not contain an active driver- they emit a raw AC waveform and thus require an external circuit to derive a TTL-compatible squarewave from them.
#47
Ok I went to the yard and picked up a CAS. I have some interesting findings for you guys:
1) A Ford Festiva has the exact same optical CAS as the 90-93 miata, except that there is only one inner slot. It looks the same as the pic Joe posted, except that the inner lower slot isn't there. This would give the required 4 + 1 pulse.
1) A Ford Festiva has the exact same optical CAS as the 90-93 miata, except that there is only one inner slot. It looks the same as the pic Joe posted, except that the inner lower slot isn't there. This would give the required 4 + 1 pulse.
#48
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No, I believe The Pipefathers observation was that the Ford CAS is a direct fit, both electrically and mechanically, into the Miata. Thus, no need to dismantle anything, just remove the Miata 4-2 CAS and install the Ford 4-1 unit.
#54
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Once you've dealt with the matter of having one cam pulse per cam revolution, all you need to do is enable SparkC and SparkD as outputs in the software, and the build a pair of spark output drivers to mirror what you've done on the primary (D14/D16) drivers.
#57
Also I remember when building the harness that your supposed to pair pin 32 and 33 together as well as 34 and 35 for the spark out. In theory couldn't you just keep them separate and run the triggers individually off each pin? Again I know nothing about circuit design.
#58
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Spark D is a little weirder. You remove R1, and wire to the bottom pad of where it came from. Then build (in the proto area) and circuit which replicates the LED driver circuis (you can omit the LED itself) and connect R1 through a 1k resistor to the base of the new transistor.
Also I remember when building the harness that your supposed to pair pin 32 and 33 together as well as 34 and 35 for the spark out.
#60
MS2-Extra Hardware Manual
Sequential Injection Code for MS2
MS2-Extra Ignition Hardware Manual
Frank's Westfield MX5 - Megasquirt
I've been looking to do the same stuff and these pages are all you need.
Sequential Injection Code for MS2
MS2-Extra Ignition Hardware Manual
Frank's Westfield MX5 - Megasquirt
I've been looking to do the same stuff and these pages are all you need.