Anyone ever "de-tuned" a Cummins 5.9 for mileage?

[Peacock]

My 3.54 geared truck has gotten as high as 18.6, but that was loaded up with 4 people and a small trailer with 2 atvs.

 

[JerryK]

My 2002 [old BR body style, 24 valve, 6 speed, 3.54 Dana 80 rear, 4X4 Club Cab] gets around 21 if I keep her around 60mph. Drops off quickly if I try to push her 75, especially if it is windy. I have got as high as 22 every once and awhile. More like 17-18 if I push it.... Empty truck weighs around 7100 pounds. GVW is 8800. But with the sweet sound of the turbo whining, and the Cummins growling down the road.... who cares about fuel mileage...

 

[90cummins]

I purchased a first gen 1990 Dodge W250 new with a five speed & 4:10 gears.
I've recorded virtually every gallon since new which averaged out to 20mpg.
When that truck rusted away I installed that engine & transmission in another 1990 w250 with 3.07 gears and the mpg went up to mid to upper 20's if driven normally.
The 3.07 gears turned it into a real cruiser with a top end of approx. 115 mph per GPS versus 80mph with the 4.10's
No changes or repairs were ever made to the engine.
I currently have a rust free W350 in good to excellent condition that only see sunny days.
As was said the first gen VE pumped engines are capable of very good mileage with minor adjustments to the timing and a gearing change.
Diesel Power magazine had a project named Rust Bucket where they took an old 1990 Dodge CTD and turned it up to 700hp while also achieving close to 30 mpg.
Those old Dodge Cummins are awesome!
90cummins

 

[buickanddeere]

How does detuning an engine boost mileage when the truck still requires 45HP to roll down the highway at 55mph? To overcome aerodynamic drag, rolling friction of the tires, drivetrain friction/windage/pumping losses and acessory loads.
If you want diesel and mileage purchase a VW Tdi.
If you want lowest cost per mile purchase a direct injection gas.
Some people are still stuck in 1989 thinking Cummuns diesel with a 5 speed vs. a carburated gasser with a three speed automatic, no lockup torque and no OD.

 

[Rustyiron]

Back to my original post here, I was just wondering what could be expected from an early Dodge/Cummins, set up for the best mpg's , obviously gearing, aerodynamics, engine help (breathing & exhaust), without a concern for trucking ability. I still have my 350 & 450 7.3's for working (and a 2000, 3/4ton Sub 4x4). I just don't want to "surrender" yet to a car. Me & wifey are not comfortable sitting 5" off the floor (posture) in small vehicles, and looking up at a little suv on the road. There was a mention (here) of the smaller 4bt? Cummins, I wonder if that would be complicated to "tie" to a modern trans.? That would be pretty sweet in a small shortbed, 2wd fullsize 1/2 ton. I do understand that you have to "feed" the cubic inches, and that if you do not requier them for your purpose, they still need to eat. That's why the Cummins question rather than fooling around with one of my 7.3's. Anyone know what hp you can squeez out of the 4 cyl.

 

[DT86]

There was a mention (here) of the smaller 4bt? Cummins, I wonder if that would be complicated to "tie" to a modern trans.? That would be pretty sweet in a small shortbed, 2wd fullsize 1/2 ton

The 4bt is the same design as the 6bt, just shorter.
I'm thinking they can easily reach 200 HP, even more. Basically your biggest limitation is your wallet.

You may want to check out "4btswaps.com "

 

[90cummins]

The 4bt is a popular swap and they easily put out 400 hp.
90cummins

 

[sd455dan]

There is no reason to de-tune a 5.9 Cummins, the brother in law runs a 3/4 ton 4wd 1996 Dodge with some Banks upgrades and gets over 20 mpg. (yea, I thought he was a liar too, until I took a long trip with him and did the fueling).
The 1996-1997's with the Bosch P7100 was the best Dodge Cummins engine for power and economy. The later engines became lame because of emission requirements.

Get a 1996 5.9 Cummins and put it in 2wd pickup with a NV4500 tranny and a Dana 44 2.72 (or 3.07) ratio differential. 25+ mpg should be easy to achieve.
You don't want the VE pump series engine, they are limited in RPM to about 2200, lots of torque but they're miserable out on the interstate. My old 1992 Dodge Cummins wouldn't go over 85 mpg.

Me? I am so sick of the lack of performance and economy of my 2001 24V Cummins I am pleased it needs a head gasket.
I was told to put a "non-emission" cam in it when I installed the engine, like a hardhead I didn't heed the advice.
The 24V Cummins cam is ground so that it actually lets some exhaust overlap into the intake to decrease emissions, that's astonishing government regulated idiocy. Better emissions, but burn 1/3rd more fuel, only government could come up with such goofiness.
Going to install a cam when I do the head gasket.

Is it possible the overlap is to increase scavaging effect

 

[dodge man]

Is it possible the overlap is to increase scavaging effect

On 2004.5 and new common rail Cummins, the cam was designed to close a little early and leave some exhaust in the cylinders, hence the term in cylinder EGR. The person that originally posted about this has an earlier 24v Cummins, before the common rail, and I don't know if they had in cylinder EGR or not. But to answer your question, the cam grind was not to increase scavenging effect.

 

[EdK]

I bought what the OP is looking for last year while I was visiting a friend in SC: 1995 2500 2WD w/ 5.9 Cummins, under 100K miles, manual trans, 3.55 gears, always stored indoors. I got 24MPG on the way home driving 65-70 - never faster. Bone stock except straight piped and timing played with a little. Decided I would change my avatar while I'm posting