2006 dodge ram diesel quad cab hypermiling

[eou_edu]

So I have my project started. I now am the proud owner of a 2006 dodge ram diesel, 4x4 quad cab 6 speed manual ST. I bought the truck with a dead 5.9 common rail and had it swapped out for a 3.9 mechanical 4bt cummins. The engine was rebuilt and had a new cam swapped into it. So far I'm very happy with the results. The truck was built in Texas and I live in oregon. As of now it still is a work in progress.

First off despite what most people speculate it's not underpowered. These engines were in ford f350's in South America for many years. There also made it in several million 10,000 lb plus box vans. I did this project for 3 reasons. One it was actually quite a bit cheaper to swap this engine in than rebuild the cr5.9. I also wanted something for good MPG. A 3.9 vs 5.9, 300 less lbs, 2.0 less cid, and two less cylinders should get better mileage. Especially when you consider how little horsepower it takes to cruise down the road. When you aren't using that power to cruise, 2 extra cylinders is essentially just drag and weight. I also like the simplicity and reliability of mechanical engines. All in a truck that you shift your own gears, roll up your own windows, lock your own doors, no carpeting, and a pull to kill switch. It's kind of like an old 70's era pickup trapped in a 2006's body.

My first tank I was very disappointed with the results. 16.5 mpg! I thought I had wasted my time and every nah sayer was right. That is at or worse than what the 5.9's get! But 4.10 gears I was running hwy speeds and the thing was screaming at 75. No governor spring it was running for 400 miles right at the governor. Next tank I slowed down to 65-70 mph and returned 20 mpg. A little more happy with that but still about what the 5.9's get and running about 2250 rpms. The third and fourth tank I slowed down even more to 60-65 and returned 25 mpg..........I was much happier with this and no similarly equipped 5.9 I know of is capable of this.

My next mods on the list are for a gear swap to 3.42. Of course this won't give me all the benefited mileage I get from slowing down, but it will help. I am also planning to haul things. While the engine has plenty of power empty I would like a little more power for hauling (otherwise I'd be driving a geo). It won't take much to get at or above the power levels the standard output 5.9's put out in 2003. 250 hp, 460 ftlb torque vs my inline 4bt 130 hp and 390 ftlb. A set of injectors, water meth, timing, and possibly propane could be in my future. All of which should only improve on MPG and keep the benefits of the smaller 3.9. Already has the hamilton cam in it. I suspect some power improvement will also make the truck less sensitive to fuel mileage fluctuations by making work a little less hard to move the truck. One last benefit of 300 lb less up front is better handling. I noticed right away the suspension is better and it steers nicer with 300 lbs less up front. I also suspect it will be a lot more forgiving on front end, hubs, axles, and steering parts..............Pictures to come as soon as I find my computer cord.

[tvbd56]

It's amazing how slowing down on the freeway can improve ones mpg so significantly. That's cool hearing that you can get 25+mpg out of a ram.

[eou_edu]

It's funny in your post there was a ram advertisement that popped up on my computer that said, "dodge ram 1500 25 mpg." At first I thought you were being sarcastic and posted that then realized it was computer generated. Yes the ram 1500's are getting that, the 1500 diesel even a little better. But I needed something that would double as a daily driver and haul 10 tons of hay, 6 horse trailer, or my overly heavy camper.

[sarguy01]

I am so jealous. I would love to have a truck like this. Subscribed to see the results of the gear swap and future mods!

Good luck.

[Big Dave]

I concur with the idea of changing to a 3.42 R&P set.

That will slow down the engine speed by 17% at any given road speed. That will reduce the amount of air your engine has to pump and will reduce engine frictional HP. That approach certainly works for me. I'm getting 24 MPG in a tough winter with heavier truck.

I assume you have a NV5600 gearbox. Should be bulletproof with the 3.9 engine.

After you square away your gears, start thinking aero. Grille block, an air dam if possible (not always possible on a 4x4) and DEFINITELY some sort of bed treatment - either a tonneau (hard or soft)(good for +1.5 MPG over open bed for me) or better yet an aerolid of some description. A crude aerolid garnered me 3.0 MPG over an open bed.

Even as a 4x4, you should be able to get that truck into the low to mid 20s driving the posted limit, even in hilly coastal Oregon.

[eou_edu]

Big Dave I was hoping you would ring in. I read a lot of your posts for ideas when i got started with this project.

The 6 speed is actually a G56. They changed in mid 06. From everything I hear it's a better tranny than the NV. It's more heavy duty, more reliable, shifts nicer, and a lighter aluminum case. So I'm happy about that.

Ideally I would also like an aerolid. My mechanic skills are pretty good but my crafting skills are currently at a first grade level. I would buy an aerolid if anybody made them commercially but I can't seem to find anybody. I think Bondo on here was going to do it and is either still working on getting it off the ground, or isn't doing it anymore. So tonneau cover it is. I looked at the roll up ones but they weigh about 100 lbs! Seems like the extra weight will negate some of the benefits. So I will probably end up with a solid tri fold. I was also reading about fairings on the back of the cab adding some mileage. I might experiment with that too.

Fairing in the front just below the bumper seems like a worthy mod. Changing my mirror situation away from those huge things would help too. I was thinking an in cab or small camera set up would be ideal. Then a front fairing below the bumper. Grille block of some kind, ideally screen. It has an electric fan with a dial to set the temp. That along with waterless coolant and a little warmer thermostat I could seem helping............It's quite a list. A work in progress I will be tackling in the coming months.

[slowmover]

The stock towing mirrors aren't likely the "harm" one might think them especially in consideration of legal requirements in re towing (why buy this truck and harm its ability to do work?) and in day-to-day solo use. As I see no less than 24-mpg on-highway with a stock, manual-trans CTD, this change has no cost-to-benefit advantage that makes sense. Cameras cannot do the job, by the way.

Look into G56 ratios as they were changed just a year or so after introduction.

.

[Big Dave]

Glad to see someone taking an integrated approach to pickup MPG. Too many guys are “hammers” and see all the (pickup) world as a “nail.” Engine guys think only in terms of engine mods. Body men think in terms of aero mods, etc. The right answer is “all of the above.”

You might help us help you by burning a brain cell or two in describing what you intend to do with the truck. Cars are naturally single-purpose vehicles but the very soul of a pickup is versatility. Do you tow a lot of (like me) intermittently? Are you a commercial operator who has to drive around with a bed full of stuff all the time, or do you just haul butt? Give it some thought and fill us in.

What you do with the truck also speaks to weight management strategies. You could beat your brains out reducing weight and then defeat yourself by hauling heavy loads in the bed. You live in hilly country but where I live (central Indiana) is as flat as pool table. Kansas looks mountainous by comparison. Weight and grade interact vigorously in the road load equation. Thus weight is crucial for you, but me…not so much. Good thing. My sturdy Ford is heavy. Sadly, the two adjectives often go together.


Like you, I wish Bondo was having better success. Have you ever seen the youtube clip of his aerolid in a wind tunnel? Baby, that’s the gold standard. The smoke tells me his laminar layer stuck tightly all the way down the lid to the cut-off edge. Add in his outstanding workmanship and I would have paid good money for his stuff. But he’s right. These are not good days for startup manufacturers. But in the interim, I wouldn’t be too ashamed to have a good DIY-looking aerolid. Phil Knox (aerohead) is certainly not in bondo’s class as a fabricator, but his air flow obviously likes his truck. A number of guys seem to be teaching themselves fabrication skills making aerolids. My old aerolid looked hideous but worked like a champ. I could immediately tell it was working because the wind noise dropped to nearly nothing. Once you’ve got a handle on what you are doing read the various threads about DIY aerolids. We’ve all made our mistakes and learned from them. Mine was too steep, had no working hatch and was utterly opaque to the rear. I’ll address that on my next try.

Your truck is classicly over-geared. You can tell its over-geared because its MPG is not sensitive to other changes. I can tell I’m nearly at the optimum because every little thing affects my MPG.

Tires. What size are your tires? I’ve done some experimenting both ways and have come to the conclusion that tire selection is one thing the factory boys have a handle on. My truck’s optimum tire has a 31.7 inch outside diameter. Go down in diameter (without going to unobtainable gear ratios) speeds up the engine and the engine frictional HP eats up your MPG. Go up in diameter and the rotational moment of inertia takes a bite out of your MPG every time you accelerate away from a stop. Do you need gnarly off-road tires? Some do. Some don’t. I use road only tires, but I’m in a 4x2 use regime and can get away with it. So the times I get off pavement I have to be touchy where I go. Not a big deal to me but it might be to you. I also inflate my tires (they’re Firestones and you don’t dare under-inflate Firestones) to 25% over the sidewall max number. Anytime tire pressure drops, I notice a drop in MPG.

Watch your brakes and wheel alignment. My ford tends to drag the rear discs and that robs you of MPG. I put little springs in the calipers to promote good disengagement. I don’t know how much your 4x4 can do this but if you minimize toe-in, it reduces front tire drag. Early Honda Insights had zero toe-in and obviously Honda was leaving no stone unturned. Zero toe-in sacrifices the self-centering tendency of Ackermann steering so you have to positively hand-drive the vehicle every inch of the way. I think only Wayne Gerdes can live with this constant strain because he is so committed to getting good MPG.

Evans waterless coolant. I use it and my testing showed it improved my MPG by 0.5 MPG in an already high MPG truck. I also went to a 203 degree stat (fairly available for 7.3 Powerstrokes). This is good on-balance but be aware: At defroster on full-blast (I was fighting freezing rain) 203 degrees can crack windshields and cook your fingers if the heater vents blow on them. When converting be sure and get all the water out of the cooling system. Use a heat gun to get the last bit out of the block. I got lazy and my Evans turned black. Seems to work OK but I hate the look. I went to Evans to defeat cooling jacket cavitation. The 7.3 Powerstroke is an old school-bus motor and it has a fearsome water pump. It flows so much water that 7.3s have been known to cavitation-erode the front two jackets completely through. From the factory mine needed a maintenance-intensive water treatment. The Evans boils over 400 degrees so cavitation is no longer an issue. I’ve never heard of that being an issue to BT3.9 engines.

You have a lot of scope for improvement, and if you re-gear, you’ll remove a big obstacle.

[mikeyjd]

Originally Posted by eou_edu

So I have my project started. I now am the proud owner of a 2006 dodge ram diesel, 4x4 quad cab 6 speed manual ST. I bought the truck with a dead 5.9 common rail and had it swapped out for a 3.9 mechanical 4bt cummins. The engine was rebuilt and had a new cam swapped into it. So far I'm very happy with the results. The truck was built in Texas and I live in oregon. As of now it still is a work in progress.

First off despite what most people speculate it's not underpowered. These engines were in ford f350's in South America for many years. There also made it in several million 10,000 lb plus box vans. I did this project for 3 reasons. One it was actually quite a bit cheaper to swap this engine in than rebuild the cr5.9. I also wanted something for good MPG. A 3.9 vs 5.9, 300 less lbs, 2.0 less cid, and two less cylinders should get better mileage. Especially when you consider how little horsepower it takes to cruise down the road. When you aren't using that power to cruise, 2 extra cylinders is essentially just drag and weight. I also like the simplicity and reliability of mechanical engines. All in a truck that you shift your own gears, roll up your own windows, lock your own doors, no carpeting, and a pull to kill switch. It's kind of like an old 70's era pickup trapped in a 2006's body.

My first tank I was very disappointed with the results. 16.5 mpg! I thought I had wasted my time and every nah sayer was right. That is at or worse than what the 5.9's get! But 4.10 gears I was running hwy speeds and the thing was screaming at 75. No governor spring it was running for 400 miles right at the governor. Next tank I slowed down to 65-70 mph and returned 20 mpg. A little more happy with that but still about what the 5.9's get and running about 2250 rpms. The third and fourth tank I slowed down even more to 60-65 and returned 25 mpg..........I was much happier with this and no similarly equipped 5.9 I know of is capable of this.

My next mods on the list are for a gear swap to 3.42. Of course this won't give me all the benefited mileage I get from slowing down, but it will help. I am also planning to haul things. While the engine has plenty of power empty I would like a little more power for hauling (otherwise I'd be driving a geo). It won't take much to get at or above the power levels the standard output 5.9's put out in 2003. 250 hp, 460 ftlb torque vs my inline 4bt 130 hp and 390 ftlb. A set of injectors, water meth, timing, and possibly propane could be in my future. All of which should only improve on MPG and keep the benefits of the smaller 3.9. Already has the hamilton cam in it. I suspect some power improvement will also make the truck less sensitive to fuel mileage fluctuations by making work a little less hard to move the truck. One last benefit of 300 lb less up front is better handling. I noticed right away the suspension is better and it steers nicer with 300 lbs less up front. I also suspect it will be a lot more forgiving on front end, hubs, axles, and steering parts..............Pictures to come as soon as I find my computer cord.

5.9's can get <25mpg

[JQmile]

Originally Posted by mikeyjd

5.9's can get <25mpg

I've got 27mpg with mine, and 23-25mpg a bunch of times. It would probably do a lot better if I took out the 1,000rwhp (ok, 972), "dyno" injectors.

There was a dude who went by Crabelle over on Competitiondiesel.com that got 35mpg out of his 6bt, with a double overdrive, and a bunch of other stuff.

Anyways, neat build, mpg should get substantially better with a re-gear. Might want to try electric fans and a grille block too, they were worth a good 3mpg on a 97 Ram I used to have.