Hypermiling a 2001 Dodge Durango 4WD...
 

Well, got the Red Sled back on the road, after 6 months of off-and-on working on it to replace the dead 4.7L V8 engine that spun #8 piston's conrod bearing.

The replacement engine is also a 4.7L V8, but it is out of a 2009 Dodge Durango 4WD. The engine has 2 spark plugs per cylinder, a compression ratio of 9.8:1, and a revised exhaust manifold set. It also generates quite a bit more power and torque over the rating of the engine I pulled out.

The replacement engine is also drive-by-wire, so I replaced its intake manifold with a 2002 HO manifold out of a Jeep Grand Cherokee. I also installed 12-hole fuel injectors, and a 65 mm throttle body out of a 2000 Dodge Dakota. I replaced the transmission computer with one out of a 2004 Jeep Grand Cherokee, so now I have a 5-speed transmission instead of a 4-speed. Along with the 12-hole fuel injectors, I installed the same fuel rail temperature equalization modification that my Fiat Dakota currently has.

With this modified Durango, I took the family on a trip to Ohio and back, putting about 1700 miles on the frame over the course of a 5-day trip. Average fuel economy is apparently 25% over EPA estimate.

I will, of course, work to improve this even further. The Durango, being the new family hauler, will see a lot of city driving, and I expect the average fuel economy to drop somewhat.

Hyper mile that thing straight to the used car lot..

Improvements on the worst gas guzzlers is a bigger pay-off than improvements on a fuel miser, so I applaud your efforts.

But... can you clarify something:


EPA for yours is 12 city/16hwy 13 combined.

For a long trip, I assume that is almost all hwy, so are you saying you average 20mpg (16 * 1.25)? Or are you saying you are at 25% over EPA combined, which puts you at about 16mpg?

The former, I would say is pretty good.

The latter... well, that puts you on par with similarly equipped, stock Tahoes from back then which makes me wonder if the effort was worth it.

For reference, we typically average 21+mpg on family trips in our '05 Tahoe, no hypermiling, just set cruise at 65mph and go. It's stock other than being lowered a little and 20" wheels.

According to Ecomodder's own fuel tracker, I'm averaging 27.7% over EPA combined for the 2001 Dodge Durango, using the EPA revised numbers.

Out of the past 5 tankfuls, 2 were almost all highway driving, 1 was about a 50/50 mix of city/highway driving, and 1 was mostly city driving. The remaining 1 tankful was a combination of highway driving and 2.5 hours of idling to flush the coolant system, do performance testing, and conduct leak detection after the engine was installed.

The 2 highway tankfuls saw average FEs of 17.0 MPG and 17.2 MPG, which is about 6% better than highway figures for stock (and 24% better than combined). The 50/50 tankful saw an astounding 18.4 MPG (almost 30% better than the stock combined figure), and the mostly city tankful saw about 15.5 MPG (still a respectable 15% above combined). The first tankful, the combination of highway and idling, saw about 14.3 MPG (9% better than combined).

Judging by the completely in-city performance so far, I estimate that the Red Sled will probably see around 13 MPG now, which itself is an 8% improvement over stock city figures (and equal to combined).

Of course it's worth it. Wouldn't even bother, otherwise. Both the wife and I are partial to Dodge, and I like older vehicles that I can still repair.

To be honest, there's not a whole lot of highway-friendly hypermiling driving techniques for an automatic-equipped 4x4, 5000 lb gasoline-powered beast. Suffice it to say, the vast majority of my hypermiling is of the "vehicle modification" variety.

I think that the Red Sled will respond well to basic aero mods (I already deleted the roof rack prior to the trip), since it is so incredibly aerodynamically hideous. It should also respond well to my installing a coolant-based intake air heater, and to my modifying the power steering pump to incorporate an electric clutch.

A small gain is still a huge percentage jump, and that's nothing to sneeze at. But there had better be some huge compensation for dealing with what is still, by any standard, horrible mileage. Things like having it dropped in your lap, doing your own work on a platform you have familiarity with, having an insecure, irrational family member who thinks it's "safer" or using the towing capacity often enough to matter. All of these are okay reasons to put up with it- I drove an Xterra for several months because I needed something and it was just parked in the backyard taking up space. "Free car" is worth crappy mileage, and I did get a decent percentage improvement over EPA.

Bad mileage isn't an absolute, even though it is. If you're getting real utility that you can't get in something with better mileage, it's fine- and improving mileage within that context is awesome!

Is a manual transmission out of question?

Does it have an electric engine cooling fan?

If the transmission goes out, then it'll be replaced by a manual. Otherwise... yah, not going to go out of my way to install one.

Yep, tore out the stock engine-driven fan, and replaced the aux electric fan with a larger 4000 CFM one meant for a Jeep Grand Cherokee.