What Gary and Carl and Red and Bill are trying to say is that the FEH has been maximized for FE.....virtually any change to some sort of off-the-shelf item (wheel, tire, spoiler, etc.) is going to be a hit to FE. [Or Ford would have easily incorporated it in the design]

Notice how most folks report a 1 - 3 mpg increase immediately upon inflating the tires to 40psi. When you do that you have minimized the contact patch that affects friction. Think if you ran on bicycle tires how much less friction would be in the tires (not the best for braking, everything is a trade off) and how much FE would improve.
The contact area is the first number the "235". 255 is going in the opposite direction of reducing the contact patch.....but may improve handling, comfort, noise, braking, etc.

MIL = malfunction indicator lamp, you know "check engine", etc.

You probably won't be able to think of something overnight that the Ford Engineers haven't considered over the last 6 years.

 

DesertDog, perhaps I'm missing something obvious, but how does the FEH know how many tire rotations per (real) mile? It can't see the mile-markers, and they're not all equiped with GPS.

If one puts larger diameter tires on their FEH, in an attempt to create an overdrive, the eCVT will simply think that it is always going uphill, and reduce it's gear ratio accordingly, so no net gain. Yes-no-maybe?

-Jiml

 

Look, the size of the rim has no effect on the overall diameter of the tire. You can use any number of rims sizes and still have the same tire circumference - thus no change in revolutions per mile. That only changes when you change the circumference of the rim/tire combination. That is not an opinion, but it was clear you didn't get it.

 

One would think, but the FEH calculates vehicle speed three different ways and compares them. If they differ by some amount (don't know what is the threshold) a DTC of P1635, Tire/Axle Ratio out of acceptable range, is stored.

 

yes it is, until you can PROVE what you said. You said you can gain MPG and others here who have tried it or know someone who has say that you lose MPG.

 

John was a frequent poster here in the past and is currently in auto sales. He complained about the road noise with the stock EcoPlus tires. His new tires solved this problem. The EcoPlus tires are not "great" winter tires and he lives 'up north'. He felt the ride improved with the new tires. If you search hard enough, you can find him elsewhere. No, I'm not going to point where he is.

 

DesertDog, I believe the DTC of P1635 compares the relative revolutions between the 4 tires on the vehicle. Seems like that code used to come up often when modules were replaced. I suspect it was designed to prevent mismatched sized tires on vehicles, especially 4X4's. I didn't find any reference to the Escape and this code in any service messages.

Back to overdriving a FEH, if you reduce weight, drag, rolling resistance, etc. in combination with fewer tire revolutions per mile (thereby not loading the transmission and dropping the overall ratio down), you should see an improvement in fuel economy.

For example, replace the stock tires with 235/75-16's and reduce the revolutions per mile from 695 to 674 - a 3% reduction. Leave the spare tire in the garage. I think that would be good for 2-3% MPG improvement without any recognizable transmission load that might prompt lower gear usage.

If you can still generate 695 wheel revolutions from the same amount of energy as before, you will have gone 3% further on the same gallon of fuel.

 

Hi Red

Desertdog (Carl) is quoting the '05 Powertain Control Module/Emmisions Manual and I agree with him in that regard. What you think is good for a 2-3% increase is yet to be determined. What is the rim weight? What is the tire weight and what LRR tire are you talking about?

In my prior post, I gave the tire and rim for the best MPG possible. Can you give the best tire and rim to buy for the best MPG possible that you've experience so far?

Red, you have no idea what Carl has done for us and me for mileage improvements.

GaryG

 

That would be true... but I believe you won't use the same amount of energy as before. The tires ALSO perform a torque conversion (ie they are effectively a part of the gear system in a way). If you have a larger diameter tire... and are pushing a 4000lbs weight, and you are pushing it FURTHER from the application of force, the Axel. Therefore it will require MORE torque to turn and more energy.

You COULD end up still in the positive if the extra distance is MORE than offset by the increased load, but you might not as well. Not saying it won't work... just that people have to be careful because it does change the load on the system, in more ways than just the inertia of the wheels and such.

 

If the P1635 just compares revolution differences between the tires, why have a tire size programmed into the VID? In the Powertrain/Emissions diagnostic manual, the three probable causes for this DTC are: Tire size incorrect, Tire size in VID incorrect or corrupted, Transaxle bad. Also, I had a flat tire a couple of months ago that I drove on for a few miles with no DTC. The revolutions/mile for that tire was obviously much less than the other three.
But, the bottom line is that the FEH has an eCVT and is torque-based control, so using a larger diameter tire will probably force the ICE to run at a higher RPM, not lower. Really, the only way to try to control the drive ratio is with the fake shift method GaryG discovered many moons ago.

On the plus side, larger tires will extend your effective warranty time slightly, provided the dealer doesn't figure that out.