My Tip - Twin coils easy as 1-2-3
Started by
_NZ Toranaman_
, Feb 28 2009 06:41 AM
90 replies to this topic
#52
Rockoz
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Posted 02 March 2009 - 10:00 PM
Good theory. Brings back memories.
Edited by Rockoz, 02 March 2009 - 10:04 PM.
#53
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Posted 02 March 2009 - 10:01 PM
If you take out the 4 ohms circuit resistance in my example you will see that the risetime for just two coils will not change. (perfect zero ohms wiring)
It stays at the half second no matter how many coils you put in parallel if there is no other circuit resistance.
but when you add external resistance that is not easily reduced the rise time will go down.
It stays at the half second no matter how many coils you put in parallel if there is no other circuit resistance.
but when you add external resistance that is not easily reduced the rise time will go down.
#54
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Posted 02 March 2009 - 10:04 PM
Even in a set of points, we are only taking about fractions of an ohm, connecting wire- add another fraction of an ohm, cant see that is going to make much difference.Its the total circuit that matters in this case.
What causes the main problem is the parasitic wiring resistance outside the coil.
Really this is the part having trouble with, the inductance "in front" of this coil remains the same, so how can the rise time decrease.The single coil current stays the same at saturation but the rise time of the current is faster meaning that you get to saturation quicker so better spark ensues.
#55
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Posted 02 March 2009 - 10:07 PM
for rockoz:
resistors and inductors in parallel add up to the reciprocal sum of the individual units. Lt=1/L1+1/L2
Capacitors in parallel add up to the sum of the indivdual units. Ct= C1+C2
resistors and inductors in parallel add up to the reciprocal sum of the individual units. Lt=1/L1+1/L2
Capacitors in parallel add up to the sum of the indivdual units. Ct= C1+C2
#56
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Posted 02 March 2009 - 10:09 PM
whoops 1/Lt=1/L1+1/L2 sorry its getting late!!!
#57
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Posted 02 March 2009 - 10:29 PM
Possibly Im just not smart enough to be able to understand what victalj is saying.
The other thing for me which is not adding up with explanation of the faster rise time, is the above dyno graph, the volvo driver and fasteh'sexperience.
If it were just faster rise time, then we'd really expect to so no difference at lower rpm, where the coil has plenty of time to reach saturation current?, but volvo driver experience 100rpm increase in idle speed with this setup, also the dyno graph shows a fairly constant difference, not just at higher rpm and fastEH actually burning out plugs suggests the firing voltage increases moderate rpm as well.
For the moment, Ill think about it some more, but it seems more likely to me that the increase in spark comes from the collapse part of the primary current where the two coils are in a closed series circuit.
The other thing for me which is not adding up with explanation of the faster rise time, is the above dyno graph, the volvo driver and fasteh'sexperience.
If it were just faster rise time, then we'd really expect to so no difference at lower rpm, where the coil has plenty of time to reach saturation current?, but volvo driver experience 100rpm increase in idle speed with this setup, also the dyno graph shows a fairly constant difference, not just at higher rpm and fastEH actually burning out plugs suggests the firing voltage increases moderate rpm as well.
For the moment, Ill think about it some more, but it seems more likely to me that the increase in spark comes from the collapse part of the primary current where the two coils are in a closed series circuit.
Edited by torbirdie, 02 March 2009 - 10:33 PM.
#58
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Posted 02 March 2009 - 10:32 PM
torbirdie: yes its only fractions of an ohm and coil is probably fractions of a henry but at the same time we are talking pulse times of tens of micro seconds for real world conditions. I used gross values to show the effect plainly.
In the real situation it may only be getting you 10 micro seconds of risetime improvement, which might be enough to give a good spark throughout the rev range wanted
I would have to go out and measure everthing to get a real figure and dont have the equipment for that anyway.
You would be surprised at what the resistance of car wiring is. The manufacturers use the lightest cheapest wiring they can get away with. Thats why people who want good headlights from older cars fit relays and heavy wires .In ignition circuits you are talking about reasonable current levels and the old points system has a fairly high resistance wire to the coil +ve to drop the volts.
In the real situation it may only be getting you 10 micro seconds of risetime improvement, which might be enough to give a good spark throughout the rev range wanted
I would have to go out and measure everthing to get a real figure and dont have the equipment for that anyway.
You would be surprised at what the resistance of car wiring is. The manufacturers use the lightest cheapest wiring they can get away with. Thats why people who want good headlights from older cars fit relays and heavy wires .In ignition circuits you are talking about reasonable current levels and the old points system has a fairly high resistance wire to the coil +ve to drop the volts.
#59
rodomo
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Posted 02 March 2009 - 10:32 PM
You might want to read the Volvo bit again.
#60
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Posted 02 March 2009 - 10:40 PM
Did I miss something:You might want to read the Volvo bit again.
This was on an injected Volvo engine with points ignition (don't ask...) The engine started straight away and seemed to be idling faster and smoother than normal. So I pulled the wire (gingerly) from the extra coil as it was running and the idle retuned to normal; reconnecting the wire increased the idle speed very perceptively (by about 100rpm) and also perceptively smoothed the idle.
#61
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Posted 02 March 2009 - 10:46 PM
Did I miss something:
Yes.
"So I grabbed a coil (just a normal 12v resistor coil) and ran a wire from the output post to the output of the existing coil and left the other terminals disconnected."
#62
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Posted 02 March 2009 - 10:54 PM
yes, I see what you mean...he added just a wire between the two ht terminals? (however that was achieved), another puzzle to solve, how did that cause the observed effect!Yes.
"So I grabbed a coil (just a normal 12v resistor coil) and ran a wire from the output post to the output of the existing coil and left the other terminals disconnected."
#63
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Posted 02 March 2009 - 10:57 PM
Good question 
I'm not doubting that it happened, but why?
I'm not doubting that it happened, but why?
#64
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Posted 02 March 2009 - 11:09 PM
I think if it were that good then every HZ and VB would have had this set up with the problems they faced with emissions one would think.
#65
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Posted 03 March 2009 - 02:58 AM
Simple fact is when i had this twin coil system setup running with splitfire plugs it would run very differently when you took the 2nd coil out of the circuit
apart from a little bit of explaination problems....what happened with the volvo is what happened with the EH...have 2 coils hooked up it idles better...pull the wire it goes back to "normal".
That is the exact article I said I would post...if a mod said i could...hope it gets to stay up.
I've still got all the gear in a box in the shed....if nothing else you (collectively) have made me determined to get it out and use it again...I'm currently using a HQ Premier to drive to work in and I have been checking its economy (or lack there of)....I'm going to fit the 2nd coil in the morning.
I'm just wondering if you thinkers have covered all the bases? Is there something that you haven't considered? for example what (if any) role does the capacitor play in all this.
#66
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Posted 03 March 2009 - 08:06 PM
I'm with torbirdie in that I can't see how another primary winding in parallel - on a separate core - can have any effect on the inductance of the active coil. Sure, the total inductance of the circuit will increased but I don't see it changing the behaviour of the active coil during the charging part of the cycle. Maybe thats the answer, maybe the benefits come in the second part of the cycle when the points or the transistor opens.. If the two primary windings shared a common core I could see that changing the coils behaviour WRT to time to saturation, but not separate units. I'm not saying that there is nothing happening, just that I don't think we understand it yet.
As for the old Volvo with one end of a secondary winding connected and the others just floating in nothingness, well I think I'd have more chance understanding the inner workings of a woman's mind than that.. Might rerun that experiment on a red six just to see what happens...
As for the old Volvo with one end of a secondary winding connected and the others just floating in nothingness, well I think I'd have more chance understanding the inner workings of a woman's mind than that.. Might rerun that experiment on a red six just to see what happens...
#67
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Posted 03 March 2009 - 11:57 PM
I dragged the coil out...was running late to work so didn't fit it yet...watch this space.
#68
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Posted 03 March 2009 - 11:59 PM
I think if it were that good then every HZ and VB would have had this set up with the problems they faced with emissions one would think.
I'm pretty sure that the great automotive innovaters were not employed by Holden during this period.
#69
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Posted 04 March 2009 - 04:47 AM
I am totally with you OldJ, I understand how coils work in principle but had trouble seeing how this worked but decided if it has the chance of increasing HP at a cost of zero then I am all for it.
In particular I wanted to improve my 4000rpm+ rev range as When I change into 4th in the quarter my revs drop off the cam and I rely on torque to pull it back into the HP range. The characteristics of my engine are probably like any warmed 202 until it gets to about 4300-4400rpm and then its like a turbo coming in and thats why its capable of 13.5 instead of 14.5
In particular I wanted to improve my 4000rpm+ rev range as When I change into 4th in the quarter my revs drop off the cam and I rely on torque to pull it back into the HP range. The characteristics of my engine are probably like any warmed 202 until it gets to about 4300-4400rpm and then its like a turbo coming in and thats why its capable of 13.5 instead of 14.5
#70
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Posted 04 March 2009 - 08:19 PM
Don't be stuffed mate! You've got me stuffed in the tacho thread.
This whole thread has me stuffed
However, since I've got nuthin of my own, here's something that got me thinking from Wikipedia discussing the instant when the points open. At the same time, current exits the coil's primary winding and begins to charge up the capacitor ("condenser") that lies across the now-open breaker points. This capacitor and the coil's primary windings form an oscillating LC circuit. This LC circuit produces a damped, oscillating current which bounces energy between the capacitor's electric field and the ignition coil's magnetic field. The oscillating current in the coil's primary, which produces an oscillating magnetic field in the coil, extends the high voltage pulse at the output of the secondary windings. This high voltage thus continues beyond the time of the initial field collapse pulse. The oscillation continues until the circuit's energy is consumed.
Now assuming this is correct (and it's on the net so it must be) I'm thinking that maybe the additional current from the extra coil into the LC combo may cause a higher amplitude/longer duration in the oscillating current giving a better spark and all that.
What do you reckon?
#71
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Posted 04 March 2009 - 08:54 PM
This whole thread has me stuffed
At the same time, current exits the coil's primary winding and begins to charge up the capacitor ("condenser") that lies across the now-open breaker points. This capacitor and the coil's primary windings form an oscillating LC circuit. This LC circuit produces a damped, oscillating current which bounces energy between the capacitor's electric field and the ignition coil's magnetic field. The oscillating current in the coil's primary, which produces an oscillating magnetic field in the coil, extends the high voltage pulse at the output of the secondary windings. This high voltage thus continues beyond the time of the initial field collapse pulse. The oscillation continues until the circuit's energy is consumed.
Now assuming this is correct (and it's on the net so it must be) I'm thinking that maybe the additional current from the extra coil into the LC combo may cause a higher amplitude/longer duration in the oscillating current giving a better spark and all that.
What do you reckon?
I reckon that sounds plausible. And if this is indeed what is happening there may be a case for a bit more capacitance. For points systems you could use the minus-minus-minus rule to verify ie. if the minus (negative) contact point is minus material (pitted, the + one picking up material) then the condensor is minus capacity (too small)
#72
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Posted 04 March 2009 - 09:56 PM
Nice simple rule. I like itFor points systems you could use the minus-minus-minus rule to verify ie. if the minus (negative) contact point is minus material (pitted, the + one picking up material) then the condensor is minus capacity (too small)
#73
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Posted 04 March 2009 - 11:15 PM
The same effect could be theoretically achieved by changing the capacitance instead of adding the coil.
Adding the coil wont do the points much of a favour I wouldnt think.
Changing the capacitance to save the points may negate the effect of the coil.
All to do with theory of filter circuits.
For all the stuffing around there really would be better more reliable and cost effective options.
Will still try it out when I get a chance just for the sake of it.
Adding the coil wont do the points much of a favour I wouldnt think.
Changing the capacitance to save the points may negate the effect of the coil.
All to do with theory of filter circuits.
For all the stuffing around there really would be better more reliable and cost effective options.
Will still try it out when I get a chance just for the sake of it.
#74
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Posted 05 March 2009 - 01:55 AM
I've got mine up and running again...however there isn't a great deal to report..and the only result is little bit "non scientific"...I am waiting to see if economy has changed. The non scientific results are that with the coil hooked up and the throttle blipped the fan belt would squeal for an instant...but not when it operates one coil....completely non quantifiable 
I'm not expecting much...however if I put this gear back onto the EH it might be easier to see benefits as the LPG is a bit harder to light.
I'm not expecting much...however if I put this gear back onto the EH it might be easier to see benefits as the LPG is a bit harder to light.
#75
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Posted 05 March 2009 - 03:24 AM
Was this latest effort just using the conventional points setup, with original resistance wire powering both coils etc?I've got mine up and running again...however there isn't a great deal to report..and the only result is little bit "non scientific"...I am waiting to see if economy has changed. The non scientific results are that with the coil hooked up and the throttle blipped the fan belt would squeal for an instant...but not when it operates one coil....completely non quantifiable
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