Non-resistor plug caps

[footgoose]

not sure if these are appropriate but... they're red!  http://motociclo.com.au/node?page=105

 

[coreytrevor]

Those look good but I guess I have to order one to see if I can take it apart.

[MartyNZ]

...It seems like more resistance in the circuit could mean a weaker spark...

Actually I don't think your plan to reduce HT circuit resistance will change the spark enough to notice, but it won't cost much to try it out.

If the resistor plug is 5k Ohms and the resistor cap is 5k Ohms, then we are considering the difference between 5k & 10k in the HT circuit.

20,000 volts through 10k implies 2 Amps, and 20,000 volts through 5k implies 4 Amps of current. However, Ohms law doesn't apply because of the coil in the circuit.

The actual current through your leads is zero until the voltage rises enough to flash over the plug gap, at 8 times atmospheric pressure. After flashover, the current is closer to 0.01 Amps (10ma). So plug and cap resistance have a small effect on spark duration, but no effect on firing voltage or the energy in your spark.

The things limiting your spark current are the coils and ECU. Inductive reactance (the resistance to current change) in the coils has a big effect, along with the ECU's ability to deliver 12 volts to the LT side of the coils with a very fast rise/fall time.

If you want more power, then the usual mods are better, but much more work.

I'd suggest starting with Docc's tune-up, then look at Guzzi Diag as the best return on your efforts.

http://www.v11lemans.com/forums/index.php?showtopic=19610

http://www.v11lemans.com/forums/index.php?showtopic=17865

[luhbo]

The Non-R plugs are easy to get. So why do you not change the plugs? Too easy or what?

I too wouldn't want two resistors.

But instead of trying to get answers by applying Ohm's law to such a highly capacitiv, sorry - must be inductive, and highly dynamic problem I'd suggest to compare Osci pics of the resulting sparks. I havent seen this equipment since years, but normally any good car shop still should have it.

[Chuck]

 

 

The Non-R plugs are easy to get. So why do you not change the plugs? Too easy or what?

this

[coreytrevor]

MartyNZ:  Thanks for the detailed info on the operation of the system. Your knowledge of electricity is greater than mine. I guessed that less resistance would mean more energy for the spark but if you say no, I believe you. I suppose that also means that cutting the resistance in half won't allow a larger plug gap.

I have taken care of all the tune-up stuff, and TPS and CO trim settings. Also using Tunerpro, I have a bin file Meinolf sent me which was very good but I have added some fuel in 2 spots in the map to get rid of lean spots. Also planning on buying a air fuel datalogger to optimize the fuel map. And waiting on Mike Rich to make more pistons. Also I want to advance cam timing about 4 degrees to pull some top end power down into the midrange. I have fun optimizing all the little things I can because you run out of big things pretty fast.

 

luhbo: I like Iridium plugs, with a slightly larger gap. I've had good results with them, a little bit better fuel mileage on a number of vehicles, and they last almost forever. They reduced the lean surge on my 1150GS. But I never see them without resistor, that would be too easy.

[MartyNZ]

Given your experience with the 1150GS and if I understand correctly, you are using NGK BPR6EIX iridium plugs in your V11, can you let us know how your V11 performs compared to the NGK BPR6ES standard plugs.

Opening the plug gap, and raising the compression (assuming Mike Rich's pistons do this), both have the effect of making the HT voltage rise higher before the plug fires. On the other hand, NGK BPR6EIX iridium plugs have a thin centre electrode which will let the plug fire at a lower point in the voltage rise. You will only know the effects of plug gap by trying different gaps. If opening the gap too far causes a misfire, then the HT voltage is finding an easier path to ground somewhere else. Then you need to either close the plug gap a little, or improve the HT circuit insulation by cleaning the coils or renewing the leads.

 

I like your plan to optimise everything you can. Tunerpro, with an air/fuel data logger, in the obvious way to optimise fuelling and ign timing, but I haven't tried it yet. Have you thought about writing a "how to" for Tunerpro? It could be something that would interest others.

 

Meinolf mentioned a method of making adjustments to valve timing here:http://www.v11lemans.com/forums/index.php?showtopic=19557&do=findComment&comment=212299

 

BTW, if your heart is set on getting those red plug caps from Motociclo in Australia that Footgoose mentioned, my experience is that their website is a bit manky. Let me know if you would like me to call them to get them shipped. I speak fluent 'strayan.

 

Edit...Oh, and I just checked, the standard plug recommended for the V11, the NGK BPR6ES, has a 5K Ohm resistor built in. So a stock V11 has a 5K suppressor cap, and a 5K suppressor plug, 10K total. https://www.ngk.com/product.aspx?zpid=9482

[gstallons]

Can you explain how center or ground electrode diameter has any effect or affect on when the spark jumps the gap ?  I assumed the superior spark would take place at the greatest piont in coil saturation ? I was taught spark takes place the when igniton is triggered with ignition pionts or trigger device have gone from a closed to open condition ?

[luhbo]

when ignition is triggered by whatever mechanism, contacts or electronically, then that only means, that a spark is brought on its way. When will it finally jump is a complex question, for how long it will burn and how long it will take to get the combustion going, quick and easy answers can't be given neither.

Just yesterday, down on my knees in front of my Greeny, I looked at her twin plugged heads and this thread came to my mind. The dual plugging was cheaply done, as usual, by just switching the standard coils against FIAT wasted spark ones, means the spark has to pass two cables, two caps, two gaps - and of course all of the extra resistors eventually added inline. That's a real interesting setup I'd say. What time behaviour can I expect? Can such a setup really be superiour to the standard one plug solution? Is it more or less robust against moistured caps or rotten wires etc. etc.

[MartyNZ]

Can you explain how center or ground electrode diameter has any effect or affect on when the spark jumps the gap ? I assumed the superior spark would take place at the greatest piont in coil saturation ? I was taught spark takes place the when igniton is triggered with ignition pionts or trigger device have gone from a closed to open condition ?

This picture shows the effect of electrode shape on firing voltage. There is lots written about electrode shape if you are interested in reading more.

 

The workshop manual tells us this: "The ignition is an inductive discharge static type with dwell control in the power modules (incorporated in the ECU) and a mapping of the spark advance stored in the ECU. The coils receive the commands from the ECU I.A.W. 15 M, which processes the spark advance, through the power modules".

 

This picture shows an example of the timing of coil saturation relative to spark plug firing.

Gstallons, you are right when you say "igniton is triggered when trigger device goes from a closed to open condition". This is when the saturated low voltage coil current drops very quickly back to zero, which generates high voltage in the secondary coil.  This event does not have a label on the graph, but I believe that it is at about -0.05 ms.

The KiloVolts reached before the plug fires depends a lot on the dielectric breakdown strength of the air in the plug gap between the electrodes.

* High compression pressure > higher voltage.

* Wider plug gap > higher voltage.

* Rich mixture > lower voltage.

* Pointy electrode (or sharp edges on standard plug electrodes) > lower voltage.

[coreytrevor]

That's correct, I'm running BPR6EIX plugs. I didn't really do any back to back comparison, I just did it when I got the bike as part of a lot of maintenance. I think I opened the gap .004 to .006" over stock. I have read that iridium plugs can actually work worse unless you open the gap, I don't have a way to test this but I want a larger gap if I can have it. I should probably try even larger gaps to see what happens. Is it possible to harm the coil if you go too far? I wouldn't mind finding better coils and gapping at .040 to .044" as done on some vehicles that come stock with iridium plugs.

 

Another detail, regarding running a waste spark/dual lead coil like luhbo runs, what I understand is that with an iridium plug, the plug only really has a benefit on the plug where the voltage is jumping from center to ground electrode. The second plug is firing from ground to center electrode. I have also seen on my vehicles with waste spark and iridium plugs that on half of the plugs the ground electrode erodes away before the iridium center does. The iridium lasts a long time.

 

Regarding Tunerpro, I am a complete beginner and could really only be helpful with the absolute basics. There is a good tutorial of the basics on Wildguzzi.

 

http://wildguzzi.com/forum/index.php?topic=73938.0

 

Marty, thanks for that link about changing valve timing, I hadn't seen that before. Meinolf seems to know everything about tuning these bikes and I can usually understand what he writes about. Also thanks for the help with the plug caps, I haven't decided what to do there yet.

[MartyNZ]

I should probably try even larger gaps to see what happens. Is it possible to harm the coil if you go too far? I wouldn't mind finding better coils and gapping at .040 to .044" as done on some vehicles that come stock with iridium plugs.

Good question. The answer is yes, it is possible to damage the standard leads and coils.

If the plug gap is too large to allow the plug to fire, the voltage keeps rising in the coil until it reaches it's maximum. It may not discharge anywhere, and the voltage may just fall again. Or if there is some weakness or contamination in the high tension/secondary circuit, then it may flash to ground somewhere other than at the plug.

Either way, you will feel a misfire.

If  you get a flash to ground, this electric arc could pass over or through insulation, burning stuff in its path, leaving a carbon track. This track can become a conductive path with less resistance than the plug gap if the misfire persists. Dirt and moisture make things worse. Usually we don't know that this has happened, just that a coil or lead causes a misfire, so it gets replaced. I don't know for sure, but you are probably safe with plug gaps up to 2.5mm (0.100").

 

As an aside, there was an old 1909 Fairbanks Morse stationary engine which wouldn't run, so I was asked to look at it. The "trip lever" magneto gave a good spark over 0.64mm (0.025") plug gap with the plug outside the engine. After lots of messing about, an expert suggested a plug gap of 0.15mm (0.006"). Then it started right away. This shows the effect that plug gap can have on spark, even at a low compression ratio of 5:1.

Luckily modern ignition systems have energy to spare.   

 

Another detail, regarding running a waste spark/dual lead coil like luhbo runs, what I understand is that with an iridium plug, the plug only really has a benefit on the plug where the voltage is jumping from center to ground electrode. The second plug is firing from ground to center electrode. I have also seen on my vehicles with waste spark and iridium plugs that on half of the plugs the ground electrode erodes away before the iridium center does. The iridium lasts a long time.

I've been thinking about Luhbo's remark too. My daughter's Toyota has that waste spark system - two coils and four plugs in a four cylinder engine. Last tune-up, I took out plugs which had 2 massive earth electrodes. I then fitted iridium plugs, but my plan is to swap the paired plugs over after 20,000 km, so that the electrode erosion is evened out.

The old timers who worked on vintage British cars, which had positive earth, said that spark plugs lasted longer on positive earth cars than the negative earth cars. I'm sure that is because of the effect you mentioned. The whole world standardized on the wrong polarity (if plug erosion was the only concern).

[luhbo]

It's like galvanisation. The material follows the current.

I don't have the details, but the newer twin plugged engines of the Breva types use two different plugs per head and also have the cables explicitly marked inside/outside. Swaping them would ruin the plugs I read somewhere.

[coreytrevor]

 That is my plan also. I have a 4Runner, 3RZ engine with waste spark and I'm watching the iridium plugs to get an idea when to swap them to opposite cylinders to even the wear. I want to try plugs like these when mine wear out. They seem like the best of all worlds for waste spark systems. I like how they unshroud the spark with the 2 fine electrodes.

 

http://densott.com/

 

luhbo, I bet these would work well in your dual plug bike, and last almost forever. I don't know if they have a plug close to what your application requires.

[Kiwi_Roy]

Resistor leads were a problem on my EV, they opened up at the coil end causing a bad miss under acceleration.

Check your leads and coils by measuring the resistance from plug cap to chassis, should be identical on both sides, about 8k I think.

 

 

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