how is your afc set up?
what size fuel lines and pump?
star wheel height?
what fuel pin?

for the life of me i cant get better then 12mpg and to me doesnt make the power like it should


ill post a short vid later what mine is

ive got a powerstroke intercooler,sdx 5x14,head studs,.10 head gasket and PDR port job going in the next month....................or maybe ill sell it and buy a newer one 03-06

put a programer in it and out tow mine all day long

 

winter fuel is putting a huge damper on your mileage. Also, city driving (even if it's short hwy runs, where the truck doesn't get to warm up and just cruise for extended periods) for the auto is just pathetic.

In the winter I'll get as low as 10mpg. Then I do a 7-8hr strictly hwy drive and get 18mpg (US gallon, in the winter). The auto does not like any form of stopping and going

I'm going to venture a guess that its a few things.
1) your truck is a 4x4
2) it's a dually
3) it's an auto
4) your probably still running winter fuel
5) you're in kamloops so the elevation isn't helping any

 

my d350 91 38 in. ex. cab stk. as far as i know, 60-65 hwy. 18-18.4mpg, 14 around town.( 727 auto, n/ic) Does your trk., blk. smoke very much? to much fuel????

 

My 92 auto is only getting 12.

 

rick12v, good point about elev., years ago we had to jet or tune our carbs, to the altt., we were running in, other wise they bog down smoke or ran lousey. Lucas might be worth looking into.

 

you all make grood points

where is this 18+ mpg 500hp myth come from

yes its a dually and has bigger injectors but 11 mpg is bad no matter what way you look at it.

with 4 10 gears around town it should be better.
and on the hyway at 1800 rmp it should be as good to stock or close to it.
obviously rolling restistance with the tires and mild lift wont help but i would expect 16-18mpg.

porting will help but i wonder how much..

bottom line is the truck has too much money in it to perform the way it does

my starwheel is almost as high as i can get it .but then the turbo spools slower and it smokes bad off the line below 5psi because the converter is tight.

iam taking out my fuel pin and putting in a stock one..i barely notice the hp gain..if any

the powerstroke intercooler with 3" charge pipes and new airfilter are going in after next weekend

ill post a video later about my fuel pressure and ill report back how these adjustments helped

 

Your sig says 5" lift and 35" tires....on a 4x4 automatic dually. I'm sure it looks sweet, but its not exactly the best setup for performance or mileage. What does your truck weigh? Before I went with twins, big injectors, head work etc. I had everything else in my sig and got 24.93 mpg on a trip. A lot of interstate driving, but some in town and quite a bit of 2 lane roads. Miles were checked with a GPS. Total weight for the truck with me in it and a toolbox full of junk was 5640 lbs. 265/75/16 tires and 3.55 gears. This was pump to the head timing, stock injectors, ve close to run away, and stock turbo making 33psi. I averaged 22mpg in mixed daily driving with that setup. I'm sure your truck would be quite a bit heavier than my D250 though.

I would recommend loosening up you afc some and making sure your fuel pin is getting full travel, both up and down. The smoke screw should be up as far as it can go. If your starwheel is up too far, your afc spring could be binding and not allowing the fuel pin to come down all the way. Also make sure you are getting full throttle travel. The throttle lever should be able to hit the pump where the high idle screw "used to be".

 

most of this makes no sense to me
"loosening"up my afc will allow full fuel at less psi of boost pushing the fuel pin farther down into the cut portion.how is that going to increase economy having my starwheel up is trying to limit full fuel to 15psi or more.hoping my ***** footing around would help with economy.the way the fuel pin is cut would make a difference though.

the 35" tires were installed because with 410 gears and stock tires this thing would rev like 3000rpm at 60 mph
the %" lift in the front ONLY leveled the truck...no rear lift-stock height.
thats how much of a rake this thing had.

the truck only weighs a few hundred pounds more then a non dually and still considerably less then a newer diesel

IAm positive the BD injectors in this thing are the cause of the problem. 19mpg stock
then 10.5 since injectors all the mods in my sig.

hence why there is a set of sdx's on there way.

what kind of increase in milage and egt drop did you see with the twins?

are you running your pump at runaway with the starwheel bottomed out?

 

You originally said:



You can have your truck run better and get decent fuel mileage.
When I got my '93 it only made 11psi of boost. Low, I know, but someone had the pump to the head,etc.,etc. By setting the truck up the way I said, I got up to 33psi, with egts 1250* max. Mileage was the SAME. Ran like a completely different truck. From my limited experience, setting your AFC to either extreme (starwheel all the way up or down) does not work well. I have mine set 2 turns lower than when I got it (don't know where it was stock). I have tried it a lot higher, and a lot lower, but wasn't happy because of the smoke when it was too loose, or lack of spool and power when it was too tight. You want the right amount of fuel at the right time. By setting my smoke screw as high as it will go, I can drive with 6x16s and no smoke if I want.


With the twins, bigger injectors, and ported head I have about the same egts that I had with stock injectors and turbo.....pump settings being the same. 1250* max while brake torquing the truck. Mileage has dropped some, but as I have said in other threads, I don't know an actual number yet. I won't know until I replace my dead VE. I don't think anyone adds that much fuel and air and expects to get better fuel economy.


As far as tires, lift, and being an automatic dually...
You have more tire to get moving, no matter what the gearing. You don't get that power back. Gearing helps, but you don't put the power to the ground that you would with smaller tires. I'm sure you know this but I was just getting at the fact that I would not expect you to get the same fuel mileage with your W350 as I get with my D250 five speed.




Problem solved.

 

i dont think iam over fueling it the pyro doesnt spike.

this is with 6000+ lb trailer behind me



whats the deal with the fuel pressure guage i understand this is a piston pump but seams to flutter too much

 

what should you do to the pump to try to get better milage, my 92 in my sig seems to be a real dog lately, and the seems i am at the gas station all the time.

 

On my last couple tanks I've been getting 17-18mpg with my 91 d350 it has the 727 auto.
For my pump tuning all I did was bump the timing 1/8, smoke screw all the way up and even shaved some of the metal off the pump top to allow the cone to travel all the way up, my star wheel is down far enough to allow the cone to go all the way down ( that took a lot of tinkering), my fuel fuel screw is in to the collar, and I made sure I had full throttle travel.

I have been running 1/2 liter of 2 stroke oil in every tank along with white bottle power service.

This set up works for me if gives me decent mileage but I also have some power to spare for when I want it.

I don't drive like a maniac but I don't drive like my grandfather either.

 

I am still getting 16-18mpg on the freeway but around town forget it I drop down to the 12-13mpg range.

June 5th there is a dyno day @ BD I will be there and can chat more then with you.

W350 4X4

 

Are your mileage figures corrected for tire size? I had to use a GPS, mile markers, and some google map directions to get a conversion factor that would work right.

I am running a manual truck with 38s, 3.54 gears, and almost no lift. My mileage stays in the high teens for the most part. The engine is still stock for the most part. No air box, 3" straight pipe, and turned fuel pin. The truck is only pushing about 1-2psi at 50mph in 4th.

The automatic is probably a little loose costing you some rpm's and mileage?

It seems that most of these truck are different. Everyone drives them different too.

Don't forget that pushing 2 more tires is going to add a bit of resistance.
These trucks are as aerodynamic as a barn door. Speed kills mileage. If I try and push my truck at 75-80 the mileage will drop to 15mpg or so.

 

Any chance the converter is giving up? Tons of slip can kill MPG no matter what your pump tuning is.