Hi Tom: It was not a total WAG; I remember Car and Driver or one of the other magazines publishing horsepower needed to run their test cars at a couple speeds, and 50 hp felt about right for a freeway speed in a full size truck.

Good point on zero vacuum; and obviously one other factor would be the amount of engine and drivetrain friction; a 6.2 V8 would have more piston and crank friction than a smaller engine. It's all about balance--a CVT takes more power to run pumps to keep the belt tight than the pump in a traditional automatic, but has infinite ratios within its range.

We'll know soon enough how the 2.7 does in the real world...
George

 

The smaller the displacement of a turbo engine, the more it will have to rely on boost to make it go. Any time you are under boost, the fuel curve needs to be fatter which would make the EB engines less fuel efficient under certain conditions. As others have reported on this and other forums, the 5.0 and 6.2 engines, which are naturally aspirated, tend to get better fuel economy when towing than the 3.5 EB engine does. That's because the EB is under boost more, thus needing more fuel. The EB does better when not towing than the 6.2 or 5.0 engines because of its smaller displacement and not being under boost as much.

 

"Auto manufacturers typically equip new vehicles with tires that have lower rolling resistance than their average after-market replacements, in order to meet corporate averge fuel economy
(CAFE) standards."

Got this information from the folks at Wikipedia on the subject of low rolling resistance tires. In 2012 in Europe is now manatory that tires manufactures state the rolling resistance factor rating on the tire along with thread wear and temperature rating.

Believe Ford might be experimenting with different tires before publishing the EPA MPG ratings.

Found a list of the top 20 low resistance tire. Of course Michelin is at the top of the list.

Suprisingly, Michelin Energy MXV4 Plus was # 20 on the top 20# list with a rolling resistance factor = .00855 lbs/lbs , rolling reistance force/wheel load.

Interested to find how much vehicle weight influences highway MPG on flat ground, as simulated by the EPA testing equipment.
and
percent of aerodynamic energy vs rolling resistance energy required the move the vehicle

So inputing the .0085 tire reistance factor into the "MPG calculator" along with vehicle curb weight = 4050 lbs ( 2015 F150 regular cab, 2WD, 3.7L standard engine) , .36 aerodynamic drag coefficient(latest RAM data) and adjusting the engine efficiency and drive train efficiency to get 25.2 MPG ~ to the RAM 1500,
found that at 65 MPH the aero load was 82% of the total energy load to move the vehicle and the tire rolling resistance energy load was the remaining 18%.

At 40 MPH the aero resistance energy load is only 64% and rolling resistance load is 36%.

Then adjusted the weight of the vehicle to 4685 lbs( 2014 regular cab, 2WD, standard 3.7L V6 engine) with all other factors unchanged and got 24.6 MPG,
only .5 MPG difference at 65 MPH.

Believe the 13.5% weight reduction from 2014 to 2015 affects MPG for city start and stop, hills, and acceleration operation and not constant speed highway driving.

 

The test you refer to is from 2003 and it's a different world now in terms of LRR tires. The Primacy MXV4 is 2 generations beyond the MXV4 Plus and itself is being phased out for newer designs.

It would be nice for all tires to be rated for rolling resistance but this daunting based on the different sizes offered in every single tire, and all the different pressure and vehicle weights...

One "feature" that Michelin is using on car tires is going to longer wearing rubber on the tread and shallower depth (10/32 instead of 12/32) which reduces squirm and tire weight.

I did put some Conti LRR tires on my Subaru Forester a couple months ago to replace the prior BFG Long Trail TA Tours and picked up 1.5 mpg (doing 1000 mile samples on my dash lie-o-meter which is consistent within its own readings). Mileage went from 24.5 to 26, which is a decent improvement. And the new Contis had a tread wear warranty of 90k miles(!!)

I would assume that trucks, especially the high gas mileage versions, are coming with the lowest rolling resistance tires available if they meet mfr specs and price points.

George

 

This is one reason people don't get EPA mileage on thier trucks. Folks love to buy larger and more aggressive tires.
My Brother runs a fleet, and has dozens of F150's at any time. He figures going from P-metric factory tires to an AT LT tire you'll love 1 MPG. None of his trucks have anything but factory tire size, and none have an lift or level kits. So it's a pretty apples/to-apples comparison. Or as good as I've ever seen.

 

Could not find rolling resistance test data on the latest generation of Michelin tires.

Used the RRC 2003 test data for Michelin MXV4 Plus tire to estimate the percent of aero drag energy and tire rolling resistance energy at different speeds.

Based on the calculations it appears the split of 50% aero load and 50% tire energy occurs at ~ 30 MPH. Less than 30 MPH the aero load < tire load and greater than 30 MPH, aero load > tire load.

U-Tube video by Michelin discusses the tire can be design optimized for thread wear, minimum rolling resistance, stopping efficiency, temperature.
and that the final design is a trade off.



Michelin CEO indicated for the most part the tires are optimized for rolling resistance effiency.

High end tires are found on many new vehicles to increase MPG ratings.

Hopefully the USA will someday require that all tires are labeled with scale rating for thread wear, traction, temperature as is required in Europe, so the consumer is better informed on purchasing replacement OE tires. Currently rolling resistance coefficient, RRC, is not part of the mix, but reflects the energy efficiency of the tire and affects MPG.

Drag coefficient
My 1985 full size Ford Bronco has a drag coefficient = .65
The Ram 1500 has a drag coefficient = .36
Quite a reduction over the past 20 years in improve MPG at highway speeds..

 

We are in agreement that tires should have some kind of rolling resistance rating. Only thing to go on now is to buy tires that specifically advertise LRR.

And I agree that many pickup truck buyers sabotage their mileage by using leveling or lift kits to increase underbody drag, along with adding heavy tires with a lot of squirming tread. There is certainly a compromise needed between looks and function.

As for drag coefficient, the one problem with comparing one vehicle to another is that you don't have total aero drag until you multiply drag coefficient by frontal area. A compact car with a drag coefficient of .36 is gonna be a lot more slippery than a Ram 1500 because of its size. I'm sure that all mfrs are making vehicles as slippery as possible with respect to their size by closing seams, making subtle changes in contours.

I remember that gen of Ford pickups and Broncos (1980 and up) was supposed to be way more slippery than the "dentsides" like my 1978 F100 back in the day....

George

 

Agree the aero drag coefficient X frontal area = total drag area

There is only so much aerodynamic modification allowable and still have the basic architecture of the PU look like a real PU with ground clearance.

Tire resistance
Some research indicates the Rubber manufactures association(RMS) is all over this rolling resistance and have decided that rolling resstance coefficient (RRC) is a better consumer indicator than rolling resistance force (RRF).

RMS recommends that the normal range in RRC from 12 kg/tonne to 7.5 kg/tonne be indicated on the tires with a star system. Five stars are for tires with lowest RRC and one star for tires with the highest RRC. Five star is the best rating and one star is the worst rating.

If the percent of energy required to move the truck at 65 MPH is 18% of the total energy then going from a one star tire to a five star tire would improve gasoline fule consumption by ~ 1.7 MPG.

 

I've got an '02, 5.4 as well w/an H9 Tranny, 3:55. Have you done any mods to your for the $20 mph? How many total miles on it? And do you do any towing with it?

I'm looking at getting a travel trailer that fits my GCVW range and doing some trips next year. Plan on getting a tow tune, electric fan and trans cooler before hitting the road. Looking for any help with the fuel economy, performance and overall preventative maintenance and add-ons.

 

Looks like MT has now tested a fully loaded 2015 Platinum with the 3.5 EB.
http://www.motortrend.com/roadtests/...ew_first_test/
Here's how it did:

2015 SCrew Platinum
3.5 EcoBoost
3.31 Axle
5,532 lbs
6.4 0-60
15.0 @ 92.5 1/4 mile
14.8 /19.9 /16.8

Here's the 2.7 for comparison. 600 lb weight difference compared to the Platinum with the bigger cab and all the options.

2015 SCab Lariat
2.7 EcoBoost
3.31 Axle
4,935 lbs
6.5 0-60
15.1 @ 92.8 1/4 mile
16.6 / 21.5 / 18.5

 

If I read in between the lines on those stats, and knowing there are a myriad of options and configurations but......I'm guessing that the 3.5L in the same configuration would get basically the same real world fuel economy.

While I'm impressed with the power levels of modern engines with the V6s both normally aspirated and forced induction, I would have thought the swap to aluminum combined with the smaller engine would have done better than 18-19mpg combined.

From my personal perspective, I just got done with a 3400 mile road trip with our 2001 Tundra which is 7/8 the size and producing only 240hp at the crank.....but we got 16.5mpg mixed and 18.2 highway with 195K miles on it. So basically in 14 years Ford has upped the power significantly on a full sized platform with more tech and interior comfort features while increasing fuel economy 10-15%........that is my read on it.

All that said, I still have no idea why the 2.7L is in the F150......it feels like a marginal improvement over the 3.5L from a value proposition.

 

2.7L is a much shorter engine package which lends itself to many configurations, many of them will be front wheel drive.

 

EPA mileage averages are really, really important for the truck market, so offering the 2.7 with even small incremental gas mileage improvements over the 3.5 EB may make enough of a difference to save Ford a million or three in fines that they would have to pay if they don't hit the averages.

And as Papa Tiger says, it's a smaller engine package that is likely to be used in Explorer, Flex, Taurus cop cars, etc. The 2.0 4 cyl Ecoboost in the Explorer makes no sense to me--the 2.7 is getting into "just right" territory and has a lot more power than the old 4.6 V8 that used to be the base engine in so many of Ford's trucks and vans.

George

 

How could someone possibly hand calculate the MPG with a 20 mile or less test drive without having truck full of fuel then after the drive getting exact amount back in it.

Total bogus claim by whoever came up with that.

 

Pretty confident they used the computer's calculated MPG display for that, which is definitely not a precise way to do it. They generally are close though, and tend to be optimistic, so I think the test results are still meaningful on some level.