Grambo99

I put Nitto 305/55/20 grapplers on my 2015 2.7 Eco boost (2wd)
I know its only the 2.7 which isn't the best motor but do I put a after market programmer (which one is the best out there today)on it to restore and gain power and most importantly Gas Mileage!
OR
is it just a matter of putting a recalibration on it, Forscan? I know hypertech makes one?
What have other 2.7 or 3.5 Eco boost owners done with larger tires?

zeromarine

Of course you will loose power and mpg. You have a lot more rolling resistance and have effectively changed the gearing of the truck. Either change them back to stock to get your power and mpg back or change the rear ended gearing so your ratio is back to what it equals to stock. That will get your power back. You will still have a loss of mpg regardless though I believe.

tvsjr

You installed larger, heavier tires with a larger road contact area (and thus higher rolling resistance)... which also reduced your effective final drive ratio.,.. and you're surprised that you lost performance and gas mileage? These issues will be exacerbated if you had a lower ratio rear end to start with (like 3.31s).

Fix the speedo (and thus the shift points) with Forscan. A tune will help. You may need to consider regearing if you had a low gear in the first place. But the only way to get everything back - especially the gas mileage - is to go back to the factory tires.

Napalm

I'd like to also point out you didn't lose any power. you lost acceleration. Engine puts out what it always did.

bigger diameter tires - move your effective gear ratio down - which reduces your acceleration and mucks up your speedometer. The speedometer fix is easy. YOu could change your rear gear ratio to readjust your final drive ratio back which would give you some of your acceleration back.

You won't get back your MPG because you are using more power to turn the heavier wheel and tire around. correcting the tire size in the computer and fixing the speedometer will correct your mpg estimate too - as it also corrects your miles driven. right now your truck thinks you drive X MPH faster than it really is - and you are going X miles further than you really are.

chimmike

What were you expecting would happen when you put taller, heavier tires on without changing gearing?

the 2.7 makes plenty of power.

Do you know what your stock rear gears are?

Grambo99

how do you correct the tire size in the computer?

Grambo99

I do not but need to find out if its not too expensive I would be willing to re-gear?

Napalm

most standalone tuning systems will do it. Forscan will do it

and PC based tuning systems will do it. (hp tuners, efi live, etc)

I'd recommend forscan and a quality BT OBD connector. (I use the OBDlink MX)

Napalm

THe gears alone will probably be north of 350 dollars. work to put in , is a decent DIY job but a shop would probably charge another 150 or so with fluid and the like.

Never looked it up for the F150 but for my 4 door family car it's a 800 dollar question.

FourBitty

I'll never, ever understand why people complain or even ask about 'fuel mileage' when discussing bigger tires and/or lifts.

You buy a pickup truck which already should be expected to have worse fuel mileage then any car, reduce its usefulness as a truck by lifting/leveling/installing bigger tires which means you probably mostly just commute with it, then complain about losing a MPG or two? Good lord.