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Coil Packs and Dwell Time


belize1334
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Galant VR-4 org Post #: 920233 posted 08/04/10 01:28 PM     Remind Me!  Send Private Message   Edit Post      
I've been reading threads about dwell time ever since I put in my COP setup. It runs quite well actually but I wanted to be sure that I'm not giving up performance in ways that I don't notice.

The primary argument against COP seems to be that, when wired in series, the Intrepid/300m coils don't have the same dwell time as OEM coils and so they don't fully charge in time for the ignition event. In parallel their dwell times are lower than the OEM coil-pack (or so I heard) and are thus able to full charge... but the igniter can't handle the current draw from a 0.5 Ohm impedance load.

So here's my thought. Clearly the intrepid/300m coils were meant to be charge at 12v since they're not actually intended for wasted spark. So, drop the "wiring in series in order to protect the ingiter" philosophy and address the problem of the igniter not being stout enough to handle the load from two coils. How about running two OEM igniters in parallel, each driving a different "bank" of coils. That is, two igniters being driven by the same ECU signal, but with outputs for 1-3 and 2-4 respectively. Or, alternatively, run the two igniters in TRUE parallel with input and outputs fully shared so that they behave as one and then run the coils in parallel as well.

Would two igniters play nice if they were driven off of the same ECU output? Since they're transistors I don't imagine they would draw too much current from the ECU... but would they interfere with each other?



Roger B. Scott
'91 Belize Green


Edited by belize1334 (08/04/10 01:30 PM)

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Galant VR-4 org Post #: 920262 posted 08/04/10 02:51 PM     Remind Me!  Send Private Message   Edit Post      
This may help. web page



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Galant VR-4 org Post #: 920298 posted 08/04/10 04:27 PM     Remind Me!  Send Private Message   Edit Post      
I have wondered about running the same set-up with my COP two.
I hope this thread continues and gets deep and full of knowledge.



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belize1334
well bread and nobly conceived
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Galant VR-4 org Post #: 920654 posted 08/05/10 06:56 PM     Remind Me!  Send Private Message   Edit Post      
I've got an extra 1G coil that I'll take down to the EE lab and test the inductance of the primary coil. Then I'll pull my COP and do the same. This should settle, for once and for all, how the charge time requirements of the chrysler coils compare to OEM coils and whether the stock dwell times should be altered when running COP.

As for the voltage issue, I don't see how the chrysler coils could possible store as much energy as OEM when configured in series as mine are. I'll be able to make a more exact statement to this effect once I've measure the inductance but my instinct tells me that if you want good spark then they should each see the full 12v. To that end I'm going to keep this dual-igniter in mind and see if I can get it set up and running.



Roger B. Scott
'91 Belize Green

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Galant VR-4 org Post #: 920721 posted 08/06/10 12:02 AM     Remind Me!  Send Private Message   Edit Post      
Keep me posted, I am very interested in this and will be following you in this adventure. In the last few months it seems that everyone who was running COP set-ups have switched back, blaming the coils for weak spark issues. I know our factory transistor can't handle much without getting overloaded. I am using mine in series like everyone else. I love my COP due to the smoother idle.

Good work and thanks for getting into it and getting it all tested, I look forward to the results.



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Galant VR-4 org Post #: 920748 posted 08/06/10 02:54 AM     Remind Me!  Send Private Message   Edit Post      
I have an automotive genius friend attempting the same thing with the two ignitors for his COP setup, 300m coils as well, IIRC. Will definitely update here if I hear any specific results from him. He is also planning some type of heatsink to keep them cool from what I understand.

I'm interested to see the results.

However, I still don't understand, even running two ingnitors, how it would be better than running a DIS-2, for example, with the COP setup, as it has not only been covered more, but many have yielded excellent results for those that do need the extra spark, despite our stock ignition setups being pretty good up to 500HP from what I understand. If it's not broke, why fix it?

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broxma
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Galant VR-4 org Post #: 920750 posted 08/06/10 03:10 AM     Remind Me!  Send Private Message   Edit Post      
Oh ye of little faith.

click

Same post but actually got it working properly. System is still on my Evo and running like a champ. If you continue read from that point you see I made that system work very well. Post 90 in the same thread has all the part numbers from your local store.

I have a COP system right now but I am probably switching over to this system in the next few days.

Tell your friend with the heatsink idea that Ford coils off the new trucks already have a integrated heatsink. Also, we tried the dual ignitor system on a few cars and could never get it working proper. It became an issue with timing. Not engine timing, but timing between the coils. When you are talking periods in the range of 50ms, having two ignitor only a few ms out of sync screwed it up. He may have better luck however. I actually make mention of a dual ignitor idea in the EvoM post a bit into it.


/brox



I am big into recycling though and if your not into sacrifice or burnt offerings, you may want to stick with 93 octane.

/brox


Edited by broxma (08/06/10 03:13 AM)

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belize1334
well bread and nobly conceived
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Galant VR-4 org Post #: 920815 posted 08/06/10 12:08 PM     Remind Me!  Send Private Message   Edit Post      
I do really like that setup and the fact that you've got it working with a DSM igniter makes it even more attractive. The reason that I'm continuing to try to get more out of my intrepid coils is that I like the clean install with no cables and I've already got the setup built.

As for the DIS-2, I don't think that there IS an advantage to dual igniters over something like that other than the fact that I can probably get on at the junk yard and have it all running for the cost of my soldering time. This is an adventure in cheap, DIY solutions to known issues.



Roger B. Scott
'91 Belize Green

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broxma
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Galant VR-4 org Post #: 920821 posted 08/06/10 12:37 PM     Remind Me!  Send Private Message   Edit Post      
The Intrepid COP I built has worked decent thus far but I am now at a point where I am concerned about its ability to maintain spark. I am looking at two options.

First, buying brand new Intrepid coils. The ones I get are junkyard captures and while I have 50 of them, I know of no test procedure to differentiate between good and really good ones.

Second, just move over to the GM/Aurora coil setup using MSD coils. I have a set of VatoZone GM OEM replacement coils which would probably be fine but I think I am going to spend a little more on it this time since I am expecting more from the Galant than I did from the Evo.

If I could verify a coil with a higher natural voltage and better dwell time I would make a plate for them to test them out but information on such things is often not available. I do have some Toyota coils from a V6 Camry or something that appear beefy but who knows how they perform in reality.

/brox



I am big into recycling though and if your not into sacrifice or burnt offerings, you may want to stick with 93 octane.

/brox

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belize1334
well bread and nobly conceived
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Galant VR-4 org Post #: 920833 posted 08/06/10 01:14 PM     Remind Me!  Send Private Message   Edit Post      
More on this...

My current plan is to attempt to run a '90 Power TR (J122) in parallel with the '91+ Power TR (J722T) that I already have. My reasoning for this is that both units should satisfy the same energy demands but the '90 unit doesn't have the integrated tacho module which will (hopefully) avoid some confusion in terms of which unit is talking back to the ECU. Also, I have an extra '90 in my hand from the Talon that I parted and I figure the harness for it should be easier to find since people cut them out when switching to '91+ ignition setups. My only concern is getting the wiring to work out so I'm on to trying to understand the circuit diagrams...

According to the '90 FSM, the 5-pin power transistor operates as a variable ground for the primary coils which are always powered. The ecu sends a signal to pins 2 and 5 which close the pathways from pins 1 and 6 (respectively) to pin 3 which is a common ground.

By contrast, the '91+ power transistor appears to have two more pins which work in conjunction as the tacho module...



It looks like 7 and 2 open pathways from 8 and 1 (respectively) to 3 which is common ground. Then, there seams to be an on-board IC which buffers the signals from 8 and 1 to create an output signal. 6 would seem to be the VCC for this IC.

So, as far as I can tell wiring the '90 in parallel with the '91+ is as simple pin-mapping (2,5,1,6,3) from the '90 onto (7,2,8,1,3) on the '91+. This should essentially double the current rating of the "effective" system while leaving it's down-stream functionality untouched.

Anybody have a '90 plug/harness that they want to donate to this project?



Roger B. Scott
'91 Belize Green

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Galant VR-4 org Post #: 920851 posted 08/06/10 02:08 PM     Remind Me!  Send Private Message   Edit Post      
Interesting project you guys are working on.

Quote:

Anybody have a '90 plug/harness that they want to donate to this project?




Pm me your shipping address, (and if you can wait untill monday,) I'll get one in the mail.

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belize1334
well bread and nobly conceived
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Galant VR-4 org Post #: 920876 posted 08/06/10 03:22 PM     Remind Me!  Send Private Message   Edit Post      
More on this...

I just got back from the lab where I bench tested my current COP setup (intrepid coils wired in series) as well as my spare OEM coil-pack.

Intrepid coils in series:
Primary Resistance: 0.8 Ohm
Primary Inductance: 2.9 mH

OEM coils:
Primary Resistance: 0.8 Ohm
Primary Inductance: 3.9 mH

As you can see, the intrepid coils actually match the intended resistance of the OEM coils when wired in series. That means that, given sufficient charge time, both configurations would come to the same final current value of 15 Amps (I = V/R = 12v/0.8Ohm). Now, somebody quoted that the spec'd current is only 6 amps. This corresponds to a charge time of roughly (1/2) the characteristic time. So, if 6 Amps is in fact the typical current then the dwell time of the ECU is t=(1/2)L/R or ~1.75ms.

Now for the interesting bit...

I plotted the current as a function of time for both configurations (found by I=Io * (1-e^(t/tao))) and then plotted the stored energy for this current for each configuration (found by E = (1/2) L I^2). The results clearly show that for charge times shorter than the characteristic time of the OEM coils (just under 4 ms), the intrepid coils (with lower inductance) actual have a HIGHER stored energy... as the charge time decreases the effect is increased... as the charge time increases both currents move toward their asymptote of 15A and the OEM coils ultimately store ~33% more energy... but it takes a while. So, what this really tells us is that we need to know the ACTUAL dwell time that the ECU uses in order to state definitively whether the intrepid coils have a weaker spark when wired in series. But, for anything shorter than about 6 ms it's at least a wash and at best the intrepid coils have more energy than the OEM coil pack. One thing is for CERTAIN though! Wired in parallel, the intrepid coils would KILL the OEM coils in stored energy.

But, of course, there's more to the story. I wasn't able to measure the secondary inductance so I don't know the winding ratio. That means that we can't say for sure at this point how the energy is delivered. It may be that the intrepid coils have a longer duration spark that's not as hot...




EDIT: According to stealth316 the charge time of 3si motors is about 4ms and the current is regulated to cap at 6 amps. If that's true for our system as well then the intrepid coils would reach 6 amps faster but would be capped there just the same as the OEM coils. At that point, the stored energy of the intrepid coils would be roughly 75% of what's in the OEM coils. So, just plugging in a COP setup with coils in series and no other modifications you can expect to get about 75% of the stored energy as you do in an OEM setup. Running two igniters in parallel would raise the cap to 12 amps. Over 4ms the current through the intrepid coils would reach almost that value (11 amps). That means that the Intrepid coils would win again (even in series) for times less than 6 ms and would be a significant improvement over the OEM configuration (with a single igniter). Running the coils in parallel has no significant advantage at this point ( so long as the charge time never goes below 4ms) since the charge time is already enough to reach the capped current when run in series. If the dwell time allotted were to drop to below 4ms then the coils would no longer be reaching their capped current value and you'd start to lose energy. Run in parallel they reach the capped current in 1/4 the time so the dwell time becomes MORE than enough. This could itself be an issue as excessive dwell times create more heat in the coils and may lead to failure. One very useful thing to know at this point would be the rated current through the Intrepid ignition system. It may be that 11 amps is just way too much for these coils...


Edited by belize1334 (08/06/10 03:50 PM)

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broxma
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Galant VR-4 org Post #: 920896 posted 08/06/10 04:48 PM     Remind Me!  Send Private Message   Edit Post      
The 91+ ignitor actually only has 7 wires if I recall. One is absent so the only extra wire would be the white tach wire.

My concern is wiring the ignitors in parallel is going to put a strain on whatever part of the ECU is powering it or will the extra power be isolated past the ignitor essentially using the ignitors as transformers of sort?

I am going to take my COP ignition off tonight and have a look see at how it is wired. I believe it is wired power to 1, out 1 to 4, and 4 to ground so a series configuration. 2 and 3 are set the same way. I have an extra ignitor in the garage and a harness for it. If you have a diagram wiring them in parallel I'll be happy to pull out the gun and solder it up to test it.

I am trying to visualize how to do that but I can't imagine it in my head. Are you taking output from one ignitor and feeding it to the input of the other?

What is the lim fac for wiring the coils in parallel? Possible overheat of the ignitor?

/brox



I am big into recycling though and if your not into sacrifice or burnt offerings, you may want to stick with 93 octane.

/brox


Edited by broxma (08/06/10 04:51 PM)

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belize1334
well bread and nobly conceived
1334/2000


Galant VR-4 org Post #: 920897 posted 08/06/10 05:02 PM     Remind Me!  Send Private Message   Edit Post      
For running the igniters in parallel I'm talking about take the ECU signal for 1/4 and 2/3 and splicing it to both igniters and then splicing the igniter outputs for those cylinders back together again. If you think of the igniters as relays, then I'm just talking about having both relays run off of the same signal and then having their outputs tied together to drive the same load. It is possible that two igniters could put extra load on the ECU but I highly doubt it. Normally a transistor switch draws effectively no current (on the order of micro-amps) so that shouldn't be an issue.



Roger B. Scott
'91 Belize Green

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broxma
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Galant VR-4 org Post #: 920905 posted 08/06/10 05:21 PM     Remind Me!  Send Private Message   Edit Post      
Ok. I see what you are saying. Drop resistance of the ignitor with the parallel circuit, then the coils wired in series will see double power.

Well I can't do a scientific test of said system I can do a "does the car still break up" test tonight and report the findings. I'll even take video.

/brox



I am big into recycling though and if your not into sacrifice or burnt offerings, you may want to stick with 93 octane.

/brox

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belize1334
well bread and nobly conceived
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Galant VR-4 org Post #: 920914 posted 08/06/10 06:33 PM     Remind Me!  Send Private Message   Edit Post      
It's not so much dropping the resistance as it is sharing the duty. The coils will see the same voltage and provide the same resistance regardless of the igniter configuration. Having two igniters just means that each only has to supply half the current.

Now, the effects of that are a little unclear because I still can't find out for certain whether the igniters are current-regulated. As I mentioned, the stock coils reach 6 amps after only 2(ish) ms. If the dwell time is more like 4 or 5 ms (as suggested) then the current would rise to more like 15 amps. Now, if it's also true that the stock system is designed to have 6 amps through the coils... then the igniter itself must have some kind of internal regulation that keeps the current at or below 6 amps.

So, the result of running two igniters depends on whether they are individually current controlled. If the ARE, then doubling them up effectively doubles the max current that the coils are allowed to pull. This would raise the stored energy without having the run the coils in parallel. If the aren't, then the coils pull as much as they want already and doubling them up just lets us run the coils in a different configuration (to draw more power) without burning the igniters out (since they presumably have a max current rating).

But, as I showed above, if the igniters aren't current capped at 6 amps, then for charge times of less than 6 ms the intrepid coils already store more energy then OEM so there's no point in messing with anything... we're already winning. On the other hand, if the igniters ARE capped, then doubling them up raises the max current to 12 amps (which the intrepid coils will pull after 4 ms even without putting them in parallel) and triples the stored energy.

This leads me to conclude that there is no reason to rewire the coils themselves for parallel duty. The only improvement would instead come from doubling the igniters (in parallel) which will increase the energy of the spark by a factor of 3 if they're already current limited to 6 amps. If they're not, then it won't do anything.

Edit: I also finally found a thread which quotes dwell time for the stock ECU. Now, this is for a 2G mind you so I don't know if it's directly applicable. Can anybody comment on the difference between 1G and 2G ignition coils? dwell times



Roger B. Scott
'91 Belize Green


Edited by belize1334 (08/06/10 07:03 PM)

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broxma
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Galant VR-4 org Post #: 920947 posted 08/06/10 09:15 PM     Remind Me!  Send Private Message   Edit Post      
I suppose finding out if they are in fact current capped is going to be impossible to test for?

Since I have multiples of everything and enough parts to rebuild the ignition system 5 times over and a new ECU in case it blows, I will proceed with the install. Should only take me an hour or so. Steve and I just took the car out and it has a slight break up at high RPM which I am hoping will go away if the hypothesis is correct. If it does and we can repeat it a few times we can push this into theory land.

/brox



I am big into recycling though and if your not into sacrifice or burnt offerings, you may want to stick with 93 octane.

/brox

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broxma
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Galant VR-4 org Post #: 920957 posted 08/06/10 10:32 PM     Remind Me!  Send Private Message   Edit Post      
I wired them up. The car defintely runs but I have a small exhaust leak at the turbo flange I need to tighten up before I head out. I'm going to leave the spark gap and boost where it is and see if I have any noticeable change.

/brox



I am big into recycling though and if your not into sacrifice or burnt offerings, you may want to stick with 93 octane.

/brox

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Galant VR-4 org Post #: 920959 posted 08/06/10 10:35 PM     Remind Me!  Send Private Message   Edit Post      
Thats awesome, let us know asap>



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Galant VR-4 org Post #: 920968 posted 08/06/10 11:23 PM     Remind Me!  Send Private Message   Edit Post      
Alright let's lay out the conditions from earlier and compare.

About 3 hours ago - Temp about 92, Dry, 17 PSI, Single ignitor. Spark break up occurred at higher RPM above 6K till 9K randomly

Just now - Temp about 87, dry, 17 PSI, Dual ignitor. Full throttle pull in 3rd gear, no break up.

I cannot say for certain that it is the ignition because the variables have changed. I am going to crank up the boost to about 21 or so and see if I have break up. I had a noticeable increase in spark break up between 17 and 19 PSI today under similar environmental conditions. I would think this spark break up would be more pronounced given a further increase in boost. If someone disagrees with this let me know but sounds logical to me.

I will say this, the last run I just did on the highway here was in the identical locations I took Steve for a ride at earlier. This most recent run felt like a different car. It was smooth, and felt as strong as the car has ever felt. Chalking it up to the dual ignitor may be premature but it is certainly different in a positive way, very positive.

/brox



I am big into recycling though and if your not into sacrifice or burnt offerings, you may want to stick with 93 octane.

/brox

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belize1334
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Galant VR-4 org Post #: 920989 posted 08/07/10 01:36 AM     Remind Me!  Send Private Message   Edit Post      
That's awesome.

I don't think it will be hard to determine if the igniters are current-capped. I'll just throw one on a variable voltage source with a 1 Ohm resistor and crank up the voltage. If the current rises over 6 amps then we'll know.

Just to be clear brox, you hooked up a second igniter in parallel but are you still running the intrepid/300m coils in series?



Roger B. Scott
'91 Belize Green


Edited by belize1334 (08/07/10 01:37 AM)

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broxma
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Galant VR-4 org Post #: 921048 posted 08/07/10 11:54 AM     Remind Me!  Send Private Message   Edit Post      
Correct.

Essentially there are 6 wires which need to be cut on the main harness. I pulled the friction tape back, cut them one at a time, stripped both ends, and soldered all three wires together. I left the white tach wire alone on the clip from the harness and just doubled over and taped the one on the additional clip. I mounted both ignitors on the back of the manifold in the two bolt holes left from removing the intake brace. This allowed me to sort of face them together and up. I needed this close proximity because I did not extend any of the wires so I only had a short length to work with.

The main power wire is a bit of a bear to solder since it is much larger than the others. I am going to leave it in this condition for a few days and see if I have any problems. If not, I will go back and do a more professional job with the soldering a wiring.

I left the coils alone, still wired parallel. Today will have a better condition to test against the norm from yesterday. Temperatures are expected to be the same and I am going to increase boost to about 21 as I said last night. I think running under the same conditions with a 4 PSI increase in boost is a fair comparison. Steve noticed the spark yesterday when I took him for a ride so I'll have him with me again if possible to get an objective assesment.

/brox



I am big into recycling though and if your not into sacrifice or burnt offerings, you may want to stick with 93 octane.

/brox

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belize1334
well bread and nobly conceived
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Galant VR-4 org Post #: 921076 posted 08/07/10 02:14 PM     Remind Me!  Send Private Message   Edit Post      
I haven't had a chance to test the igniter yet... I'll get to it later... But I have had a thought about the way in which we wire the coils together.

First, I think that series is the only configuration that should be considered. In parallel their collective resistance drops to 1/4 of the OEM coil which means even two igniters might be under too much load (double OEM). Further, the parallel configuration would have them come to full charge MUCH faster which means they'll spend longer with a high current flow and could potentially overheat.

Second, when we wire them in series, I think we're doing it incorrectly. Granted, it works. But, it's not ideal.

The current configuration calls for power to the pos terminal of coil one. Then the neg of coil one goes to the pos of coil four. Neg of coil 4 goes to ground. When the coils charge current flows through them both in the same direction (pos to neg). Then when they dischage, same thing... The current flows through the secondaries in the same direction (pos down to plug and into head). That means that the current must then go through the chassis and through the wiring and into coil one where it branches to plug one and over to coil four and finally to plug four. This has two effects. Firstly it means that the path to coil four has more resistance and thus less spark intensity. This may or may not be noticeable given the breakdown resistance of the plug. Secondly, it means that all the current crossing the plugs for the ignition even must flow through the chassis and the main wiring harness.

If, by comparison, you look at the schematic for the factory coil, you'll see that it's much simpler. There's only one secondary for both plugs. Current flows down plug one, through the head to plug four, back up to the secondary, and back down to plug one. It's an isolated path that removes the wiring harness entirely.

I propose a new wiring scheme. Instead of going from power to coil one pos and then from coil one neg to coil four pos, I suggest it go from power to coil one neg and then from coil one pos to coil four pos and then coil four neg to gnd. Essentially you wire coil one backwards. What this does is cause it to charge in the reverse direction as it's twin. It then also discharges in the reverse direction. Then the discharge spark flows from plug one, up to coil one pos, over to coil four pos (via the wiring) down to plug four, through the head and back to plug one and up into coil one again. Just like the factory coil this creates an isolated circuit path that doesn't involve the chassis and only incorporates one wire (from one pos to four pos) which can be made heavier gauge than the rest of the wiring.

The only possible drawback to this design is that the coils MIGHT have directionality. But since these are all AC currents by the time the secondaries are energized, it shouldn't make any difference whatever. When I measured the inductance of the coils, for instance, I got the same value both ways... no directionality as far as I can tell.



Roger B. Scott
'91 Belize Green

Posts: 3295 | From: Dundee, Scotland, UK | Member Since: 11/18/03 | IP: (174.45.93.14) | Report this post to a Moderator

SouthCaliVR4
Gas Analyzer
825/2000


Galant VR-4 org Post #: 921084 posted 08/07/10 02:51 PM     Remind Me!  Send Private Message   Edit Post      
Gotta say, you guys rock! this is the best info I have seen on the COP set ups to date & am following this thread with great interest. Hope you don't mind but I'm going to hold off on building a COP till I can do so using your final results. Thanks for the efforts of all involved



How do you make a small fortune racing? Start with a very large one!!!

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belize1334
well bread and nobly conceived
1334/2000


Galant VR-4 org Post #: 921092 posted 08/07/10 03:51 PM     Remind Me!  Send Private Message   Edit Post   
Ok, just got in from testing my '90 igniter.

I used two 0.6 Ohm resistors in order to vary the load in the system. The first thing I noticed is that the resistance values change when current is applied. With one resistor (supposedly 0.6 Ohm) current was 13 Amps. With two resistors (supposedly 1.2 Ohm) current was about 7.5 amps. So, clearly they act more like 0.9 Ohm resistors once current is flowing and the resistance increases with current. That's gonna make the results a little vague cause it's hard to say what the resistors are really doing.

I hooked up the igniter by grounding pin 3, hooking pin 1 to the resistor and then hooking the other end of the resistor to 12V. I then touched pin 2 to power. With 2 resistors (~ 1.8 Ohm resistance) current was about 6 amps. With 1 resistor (~ 0.9 Ohm resistance) current was about 9 Amps.

This suggests that the igniter is NOT current capped, but does have it's own internal resistance which varies strongly with voltage. Assuming that the resistors both acted as 0.9 Ohm the whole time (decent approximation) then the igniter has a resistance of ~0.5 Ohms at 9 amps and ~0.2 Ohms at 6 amps.

So, what does this mean. Well, it means that as the current rises the resistance over the ignite grows compared to the resistance in the coil. That will slow the charging and will also lower the peak current and thus lower the peak power. By putting two igniters in parallel, they split the current. So, where the resistance would have grown to 0.5 Ohms by 9 amps, now each one will still be down at 0.2 Ohms (or less) up until 12 amps.

To quantify it, lets assume that the coils are better than my resistor and that they maintain their 0.8 Ohm rating. At 12 volts, the total resistance is now the sum of 0.8 Ohm plus the resistance of the igniter. Lets suppose that the final current is about 9 amps. 12V/9amps = 4/3 Ohms = 0.8 Ohm + 0.53 Ohm. That's right on spec because we said that the igniter had a resistance of 0.5 Ohm at 9 amps. Now let's put two in parallel. They split the current so each has a resistance of less than 0.2 Ohms and, summed in reciprocal, their net resistance is 0.1 Ohm. At 13 Amps, the total resistance is 12V/13amps = ~ 0.9 Ohm = 0.8 + 0.1. That's right on spec again. 12 amps split between two igniters is 6 amps each where they both have a resistance of 0.2 and combine to give resistance of 0.1 Ohm.

So... the moral of the story. If you change NOTHING about the coils. But you put a second igniter in parallel, the theoretical maximum current will be as much as 50% higher than with a single igniter and each igniter will carry less current than it would alone which will increase it's lifespan. Further, the decrease in total resistance also decreases the necessary charge time so the coils will rise to a current which is closer to the peak theoretical value in the time alotted. This amounts to a further improvement in current at the time of discharge.

Now, this affect is independent of whether you're on OEM coils or COP so long as the resistance is still 0.8 Ohms. Recalling that the intrepid coils have 3/4 the inductance and thus 3/4 the stored energy at a given current, we can estimate the final stored energy in the intrepid coils with dual igniters as at least (3/4)*(1.5) times the OEM energy. That is, dual igniters with intrepid coils wired in series gives at least 25% more stored energy than OEM coils - probably more considering that they charge faster...



Roger B. Scott
'91 Belize Green


Edited by belize1334 (08/07/10 05:18 PM)

Posts: 3295 | From: Dundee, Scotland, UK | Member Since: 11/18/03 | IP: (174.45.93.14) | Report this post to a Moderator


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