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

Rustyiron · Mar 30, 2013

I'm to the point where I'm looking for a vehicle that gets (REALLY GETS) 25-30 mpg. I have never owned a car other than my fun car (74 Caddy El Dorado conv.) Been thinking Suburu of Volvo xc70, and used, (4-6 years old).
Now I don't really see myself in a real "car" and some years ago I saw a nice looking Dodge, 4x2 with nice looking wheels, it sat pretty low, with the Cummins. I still have my bigger trucks (holdin on to them 7.3's) for heavier work & towing, so I don't need the ego machine and that makes me wonder about "turning down" an older 5.9 for economy. Does anyone know of someone doing this, and what could be expected?
Detroit finds ways to squeeze more hp out of smaller motors, how about an optional motor with more mpg's and just adequate hp? :confused2:

Code54 · Mar 30, 2013

Check out Cumminsforum dot com. It is a big site dedicated to the Cummins trucks and there is a lot of good info on there. Someone maybe able to help you find the correct parts.
On another note, I recently bought my wife a Subaru Crosstrek (all wheel drive Impreza based hatchback that is sort of jacked up with fender flares) and it gets great mileage - been getting between 26-31 here in WV even with all the hills. Overall a nice little all wheel drive that gets great mileage but it is newer - it seems they really got there mileage up in the last few years.
Good luck

whistlepig · Mar 30, 2013

I kind of wonder about Detroit and the gas mileage thing. My first new Chevy pickup was a 1/2 ton 4x4 5.7 liter. It had 195 HP and did what I needed a truck to do and got about 15 MPG on the highway. My present 2007 4x4 Chevy is a 5.3 liter with over 300 HP and still gets about 15 MPG highway. I really don't need 300 HP. I wonder what kind of mileage my 2007 5.3 would get if it was only 195 HP.

Rustyiron · Mar 30, 2013

Code54 said:
I recently bought my wife a Subaru Crosstrek (all wheel drive Impreza based hatchback that is sort of jacked up with fender flares) Good luck

Thanks for the link & the cross treck is a nice looking vehicle.

Rustyiron · Mar 30, 2013

whistlepig said:
I really don't need 300 HP. I wonder what kind of mileage my 2007 5.3 would get if it was only 195 HP.

That is exactly what I'm talkin about!
You'd think that it would be at least an option.

Peacock · Mar 30, 2013

Get a VE pump Cummins 4bt and swap it into a pickup. They have torque to spare, great fuel economy and will outlast whatever engine they are replacing, except a 6bt.

JimRB · Mar 30, 2013

I put bigger nozzles and a tune in my 2003 VW TDI. So I guess I make another 15-20 hp. I never went to a dyno to see. My fuel mileage did not change. The nozzles and tune just let me have more overall horsepower. That year TDI had the same basic fuel pump/distributor as the older Cummins. That said I think there are some tuner boxes that play with timing on the Cummins that can help with mileage.

By the way I get 47-50 driving the posted speed limit in Atlanta in my TDI. It got 44 driving 75 actual mph. Winter fuel and cold weather pulls that mileage down a bit. The Touregs with a diesel get in the 30's. Kind of pricey for those though.

Dmace · Mar 30, 2013

I've been saying this for years!

Give me a new diesel making 300HP/400lb.ft. and 25+ mpg's with a 10-12k tow capacity and I'd be happy.

http://www.tractorbynet.com/forums/trailers-transportation/247490-diesel-truck-best-mpg.html

It's coming, the RAM's new V6 3.0l diesel should be around 250HP/430lb.ft. and over 23 mpg. We'll see...

Even detuned, the Cummins is still a large displacement engine. Maybe just taller gearing to keep the diesel in it's low RPM sweet spot

Rustyiron · Mar 30, 2013

Peacock said:
Get a VE pump Cummins 4bt and swap it into a pickup. They have torque to spare, great fuel economy and will outlast whatever engine they are replacing, except a 6bt.

I've seen a few of these in "Farm Show" mag.

Rustyiron · Mar 30, 2013

Dmace said:
I've been saying this for years!

Give me a new diesel making 300HP/400lb.ft. and 25+ mpg's with a 10-12k tow capacity and I'd be happy.

http://www.tractorbynet.com/forums/trailers-transportation/247490-diesel-truck-best-mpg.html

It's coming, the RAM's new V6 3.0l diesel should be around 250HP/430lb.ft. and over 23 mpg. We'll see...

Even detuned, the Cummins is still a large displacement engine. Maybe just taller gearing to keep the diesel in it's low RPM sweet spot

Hey, I'm in Maine, you can't afford the annual (registration) sticker on a new vehicle here! I think that the registration fees "bottom out" as a percentage of new value at 6 years old. These silky smooth roads we have here do not come cheap! :confused3: