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Fire a coil from another coils primary

lenny1

New Member
I am fitting an eight plug head to a four cylinder engine. The current ignition runs two double ended coils in wasted spark mode and the two channels control dwell by monitoring primary current. The primaries are earthed by two igbt's in the ignition box (dyna 2000). I need to add another coil to each channel triggered by the primaries. I have bosch bip373 coil drivers and ixd1604 inverting gate drivers (the signal will need to be inverted). Any ideas how I can connect to another coils primary and get a signal that will control a bip373? When the coil current is interrupted to create the spark there is a 300 volt spike on the primary then oscillating around 30v while the spark is happening before it drops to battery voltage. Is this a use for an optical isolator?
 

lenny1

New Member
I would need to purchase four coils half the resistance of the current coils, of which I currently have two spares already. I also believe I would get a more powerfull spark running separate coils. I am looking for the best spark possible with the current equipment. There must be a way of using the primary to supply a logic signal to the extra coil drivers.
 

shortbus=

Well-Known Member
Why do you need the Bosch coil drivers? Isn't that what the Dyna2000 is for? Every time you add some new driver or other component into the ignition chain you are going to need to modify the advance curve, due to the propagation delay of the added components. From the little I looked at the Bosch drivers they are used for the Megasquirt that doesn't have built in drivers, but the Dyna does have them built in.
 

lenny1

New Member
I don't think you understand what I'm trying to do. I need an inverted logic signal from the primaries to trigger the bip373 coil drivers to power an added coil to each channel. The ignition box will not "see" the added coils so your comment about "propagation delays" seems irrelevant. Part of the reason I want to do it this way.
 

shortbus=

Well-Known Member
So you think there is a way of doing it with no propagation delay? You do understand that logic chips, that would normally be used for something like inverting a signal do have a propagation delay listed in their data sheet, don't you? And without looking I'd bet the bip373 shows one too.

You are just making a 2 plugs per cylinder set of heads aren't you? Why not modify the reluctor ring or what ever the engine is using to signal the timing then use 2 of the Dynas? Or just wire four coils into the existing Dyna? Then each coil would be firing both plugs on one cylinder. You really haven't given much information on your motor or what you really want to do.
 

lenny1

New Member
So you think there is a way of doing it with no propagation delay? You do understand that logic chips, that would normally be used for something like inverting a signal do have a propagation delay listed in their data sheet, don't you? And without looking I'd bet the bip373 shows one too.
I am aware of propagation delay which for most logic devices is in the low microseconds range. A problem for high speed/accuracy/frequency systems, which this application is not. I have read research that found advantages from slightly (microseconds) offsetting the sparks anyway.
You are just making a 2 plugs per cylinder set of heads aren't you? Why not modify the reluctor ring or what ever the engine is using to signal the timing then use 2 of the Dynas?
You seem so obsessed with propagation delay yet you suggest two separate ignitions which you could probably never synchronise as closely as a single system with its propagation delay. Then theres cost, weight and more failure points. All important here.
Then each coil would be firing both plugs on one cylinder.
In wasted spark mode you cant run both leads to one cylinder,they must go to different cylinders to work.
You really haven't given much information on your motor or what you really want to do.
What do you think I left out that's relevant, ring gap, oil viscosity?. I don't understand why you say that. I made it very clear "what I really want to do", if you don't understand maybe your not the person I need help from. Or will this develop into typical forum " I'm smarter than you" childish crap.
 

shortbus=

Well-Known Member
OK, since I was the only one willing to even give you some help, and my help isn't what you want I'll bow out.
But I do dispute what you said in the statement,
In wasted spark mode you cant run both leads to one cylinder,they must go to different cylinders to work.
Just how in the world do both plugs care or know they are in separate cylinders???

Most people come to forums to get other ideas(for free) when they can't figure things out alone. It's called "brain storming". But you don't seem to be one of those type of guys.

Aircraft engines , many Harley racers and top fuel drag racers have done this for years with no problems but you seem not to want or need any help, so why ask on an electronics forum?
 
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lenny1

New Member
Aircraft engines and top fuel racers use two separate magnetos firing separate plugs in each cylinder, for two different reasons. Nothing to do with wasted spark ignition. Wasted spark relies on one cylinder being on the compression stroke and the other lead connected to a cylinder on the exhaust stroke. The great majority of spark energy is developed across the plug under compression, the plug in the exhaust cylinder will give a feeble spark. Next two rotations of the crankshaft, the previous exhaust cylinder is now the compression cylinder and the major spark happens in that cylinder. If you connect both leads to one cylinder both ends of the coil are trying to fire under compression and no spark will occur. This is why all wasted spark engine are wired this way.
Your passive/aggressive tone, as though you were correcting me was bogus. Almost everything you said was wrong. Where is the "help" you talk of? I'm all for brainstorming, but it requires that the participants have at least some grasp of the problem. Sorry if I'm being over the top but I've had enough of people answering posts with an agenda instead of really trying to help.
 

shortbus=

Well-Known Member
Your passive/aggressive tone, as though you were correcting me was bogus. Almost everything you said was wrong. Where is the "help" you talk of? I'm all for brainstorming, but it requires that the participants have at least some grasp of the problem. Sorry if I'm being over the top but I've had enough of people answering posts with an agenda instead of really trying to help.
Call it what you want. But it seems like you are (from your, "people answering posts with an agenda") comment are the one with the agenda. You are looking for someone to pat you on the back and say how smart and knowledgeable you are, that is an agenda.



Have you even looked at how the Dyna is wired on the primary side? The coil is triggered, sent to ground,inside of the module, so where are you going to get the signal you want to control the bip373 from?

The great majority of spark energy is developed across the plug under compression, the plug in the exhaust cylinder will give a feeble spark.
And to state how the wasted spark works is just another way of showing you're out of your league with this. It is harder to create the spark in the cylinder being compressed than in open air, like in the cylinder on the exhaust stroke. This is just simple physics.

This along with an earlier statement about dely in the spark on one plug being OK. Do a Google on detonation or knock in cylinders.

And I sked about you engine to determine if it is even going to give any added power output. Flat chamber heads don't get any extra from 2 plugs per head but hemi chambers do. That is the reason that aircraft and top fuel use them. And you lead right back into my argument for using two Dyna modules by bringing up two Mags.
 
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lenny1

New Member
And to state how the wasted spark works is just another way of showing you're out of your league with this. It is harder to create the spark in the cylinder being compressed than in open air, like in the cylinder on the exhaust stroke. This is just simple physics.
I came to this forum hoping to get help from someone who knew what they were talking about. Instead you have hijacked this thread with ignorance.. Who has the agenda?Instead of attacking me, why don't you spend two minutes researching wasted spark ignition to see if you are correct or not. Who is out of their league?
You are looking for someone to pat you on the back and say how smart and knowledgeable you are, that is an agenda.
I don't have to "pat myself on the back" ,you are just embarrassing yourself with your lack of knowledge of the subject. This thread has degenerated into you making stupid statements. Do I have an agenda by not agreeing or is it you by not Knowing what your talking about? Stop being such a fool and do some research before you open your mouth.
Have you even looked at how the Dyna is wired on the primary side? The coil is triggered, sent to ground,inside of the module, so where are you going to get the signal you want to control the bip373 from?
Wow, more loudmouth ignorance.. If you actually read and understood the question before opening your mouth , you would know I already described
this. To say you cant get a signal from a grounding input is more ignorance. Primary voltage goes from virtually zero with coil current flowing to battery voltage when coil current stops and a 300v spike as the coil fires. Getting a signal is not the problem, dealing with the 300v spike is. and is what my question was about. (whos out of their league?)
This along with an earlier statement about dely in the spark on one plug being OK.
I will use your agenda language. Do you really think you can physically time two magnetos to fire within microseconds of each other. Do you know what a microsecond is? Do you know what "dely" is. Do you know the mistake I made in my wasted spark description? Do you know whos really looking for a pat on the back? You do know this don't you?
And I sked about you engine to determine if it is even going to give any added power output.
You say "to determine" as if you know what your talking about(more agenda). I'm guessing with your attitude of opening your mouth before you think that you know as much about engines as you know about electronics and ignition systems..
That is the reason that aircraft and top fuel use them.
Aircraft engines use two separate ignitions for safety (redundency) Top fuel because they have to ignite an almost liquid charge.
And you lead right back into my argument for using two Dyna modules by bringing up two Mags.
Did you think of that obvious solution yourself? I explained why I am trying to go down a different route, but your agenda wont accept that. You are a perfect example of why it is so hard to get an intelligent answer to a problem on the internet. Thanks for hijacking this thread with your ********. I will not replay to your moronic crap. Do a fact check on every STATEMENT you have made idiot. Hopefully someone with some knowledge and no agenda will help.
 

shortbus=

Well-Known Member
If your done ranting.

While what you say about how the 2 output ignition coils work is true in a car that uses them, it isn't right when they are used in a situation like you are wanting. The coils, if put on a bench and fitted with plugs and plug wires WILL fire both plugs at the same time. Having the plugs in two separate cylinders is NOT REQUIRED. That is just how the OEM chose to use them. I have a small machine shop and drilled and tapped a set of Harley cylinder heads for a guy, to use two plugs per cylinder. He used 2 coils from a GM V6 that were for wasted spark, they used both plug leads from a coil to one cylinder and it worked fine.

And back to your 2 magnetos not being able to be timed to fire simultaneously you seem to forget they are both infinitely adjustable for timing. It is mechanical driven from the cam shaft and then split into two gears diving the mags. You run the engine and time one, then put the timing light on the other and time it.

And that is how using two Dynas would work, one for cylinders 1-3 and the other for cylinders 2-4 or what ever your engines firing order is.
 

lenny1

New Member
I cant help myself, you are comedy gold. You have dug yourself a pit of ignorance and are trying to dig out with more desperate ignorance.
While what you say about how the 2 output ignition coils work is true in a car that uses them, it isn't right when they are used in a situation like you are wanting.
WTF, wasted spark is wasted spark and is exactly the situation I am wanting, the principal is the same.
The coils, if put on a bench and fitted with plugs and plug wires WILL fire both plugs at the same time. Having the plugs in two separate cylinders is NOT REQUIRED. That is just how the OEM chose to use them.
Firing plugs on a bench at ambient pressure has little to do with firing plugs in a motor. Wasted spark coils are designed to fire one plug on compression,one on exhaust. 80-90% of coil energy is released across the plug on compression where it is needed, 10-20% across the plug on exhaust. Firing two plugs on one cylinder splits coil energy 50-50= two weak sparks. To quote you when you were trying to be a smartarse "its just simple physics". This may sort of work (badly) on a low compression/speed Briggs and Strat...….sorry Harley Davidson, try it on a motor with 12:1 compression and 10k redline and the motor would not be happy.. How much did you charge the chump for your "performance" mod? To say OEM's "just choose" to do it the way they do is more of your desperate ignorance. You know more than them.
I have a small machine shop
How do you type this crap with all those missing fingers.
And back to your 2 magnetos not being able to be timed to fire simultaneously you seem to forget they are both infinitely adjustable for timing. It is mechanical driven from the cam shaft and then split into two gears diving the mags. You run the engine and time one, then put the timing light on the other and time it.
What a gem. I don't "seem to forget" (more agenda bull). And you got it wrong. I've been licenced aircraft engineer for 35 years. Maybe you can teach me all about aircraft ignitions too. You can't physically time two magnetos within microseconds of each other except by pure chance. I don't think you have any appreciation of how small a microsecond is.

And that is how using two Dynas would work, one for cylinders 1-3 and the other for cylinders 2-4 or what ever your engines firing order is.
How ironic. The very setup you mention is the perfect setup for a stagger fire engine like a Hurley. Yet in your wisdom you chose a very inferior setup.
I guess you have totally kidnapped this thread so I might as well have fun with it.
 

rjenkinsgb

Active Member
The simplest solution is likely to connect a second Dyna 2000 unit to the same crankshaft sensor.

It would probably need one connection (sensor power feed) omitting - the makers should be able to provide details of how to connect it.


Anything involving picking up from the coil primaries is going to need a lot of filtering and it will be pretty much guaranteed to generate false signals, as the coil back EMF and resonance waveforms cannot be distinguished from the actual drive signal from the ignition module.

If possible at all it would almost certainly need some extremely complex processor based electronics to track the revs and dynamically adjust the filtering & edge detection.
 

shortbus=

Well-Known Member
just incase anyone else comes to this thread in their research into dual plug cylinder heads and wasted spark -
Twin plug combustion
Since the earliest gasoline engines, some have used twin spark systems. These have two spark plugs in each cylinder. Each set of plugs is supplied separately. There may be several reasons for this: reliability (typically aircraft), starting, or better combustion performance by initiating the flamefront at opposing points simultaneously (e.g. Alfa Romeo). These are not considered as wasted spark systems, as their sparks all take place after the useful compression stroke, rather than "wasted" in the exhaust stroke. From here - https://en.wikipedia.org/wiki/Wasted_spark

This is the reason Harleys, Hemi drag racing engines and the new Dodge hemi cars and most aircraft engines use them, because of the hemispherical cylinder heads. Twin plugs allow a better flame travel and more output power.
 

lenny1

New Member
I need a laugh today. I am certain that you are stupid enough to think that the above information somehow backs up the crap you write. The internet is overrun with fools like you who only know enough to confuse the issue and sprout their guesses as though they were facts. Or maybe you heard it at the pub from your equally knowledgable friend, maybe the Harley guy you made the killer ignition for. I have looked at some of your other posts, you have a real talent.
 

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