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WhatI am saying is, the coil puts out voltage in both directions but because that voltage is assymetrical the plug only conducts current in one of those directions, hence my assertion that the coil puts out an AC voltage but a DC current flows on the secondary side. The plug is acting as a crude rectifier.
Do you have a diagram showing the diode you're talking about? There really shouldn't be anything (especially a diode or a rectifier) near either the primary or secondary coils.
There's no reason the spark plug shouldn't conduct current in either direction, for the time that the coil output is positive the arc would just fly from the center electrode to the ground electrode (on the plug) and when the output is negative the arc would fly from the ground electrode into the center electrode. That's why you see wear on both the center and outer electrodes on well worn spark plugs.
In order for a pair of coils to work at all you need a changing magnetic field, which is why the input of the primary coil has to be AC, and the output of the secondary coil has to be AC. The alternating current through the primary coil produces a changing magnetic field, that changing magnetic field then induces an alternating current in the secondary coil. If the secondary coil was rectified in any way you would be missing out on 50% or more of the potential spark energy that you'd have built up from that conversion.
Do you have a diagram showing the diode you're talking about? There really shouldn't be anything (especially a diode or a rectifier) near either the primary or secondary coils.
In order for a pair of coils to work at all you need a changing magnetic field, which is why the input of the primary coil has to be AC, and the output of the secondary coil has to be AC. The alternating current through the primary coil produces a changing magnetic field, that changing magnetic field then induces an alternating current in the secondary coil.
With a 100:1 coil when you apply normal polarity 12 volts to the primary, about +1200 volts appears at the secondary (this is the voltage that the diode has to block). All the while the current is ramping up during the dwell period the magnetic field is also changing (increasing) and so the secondary voltage stays at +1200V. When you break the primary connection, both the voltage across the primary and the secondary reverse polarity, and once the plug strikes, the secondary voltage drops from a very high negative figure down to about -1500V or so for the remainder of the arc. During this time the magnetism is again changing (decreasing) and so does the secondary current all the way down to zero (at low and medium speeds at least). So there is an AC voltage across each side of the coil by virtue of the primary being driven one polarity and allowed to flick back the other polarity. The secondary follows suit but only one of those polarities has enough voltage to reliable fire the plug, and so you have one-direction current flow in the plug.
Last edited by bandaid_boy; 09-06-2016 at 03:30 AM.
Nah, for the most part the spike in the primary voltage that would cause arcing in the points or damage to the switching transistor is a function of the primary leakage inductance of the coil. The primary and secondary are not perfectly coupled, and something like 10% of the total coil energy that is in this leakage inductance has to be dealt with by the points condenser or some voltage clamping thing across the switching transistor. When the transistor turns off to make the spark that secondary diode conducts so it is like a piece of wire and therefore has no particular effect. Only when the transistor turns on to recharge the coil does the secondary voltage reverse and so the diode blocks any secondary voltage.
And, with the lengthy conversation on AC versus DC, are we now saying that plug wire resistance DOES matter in terms of available spark at the plug? (the topic of which was why I brought it up in the first place)
From the measurements I have taken, resistive plug wire does the following: 1/ Reduces the strength of the *extremely* short initial current spike when the plug first fires. 2/ Shortens the duration of the arc once the plug has fired. More resistance = shorter arc duration. The available voltage and (within sensible limits) arc current is the same as if you had a copper wire plug lead. Because the coil has to deliver enough voltage to maintain the arc (~1500V) and also whatever voltage drop there is along the resistive plug lead, the current runs down to zero quicker than with a low resistance lead. This is an exact mirror image, so to speak, that more battery voltage charges up a coil faster and more required output voltage during the arc empties it out faster. Up one side of the hill and down the other side.
As for how much plug wire resistance, if your coil already has 4-6000 ohms secondary resistance then adding several hundred more with a slightly resistive wire is not going to matter much I wouldn't think. When you get into several 1000's of ohms that may be a different story. I like the idea of spiral wound low resistance wire. The inductance of that wire should lessen and broaden the initial current spike instead of just wasting it like a resistive wire would.
I read that Magnecor thing two days ago and can't remember all the details now, but one or two things stood out. They made a point of rubbishing plug wires that have an outer braided metal sheath. Specifically:
Like many in the past, Nology cleverly demonstrates a brighter free-air spark containing useless flash-over created by the crude "capacitor" (effect) of this style of wire. In reality, the bright spark has no more useful energy to fire a variable compressed air/fuel mixture than the clean spark you would see in a similar demonstration using any good carbon conductor wire. What is happening in such a demonstration is the coil output is being unnecessarily boosted to additionally supply spark energy that is induced (and wasted) into the grounded braided metal sleeve around the ignition wire's jacket. To test the validity of this statement, ask the Nology demonstrator to disconnect the ground strap and observe just how much energy is sparking to ground.
Any honest electrical engineer can tell you that what is happening is with the braid grounded the cable capacitance gets charged up until the plug strikes, then the sudden drop in voltage forces the cable capacitance to deliver a very high (and very short) current. If the ground connection is disconnected the cable capacitance hardly charges at all, and the energy that would have gone into the capacitance now goes into the spark from the ground strap to ground. Nothing unusual there.
Claims by Nology of their "HotWires" creating sparks that are "300 times more powerful," reaching temperatures of "100,000 to 150,000 degrees F" (more than enough to melt spark plug electrodes), spark durations of "4 billionths of a second" (spark duration is controlled by the ignition system itself) and currents of "1,000 amperes" magically evolving in "capacitors" allegedly "built-in" to the ignition wires are as ridiculous as the data and the depiction of sparks in photographs used in advertising material and the price asked for these wires! Most stock ignition primaries are regulated to 6 amperes and the most powerful race ignition to no more than 40 amperes at 12,000 RPM.
Physics being what it is, there are many systems that are very different and yet similar in many aspects. Compare a flywheel and a capacitor. With a flywheel, if you apply x lb/ft of torque it will increase speed at an exact amount of rpm per second. The kinetic energy in joules varies with the square of the rpm e.g 3x rpm = 9x energy.
With a capacitor if you apply x amount of amps it will charge up at an exact amount of volts per second, and the energy in Joules contained in the capacitor depends on the square of the voltage. 3x voltage = 9x Joules energy. So far so good.
With a flywheel, once you have gotten it revved up you can extract that energy as quickly as you like e.g. sidestepping the clutch. The faster you extract that energy the more torque comes out but for a correspondingly shorter time. Enough to break all sorts of driveline parts. What's more, the rate you can extract that energy has absolutely nothing to do with how long or short you took to rev up that flywheel. A big motor for a short time or a tiny motor for a long time.
With a capacitor you can charge it up gently over several seconds and discharge it quickly with a big splat. No different at all in principle with the flywheel. How quickly or slowly you charged it does not affect how quickly you can discharge it, and 4 nanoseconds of arc at 1000 amperes is not a big deal given the foregoing, so where do they get off saying
Most stock ignition primaries are regulated to 6 amperes and the most powerful race ignition to no more than 40 amperes at 12,000 RPM.
They are saying (truthfully) that the ability to charge the cable capacitance is limited, and therefore (untruthfully) it is impossible to get this very high discharge current. Actually it's the secondary side current at 60 mA and approx 1.2A respectively, not 6 and 40 amps primary side current they quote.
Whether those wires make a difference or not I have no idea. My point is Magnecor is here being deceptive in their spiel "truth about ignition wires".
Last edited by bandaid_boy; 09-09-2016 at 08:23 AM.
Ironically, many in the rotary community consider Magnecor to be the best wires around.
I'm sure Magnecor's wires are quite good. My beef was not with the wires but with their sales and marketing dept badmouthing other companies wires for what I think are invalid reasons. Of course, there is stuff out there that should be condemned, but I don't think this was one of those occasions. I have never used the Nology wires so I am not a fanboy either.
So Charles, in plain talk, you think the IGN-1A coil does not fire as efficiently at higher RPM as the GM coils you use.
Am I correct?
Legot, I am still learning about these things, and because of certain influences beyond my control, at times I have had trouble grasping things.
(Sometimes the little hamster falls asleep in the wheel )
If I understand you correctly, you are saying that you believe the 40% duty IS detrimental.
The reason I'm asking so specifically is that my 8 is still running great, but I have noticed at the upper end of the RPM range a type of momentary stumble or plateau that I had assumed may be because I forgot to clean the ESS when I installed the SBG kit, or perhaps some other reason I'm not aware of.
If there is a real possibility that the SBG coils are responsible, I would seriously consider re-installing the BHR kit without doing anything else, to see if that stumble goes away.
It would be a PITA to do it for no other reason, but I am willing to do it for the greater good.
Well, after pondering the possibility of my coils causing some hesitation issues at high RPM, I have recently tried to replicate the condition on several occasions only to find it won't do it anymore.
So, I have no idea why it was occurring, and it seems I can't definitively blame the IGN-1A coils.
o_0
This is definitely a very interesting discussion, as I have also purchased SBG's coil set, just like BC. My reason, on the other hand is more of an irrational one, if you would. I have been a SBG fan and supporter, because I know they are a big contributer in the RX7 community, so I just assumed that they know what they are doing with rotaries. Reading the logical, scientific, and mathematical responses from everyone - I was so confused, and cannot understand all of it - I am starting to feel like maybe I should not have purchased the kit, and that I could cause more harm to my car than good.
I am still trying to understand the comprehend the dwells of an ignition system, but based on what I am reading from you all, an IGN-1A coil is just not compatible with a performance of a rotary engine. This also makes me wonder why it seems so popular with the RX7 community?
I do agree with BC that I also like the setup of my current kit, because it just looks aesthetically nice. Also, because of the size of the coils, it gives off the impression that it is powerful and robust. Not to mention I even like the name "SakeBomb". These are all emotional reasons, not logical ones, so it is really irrelevant, and quite foolish. Though I know sometimes, as humans, we often make decisions based on how we FEEL.
Anyways, I know that performance changes from one car to another. Some cars just works, while others does not work with certain upgrades. However, I want to know, definitively, what is the best choice for my car? I guess the answer is already here, because all the information are here for me to make the most logical decision...
P.S. For some reason I thought IGN-1A coils have a duty cycle of at least 60/40? Because, for some reason, I thought during my research the IGN coils doesn't take as much time to rwcover it's energy (lower dwell)? Maybe I was misinformed?!
Christopher
Last edited by Sato Tatsuya; 09-13-2016 at 09:39 PM.
After some recent concerns, I'm still satisfied with it, as my 8 is running as good as it ever has at high rpm.
I have no idea why it was stumbling before.
0_o
As others have said, those are LS1 style coils. Which, work well for some cars. Our cars seem to prefer the D-585 coils, like what are used on the LS2 in the Yukons and such. I upgraded my coils from some no name D585's that came on the kit that came on my car to OEM ACDelco's and saw a 2MPG increase (which makes me happy) over the last like 8 tanks of fuel. I also have a pretty set driving schedule with little deviation, so, the test is about as accurate as it gets for not using a "sterile" environment.
i learned that LS1 coils don't work with the harness so I ordered four D580 pigtails. I got them soldered up today. Here's a pic of my cobbled together harness.
I still have to crimp the boots on the spark plug wires and make a bracket. I have 11 ga 4" wide aluminum flat bar. Mounting the coils so everything fits is another issue.
Tbh that mess of hoses under the hood is a little intimidating. I'll try to get it done on a weekend, weather permitting.
the weather was nice so I removed the stock coils and mocked up the ICE coils. The coils aren't dead and showing signs of overheating. I think I've found a very simple solution to the bracket. The plug terminal on the ICE coils are the same height as stock, and they're much beefier! I'm going to model something up in 3D today. I'll change out the plugs later this week. I find it strange that diy videos don't recommend anti seize for plugs or dielectric grease for wires.
ICE uses the D580 form factor, but they're not GM/MSD coils. Sorry, I don't know their current draw.
Totally unrelated, my air filter is filthy! Green air filter has pn2476. I'll pick one up in the spring. My car is in the garage for the winter. Also The zip tube had what looked like grease in it.
The white spots don't mean anything really and NGK and others specifically recommend against using anti seize on the plugs. Dielectric grease is also unneeded.
It's a balmy 9C today and I made some good progress on the install.
Thanks 9k. Even though it was a birch to remove the plugs, I didn't use anti seize on the new plugs. I did use a little dielectric grease though. Took me about 20' to replace them.
I fabbed a template to make sure everything will fit before I have the final bracket made. I'm happy with the bracket I've designed.
The coils are much bigger than stock and they fit well. I purposely left the harness super long...i may take out the extra length at some point.
ICE made the plug wires 15" long and left me to terminate the plug side. I made the wires 1" longer. The crimping tool was simple to figure out. Took me under 30' for all four wires and I've never done it before.
Holy geez hoses. Must be the hardest small engine to work on.
Got everything back together after work today. Barely squeezed the coils into the stock location and got the wires plugged in. Had to run two vacuum hoses to the other's nipple, and the long hose now runs over the zip tube. In all took 30 minutes. The billet bracket isn't perfect, but it keeps everything in place (it took a week to find the 3.5" long SS screws I needed).
Started up on the first try, idles at 750 rpm, pulls smoothly. Decent power for a 140k km rotary; not any more than it did when I first bought it. At least I have peace of mind that it won't die for a long time. And it's back in the garage for the winter. I'm very happy it's done and works Can't wait for spring.
Those little rings on the stock wires are there for a reason and should be replaced on the new wire set. They prevent the wires from touching the irons (engine).
09-05-2016, 06:41 PM
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