Spark Plug Gap Variations ... Platinum, Iridium, Copper
07-10-2015, 10:14 AM
#1
Spark Plug Gap Variations ... Platinum, Iridium, Copper
I know there are as many spark plug threads as there are motor oil threads so I apologize for mucking up the database with yet another, but I'm not sure variations in plug gap has been discussed.
I've been doing some reading lately on plug materials and specifically (as I can find it) plug materials most suited to the VQ30 ... not much to find.
However, I have run across some interesting specs and am wondering if any of you guys who actually know about this stuff ... and not necessarily those who simply have opinions ... care to provide some input.
I had a bout of mechanical failures over the past number of months that lead me to do a butt-load of work on my car. In doing so I replaced an equally notable butt-load of parts and pieces, 6 of which were the spark plugs. I used NGK copper plugs this time instead of the OE Platinums.
Always **** retentive, I've since been wondering if my car might have appreciated the OE Platinums more ... so I did and continue to do some reading.
Some of the information I've found suggests that in the situation that you're using Platinum or Iridium plugs, the gap should be .039 to .044. Our owner's manuals (at least mine does) states the .044 spec and also states that if OE plugs (Platinum) are used, gapping is not necessary or recommended. So with my coppers, I gapped them to the OE .044 spec.
But what I've read is that if your using coppers, the gap should actually be .031 to .035, not the manufacturer (Platinum) spec of .044.
Any of you guys have any insight into this ... is this common knowledge I'm just now learning about?
If this is a fact then my coppers are gapped way too big.
I've been doing some reading lately on plug materials and specifically (as I can find it) plug materials most suited to the VQ30 ... not much to find.
However, I have run across some interesting specs and am wondering if any of you guys who actually know about this stuff ... and not necessarily those who simply have opinions ... care to provide some input.
I had a bout of mechanical failures over the past number of months that lead me to do a butt-load of work on my car. In doing so I replaced an equally notable butt-load of parts and pieces, 6 of which were the spark plugs. I used NGK copper plugs this time instead of the OE Platinums.
Always **** retentive, I've since been wondering if my car might have appreciated the OE Platinums more ... so I did and continue to do some reading.
Some of the information I've found suggests that in the situation that you're using Platinum or Iridium plugs, the gap should be .039 to .044. Our owner's manuals (at least mine does) states the .044 spec and also states that if OE plugs (Platinum) are used, gapping is not necessary or recommended. So with my coppers, I gapped them to the OE .044 spec.
But what I've read is that if your using coppers, the gap should actually be .031 to .035, not the manufacturer (Platinum) spec of .044.
Any of you guys have any insight into this ... is this common knowledge I'm just now learning about?
If this is a fact then my coppers are gapped way too big.
Last edited by Turbobink; 07-10-2015 at 12:26 PM.
07-10-2015, 02:33 PM
#2
How big of a gap you need is determined by 3 factors.
The compression ratio of the engine. The higher the compression, the smaller the gap. But this is total opposite of what you want to do and this gets compensated for.
The material the plug is made out of. The harder the material, the smaller the gap. Again this is opposite of what you want to do and gets compensated for. Copper is the softest metal and will give the best spark. Next is platinum and gives a lesser spark, followed by iridium plugs that give less spark than platinum. But the softer the metal, the quicker the plug wears out.
The third thing is the voltage of the spark. The higher the voltage, the more powerful the spark and can jump a bigger gap. This is the compensating factor
Ideally, you want a bigger gap for a bigger spark to ignite the fuel mixture faster. Years ago car ignition systems only had 30K volt systems. Now they are over 60K volts. This allows the manufacturers to put in iridium plugs and advertise that you don't have to change plugs as often.
Nissan feels the .040 is the best gap for a platinum plug, so I would go with that. If you put in copper plugs, I would go with .040 minimum. I would try .050 and see if there seemed to be any problems under full load.
The compression ratio of the engine. The higher the compression, the smaller the gap. But this is total opposite of what you want to do and this gets compensated for.
The material the plug is made out of. The harder the material, the smaller the gap. Again this is opposite of what you want to do and gets compensated for. Copper is the softest metal and will give the best spark. Next is platinum and gives a lesser spark, followed by iridium plugs that give less spark than platinum. But the softer the metal, the quicker the plug wears out.
The third thing is the voltage of the spark. The higher the voltage, the more powerful the spark and can jump a bigger gap. This is the compensating factor
Ideally, you want a bigger gap for a bigger spark to ignite the fuel mixture faster. Years ago car ignition systems only had 30K volt systems. Now they are over 60K volts. This allows the manufacturers to put in iridium plugs and advertise that you don't have to change plugs as often.
Nissan feels the .040 is the best gap for a platinum plug, so I would go with that. If you put in copper plugs, I would go with .040 minimum. I would try .050 and see if there seemed to be any problems under full load.
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