Spark gap, .50 or .45?

[clevelandmike]

A few months ago, several folks suggested reducing the gap from .50 to.45 for less hesitation and smoother acceleration. I tried it and took a hit on MPG. If you changed also, let me know if your MPG changed and if you actually noticed an improvement in performance. I am using the double platinum plugs.

[quicksilverdon]

I did mine over a year ago (Champion platinums) and set them at 0.050.
My mileage has consitently crept upward to about 25+ now at nearly 80,000 miles.
I find it hard to fathom that the plug gap could have much impact on mileage. What I have read is that when folks check the gap of plugs they take out (I didn't) the gap has grown.

[Cal Cruzer]

quote:Originally posted by clevelandmike

A few months ago, several folks suggested reducing the gap from .50 to.45 for less hesitation and smoother acceleration. I tried it and took a hit on MPG. If you changed also, let me know if your MPG changed and if you actually noticed an improvement in performance. I am using the double platinum plugs.

On a turbo you can get a "blow out" effect @ high boost / high RPM. Closing the gap can reduce this problem. I run a .42-.45 on my turbo. It has helped some. On a NA car I don't believe it is necessary.

[Mike-in-Orange]

I agree with Cal. All of the talk I've heard about dropping the plug gap has been with the Turbo only.

[Jimbo]

Let me see if I got this right 50 on the NA's
and 45 on the turbos?

[sca037]

Based on my interpretations of the recommendations of the good folks on this Forum, I set our NA car's plug gap at .042"
I did this because the original plugs (at 60K miles) were at a giant .085" (!) when I took them out...and figured I could get better "area under the curve" sweet spot time by initially setting the Double Platinums to the low side of the scale.

10K miles later.....so far so good [?]
Brian

[KingKole02]

I guess I could say I did notice a slight change in gas mileage. I did record to runs of 21, then installed my DBL plats and 8.5mm wires, changing the gas from .5 to .45 and now record 19 MPG. I have notice a slight better performance change however.