Spark Plug Gap Question

[virgamanda]

I have heard that if you increase the gap from .054 to about .060 or so, you will gain more fuel mileage and a little power. Does anyone here have any ideas on this? I have a 97 Explorer 4.0 SOHC I am replacing the wires and plugs this weekend.

[Scrapper]

i'd say thats about right on 60 but i would call autozone or advanced to see. but it should tell you under the hood on the gap.

[shorod]

Don't you think if it were that simple to gain a few HP and improve the fuel economy, Ford would spec it that way?

If you increase the gap, you're effectively reducing the intensity of the spark, right? Reducing the intensity of the spark is not going to make more power, and I doubt it would increase economy either. A less intense spark would create a less abrupt explosion of the air/fuel mixture. This could mean that the piston is already traveling downward on the power stroke as the mixture is still igniting. Since the piston would be traveling downward, any unburned air/fuel mixture is under less compression and therefore less explosive. What's one way that manufacturers increase horsepower? Right, they start with a high compression engine. Seems to me like a good way to cause a rich exhaust stream, which your PCM will compensate for by adjusting the timing. So, ultimately I think you'd end up with less power and no improvement in fuel economy in an extreme case.

However, I doubt you'll notice ANY difference by changing your gap by 6 one thousandths of an inch. It wouldnt' surprise me if the tolerance of your gap gauge is larger than that.

-Rod

[Scrapper]

well i've always heard the alonger spark will save you gas and i know why and if you wana get more hsp gap them less but burn more gas..

[shorod]

I'd agree with less gap may equal slightly more HP. Not sure how larger gap would save fuel. I haven't read anything either way, just trying to rationalize. It sounds like we both agree that you're not going to get both improvements out of a larger gap. I also doubt that changing the gap by a few thousandths of an inch will make a noticeable difference either way, at least if you stick with the same plug. If you start dinking with heat ranges, then you might be able to notice a difference.

-Rod

[way2old]

Wider gap makes the coil produce more current to allow the spark to jump the wider gap. So in effect, you are over working the coil to get the spark to cross the wider gap. So if your theory is true---the older the plug is, the wider the gap is--the more mileage and power you get? In my years of experience, the opposite is usually true. Gap your plugs to the lower limit so it will last you longer.

[virgamanda]

I appreciate all your input. The decal under the hood says .052-.056 so I went middle of the road and gaped them at .054 and I noticed a huge difference in power. The old plugs had about 60000 miles on them and they looked like they were burning normal, but the gap had increased to about .060-.064 on most of them. I went ahead and replaced the wires as well.

[Scrapper]

so are you up ang going now? let me know.and yes on the 60 gap..