Spark Plug Wires..??
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Seasoned HDF Member
Joined: Mar 2010
Posts: 21,116
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From: Poolville
Spark Plug Wires..??
I've seen discussions about spark plugs and heat ranges as well as Header pipes and lengths and even diameters of plug wires but have not seen anything on lengths..
Why are we using 2 different lengths which equates to different total resistances. With a rear cable length of 7" and 2k ohms plus the spark plug of and a stock 6R12 plug with 110 ohm the resistance of the rear circuit is roughly 2100ohm.. Now the front cable measures 4k ohm plus the 6R12 plug puts it at 4100 ohm which is twice the rear.. Will this affect spark timing or should both circuits be equal lengths or does the ECM compensate for this.. Another thing I noticed was the difference in resistance between a 6R12 and an NGK DCPR7E (which is the direct replacement) is approximately 5k ohm.. Could this be the reason I saw spark knock retard with the NGK's in my data logs at times and none with the OEM's.. AND should we run equal plug wire lengths..? Thanks..
Why are we using 2 different lengths which equates to different total resistances. With a rear cable length of 7" and 2k ohms plus the spark plug of and a stock 6R12 plug with 110 ohm the resistance of the rear circuit is roughly 2100ohm.. Now the front cable measures 4k ohm plus the 6R12 plug puts it at 4100 ohm which is twice the rear.. Will this affect spark timing or should both circuits be equal lengths or does the ECM compensate for this.. Another thing I noticed was the difference in resistance between a 6R12 and an NGK DCPR7E (which is the direct replacement) is approximately 5k ohm.. Could this be the reason I saw spark knock retard with the NGK's in my data logs at times and none with the OEM's.. AND should we run equal plug wire lengths..? Thanks..
Grand HDF Member
Joined: Aug 2020
Posts: 4,798
Likes: 5,889
From: Knoxville
I've seen discussions about spark plugs and heat ranges as well as Header pipes and lengths and even diameters of plug wires but have not seen anything on lengths..
Why are we using 2 different lengths which equates to different total resistances. With a rear cable length of 7" and 2k ohms plus the spark plug of and a stock 6R12 plug with 110 ohm the resistance of the rear circuit is roughly 2100ohm.. Now the front cable measures 4k ohm plus the 6R12 plug puts it at 4100 ohm which is twice the rear.. Will this affect spark timing or should both circuits be equal lengths or does the ECM compensate for this.. Another thing I noticed was the difference in resistance between a 6R12 and an NGK DCPR7E (which is the direct replacement) is approximately 5k ohm.. Could this be the reason I saw spark knock retard with the NGK's in my data logs at times and none with the OEM's.. AND should we run equal plug wire lengths..? Thanks..
Why are we using 2 different lengths which equates to different total resistances. With a rear cable length of 7" and 2k ohms plus the spark plug of and a stock 6R12 plug with 110 ohm the resistance of the rear circuit is roughly 2100ohm.. Now the front cable measures 4k ohm plus the 6R12 plug puts it at 4100 ohm which is twice the rear.. Will this affect spark timing or should both circuits be equal lengths or does the ECM compensate for this.. Another thing I noticed was the difference in resistance between a 6R12 and an NGK DCPR7E (which is the direct replacement) is approximately 5k ohm.. Could this be the reason I saw spark knock retard with the NGK's in my data logs at times and none with the OEM's.. AND should we run equal plug wire lengths..? Thanks..
Thread Starter
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Seasoned HDF Member
Joined: Mar 2010
Posts: 21,116
Likes: 7,640
From: Poolville
Not sure, that's why I'm asking.. With the way everything else is always got to be the same from front to rear cylinder How come the wires aren't and does it make a difference...???
Seasoned HDF Member
Joined: Aug 2008
Posts: 5,071
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hype is hype be it oil filter, plug or wires.
that resistance is there for one reason only, to reduce electrical interference. with the advent of electronic control and emf being inducted into surrounding wire systems that use data control that will go stupid when the two mix. the computer is stupid and can only do what told.
if you are old enough to remember radios in cars back when where there was wine from the alternator and static from the ignition you will get the idea, they shunted the ac to ground via a filter capacitor.
the resistance is NO issue to the high tension lead, even for ion sense.
that resistance is there for one reason only, to reduce electrical interference. with the advent of electronic control and emf being inducted into surrounding wire systems that use data control that will go stupid when the two mix. the computer is stupid and can only do what told.
if you are old enough to remember radios in cars back when where there was wine from the alternator and static from the ignition you will get the idea, they shunted the ac to ground via a filter capacitor.
the resistance is NO issue to the high tension lead, even for ion sense.
Thread Starter
|
Seasoned HDF Member
Joined: Mar 2010
Posts: 21,116
Likes: 7,640
From: Poolville
hype is hype be it oil filter, plug or wires.
that resistance is there for one reason only, to reduce electrical interference. with the advent of electronic control and emf being inducted into surrounding wire systems that use data control that will go stupid when the two mix. the computer is stupid and can only do what told.
if you are old enough to remember radios in cars back when where there was wine from the alternator and static from the ignition you will get the idea, they shunted the ac to ground via a filter capacitor.
the resistance is NO issue to the high tension lead, even for ion sense.
that resistance is there for one reason only, to reduce electrical interference. with the advent of electronic control and emf being inducted into surrounding wire systems that use data control that will go stupid when the two mix. the computer is stupid and can only do what told.
if you are old enough to remember radios in cars back when where there was wine from the alternator and static from the ignition you will get the idea, they shunted the ac to ground via a filter capacitor.
the resistance is NO issue to the high tension lead, even for ion sense.
Old school to new school is quite a curve... But I'm getting there thanks to you guys and researching and having the ability to know the difference between a mekanic and a Mechanic... Lol...
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Road Warrior
Joined: Mar 2013
Posts: 1,923
Likes: 587
From: Alorton, Illinois
There is accessible delay setting in some ECU's. Time from triggered spark to actual spark. This includes all latency and not just plug wires. The way to test is to set timing at a constant and with a timing light. See if the timing drifts as rpms goes up. You can't change it in the HD Delphi but if it really mattered. One could test a short wire to an extremely long one to see if it makes a difference to the error of what we have to test with.
If one has set timing for the build, on the build, with the tools available. Does it really matter? If we are dealing with a delay in the .03-.05 milliseconds. How much does that .02 ms swing equate to ignition degrees at 2000 rpm compared to 6000. If we have our base angle set and add subtract all other ignition tables to get an actual ignition degree of trigger at 25 and it is actually 26 because of latency. Isn't it stilled tuned for best power by our indicated numbers?
Look at piggyback tuning of ignition. Without even knowing the base ignition numbers. You can still get the bike in a decent state of tune.
If one has set timing for the build, on the build, with the tools available. Does it really matter? If we are dealing with a delay in the .03-.05 milliseconds. How much does that .02 ms swing equate to ignition degrees at 2000 rpm compared to 6000. If we have our base angle set and add subtract all other ignition tables to get an actual ignition degree of trigger at 25 and it is actually 26 because of latency. Isn't it stilled tuned for best power by our indicated numbers?
Look at piggyback tuning of ignition. Without even knowing the base ignition numbers. You can still get the bike in a decent state of tune.
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Seasoned HDF Member
Joined: Aug 2008
Posts: 5,071
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ion sense has a greater range than one thinks. ion sense goes back a long ways, we used it in the 90's on industrial drivers.
ion sense can tell a lot of info, like plugs resistance under fire, current draw, miss fire and more. all it is basically a piggy back current ride on a already established current flow, without that ion sense is dead.
think about it, a normal plug fires around 8k but a time goes on and wear sets in, the plug will fire at higher levels until the coil can no longer support ignition and will fire at max capacity, if the coil is say 50k, then that is the ball park number. not saying resistance has no effect as it does, reason why ion sense can detect issues, just that there is a wide berth.
there are many wire types each with their own hype from carbon core to dual core from resistive to capacitive.
ion sense can tell a lot of info, like plugs resistance under fire, current draw, miss fire and more. all it is basically a piggy back current ride on a already established current flow, without that ion sense is dead.
think about it, a normal plug fires around 8k but a time goes on and wear sets in, the plug will fire at higher levels until the coil can no longer support ignition and will fire at max capacity, if the coil is say 50k, then that is the ball park number. not saying resistance has no effect as it does, reason why ion sense can detect issues, just that there is a wide berth.
there are many wire types each with their own hype from carbon core to dual core from resistive to capacitive.
Thread Starter
|
Seasoned HDF Member
Joined: Mar 2010
Posts: 21,116
Likes: 7,640
From: Poolville
ion sense has a greater range than one thinks. ion sense goes back a long ways, we used it in the 90's on industrial drivers.
ion sense can tell a lot of info, like plugs resistance under fire, current draw, miss fire and more. all it is basically a piggy back current ride on a already established current flow, without that ion sense is dead.
think about it, a normal plug fires around 8k but a time goes on and wear sets in, the plug will fire at higher levels until the coil can no longer support ignition and will fire at max capacity, if the coil is say 50k, then that is the ball park number. not saying resistance has no effect as it does, reason why ion sense can detect issues, just that there is a wide berth.
there are many wire types each with their own hype from carbon core to dual core from resistive to capacitive.
ion sense can tell a lot of info, like plugs resistance under fire, current draw, miss fire and more. all it is basically a piggy back current ride on a already established current flow, without that ion sense is dead.
think about it, a normal plug fires around 8k but a time goes on and wear sets in, the plug will fire at higher levels until the coil can no longer support ignition and will fire at max capacity, if the coil is say 50k, then that is the ball park number. not saying resistance has no effect as it does, reason why ion sense can detect issues, just that there is a wide berth.
there are many wire types each with their own hype from carbon core to dual core from resistive to capacitive.