Just changed the spark plugs

[Howard]

The gap size was almost double the initial setting. :shocked:

 

[Mark R]

Meh.

My Dad once ran his Camry for 60k on one set of plugs (not platinum either). The center electrode had dug itself a hole in the central insulator.

Car ran fine.

 

[DarkManX]

Originally posted by: Mark R
Meh.

My Dad once ran his Camry for 60k on one set of plugs (not platinum either). The center electrode had dug itself a hole in the central insulator.

Car ran fine.

isnt that what plugs are supposed to last u for?

 

[Mark R]

I think the service interval was 10 or 20k.

60k is supposed to need platinum plugs.

 

[Zenmervolt]

Originally posted by: Mark R
Meh.

My Dad once ran his Camry for 60k on one set of plugs (not platinum either). The center electrode had dug itself a hole in the central insulator.

Car ran fine.

I'm sure it ran. I'm extremely doubtful that it "ran fine". It's possible that your dad simply didn't pay enough attention to notice the difference, but I guarantee that there was a difference.

Interval for copper plugs is inspect at 15,000 miles, replace at 30,000.

ZV

 

[Pacfanweb]

That's normal. I've been 90k+ on regular copper plugs. Today's ignition systems can jump a plug gap far larger than the factory spec.

The ignition system has to discharge a bigger/hotter spark to jump the big gaps, so your gas mileage will tend to increase as the gaps get bigger.
I will say that the increase isn't as dramatic with today's OBDII systems and distributor-less ignitions as it used to be.

I remember in the early 90's when the Explorers came out. They had platinum plugs, good for 60k. So I did a few, and other guys in the shop did them when they started hitting that mileage, and customers started coming back a couple weeks later complaining about reduced fuel mileage since the tune up. Reason was, the gap had gotten large enough to create a really big spark, and the combustion was better.

 

[Eli]

Originally posted by: Pacfanweb
That's normal. I've been 90k+ on regular copper plugs. Today's ignition systems can jump a plug gap far larger than the factory spec.

The ignition system has to discharge a bigger/hotter spark to jump the big gaps, so your gas mileage will tend to increase as the gaps get bigger.
I will say that the increase isn't as dramatic with today's OBDII systems and distributor-less ignitions as it used to be.

I remember in the early 90's when the Explorers came out. They had platinum plugs, good for 60k. So I did a few, and other guys in the shop did them when they started hitting that mileage, and customers started coming back a couple weeks later complaining about reduced fuel mileage since the tune up. Reason was, the gap had gotten large enough to create a really big spark, and the combustion was better.

 

[Zenmervolt]

Originally posted by: Pacfanweb
The ignition system has to discharge a bigger/hotter spark to jump the big gaps, so your gas mileage will tend to increase as the gaps get bigger.
I will say that the increase isn't as dramatic with today's OBDII systems and distributor-less ignitions as it used to be.

The ignition discharges what the coil generates. Are you saying that the coil increases the amount of voltage it supplies when the gap is larger? I have always been under the impression that the coil output voltage was fixed.

Also, every single time I have replaced spark plugs, mileage has improved not gotten worse.

ZV

 

[Pacfanweb]

Originally posted by: Zenmervolt

Originally posted by: Pacfanweb
The ignition system has to discharge a bigger/hotter spark to jump the big gaps, so your gas mileage will tend to increase as the gaps get bigger.
I will say that the increase isn't as dramatic with today's OBDII systems and distributor-less ignitions as it used to be.

The ignition discharges what the coil generates. Are you saying that the coil increases the amount of voltage it supplies when the gap is larger? I have always been under the impression that the coil output voltage was fixed.

Also, every single time I have replaced spark plugs, mileage has improved not gotten worse.

ZV

The coil has to generate a bit more energy to jump the larger gap. It's very well known that a larger gap=hotter spark. Basically, the voltage is the pressure that makes the spark jump the gap. It takes more pressure to jump the larger gap, so if you gap the plugs wider, you'll get a hotter spark...to a point. You can obviously gap them so wide that they won't spark.

That's why, back in the day, if you had a flooded engine, you could take the coil wire loose and just set it on the coil tower, but not with the metal in the wire touching the tower. That would let you get a hotter spark and help burn off the excess gas.
Obviously not a problem particularly with today's EFI cars...if they flood, they really flood, plus, you obviously don't have distributor caps much, if any.
I guess you could still do this with an engine that had coil packs, but it'd be a pain taking every one loose.
Works great on lawnmowers and other small engines, though.

Google "larger gap hotter spark" and you'll find tons of links that will probably have a more in-depth explanation of this.

 

[Pacfanweb]

Originally posted by: Eli

Originally posted by: Pacfanweb
That's normal. I've been 90k+ on regular copper plugs. Today's ignition systems can jump a plug gap far larger than the factory spec.

The ignition system has to discharge a bigger/hotter spark to jump the big gaps, so your gas mileage will tend to increase as the gaps get bigger.
I will say that the increase isn't as dramatic with today's OBDII systems and distributor-less ignitions as it used to be.

I remember in the early 90's when the Explorers came out. They had platinum plugs, good for 60k. So I did a few, and other guys in the shop did them when they started hitting that mileage, and customers started coming back a couple weeks later complaining about reduced fuel mileage since the tune up. Reason was, the gap had gotten large enough to create a really big spark, and the combustion was better.

What's the face for? Read my post right above this one. Explains a little further.

 

[LTC8K6]

The coil has no clue what the gap is and it generates the same voltage all the time.
The fact that that voltage will also jump a larger gap, doesn't mean that it's better.
If a larger gap would work better, the mfg would use it.

 

[Pacfanweb]

Originally posted by: LTC8K6
The coil has no clue what the gap is and it generates the same voltage all the time.
The fact that that voltage will also jump a larger gap, doesn't mean that it's better.
If a larger gap would work better, the mfg would use it.

No, they wouldn't because they know the plug is going to wear and the gap is going to increase. They know where to set the gap from the factory and they know at what rate the plug gap is going to increase, so they know what mileage to recommend the plugs be changed before a misfire starts.

As the plugs wears, you get a hotter spark. Google it, it's not a debatable fact. I was taught in CC that the coil has to generate more voltage to do this, and I've never heard different in my entire professional life.
Bigger gap=hotter spark. That's the way it works. Maybe the coil generates the same voltage all the time, and the factory gap just doesn't make use of that voltage.....I could see that.
But the fact of the matter is, it takes additional voltage to jump a larger gap. Makes sense that the factory would engineer more coil voltage than needed to allow for plug wear.
If they started the plugs out at the max gap the ignition system was capable of jumping, the car would obviously start missing as soon as the plug wore a bit.

 

[LTC8K6]

When tuners want to open the gap for a desired effect, they change the ignition components to provide the hotter spark across the larger gap.

Simply opening the gap does not make the spark hotter.

The denser the air/fuel mix in the cylinder, the smaller the gap, iirc. High compression or turbos, blowers, usually require a smaller gap.

To go with a larger gap, you'd need to change ignition components.

 

[Zenmervolt]

Originally posted by: Pacfanweb

Originally posted by: LTC8K6
The coil has no clue what the gap is and it generates the same voltage all the time.
The fact that that voltage will also jump a larger gap, doesn't mean that it's better.
If a larger gap would work better, the mfg would use it.

No, they wouldn't because they know the plug is going to wear and the gap is going to increase. They know where to set the gap from the factory and they know at what rate the plug gap is going to increase, so they know what mileage to recommend the plugs be changed before a misfire starts.

As the plugs wears, you get a hotter spark. Google it, it's not a debatable fact. I was taught in CC that the coil has to generate more voltage to do this, and I've never heard different in my entire professional life.
Bigger gap=hotter spark. That's the way it works. Maybe the coil generates the same voltage all the time, and the factory gap just doesn't make use of that voltage.....I could see that.
But the fact of the matter is, it takes additional voltage to jump a larger gap. Makes sense that the factory would engineer more coil voltage than needed to allow for plug wear.
If they started the plugs out at the max gap the ignition system was capable of jumping, the car would obviously start missing as soon as the plug wore a bit.

I don't think that "hotter" is the right terminology. It just plain doesn't make sense to me.

Now, a physically larger spark (which is what happens as the gap increases), would be less shielded and certainly could help the mixture ignite more reliably, that I can understand. I think that I got caught up in the idea of it being physically "hotter", which confused me.

110% agreement that the manufacturer's gap is set to accommodate wearing of the plugs, which is why a manufacturer wouldn't just specify the largest possible gap.

ZV

 

[Zenmervolt]

Originally posted by: LTC8K6
The denser the air/fuel mix in the cylinder, the smaller the gap, iirc. High compression or turbos, blowers, usually require a smaller gap.

I think that has more to do with preventing spark knock and pre-ignition than it does with delivering the spark. Not 100% sure though.

ZV

 

[LTC8K6]

The very low emissions of modern vehicles prove that the ignition systems designed by the mfgs are doing a great job, and no wider plug gaps are necessary or useful.

Now, if you have done mods, then you may indeed need to address the ignition system.

 

[LTC8K6]

"I think that has more to do with preventing spark knock and pre-ignition than it does with delivering the spark. Not 100% sure though."

No, the timing is adjusted for that. The smaller gap is for the denser mix, iirc.

 

[Zenmervolt]

Originally posted by: LTC8K6
"I think that has more to do with preventing spark knock and pre-ignition than it does with delivering the spark. Not 100% sure though."

No, the timing is adjusted for that. The smaller gap is for the denser mix, iirc.

I was thinking more along the lines of it maybe reducing the likelihood of a hotspot forming on the plug, but that's pure speculation on my part.

ZV

 

[LTC8K6]

Hey, as always, people can do what they want.

I see what he's saying, but the mfgs know everything there is to know about the question, and they don't pick plugs and gaps out of a hat.

 

[Zenmervolt]

Originally posted by: LTC8K6
The very low emissions of modern vehicles prove that the ignition systems designed by the mfgs are doing a great job, and no wider plug gaps are necessary or useful.

While I agree that a wider gap isn't necessary, I can see it being "useful" from a power standpoint. The problem being that the plugs to wear and people don't want to have to re-gap their plugs every 5,000 miles to prevent misfiring. With it becoming increasingly common for plugs to be specified as 100,000 mile or more items, I can completely see a manufacturer spec-ing the gap to the smallest practical gap, designing a good amount of overhead into the coil (or its more modern equivalent), and expecting the gap to increase significantly during the life of the plugs figuring that the minor power difference isn't something that drivers will care about (or even notice) enough to put up with vastly increased maintenance requirement.

I definitely see it as an area of very small marginal returns though.

ZV

 

[Pacfanweb]

Originally posted by: LTC8K6
When tuners want to open the gap for a desired effect, they change the ignition components to provide the hotter spark across the larger gap.

Simply opening the gap does not make the spark hotter.

The denser the air/fuel mix in the cylinder, the smaller the gap, iirc. High compression or turbos, blowers, usually require a smaller gap.

To go with a larger gap, you'd need to change ignition components.

Sorry, but all you have to do is google "bigger gap hotter spark" or something similar, and you'll find dozens of references to what I'm talking about.
"Hotter" may not be exactly right. "Fatter", "Bigger" might be closer to what it actually does.

But the bottom line is, you increase the gap, you get a bigger spark. I guess fire is fire, so I doubt it's physically any hotter, but a "hotter" spark usually refers to the size of the spark, not the actual temp.

You are correct about the smaller gap with blown engines. Reason is, there's so much more pressure in the cylinder, it's harder for the spark to jump the gap. Lots of tuners refer to this as "blowing the spark out".
These engines, along with higher compression engines, need a bigger spark, or more correctly, more voltage to push the spark across the gap in the more adverse conditions.
In most stock engines these days, the stock ignition can easily jump twice the gap that the factory recommends. And believe me, by the time these 100k tuneups roll around, lots of them have twice the gap, or pretty close to it.

But what I said is correct, if not worded properly. Bigger gap=hotter/bigger/fatter/whatever you want to call it, spark.

I did not recommend opening your gap up for everyone, just a general description of what happened with one particular model of car as the plugs aged.
It is an absolute fact that the early Explorers saw their gas mileage increase as the plugs wore, and also a fact that many, many people complained of reduced mileage immediately after getting plugs replaced, with nothing else done that would have adversely affected mileage. The reason behind this came from Ford, it wasn't just something we at one shop thought up on our own. And they should know since, as you said,

the mfgs know everything there is to know about the question

.

 

[LTC8K6]

I know how google works.

I stand by what I said.

I can't buy the Explorer story without evidence.

 

[Pacfanweb]

Originally posted by: LTC8K6
I know how google works.

I stand by what I said.

I can't buy the Explorer story without evidence.

Suit yourself. You know what they say "you can lead a horse to water..."

 

[Iron Woode]

very interesting thread.

let's take my old school Mopar as an example.

I am running the factory electronic ignition. My ignition puts out roughly 45,000 volts. Points were much lower usually in the 25,000 range. A coil is nothing more than a step-up transformer, with max voltage based on the ratio of windings.

Throughout the 70's, spark plug gaps got wider and wider. Some up to .060. The reason for this was due to the very lean air/fuel mixtures for emissions and fuel economy. The larger gaps allowed a longer duration spark in order to ignite the mixtures.

In a performance situation, finding the optimal plug gap is a tedious procedure. The results are usually very small, but every bit counts.

as for a flooded carbed engine, the solution is simple: pump the gas pedal 3 times and hold it to the floor while cranking the engine over. It will start after 10 or 15 seconds. I have never seen this procedure fail, assuming the engine does run properly in the first place and the battery is good.

 

[LTC8K6]

"The larger gaps allowed a longer duration spark"

Now that is correct.