I thought I'd start a fuel mileage thread for my 4BT swap, in planning for this swap I read a lot of claims of increased fuel mileage ranging from 17-30+ mpg. The 17 is very believable, older rotary pump motor and keeping the skinny pedal smashed would get you there. 30+ is likely fantasy unless you put the 4BT into a 2wd Ranger, which is done quite frequently for those folks looking to hyper mile it.

I was looking for 20+ with mixed driving, my truck is rolling 35's w/ 4.10's and if I keep it at 65mph it's in the 4BT's sweet spot of 1800 rpm. My first drive was so that I didn't keep track of mileage, I was just trying to see in the 60 mph rain! For my 2nd and 3rd tank I've kept better track of the numbers. I'll add to this thread as I drive it more and do a few mods to the motor, I'll also try to be descriptive of the driving and atmospheric conditions.

2nd tank: 19.2 mpg. City & hi way driving from Parker to Golden, run up I-70 @ 70 mph with camping gear & supplies for 3 people to Idaho Springs, ran Barbour Fork at 10 am. Gassed in Parker & Idaho Springs, temps ranged from 90 degrees in the metro area to 65 degrees in the mountains.

3rd tank: 20.5 mpg. Around Parker & two runs up to Northglenn, in town driving was at 40 mph & I-25 N was at 65 mph (sweet spot), gassed in Parker. Temps were between 80-100 degrees, almost no traffic and no intentional turbo kick. You can drive it hard and force the turbo to light early and make it maintain it if you want.

4th tank: TBD

My 1st quarter tank mileage is at the moment, I know that I filled into the filler neck when I filled it last time, but even so I'm seeing some numbers. I've rolled nearly 100 miles and with a stock rear tank that gives me around 30 mpg. I'm sure the 2nd quarter tank will yield somewhere closer to my previous 20 mpg.

Well, it was too good to be true, sending unit wasn't reading right, it's a 1/8 of a tank off. I need to pull it and fix a leak anyway, so I'll bend it a bit and hope for a better reading.

So did that make you run out of fuel?

Since you knew it was an 1/8th of a tank, that wouldn't easily be figured unless you had that 1/8th reading on the gauge when you ran out. Was it easy to fire back up? I wouldn't know what to do with a working fuel gauge in my bronco!

Didn't know about the 1/8 off until it happened. So I thought I was good to go, ran out about 15 miles from home. The lift pump on my 4BT has a priming pump built in, so I pumped it about 20 times and it fired right up.

4th tank: 21 mpg. Ran from Parker to the Golden Cruise In and back and pulled 1260 lbs of scrap (plus trailer weight) around town and dropped it off. 80% hi way driving, temps were 90 for the high & mid 70s for the low. Kept it at 65 again on the hi way, but with the trailer my foot was in it just a bit. Turbo was spooling in 2nd gear with the load, empty it usually starts spooling in 3rd.

At the moment I've achieved one of my desires with this swap, 20+ mpg.

That's awesome.

So awesome man!

Did a bunch of running around today, nice big clockwise loop around the metro area with the trailer loaded w/ 500 lbs, avg was 21.6 mpg. Wow! With the muffler gone the turbo is spooling earlier and she pulls real nice from a 1/4 throttle on up to the rpm max. Nice bonus from the side exit exhaust is that I didn't smell like a trucker when I shut it down tonight.

I won't say the increased mpgs are from the straight pipe yet, it was super cool day today and the air was dense, the driving was mixed hi-way and secondary. I kept it at the posted speed limit except for when I smashed the skinny pedal for the final leg home on E 470.

That's awesome dude! Oh that reminds me have you seen buildAbronco's SEMA 4door project?

Wow, what bottomless funds can produce! :drool:

3-seats wide tho?

That's pretty! Not a fan of rim to rubber ratio. Not only 3 wide on the second row but three deep, nice. I'd love to know the wheel base, looks to be very similar to mine as the second door opening isn't a full door width.

Ya I hate the tires/ wheels, and I asked they said its stretched 2'. I really love how they designed the rear door opening, if I ever build one it'll be like that but with full doors, and a halfcab/ pickup top

Time for an update, my Bronco is in it's summer configuration without the camper and plow mounts on it. I decided to use my commute to work and back as my test route. I also employed some fuel saving driving techniques; stayed out of the turbo, up shifted early, kept it below 60 mph and didn't down shift when coming to a stop. Temps were around 60-75 degrees both directions and I tried to stay away from heavy traffic so I wouldn't idle much. I won't be driving this nicely very often but it was fun to see what I could squeeze out of it today.

26.6 MPG!

Holy crap awesome!!


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Nice!

I should add that I used my GPS for speed and distance (accurate to less than 10 ft), went to the same fuel station and let the pump stop on the first click. Trying to report real world numbers and back it up with a reasonable technique.

Nice mileage!

I feel I should mention that going from a 33" tire to a 31" has cost me 4-5 MPG off of my average. I'm glad someone's numbers are going up.

I was wondering if diesel is like gas in that regard. Next time I'm going 2 do a multi-day test & refuel at the same time of day to limit temperature variables.

Yesterday was a very cloudy day with some rain so I'm not sure what the overall temperature impact was on my single day run.

I don't believe diesel is affected like gasoline, here's some info I found on a tdi website about fuel mileage

"Quote:
Originally Posted by Fix_Until_Broke
A typical value of the coefficient of thermal expansion for diesel fuel is 0.00046 per degree Fahrenheit. Using this value, 1.000 gallon of diesel fuel at 20°F will expand to 1.037 gal-lons at 100°F
W00t! A whole 4.7oz (fluid ounces) of expansion for an 80°F rise in temp!

I think I'll start filling up in Flagstaff, where it's about 20° cooler. Maybe I can take advantage of that extra 0.9% to raise my MPGs by that much."

Kirk I'm assuming your still running a stock tank 12 gallons or so? If so that's only
.45gal. expansion with an 80 degree temp change

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Yes, still rockin' the factory tank, I've got a saddle that I picked out of the yard that I plan to mount inside the frame rail on the driver's side. I just need to bend the flanges on the sides so it'll fit and work out a transfer pump or plumb a dual return setup.

Sweet, I look forward to seeing what else you've got in store


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My 4bt hasn't taken a hit from the winter formula, I still plug along above 20 mpg daily. But with gas a $1.00 less I'll be driving my F150 a few more times than usual.

I think I see the difference more than some other rides might. The drop isn't big-maybe 5%, but when I'm getting 45-48mpg, it shows up. The common rail TDIs are also pretty tuned, so I see differences from tank to tank depending on fuel quality. I'm waiting for the warranty to expire so I can have it chipped. I'm pretty excited about jumping from 140hp/236 ft/lbs to 184hp/333ft/lbs.