johnr9q

I have a stock 99 Dodge Turbo Diesel and I'd like to improve the fuel economy dramatically if possible. What would happen if I disconnected the turbo and modified other aspects of the motor to complement disconnecting the turbo? How about disconnecting 2 of the pistons and again making other mods as required to compensate? Any other ideas? I don't need all the power I have but would like to get much higher milage. I did a fair trial with one of the chips that claimed 10% fuel economy improvement and I did have more power but no improvement in economy.

Begle1

Err, disconnecting the turbo would put fuel economy in the pot... Look into a cheap motercycle.

westcoaster

I think you would need to change the pistons to give you a higher compression ratio....

Monty

Ditch the turbo disconnect idea. What MPG figures are you seeing right now? Good maintinance, fuel filter, air filter etc. IAT sensro cleaning, as well as a valve adjustment should be covered.

johnr9q

How about if I put a high economy 4 cyl diesel in the PU any Idea what my fuel economy would be going 65 on the flats. Currently get about 17 empty in that mode. Anybody ever put a small 4 cyl diesel in one?

Monty

The cost to change to a 4cyl engine versus buying a cheap good mpg car or truck is very one sided. If you want a change that dramatic that you would consider putting another engine in, take that money and buy a car.

j-fox

I would venture to guess that a 4Bt Cummins set up right could get you close to 30 mpg.
I have one in a step van and it will get 14 mpg! This is 11,000 lbs and a bilboard for areodinamics. The same trucks with a chevy 400 get 7 on a good day, usually 6. The 350 gas was slightly worse. This is for comparison.
I'd love to try it in a 1500 4X2 dodge.

Shovelhead

You're still going to be fighting the weight and aerodynamics of a large pickup truck.
You'll need a Diesel powered car like the VW for better milage.

12valve@heart

I recall one of the members here posting that they had put a 4BT (4 cylinder version of the same Cummins that the 1st gen has) in an old military jeep type pickup and could get 30mpg @ 55mph but dropped to around 25mpg @ around 65mph.

I'd guess that you'd be hard pressed to get your '99 above the mid-20's regardless what you did and keep in mind that you have to keep the trucks computers happy regardless of what mods you make.

If you want a diesel pickup that gets better mileage, look for some of the old mini-trucks like the LUV or Isuzu. Seems like there were some others too or if loads aren't an issue, get a 1980-83 VW Rabbit diesel 5 spd pickup. They're available on e-bay regularly and will get 40-50mpg. It's the same motor and front wheel drive transmission as the VW Rabbit but with a unibody pickup bed behind the front doors. My mom's had over 350K miles on it when we got rid of it and had a lot of life left in it.

mikmaze

have you considdered a gear splitter for the truck ya got now? slow that torque monster's revs down and watch the mileage go up! btw fill out yer sig so we know what 'yer driven'

Forrest Nearing

the 4cyl Cummins is going to be required to make the same amount of horsepower to keep you at 60mph as the 6cyl... maybe SLIGHTLY less due to the 300lbs of weight difference, and the slight loss in parasitic drag on the extra two rods and pistons.

but the amount of fuel that you could buy with the money you'll waste doing the swap would be a lot of fuel... the truck will be pretty worthless when you try to sell it also.

if you want to get better mileage, lower the truck ~4" in front, 6" in back, put a good sized chin spoiler up front to keep air from getting under the truck, put a hard bed cover on it, drive it like my grandmother would, and do 55 on the highway.

Forrest

Shovelhead

If you lower the front 6 inches and raise the back 6 inches, you'll always be driving downhill.

They're right though.
Figure how much money in fuel you'll save VS the money it will cost to make the changes.

yeah, I know it's not much help

BoostdCTD

I'd say with just disconnecting the turbos you'd lose mileage. Just stay off the boost as much as you can and keep the engine under 2000rpms. Also do you have a tonneau cover or something of this sort? Or you can just remove your tailgate, they make huge drag at highway speeds.

Raspy

Disconnecting the turbo would cut the power to half or less but I don't see why it would cost you mileage. As long as you didn't overfuel it you might increase mileage because of the easier breathing and lower horsepower. As long as you didn't push it to where it was smoking.
Cutting the fuel to one or more cylinders is a bad idea because you still have the frictional losses of those pistons and cams running, so no net gain.
Lowering the RPM is commonly thought to be good for mileage but if that was the case we could all just raise the gear ratios to where the engine was virtually stopped and expect 100 MPG or more. There's more to it than simply raising the gear ratio, so that's not the answer.
Demanding less power from the engine during acceleration and on the highway is the biggest thing you can do. Less weight (VW diesel), less frontal area (VW diesel), less rolling resistance (VW diesel). And starting out with a smaller engine that has less frictional losses (VW diesel). If it has to be a full size heavy duty diesel then the Cummins is the way to go and just drive conservatively. Oh, and get the six speed in a two wheel drive with cruise control. And slow down.
I'd love to see the results of removing the turbo, that would be fun and informative. I'm sure it would run just fine with a lot less power.

Wetspirit

Forrest Nearing

because these engines are designed to use turbos. if you increased the compression ratio to 21-22:1, it might be a different story but I still doubt it would be better. at lower boost levels, turbos actually help efficiency.