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Spitfire Multispark
- Thread starter BRUN
- Start date
Brun m8.
If the spark you have now is working.. there is no plug in the world that will work better.
If you have changed the engine parameters, then the range of the plug may need changing, or the leads, as the voltage to ionise the gap (spark) increases in proportion to cylinder pressure... the resistance of the existing leads may be too high to allow the voltage to reach the peak required in a higher pressure.
Joe.
the current spark is fine mate ive tested it with a Gunson thing and its the best it can possibly be
but this thing makes it spark about 6 times in the same spark, and in the demo the guy pours some petrol over the plug and it ignites more than the standard setup
could you think of anythin that it would use to produce the results it does, i mean more than one spark
most modern ignition setups are wasted spark.. ie, 2 per cycle., one on firing stroke, one on exhaust stroke.
The object is to ignite the mixture at a given point and after that its down to cam/ cylinder head / squish design.. in a very inefficient engine design, it may help to apply a second or subsequent spark if the flame front is crap.
You engine is not in that category though.. its a good burning, efficient design, so it wont benefit in any measurable way..
(oh, and the engine doesnt burn petrol as in pouring it over a plug - it burns a mixture of air and atomised fuel.. (FAR more volatile.. his test would do nothing much in the case of atomised mix.)
great buzz eh lol !!!
ok, well in that case, you answered your own question Luke...
your spark, as is, is fine....
it takes one match to start a fire providing it catches first time !.
subsequent matches.. or more in a bunch in one BIG light.. dont do diddly...
If you have six bombs placed around an object... is the blast pattern better than with one bomb... lol... ???
the one bomb gives a resonably circular expansion of flame front.. the 6 bombs will deflect from each point in a circular manner.. including back INWARDS... and cause multiple collisions... good for poor cylinder chamber deisgn as it tends to give a more complete burn.. but CRAP for a good cylinder chamber design where flamefront traversal is excellent and designed in.
again m8.. you dont have a demic, you have a good modern design..
you could even argue that the differing flamefront ignition point could cause a corresponding decrease in power due to differing burn rates..
aha, I see what you mean.. could be simple spacing of electrodes relative to the central core or external earth point.... (if multiple electrodes),
if single, hmmm, interwestin
probably some sort of capacitive or back emf loop.. yep, that would sorta work..
is it a device that fits in the coil HT lead ??..
if so, it could be a form of inductor ..... sorta pusing a diminishing back emf pulse...
vewy clever if it is..
Me ??..... I wouldnt bother personally lol..
Joe..
Ionising current is proportional to cylinder pressure. Voltage is taken as somewhat fixed (coil turn ratio).
Still, I wouldnt bother. Allthough the demonstration nicely shows that multi elctrode plugs only spark on one electrode not all of them at the same time like some people think.
Manufacturers spend millions on R&D of ignition systems i think they would have picked up on this point if it was needed...
Oh and it seriously interferes with your radio.
I am slightly at a loss as to your correction on voltage current and coil turn ratio Chris.
Voltage is a result of current * reisitance.
Voltage is potential difference, therefore the PD has to be high enough for the spark to jump
By reducing the lead resistance you increase the current, but in this case, the increased current causes an increase voltage or PD.. this is the cause of the spark...
if the voltage remained the same the spark would not occur... ??
Joe.
A coil, which can be thought of as a transformer has a turn ratio. That is the ratio between the number of turns on the primary windings verses the secondary windings.
http://www.tpub.com/neets/book2/5f.htmhttp://www.tpub.com/neets/book2/5f.htm
A coil ratio of 100 times would give 100 times the primary windings voltage on the secondary windings. So secondary voltage available is almost fixed (disregarding a few factors).
Modern forms of combustion sensing (including knock control) use spark gap current to derive cylinder pressure. Cylinder pressure being the main contributor to knock.
http://www.delphi.com/pdf/eandepdfs/Ignition/IonCurrentSens.pdfhttp://www.delphi.com/pdf/eandepdfs/Ignition/IonCurrentSens.pdf
http://www.forbrf.lth.se/htmlavd/arsrapport95_96/bilder/kap_44.htmlhttp://www.forbrf.lth.se/htmlavd/arsrapport95_96/bilder/kap_44.html
Gap voltage relates more to the stage of the spark (Breakdown, arc discharge and glow discharge.
Im a bit drunk so all that probebly wont make sense though...
no m8, secondary voltage isnt fixed as such (at the electrode), yes, its limited by the coil ratio at the ht output. However, the problem is that the ignition leads are often of resistance that is too high to allow the peak voltage to appear at the electrode, thats all. Usually for suppresive purposes of RFI.
You need to think of the coil lead as a resistor. (which they effectively are)
Some, not all !, competition leads (Magnecour for example) have a far lower resistance and still seem able to apply appropriate suppresive rfi.
Modern forms of combustion pressure detection, as you put it, are NOT used on the clio.. this is an emerging technology used in very high emission regulated areas of the world (certain parts of the states etc) and needs a completely redesigned system to operate
the secondary voltage (after the spark) on these systems ARE used to measure the current, but again, not on the clio... the fact still remains that even for the current sensing system to work at all, the voltage available at the electrode MUST be enough to bridge the gap in the first place for the primary spark. To be able to measure the current needed, you need to form a circuit in the first place, this happens due to the voltage difference (PD) at the electrode ends.
Bottom line is....
Coil voltage has a peak value..
This Voltage Value is NOT available in normal operation to the plug electrode gap due to the reistance of the plug leads
This is of no consequence in a normal unit though.
If you increase cylinder pressure (ie - a NON NORMAL UNIT), you NEED to increase the voltage to allow the spark to traverse the gap.
You CANNOT increase the secondary output of the coil. (but it is not normally the limiting factor (its the LEADS) )
You CAN increase the voltage at the plug electrode by reducing the resistance of the coil leads.
Joe.
Come on..... battery on a multimeter measures say 12V. Connect a resistor in series with the positive measuring lead, PD is still 12V. To alter voltage you need to use a _potential divider_, a simple resistor in series with a voltage source just acts as a current limiting resistor.
The resistance of the lead will affect current flow, and as such the discharge rate of the coil (as it acts as a capacitor).
Less resistance = same voltage, but brighter spark (more current), for a shorter period.
Yes i agree, the _breakdown_ (firing) voltage required will be greater with a wider spark gap, or higher cylinder pressures.
But its the arc discharge that created the heat transfer, and then the flame kernel. This is when we want the current flow, as energy is made up of voltage, current and time.
Of course clios dont use ion current sensing! This is only just comming out on top end cars! And I certainly wont dismiss it to just emmisions control, it will allow fully closed loop ignition to ride on the knock limit for max power! Much better than the poor excuse for knock control that knock sensors allow.
I was mentioning the system as it provides a perfect example that current is proportional to cylinder pressure! Albeit that its created from a bias voltage added, but thats for the fact of the electronics needed to measure it.
Tests on voltage required show that even with race engines its still in the 12,000 - 15,000 range. And cold starting being the worst of the situations! But, I do agree that some alterations may be needed when tuning, but thats usually in the form of gapping plugs smaller (0.8mm -> 0.7mm on Vauxhall C20LETs running 370bhp, almost double the standard power with the same ignition system)
Saw a demo thing at a service station on the way to a vaux meet.
Looked good for the multi electrode plugs as it seemed to fire all of them in one cycle rather than the normal one.
But, the spark did look duller than just the single normal spark. You can just get energy from nowhere. The bit that ignites the fuel is the bright part of the spark, so i was a bit put off by that.
Mate has one on a Cav GSi 16v, says he can notice a slight difference. But it seriously interferes with his radio so he doesnt use it.
To be honest, like CS said, the spark either ignites the fuel or it doesnt. This little device isnt gonna improve upon what manufacturers have spent years and millions developing. Spend £30 on getting pissed instead (or save it to buy my 1.7 turbo...)
Hi Chris.
Come on..... battery on a multimeter measures say 12V. Connect a resistor in series with the positive measuring lead, PD is still 12V. To alter voltage you need to use a _potential divider_, a simple resistor in series with a voltage source just acts as a current limiting resistor.
put that way, yes, I agree. We are looking at a discharge or field collapse from the secondary windings. The voltage has to reach a peak high enough to ionise the gap distance. with lower circuit current, the spark will start, but will be inneficient. (in high cylinder pressure situations). I would have been more accurate saying the resitance of the lead will efect the spark strength.
Less resistance = same voltage, but brighter spark (more current), for a shorter period.
Agreed again, however, there is an upper limit to the resistance used due to the inductive effect of the coil breaking down faster than the flow of current through the resistor.
too low is also a problem due to burning of the electrode area.
its all about getting a balance... too low, you burn!, too high and the field collapse has occured prior to the necessary FULL spark occuring over the appropriate period of time.
Joe. - (Impressed !)
