I've recently done a bunch of work to my Ex (see my build in my sig for details), including switching to 35" tires. (insert groan here )

My MPGs were awesome, into the 18+ range...unloaded.

So I hook up my camper and tow a little over 250 miles with one stop early to add supplies and food to the camper and campers, LOL.

I got about 10mpg. Why? No tune and a couple of non-tweaked upgrades, such as John Wood Valve Body, Wicked Wheel 1 (95 wheel), new injector orings, etc.

At least that's what I expected and figured. No surprise there.

But- now that the camper is parked and I'm driving around unloaded, I'm only getting about 12.3mpg

I'm wondering if I'm being out-smarted by the stock computers and maybe a learning transmission?

My 4Runner has the adaptive-shifting-learn-how-you-drive thing in it that has snuck up on me after disconnecting the batteries for a while.

Or- maybe one or more of the updates or maintenance items isn't right?

Two odd things happened on the trip.

1. A couple of hours into the trip, about 70 mph on the Turnpike, I was passing an older semi and I got a momentary but dramatic stumble just as I passed the driver's door. I thought he might have a boosted CB radio and keyed the mic- and I hear about some of the RF challenges of our trucks.

2. Getting off the turnpike I had to WOT to change lanes for a quick exit and...unhelpful drivers (LOL), no problems, but then from WOT to Zero throttle, it stalled coming off the ramp. Coasted off the road, checked my TorquePro, all looked okay, no CEL, not overheated, nothing out of the ordinary.

Turned the key off, then back on after a few secs, watched my TorquePro gauges to make sure HPOP, temps, IPR, RPMs, etc were all okay and started up after 2 secs of cranking like normal. Not a hiccup since then.

We camped a week and drove a LOT with a load of people but not towing, then towed yesterday to our new place and no problems since.

...except the mileage thing

Still making up to 18lbs of boost, stock programming, HPOP makes over 2750psi

Pulling out from a stop is about what I'd expect from adding the 35's. The WW seems to easily overcome the loss from the larger tires, but obviously it isn't spun up at idle

So I'm looking for input or suggestions ???

My guess is it's either learned the heavy load style of driving, or something let loose after a couple of hours of mountains, fast rate towing, WOT to no throttle cycle (thoughts about TPS?), harness rub (we had EVERYTHING disconnected I think ), or what else?

I brought ("stealthily stashed" so the Mrs. would see it) AE and my laptop, and small toolkits.

Oh- and I fueled up only at Sheetz stores, barely going below 1/2 tank. I do NOT have a pre-pump filter, waiting for time to make and install the bracket and unit.

Ideas? Things to check? Let 'em fly!

 

These vintage 7.3's do not have adaptive anything. from what I understand it was planned but never implemented...the individual responsible never got a 'roundtuit' so it didn't happen.

Is this hand calculated mileage or are you just looking at the "AVG" on the lie-o-meter?

 

Dont forget to recalibrate your speedometer for the larger tires.

Oh and your stumbling reminds me of a cps going bad

 

Did you change the speedometer/odometer to compensate for the new tires? If not, you're going quite a bit farther than the odometer knows about.

Ford doesn't do the learn how you drive thing. They did do learning transmissions, but in the diesels that didn't start until the 2003 TorqShift behind the 6.0L.

The 7.3L doesn't learn ANYTHING.

From where I was, working with the people that wrote this software, it was never planned for the 7.3L/4R100 combination. Those people believed it wasn't possible to do any of that in a diesel powertrain.

They were proved wrong when the software development was integrated back into the mainstream development community for the 6.0L/TorqShift.

 

I know nothing about the 5.4/6.8 gas superdutys, do the have adaptive transmission programming? Or is that where the planned but not implemented adaptive 4R100 story took place.

Or is that something I made up?

 

Are you sure the 18+ was after the tire change? I get 18-21 with my stock wheel/tire set, but when I put on the big boys I lose 3-4 mpg.

 

Exactly! When were the 35's put on? That is only about 1-2 mpg low from what a friend gets with 35's and he drives it so slow it drives people crazy. I too have experienced mileage drops due to an increase in tire diameter. Towing with larger tires will make it even worse.

 

I dropped nearly 1 mpg when I went to the 285 Michelin AT2's, and my 2" front leveling kit dropped me almost another 1 mpg.

 

...I continue to learn and appreciate the help troubleshooting

I did recalibrate the speedo under the Antilock system using AutoEnginuity. Think the closest that didn't go over was 34.5" Mine are 34.85" IIRC. Would rather be lower than high

No adaptive stuff, eh? OK, rules that out. I thought it might be doing something like the gassers when trying to tune a locked ECU using a piggyback chip. It eventually "learns" the changes out of "open loop" (or is it closed? I can't remember, LOL)

CPS- I just changed it a few weeks ago to a RiffRaff version. I have the old (not really malfunctioning) one in the truck as a spare.

My lie-o-meter has always been within a few tenths of my hand calculated results, although I haven't re-hand-calculated since the tire swap, just the computer recalibrate, so maybe something there? Either way, it read high, now reads low. Is that normal?

Most of my entire build and saga are in my build thread link in my signature, for those interested in the timing and such. Maybe something there will trigger something?

Timing- in short, we did a bunch of engine work (injector orings, UVCH + Gaskets, glowplugs, turbo rebuild, etc) and finished Tuesday eve, then left for this trip Thursday. The tires were installed a few days before that, the valve body about a week before that, LOL.

I also wondered if the Wicked Wheel forcing more air (boost) is somehow causing the computer to send more fuel. Since it doesn't have a tuner yet, it might not know how to deal with the extra air

I picked up an emergency fuel filter before we left. Not the one I wanted, but figured I should have one for this trip. The OEM one has about 5k on it, I think.

I do have a fuel pressure transducer installed, but haven't wired up the gauge and such yet- it's all at home, a few hundred miles away

 

The WW1 moves less air than stock wheel.

My first suspect for lost mpg is always boost and drive pressure leaks. Just because you still hit 18psi doesn't mean you aren't losing air someplace. Build a cheap boost leak detector and test the system.

It's very common for stock up-pipes to start leaking after pulling a turbo - be sure to give them a look too.

I'll go read your build thread for more possible clues!

 

Yes they do.

This is the first time I've heard that story. I never heard anything like that while I was at Ford.

 

WW1 moves less air than stock? Well, guess I went the wrong way What about WW2 or 4/4 billet wheels? I had a problem with incorrect threads in my 4/4 wheel, so my buddy had a 95 wheel on-hand to put it back together. That's how I ended up with a WW1

Guess I should start collecting parts for a leak detector and inspect like the dickens, LOL.

Hope you enjoy my build thread. Many, many of the items and methods came directly from good folks at FTE

 

Yeah, the early wheels are a 'fix' for turbo surge - but otherwise are not an upgrade. Honestly, I'm not convinced the other wheels are a significant improvement over stock when used with stock injectors anyway... If you didn't have a problem with surge, my recommendation is run a good stock wheel.

I haven't read it all yet, but I get all twitchy reading about MPG and how people determine what they get. Your methods and descriptions may have given me a few full body jerks!! Lol. I'm just picking on you a little, but using the lie-o-meter then doing math to compensate for tires reminds me of government math (it never adds up...).

First of all, the lie-o-meter is literally a straight up WAG. This display is a brilliant extrapolation based on things like injector PW, RPM's, etc. Anytime it is within reasonable variance with actual hand calculating - it is just a lucky coincidence... That said, it is somewhat ok at showing big changes, because it tends to be pretty consistent.

There is way to much discrepancy when filling these trucks to even consider tank-to-tank MPG. Keep a log with every mile you drive and every gallon you put in the truck and you'll soon learn your true average MPG.

Meanwhile, taller tires and the already tallish 3.73 gearing in the X are going to hurt every time. There is an insignificant difference in MPG by dropping even a few 100rpm at a given cruising speed. The physics dictate it takes a minimum amount of fuel to push your vehicle down the road at a given speed. The amount of drag however (by far the biggest enemy of mpg), increases proportionately with speed. You can get better mpg by slowing down - but you cannot get better mpg by just reducing RPM's. The taller tires hurt by making the engine 'work harder' to get the big pig rolling up to cruising speed (which is where most of is spend the most time).

I did skip to the last page and saw I got an honorable mention! Thanks!! I wish I was following along at the time - there's a couple things I would have suggested. That 30mic pre-pump filter is a bad idea IMHO. You don't want anything finer than 50mic and ideally something like the Racor PS120 (240mic). The PSD fuel pump does not like restriction on the suction side and performance and pump longevity often suffer. There is no advantage to warming the fuel. If the fuel isn't gelled, the truck will run the same regardless of fuel temp. (Remember, I heat my VO to 180-200+ degrees )

Ok, it's past my bedtime. I'll come back and be a critic next chance I get. Lol!

 

SkySkiJason covered much of what I was thinking.

When I read about factoring something referred to a "lie-o-meter" into a calculation, I thought about Robert Stack in the movie "Airplane". He's this guy with gravitas (like the type Robert Stack always played), then he flips up sunglasses to reveal a second set of sun glasses under the flip set. The exercise is entertaining, but not enlightening.

The WW1 is all about reducing surge, not increasing performance. Another wheel may help, but the stock housing and the journal bearing are all working against a significant increase in performance. I know very little specifics with turbos, but I fully understand how they work. I also see the performance envelope in the OBDII logs - and the GTP38 is dialed for stock performance.

As for your ABS calculations, don't fudge here. You want to get the tire diameter from the tire, and put that in the ABS. Then... confirm the accuracy by driving past mile markers for ten miles and noting the 1/10 mile on the odometer. Using a GPS to confirm the speed does NOT confirm the odometer reading - it's another sunglass flip.

Stinky's Speedo reads a little bit fast, but the odo is dead-on.

 

Disappointing info about the WW1, for sure, but I'm always willing to be educated I'd rather "know" than guess

The ABS settings only have those two options I mentioned for size close to mine. You can't enter a number, just select up or down with an arrow. Not sure if this is AE limitation, but it seems like it's a ECU limitation.

It wouldn't make sense for AE to hobble an option on their end, but then again, they have surprised me before

@SkySkiJason- Yep, I've been blaming you for all kinds of stuff in my thread, you should be there to defend yourself, LOL!

@Tugly- You're very right about GPS speed being wacky- especially in these hills

Taller tires, gears, etc. My idea here is more than 50% of the time the "extra" torque isn't needed when doing the longest trips (think mostly flat highways) . Boost and tuner can make up the slack and add a boost (pun intended!) to performance on demand.

And surprise of all surprises, the Mrs. LIKES the big tall tires

Now as to the testing of this theory...help me along and fix my mistakes and we can all laugh together if it shows as foolish or futile Worst case, we'll have a tight and very well performing (and looking!) Excursion

I appreciate all the help. I'm hoping my candid questions and details of my Ex can be of use and/or entertainment for others who have done or are considering doing like things to their 7.3L's