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Did you go to bigger diameter tires w/o changing speedo gears?
 

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1989 Jeep Wagoneer, 360v8, 727, stock for now,
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What are your specs: weight, tire size, axle ratio, trans type?
At what speed is this, in town or highway?
 

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Discussion Starter · #4 ·
3:31 gears
31 inch bfgs
weight about 3500lbs
around town and highway it dosen't seem to change
trans 700r4
rpm at 65 was about 1800
no mods
3inch exhaust
4bta with an alternator and ps-pump
I used a gps to verify the speed...
 

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Seems a bit low to me. You might want to check your air supply system from the filter to the post turbo engine inlet for loose clamps or leaking connections.
 

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1989 Jeep Wagoneer, 360v8, 727, stock for now,
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Your overall gearing is just a hair taller than my Scout and your weight is a lot lighter, i'm at 4300. I'm getting 23 mpg in town. Scout is a brick on wheels. I would think you should be getting better mpg too.
Right foot maybe?
But I do drive for mileage, shift at 2K, mild throttle, etc.
 

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3:31 gears
31 inch bfgs
weight about 3500lbs
around town and highway it dosen't seem to change
trans 700r4
rpm at 65 was about 1800
no mods
3inch exhaust
4bta with an alternator and ps-pump
I used a gps to verify the speed...
Did you also use the GPS to verify the distance traveled?
 

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My Carryall's curb weight is 7300#. Over 3411 miles with 539 on primative gravel I got 25.9115 mpg. The Engine is a 4BTA CPL 857, NV-4500 married to a NP-205 turning 4.89 ring and pinions and 36 inch tires. Engine is stock, nothing turned up. I run 60 mph at 1950 R's. My M37 is much lighter, with the exact same engine and drive line. I expect even better MPG.

Paul
 

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Discussion Starter · #9 ·
i use the gps just for speed...i could use it, it has that option.
yeah it might be my right foot...
i'll check for loose clamps on the intake hoses...
yeah my engine dosen't go over 2000rpms much at all...
 

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I just checked my numbers yesterday and was quiet impressed...

My weight is 5000 on the head with me in my truck, I'm set up as follows;Stock 4bt, Borg Warner 3spd w/ OD, 3.55 gears, and 35" BFG all terrains... After 2 days of drving i had 90 miles on the odometer, The driving consisted of stop and go country and city driving and on top of it was 12 miles of mudding. I ended up putting 3.6 gallons of fuel in so 90/3.6=25 but my speedo and odometer are about 20% off so my corrected economy is 30 MPG's. I was pretty suprised because of the harshness off my driving, and some poor ratios in my tranny, but I'm bounce
 

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Did you fill it up the filler neck before and after the trip - or did you just fill till the pump shut off?
Both times were until I absolutely could not get any more in. Fill, let foam die, fill, more filling, even more with the foam until I had fuel right up to the cap both times....
 

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Fuel efficiency jumped up

My fuel economy jumped up from 23 to 28.2 mpg. The 28.2 would be even higher if I had not been playing with the go pedal so much. I was noticing that at the half empty point on gauge I was doing much better so I stopped gunning it to see how good I could do on fuel economy. Here's what was changed on the engine.
1. Rebuilt turbo. Had slight score marking on compressor housing and radial play. Now I hear the turbo whistle when I accelerate hard.
2. tack welded wastegate shut.
3. added intercooler ( 1 psi drop at 27 psi).
4. added air guide plastic sheets to force all air through intercooler; not letting it flow around it.
5. Added 180 deg. F electric fan switch.
6. blocked radiator from getting cold air as a result of adding the intercooler.
7. replaced Rotela T with the synthetic Rotela T and swithc remote oil filter adapter to the mongo Ford Diesel adapter.
8. Fuel at stations probably now on summer grade fuel.

The Power is up quite a bit after adding the intercooler and I think also rebuilding the turbo. Maybe some of this is from running at 180 degreesw now. It ran about 165-170 before. I missed the dyno day last weekend. Wish I could have gone to see how much higher my numbers are.
 

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I put more fuel in again today, I had 87 miles on the odometer so thats about 104 and I put in 2.2 gallons until one of our tanks was empty then out of another tank I put less than a gallon (the tenths are worn off on that pump) so even if I put 3.2 gallons it was 32.5 mpg this time... bounce After I filled up today I put 105 miles of easy driving on so I'll see where that got me...

Edit: May have realized why I'm doing so good, my throttle cable wasn't pulling quite all the way. On my long drive today I noticed towards the end I really had to mash the pedal all the way and I still wasn't accellerating as hard. Now I changed some stuff I achieved more pedal range and less effort and definately more rpms and power than I had In this truck all along...I anticipate I will go down in economy unless I can stay off the go pedal now
 

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Well I figured it out and I used exactly 4 gallons of fuel on 150 mile trip 150/4=37.5 MPG... How the hell am I doing so good? Maybe our Diesel pumps don't read quite as accurate as they should... If I can keep doing this good and verify that I am getting this good of economy I may put narrower tires on, Intercool and propane inject just to break 40MPG... I have some doubts, there must be some fault somewhere...
 

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Checking fuel mileage with a diesel is a little different than checking the mileage of a gasoline engine. I learned this about ten years ago when I could get almost 30 mpg on short trips with a 6.2L GMC diesel. How did I get the error? I was filling up at the local mini mart which is .3 of a mile from home while the fuel in the tank was cold. Then I would do an 80 mile jaunt out and back and refuel. The fuel in the tank at this point is heated and expanded from being circulated through the engine. Then I started refueling when the fuel gauge showed around the half mark and after the truck had set over night. This method put me near a consistent 23 mpg. You should also remember to never fill your tank to the top of the filler tube because the fuel can expand on a warm day and run out onto your driveway. This will happen on a day that has a 35 degree increase in temperature. Just remember diesel fuel expands when heated.
 

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It expands with temperature, however, not a lot.
From Chevron.com

THERMAL EXPANSION
Like all liquids, diesel fuel slightly expands in volume as its temperature increases. The coefficient of thermal expansion measures the rate of the expansion. 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.
 

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Suburban tank is roughly 40 gallons x 1.037= 41.48 gallons.

Unless you have a filler neck that is over 1.5 gallons......spillage my friend
 

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To get accurate fuel consumption data, you've got to average it over as many tanks as you can.

My vehicle has issues with air getting trapped in the tank. One fill will often give a low MPG, but balanced out with the next high MPG the result is usually the old exact same figure.
 

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Well I guess no matter what I'm probably doubling the economy of my gasser, and probably tripling what this truck got with the 302 so I guess i won't complain... It would just be nice to know exactly...
 
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