Posted By : Chris Taylor,
05-Jun-2007, 03:12pm
I would expect an engine to benefit from the widest plug gap across which the ignition can reliably provide a decent fat spark, as this
will present the largest area of spark to the mixture and promote quickest combustion. Although of course the rest of the ignition
needs to be of the right type and properly adjusted to enable the coil to deliver its maximum potential, the biggest factor in
determining the width of gap which a spark can jump, is the voltage. (Yes, there needs to be enough current to provide enough energy in
the spark, but none of this is possible without the voltage to break down the resistance of the plug gap). The tune of the engine (in
particular the compression ratio) affects the "ease" with which a gap can be jumped, but I doubt even a tuned Triumph engine will be
any more demanding than most modern engines which give a specific output every day which Triumph tuners struggle to match!
ISTR that Lucas recommended 30 thou for their sports coil (the gold one) and no doubt other makers will advise on the optimum gap for
use with THEIR coil. Since the desired end result is the actual power output of the engine, I suppose the optimum plug gap with any
particular ignition set up could be determined on a rolling road?
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Posted By : Danial Phoenix,
05-Jun-2007, 07:43pm
never gaped mine just fitted, runs lovely. NKG
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Posted By : Paul
Carter, 06-Jun-2007, 00:27am
there is in theory one problem with opening the plug gaps if you do it after having your ignition timing set to its optimum;
which is that the larger gap means the coil high tension circuit has to charge slightly longer to make the jump across the
increased gap which COULD result in retarded ignition timing at peak power output ,but considering the speed at which
electricity functions i doubt this would have any effect whatsoever on our cars engines as they run at "relativley" low
revs.......
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Posted By : James
Dennison, 06-Jun-2007, 08:26pm
Thanks folks - seems I am right that I can get away with a wider gap - gone for 30 thou.
Danial - might be worth checking the gaps on your NGK if they're out straight out of the box - mine were all over the
place.
For info I'm running lumenition magnetronic ignition with luminition mega-spark coil and luminition red leads - I had
problems mix and matching components from different manufacturers so went for a matched set.
Cheers
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Posted By : Danial
Phoenix, 06-Jun-2007, 09:00pm
ok will do, iv got the clubs electronic igniton, runs fine but wont hurt to checck em, thoght they were pre set, so how
many mm then?
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Posted By : Chris Taylor, 07-Jun-2007, 07:29am
0.025" (=25 thou) is 0.6mm. 30 thou is 0.7mm.
However, for what they cost, get a set of imperial feeler gauges. Saves having to convert to9 metric ALL the
clearances specified on the Triumph engine, gearbox, diff and suspension!
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Posted By : Andy Vowell, 07-Jun-2007, 09:45am
I run 1mm gaps on Luminition "Performance" optronic ignition. Seems to work well.
I also cut the (NGK) spark plug electrodes back so the end is directly in line with the centre of the plug.
Why?, because the spark always jumps from a sharp corner at the end of the electrode to the centre of the plug.
So even if your gaps are set as (say) 0.5mm, the spark can be 1mm long as it has to stretch out to the end of
the electrode. Spark plugs are made with long electrodes so they last longer to account for the electrode
wearing away with use. As my car does very little miles plug wear is not a problem so by cutting back the
electrode I am ensuring a consistant size spark every time (until the plug wears out) and a spark that is not
shrouded by the electrode curving above it.
Well thatÂ’s the theory anyway.
Andy
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Posted By : Leon Guyot, 07-Jun-2007, 03:19pm
Andy,
Do you index your plugs as well?
Léon