more power = better fuel economy?

[93_444idi]

I'm looking at about 13mpg unloaded right now, and that's cruising down the highway not putting my foot into it. I've got lots of plans regarding adding more air and fuel but if 13mpg is about the best I can expect I may just sell it and look for a more "eco-friendly" diesel to play with. I keep reading about 1st gen cummins getting 25-30mpg and granted, they dont have all the upgrades I'd do to one of those diesels, but that's a huge difference than the 13 I get. There are trucks in dieselpower putting out 600-800 hp and still getting over 20 mpg.

My truck doesn't make a whole lot of black smoke unless I really put my foot into it, it just eats through a lot of fuel. Should I look elsewhere for economy? Maybe do a 1st gen cummins conversion into my truck?

 

[Diesel_brad]

Who ever says they are getting 25-30 out of their cummins is a LIER. And those trucks in DIESEL POWER that are getting those numbers are not a brick shaped OBS with 37" tires

 

[SparkandFire]

I've a friend who has a fleet of 12V Cummins powered dodges in the driveway (and spilling out onto the street) These are all two wheel drive 5 speed trucks (with the exception of one,) he's regularly high teens and low twenties on those rigs, the 4x4 gets an even 17-19 mpg...

All of these trucks are bone stock, except one which has 4" exhaust turbo back.

My grandfather has two 24V cummins and he averages roughly the same.

A number of things factor hugely into the fuel economy gamut. Part of which being that #2 diesel is not what it used to be. We do not have the privelage of knowing what the cetane rating is of the fuel we load our tanks with, like the gassers know octane. Cetane is a very important number because it directly coresponds to the energy content of the fuel. Cetane also greatly effects ignition timing, as cetane is a measure of a fuel's ability to autoignite under pressure.

If I ever have the time (and the money) to rig up a truck with various sensors (cylinder pressure piezo sensors for ignition timing, throttle position sensor, highly accurate pyros, strain gauges in the engine mounts, etc...) I would love to track and trend all sorts of different scenarios that these engines are subjected to. Years back I was part of the team that did all the metrology work on developing the Zond windturbine, really amazing science that goes into that stuff...

 

[flareside_thun]

You're complaining about 13? I'd LOVE to get that. A buddy's old truck got 19-21 MPG consistently with a 90 F350, ZF, NA on 38's.....The mileage can be had....But some times I think it's selective.

 

[itsacrazyasian]

I get a SOLID 16mpg with my 37's 5 speed turbo, CCLB 4x4. Thats city.

 

[FordGuy100]

I was on a couple cummins forums. I think the key to good fuel mileage in the first gens was their weight. A couple guys with regular cab long bed 2wd trucks posted their trucks weighed in at around......get this......4800-5200 pounds. My truck weighs around 6500. That's a really big difference.

 

[m67tang]

what fuel conditioner, if any, are you using?

maybe try a different place to buy fuel. I know a place I get 1 mpg less than anywhere else I fill up at

I easily get 15+ mpg on a 2wd dually, occasionally I get 20 mpg. I use Power Service conditioner or Stanadyne, when I can get it.

 

[hairyboxnoogle]

Well truck in my sig gets 17.7 all around everyday drivin the hell out of it... ive gotten 21.4 runnin 60. Ive got 35 inch toyo MTs ZF-5 and 3.55s. Truck weight right at 6500lbs. Also, since those numbers have been recorded, ive swapped injectors pump and seem to get even better. My dad claims he is only gettin 9-11 with his 92 IDI but he starts it, drives a mile shuts off about 12 times a day.

 

[93fordturbo]

I know the 95-97 12 valves get really decent mileage. i know one personally, that gets 24+ on interstate going 70. its an ext cab long box auto with 2wd. For a good mileage diesel, thats the way to go imo.

 

[93_444idi]

i occasionally use lucas fuel treatment but that's it.

flareside, that's really good for an NA truck. Mine before the turbo on 36s was even worse than it is now. Maybe I've just got a worn out fuel system or something.

i'd like to know what individuals here with a lot of work done to their idis are getting. adding an intercooler should help fuel economy right?

 

[SparkandFire]

I timed my truck recently and found the following;

This is after installing rebuilt (uhaul) IP, new BB injectors. I drive 120 miles a day so I've been running through alot of fuel lately. I drive the same way every day, I get into it a little now and then, I've got a big hill to climb on my way home.

So, with my timing set to 2.1 degrees ATDC (thats right, ATDC)
I got an average of 14.7 MPG. (averaged over 5 fillups, no topping off, filled up at Valero in scotts valley)

Set my timing to 8.4 degrees BTDC @ 2000 RPM and the last fillups averaged 18.9 MPG. (averaged over 4 fillups, no topping off, filled up at Valero in scotts valley)


So, timing has ALOT to do with fuel economy... I've got the numbers to prove it.

 

[93f250idi]

I get around 14-15 around town. That's with na zf5 4:10s on 35s. I ain't complaining but I would like to see more.

 

[93_444idi]

I timed my truck recently and found the following;

This is after installing rebuilt (uhaul) IP, new BB injectors. I drive 120 miles a day so I've been running through alot of fuel lately. I drive the same way every day, I get into it a little now and then, I've got a big hill to climb on my way home.

So, with my timing set to 2.1 degrees ATDC (thats right, ATDC)
I got an average of 14.7 MPG. (averaged over 5 fillups, no topping off, filled up at Valero in scotts valley)

Set my timing to 8.4 degrees BTDC @ 2000 RPM and the last fillups averaged 18.9 MPG. (averaged over 4 fillups, no topping off, filled up at Valero in scotts valley)


So, timing has ALOT to do with fuel economy... I've got the numbers to prove it.

i didn't change my timing at all after adding a turbo or maxing out my pump. maybe that has something to do with it. i dont know how to adjust my timing though. i may just pay a guy in town to do it by ear.

 

[rjjp]

i may just pay a guy in town to do it by ear.

Don't bother, if it's not done with a meter then it probably won't be close.

 

[flareside_thun]

You could do it yourself and it'd be free.....But the best way is with a meter like stated. Good luck finding someone around you that knows how to do it though.