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chrisflstf
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Joined: February 10, 2004
Posts: 3444
Location: San Diego
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 Posted: Tue Sep 18, 2018 12:30 pm Post subject: Re: Upgraded ignition Spark Comparison + Plasma/PCD info |
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| I get the fact that a stronger spark is better for many reasons. The bigger issue I see with a much stronger spark is finding the point where plugs can live a reasonably long life under the stress. Current plugs may not last too long under that scenario |
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Lingwendil
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Joined: February 25, 2009
Posts: 3988
Location: Antioch, California, a block from the hood
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Alstrup
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Joined: July 12, 2007
Posts: 7216
Location: Videbaek Denmark
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| Posted: Tue Sep 18, 2018 1:19 pm Post subject: Re: Upgraded ignition Spark Comparison + Plasma/PCD info |
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That IS one of the big questions. But based on other peoples/companieīs experience a carburetted engine should not see much reduction in plug life, if any if the right plugs are used. Brisk Yttrium among others seems to show really good results. On newer cars with more modern ignition systems where you typically have about a 65.000 miles replacement intervals it looks like the intervals are typically reduced to approx 50.000 miles. The downside is that a modern ECU system is not able to take the benefit of a plasma system without a remap. If you donīt you will get better power, but also higher fuel consumption.
This weekend I will install a pcd upgrade on a 1969 XJ6. The guy is going on an "Exellence" tour around Europe with the club, which will be around 6500 km round trip. That will be a good indicator on how the plugs will handle it.
This car is british, so the plugs have to be Champion of course (!) Weīll see how they hold up.
Ling. U got a pm
T |
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j-dub
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Joined: November 09, 2003
Posts: 865
Location: Phoenix, AZ
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74 Thing
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Joined: September 02, 2004
Posts: 7393
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| Posted: Tue Sep 18, 2018 10:21 pm Post subject: Re: Upgraded ignition Spark Comparison + Plasma/PCD info |
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| I'd like to see how to properly add capacitors to a spark plug wire as well. This is new to me and my electronic experience is less than stellar. |
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Fred Winterburn
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Joined: April 17, 2013
Posts: 423
Location: Ripley Ontario Canada
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| Posted: Wed Sep 19, 2018 6:43 pm Post subject: Re: Upgraded ignition Spark Comparison + Plasma/PCD info |
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Alstrup,
I do not know how you are measuring spark duration. What I do know is that the human eye and brain cannot react quickly enough to discern 3 distinct sparks in a the few nanoseconds you quote. It is impossible. It is possible in the microsecond range providing there is a long enough quiescent period between spark events, so I suspect that is the actual time frame you are observing, and that time frame corresponds with the results of my experiments. I don't trust visuals, only a scope. The separation of sparks from sound can only be discerned in the high microsecond to milli-second range, but that makes sense given how much slower sound waves travel compared to light and the limitations of our hearing's frequency response. Our brains blend distinct sound or light impulses together at very high frequencies.(which is why the flicker of fluorescent light and some modern led lighting goes unnoticed).
The question you have not answered yet is whether you have put the peaking capacitor in series or parallel with the spark plug gap. From my quick experiments I would say that you have put the capacitor in series with the spark gap as otherwise you wouldn't be getting multiple sparks. My experiment showed that with the capacitor in parallel with the spark gap, the spark is single polarity and a single spark but of much shorter duration than the standard Kettering spark (which is also single polarity but longer duration).
One thing is for sure, if you are using low ohms coils, the spark energy (and power) will be much higher than the standard Kettering system, since the energy in the coil is proportional to the current squared. Fred
| Alstrup wrote: |
OK.
Had a chance to do a little more testing last night. I specificly adressed the postulate that the PCD hook up would actually reduce voltage over the plug gab. I did not really uinderstand why this could be true since I am able to run larger plug gap with PCD compared to without. So the exercise was to find out how and why.
I tested with a regular quality blue Bosch, a 3 ohm Pertronix, a 06 ohm Bosch and a 0,6 ohm Pertronix coil. Now, if we take the differences in usable voltage out of the equation the bottom line is, that when you do this right, you will have anything from 10 to 50% higher voltage over the electrodes compared to normal kettering, points or electronic points. With a set of new Bosch points the increase in voltage with the PCD upgrade is 3-5% less. The variation in spark strength comes from the use of different capacitors. I was previusly a little worried about making the PCD too powerfull so the plug life would take a dive. Now I am more courageous. As long as the correct plugs are used and as long as one does not overdo it with wild plug gaps the plug life will remain about normal. Plug gaps in the 1 to 1,2 mm range (0,040 to 0,050) dependant on set up seems to be the sweet spot.
I deliberately drowned an almost stock 1600 engine (except from 8,2-1 CR and a free flow muffler) and started it with normal ignition and normal plug gap. Then switched system and drowned it again. With the blue Bosch coil I could start the engine just as good (or slow if you will) with 1 mm plug gap. At 1,2 mm it really struggeled to overcome the flooded plugs. With the 3 ohm Pertronix it started almost immediately with 1,1 mm plug gap. So I naturally opened the plug gap a little more to find the limit. That seemed to be somewhere between 1,25 and 1,3 mm. Also, with the 3 ohm Pertronix and 1,2 mm plug gap the engine drives great. No cut outs or anything. With the blue Bosch you get noticeable misfires at peak torque and around peak hp. Reduce the gap to 1 mm and the Bosch has no trouble.
Bear in mind, this was on an almost stock engine. On a high compression large cam duration engine this will not be the same. But the pattern will be equal. I do know that with a Bmep of about 170 psi at peak a 3 ohm Pertronix and 1,1 mm plug gap works well in a good set up. With most average set ups I would recommend 1 mm. to be on the safe side.
Now, where does this extra spark power come from you most likely ask. - It comes from being accumlated. The coil delivers the same power, but with the normal kettering system you slowly build up a voltage difference between the electrodes and the spark will begin at a relatively slow rate, go to its peak and burn out in an average of 15-17 Ns. in total. With the PCD system you use the capacitors to "suck up" the initial part of the voltage delivery from the coil. Then when the capacitors are full and the coil is on its max delivery the plug gap will be ionized and the entire load will be dumped in one fat spark in about 10-12 Ns. (In my case it is actually 3 sparks that come almost simultaniusly, only about 2 Ns. apart. If you look at the spark through a magnifier you can actually see that there are three sparks at one time. And that is part of why the spark is "fat"
It is difficult to put numbers to something that you canīt really measure. But if we look at it this way, we can say that in a good std 12V igntion system we (I) have 0,85 mm plug gap. With a good PCD system I use say 1,1 mm plug gap. The increase in plug gap alone makes for a 29% increase in surface touch to the ambient mix. And that is without taking the fatter spark into consideration. If we could find a way to determine that we could easily be talking around a 50-60% increase.
I have menthioned it before and will do it again. This is NOT a subsitute for a good CDI system. It is sort of a step on the way, but a good step.
Several people and companies that I have talked to about this keep saying that they want a good long duration spark to ignite most possible. I donīt exactly disaggree with them, but I am more and more convinced that a big fat spark, at the right time, in the beginning of the burn cycle, is just as, if not more efficient for the burn. That way you get the burn to evolve faster and be more complete before the piston passes 15 degrees ATDC. And THATīs where the increased power comes from.
I have to test more IRL, but Iīm posive that Iīm on the right track. I just need to understand it better.
T |
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Alstrup
Samba Member
Joined: July 12, 2007
Posts: 7216
Location: Videbaek Denmark
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| Posted: Sun Sep 30, 2018 2:24 pm Post subject: Re: Upgraded ignition Spark Comparison + Plasma/PCD info |
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Soo, the HD Road king I was writing about some time ago have been home for a while now. He came home with mixed results. Normally when heīs on cruise with a full camping packed bike he hovers in the 18ish km/l. On the way down the EU west coast down to Lissabon he did really well, since he was well over 19 km/l. Also, the engine ran nice and cooler than normal under southern temperatures. Then the consumption started to reduce and get back to normal from Lissabon to about Zadar in Croatia. From Zadar and back home the consumption became worse and worse with the last tank where he did only 12,5 km/l. But the power was still good. We all found that a bit odd, and several reasons to this were discussed. The general opinion was of course that the plasma unit made something go bad with the info going to the ECU.
He drove it to his normal HD mechanic who, almost naturally, told him to get rid of that crap and build it back to normal and his problem would go away. So he did. Only problem was that it didīnt help on the consumption, it just lost the power it had gained and then some. By now I was certain that it was some kind of sensor problem, but I had no idea about which. My first hunch was the O2 sensors, So he replaced those. No difference. Then he lent my LM2 and drove around for a while, and sure enough, it was pig rich. OK. Time to send it to the mechanic again. This time he took it more serius and actually went over the engine. It turned out that the cylinderhead sensor had decided to go south and stay there. It read cold all the time. Aaalllrighty. New sensor installed, and back on the road and back to normal power. Last weekend he reinstalled the Plasma unit and went for a drive, and the power and smoothness were back. So now heīs a happy man again. So I thought maybe we could tweak it a little more without going ballistic. So Friday night he came by for a quick visit and we installed sensor extensions under the O2 sensors to see if we could cheat the sensor signal just a little. That seems to work well along with the plasma. We did not check the O2 level, because I did not have time and he had to meet up with his tour mates for the first stint of a weekend tour to Berlin. He texted me this evening, coming back from the Berlin round trip that he averaged 20,5 km/l on this 1100 km tour. There is no loss in throttle response or anything. I have no real idea about whether this is good or really good for this kind of bike, but the owner says that it is significantly better than normal. I have to relate to that for now. On the other hand, more power and better fuel efficiency canīt be bad  When I get time for it I will check to see where the AFR, Nox and ppm really is on cruise. If we can keep the numbers within tolerances for inspection, weīll leave it as is.
Fred. - Oscilloscope.
WRT the 3 sparks at the same time. - Well, you can.
Most of the set ups I have made so far uses a simple Pertronix 3 Ohm coil. I have tried with blue Bosch and Beru coils too, but the spark is weaker, so I went back to black. I have yet to test and try low resistance coils with pcd. One thing at a time. A couple of my customers have experienced some odd stuff going on on semi warm engine. But not on a cold or warm engine. I need to figure out what & why before I go further into it.
The plasma units that I have installed use 0,6 ohm coils.
T |
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