PCM Learning

[PitCritter]

I drive a 2011 F-150 FX2 w/ a 5.0L engine

I have a question regarding the PCM “learning” process.

First, some background…

Most of my mileage is a 70/30 highway/city mix. I average around 17mpg. I recently got back from a long road trip. I towed my 28’ travel trailer from upstate NY to Miami via Memphis to leave it there for the winter.

Along the way, my first tank of gas got me 8.8 (gasp) mpg. As I kept going, my mileage increased every tank until I was at a far more respectable 11.3. Halfway to Miami, I stopped for a couple of days and explored Memphis. In town, I only put on around 50 miles (without the trailer) and my mileage didn’t recover all that much.

On my first tank with the trailer back on, my mileage was back down to 8.5. Once I got to Miami, my mileage was back up to 10.1.

During all of this, I was in Tow/Haul, 6th gear locked out, at 55 mph.

I spent a couple of weeks in Miami where my in-town mileage went up to around 15mpg.

When I left for home, I fuelled up and immediately hit the highway (without the trailer). It was over two hours before my mileage hit 18. After that, it climbed steadily until I was getting 22+ mpg at 70 mph while driving through the West Virginia mountains. This is amazing, since I generally struggle to hit 20mpg at 60mph on level highways.

OK, after all that, the question.

Does the PCM learn or adjust to a style of driving? It seems that every time I drive a few miles in the city, the truck forgets how to drive efficiently on the highway.

If that’s the case, would a programmer allow me to take a snapshot of the PCM in highwat tune and re-load it when I wanted to do a highway run?

With that being said, if I drove a couple of tanks strictly in the city, should I expect my in-town mileage to increase too?

I’ve also heard that if you try E85 (not for me, thanks), you shouldn’t expect the truck to settle down for a couple of tanks. Same kinda’ thing?


These may be newbie questions, but please educate me.

[shotgun]

The current AVG MPG display on the new F150s is a lot more accurate than the previous lie-o-meters, but it's still a running average. If you really want to know your MPG, calculate it at every fill-up.

Tow/haul does not lock out 6th gear. It changes the shift points (RPMs) and timing delays (upshift and downshift).

As described in your owner's manual (or at least in mine), the TCM does learn your driving habits.

A custom tune would not allow you to take a snapshot of the TCM and PCM learned parameters as many of these are always adjusting to compensate for instrument drift, wear, environmental conditions, etc.

If you've got some spare time, try reading through this: http://www.motorcraftservice.com/vdi.../OBDSM1105.pdf

[PitCritter]

I do hand calculate every tank of gas. My numbers since new are on Fuelly if anyone's interested.

I understand the function of Tow/Haul. In addition to using it, I locked out sixth gear since even on flat ground, the engine could not maintain 55mph in sixth. It would shift up and then immediately shift back down. In the interest of saving my transmission, I used fifth as my top gear.

Thanks for the info on my "Snapshot" question. Your answer makes sense.

The referenced PDF is mostly beyond me, I'm afraid, but I do understand the gist of it. It definitely backs up your statement.

[Jackpine]

Originally Posted by PitCritter

I do hand calculate every tank of gas. My numbers since new are on Fuelly if anyone's interested.

I understand the function of Tow/Haul. In addition to using it, I locked out sixth gear since even on flat ground, the engine could not maintain 55mph in sixth. It would shift up and then immediately shift back down. In the interest of saving my transmission, I used fifth as my top gear.

Thanks for the info on my "Snapshot" question. Your answer makes sense.

The referenced PDF is mostly beyond me, I'm afraid, but I do understand the gist of it. It definitely backs up your statement.

Locking out 6th is exactly what you should have done if shifting was happening constantly.

Your "later" fuel economy figures are somewhat amazing. If the Tire Size and Gear Ratio is correct so that your odometer is accurate, you are getting superb gas mileage. Whether or not your in-town mileage will improve is beyond me. I've not seen anything like you describe in my 05.

My truck is mostly used for highway driving and highway towing, so I also cannot comment on the effect of town driving hurting highway mileage.

I WILL say that winds and upslope/downslope driving have an enormous effect on fuel economy. And, if you climb and then descend, it doesn't "cancel out" due to efficiency losses. Anytime you climb, you use more gas.

- Jack

[Power Hungry]

Driving from GA to FL, we will see as much as 22 MPG on our Expedition. Driving back, it will drop to about 19 MPG. Now, this could be in relation to fuel quality between GA and FL, or maybe just differences in trip parameters (overall altitude change, headwinds, traffic, etc.), but it is pretty consistent every time we travel.

As noted, the ECM does tend to relearn driving characteristics (aggressive driving, moderate driving, loaded, unloaded, etc.) and will readjust fuel and timing curves to meet the needs of the vehicle.

[PitCritter]

I appreciate all the input.

My rear end is 3.55. My tires are 20s. My speedo (vs GPS) is accurate to within at least 2%.

If anyone's actually interested, my mileage numbers are all at Fuelly.com. Search on username PitCritter. I've set up different accounts for tracking towing vs. non-towing.

Now...how 'bout that tuner for my '11?

[Power Hungry]

Originally Posted by PitCritter

Now...how 'bout that tuner for my '11?

You need to lean on Edge about that. Actually, I think they are working on it. I'll have to check.