Spark/gap

[CarolinaMan1500]

So I didn't see too many recent talks about this and I'm not a big mech guy so here goes.

I went to buy new plugs for my '13 5.7 and there are copper, platinum, and iridium which we all know but my question is first, why two plugs per cylinder with different gaps? And 2nd, the plugs made of different metals have different gaps than each other how do you know what gaps are okay?

Sry if this is dumb, I've done plug changes before but this one just has me questioning dome things.....

 

[jlpowell84]

Great post and I will piggy back on it. I am looking into changing the plugs on my new used 2012/65k miles. I dont know when it was done last and planned on looking at one before final decision but it's not like the plugs cost hundreds of dollars. Youtube showed a few guys doing it for the first time with hardest being the back plugs do to tight spaces but nothing super technical.

So what plugs are best? I don't mind spending a couple bucks more for longer lasting/better performing.

I have only done plug changes on basic four bangers so I am curious about your question. And is there a guide on this forum for changing plugs with ALL the tech info including gaps, torque specs...?

 

[CarolinaMan1500]

Great post and I will piggy back on it. I am looking into changing the plugs on my new used 2012/65k miles. I dont know when it was done last and planned on looking at one before final decision but it's not like the plugs cost hundreds of dollars. Youtube showed a few guys doing it for the first time with hardest being the back plugs do to tight spaces but nothing super technical.

So what plugs are best? I don't mind spending a couple bucks more for longer lasting/better performing.

I have only done plug changes on basic four bangers so I am curious about your question. And is there a guide on this forum for changing plugs with ALL the tech info including gaps, torque specs...?

Carful with the torque spec stuff, I don't want this to turn into a do i use anti seize topic like the rest.

 

[jlpowell84]

Carful with the torque spec stuff, I don't want this to turn into a do i use anti seize topic like the rest.

I wouldn't know about those threads, just joined recently. Will be interesting to hear about the two diff gaps.

 

[Riccochet]

I haven't heard of there being different gaps. Just get the stock Mopar copper plugs and gap them to .043. Use or don't use anti-seize and tighten them down until snug / crushed the crush washer.

Really, the stock plugs are best.

 

[TRXHemi]

In the back of your owner's manual, it specifies the plug part numbers and the gap. Just follow that, and you won't go wrong!!

 

[Hemi450hp]

Never heard of the there being different gaps in the plugs. I always install the stock Mopar NGK plugs gapped at .044.

 

[charonblk07]

Stock plugs are gapped at .043 so anything close to that is perfectly fine. The material used will determine how often the plugs need to be changed, it won't affect power or performance unless the plugs are soft (like copper) and are very worn from high mileage. You should always check a new plug gap before installing them but keep them the same as stock unless you are running a power adder.


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[GP4L]

So I didn't see too many recent talks about this and I'm not a big mech guy so here goes.

I went to buy new plugs for my '13 5.7 and there are copper, platinum, and iridium which we all know but my question is first, why two plugs per cylinder with different gaps? And 2nd, the plugs made of different metals have different gaps than each other how do you know what gaps are okay?

Sry if this is dumb, I've done plug changes before but this one just has me questioning dome things.....

I'm pretty sure you're confusing the plugs for the 4.7L engine. The 4.7 uses 8 copper and 8 "premium" plugs, coppers at one gap, the premium at a different gap. I don't know why, but I'd guess it's mostly a redundant system, where the premium plug acts as the "backup." It could very well play a role in combustion efficiency though.

2 plugs per cylinder adds redundancy to keep all 8 cylinders firing in the event that one plug fouls out or a coil pack fails. Under normal operation, it ignites a dual flame front in the cylinder, which is more efficient than a single flame front. It's been used/proven in aviation for a LONG time, and some sport bike manufacturers started adding duel ignition in recent years, noting the same improvements aviation sees in power output and lower fuel consumption.

 

[GP4L]

Stock plugs are gapped at .043 so anything close to that is perfectly fine. The material used will determine how often the plugs need to be changed, it won't affect power or performance unless the plugs are soft (like copper) and are very worn from high mileage. You should always check a new plug gap before installing them but keep them the same as stock unless you are running a power adder.


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Um, the plug gap should be right on, and it's not hard to gap them to an exact specification. There is a huge difference if his plugs are at .040 compared to .050. Just because the engine "runs" doesn't mean that it has, or hasn't lost performance.

Also, the way you wrote the statement about materials is a little confusing, so I'll elaborate on the facts about plugs. Copper plugs conduct the best, so you will get the most efficient combustion from a good copper plug. I mean good in two ways: a quality manufacturer, and good condition. Copper plugs *typically* don't last as long as a "premium" plug does.

OP, gap your plugs exactly to specifications written in your owners manual. If you can't find it, call your favorite dealer and ask a technician. Make sure you use real Feeler Gauges, and not some cheap spark plug gap measuring tool from Autozone.

 

[chris1965]

the only material which is more conductive than copper is silver.

Conductive Materials or Metal Conductivity - TIBTECH innovations -

The only reason why other materials are used is, that they are lasting longer, especially with platinum the melting point is higher, so higher pressure and temps can be handled better and, another important aspect: the heat expansion is smaller, so the sustainable spark is more stable. the con's are: higher voltage is needed to get the same intense spark which causes need of higher quality materials in the coils to keep them cooler and lasting. But also there it is helpful if the gap is smaller. but also a smaller gap means a shorter spark and if too small, the gas-mix does not burn as good/quick. that's the reason for the gap difference of copper and platinum / iridium plugs.
A bigger gap means at the end a higher voltage from the coil, which can harm the coils. 20kv should be ok, above it gets wired. this can be checked actually with a oscilloscope. all sparks should be in the same range.
That's about it. If you have a standard plug, I would not drive it longer than 20-30k miles. therefore, standard plugs are cheap as heck and for me or others with the thumbs on the right hand, 30 minutes and 2 beer cost nothing.
nevertheless- in a hemi I prefer NGK platinum plugs due to prior explained reasons and also they are in the middle of the price range. Iridium- well- who wants it but for the hemi not necessary. NGK, because I use them since ever (actually since VW Audi threw BOSH out because of quality problems and also because they was not able to keep up with needed specification causing engine failures up to destroyed pistons). Never had a problem with NGK.