E-Fans

[Longshot270]

yeah....you might be overthinking.
If your tires are bigger but the same weight and width you might see an improvement. But when you increase the tire size you increase the weight which has significant more draw on your mileage.

I was just wondering what your rpms were because I'll be putting on some heavy 32/33 a/ts in a month or two probably.

[Jackpine]

Personally, I think the added mass has only a modest effect on the acceleration when you go to larger tires. Yes, there's more weight to get moving, but that's a small increase. Using my tire as an example, increasing the diameter by two inches adds 15# per tire, 60# for four (about the weight of a child in the truck). Remember, a tire is mostly air.

Of course, there's more rotating inertia to overcome with a larger tire but:

My tires (about 31" with "squish" factored in) spin at about 650 rpm at 60 mph, hardly a dizzying rotational speed. 33" tires spin at 611 rpms and 35" tires spin at 576. So even though there is a small increase in rotational inertia, a larger tire doesn't even have to be brought up to the same rotational speed, there's a "cancellation" effect. Once the tires reaches that speed, it wants to stay there.

But, let's assume you see 250 ft-pounds of RW torque at the real axle. This translates to a "pushing" force of 193.5# at the road contact surface of a 31" tire. If you increase the tire diameter to 33", that force drops to 181.8#. With a 35" tire, you are down to 171.5#. The change from 31 to 33 inch tires gives you a 6% reduction in accelerative force, and a change from 31 to 35 inches reduces the accelerative force you feel by 11%.

Those percentages are significant and are the result of a loss of "mechanical advantage" caused by the larger tire. It is not the weight of the tire.

- Jack

[Longshot270]

Good post Jack.

[88Racing]

To the OP.
Here's a good read on Troyer's efan kit.
Troyer E-Fan - F150online Forums

[BlackSTX]

FYI: As far as the original Motorcraft plugs in your truck being standard fare cheap copper, I believe they are actually using double platinum plugs, not copper. Hence the 100k tune up interval they suggest for plug replacement.

I also do think there are probably better plugs available, but I doubt that they will truly provide you enough of a difference to alter your mileage enough to make them worth it.