71 F250 4BT Cummins Work Horse: Just doing a little work

[KRob]

Well, project has been shelved for awhile. Traveling for work.

I am still on my third starter...which isn't even starting it...so i guess when i get home next it will be onto a fourth, thank god for Napa's return policy and knowing the owner of our local store.

I would really like to get it done so i can use it as my daily run about. 30 MPG compared to my Dodges 17-20 mpg and smaller then my Dodge....but no AC, yet.

[KRob]

4th starter installed today.

1st one was DOA, never got the truck started
2nd worked a little while then started failing
3rd was DOA on install, started the truck a couple of times.
4th seems to be working.

Since is still had all of them in my possession i did a little comparison.

1 looked fine on the out side minus the made in china stamp.
2 and 3 both had gaps/separations...i just tried to explain what area but when re reading it it confused me....so take my words they both had visible question marks.
4 looks fine.

My hope is that it is from using grind wheel on the first three. since it would make the starter vibrate...maybe that broke something inside. The fourth one i used a hand grinder so the vibration was there instead of in the starter. Or maybe the 4BT is just rattling them apart.

Anyway also worked on the transfercase shift linkage...which is now resulting in having to bend the transmissions shifter, so that the two will clear each other.

Anyway will see what happens tomorrow....between the wife coming home and going on a damage control elk hunt...that i have two tags to fill.

[KRob]

Well the wife came home for the long weekend and she rode around with me in it all weekend....she even drove it and the best part is....she loved it! Even though she stomped me this weekend shooting trap, and will not give me her Remington 1100, i think i will still keep her.

Her one comment was...."get the floor put together so we can talk when driving" I dont know maybe getting the floor put together might go to the bottom of the list, it might be more beneficial incomplete.

[KRob]

Well some driving...and not a whole lot of progress. But here is an other video and some pictures.

http://www.youtube.com/watch?v=YNpyYqhOeqU[/video]

With the heavy front bumper....i don't know if i like it though...doesn't match size wise. What your all opinions?


Till next time.

[Alstoyz]

[KRob]

So i am a little disappointed...MPG hasn't been as good as i was hoping. You guys take gander and tell me what you think

First Tank
2.29 Gallons, 69.2 Miles, 30.24 MPG

Second Tank
6.98 Gallons, 135.2 Miles, 19.38 MPG

Third Tank
8.99 Gallons, 178.0 Miles, 19.8 MPG

Obviously I have not been gone far yet, but I thought my initial tank was more what i was expecting. However the second two tanks have been used in general driving while the first tank was a drive to a neighboring town. Additionally with my Dodge Cummins, I normally get 16-20 mpg so that's why i was hoping for more. Additionally i have been told by many they are seeing 25 mpg plus. I would be thrilled with 25 mpg.

I am still very happy with it....however I am looking forward to getting a 3000 rpm spring in and getting the floor situated so I can hear myself in the cab.

Currently i think the pump (injector pump) is turned down and only has a 2500 rpm spring....do you think a little more power would help, little more rpm so that i can stay in the power bands?

Till next time.

[mcheath]

Not too sure about that big front bumper, kinda large and over in charge to my eye. IMHO

I don't know what to think about your mileage figures, I've heard numbers all over the place for this engine in our trucks. Your numbers seem on the low side, but I dunno.

Nice looking truck, by the way.

[motzingg]

This is an easy to read 4bt power/torque/efficiency curve, but it doesn't give much context if this is stock/mod or how accurate it is


Here is the curve from cummins themselves, but it is harder to read. Seems to agree for the most part with the range on the first one, if not with the actual numbers:


This tells the story pretty clearly right here, If you are revving much over 1800 your fuel economy is going to drop like a rock. Looks like the peak economy of that engine comes at 1600 or so.

Going to a 3000 rpm govenor will make you be able to go faster, but your economy is going to completely go to crap if you plan on running it that fast. Plus the torque curve drops off pretty sharply after 2100 rpm so you won't be pulling any harder revving it up that high.

[motzingg]

This is an easy to read 4bt power/torque/efficiency curve, but it doesn't give much context if this is stock/mod or how accurate it is


Here is the curve from cummins themselves, but it is harder to read. Seems to agree for the most part with the range on the first one, if not with the actual numbers:


This tells the story pretty clearly right here, If you are revving much over 1800 your fuel economy is going to drop like a rock. Looks like the peak economy of that engine comes at 1600 or so.

Going to a 3000 rpm govenor will make you be able to go faster, but your economy is going to completely go to crap if you plan on running it that fast. Plus the torque curve drops off pretty sharply after 2100 rpm so you won't be pulling any harder revving it up that high.

[KRob]

Motzingg,

Thanks for the info on the power curve that was very interesting to see. It was also interesting to see where it uses the most fuel usage curve. Very interesting.

The reason i want the higher rpm, is because i was almost in an accident a couple of days ago because i have such a limited RPM range. (I had to make a left turn off of a blind right hand corner, of course when i decided to go, was when a car came around the corner, i had to slam a gear in order to clear the road so the car wouldn't hit me because i ran out of RPM.) Currently it is falling flat on its face at about 2100 rpm, so i think by changing the spring out i should get power up through 2500. What someone else explained to me is that a 2500 spring will start de-fueling at about 2100, while a 3200 spring will start de-fueling at about 2700-3000

You are right 3.55 would be better

RPM-------------3.55/4.10
1600-----------55.7/48.1
1700-----------59.1/51.2
1800-----------62.5/54.2
1900-------------66/57.2
2000-----------69.5/60.2
2100-------------73/63.2
2200-----------76.4/66.2

Yeah i would say them 4.10 are killing me.

I am going to play with it and drive it a lot though before i think about shifting gearing around. Since the truck is going to be used as a work truck and since legally the fastest i can go with in a 100 mile radius is 55, i will give it some time and get the current bugs worked out before i start playing with gearing.

Thanks for the info that was really interesting....though i would have still done it i wish i had seen that about a year ago.

[motzingg]

yeah i've got some trans calculator spreadsheets worked out as well if you want to swap a trans and see how that would change your cruising rpm. email me an i can send them to ya, but they aren't working in my google docs for some reason so i cant link 'em.

once i get some better data with the truck running, i'll be able to find rolling resistance and mass, and i should be able to actually work out a pretty accurate figure for HP required to accelerate the truck and keep it rolling down the road. Compare that to a dyno chart and you can get a pretty good idea of where your gearing needs to be to keep your engine happy.

[averagef250]

No, you won't get the best economy cruising at 1600 and no the fuel economy won't drop like a rock past 1800. You need to be 1800-2100 RPM at 65. 4.10 gears are perfect with 35" tires delivering 1919 RPM at 65. If you ran 90 MPH at 2700 RPM you would still get better around 20 MPG unless something is wrong.

First-

Set your timing to 1.6-1.7MM at TDC. This may or may not be where it's at depending on how the engine was built. This timing spec works well with most 4BT's. Some engines need different timing to work the best. Conservative timing will not net the best mileage.

Run a 190 or hotter thermostat.

Check tire air pressure and run max inflation that results in even wear (usually max pressure is fine under a fullsize truck).

3200 spring is a good idea, more fuel is fine if you need it. Fuel/timing/turbo need to match.

Is the truck warming up when it's driven? or are the fill ups a bunch of short trips?

Brakes dragging?

Toe set properly?

Drive it over, I'll check it out if you want.

If the mileage does not improve after verifying the above I would recommend removing the intercooler and running a non-IC intake or going air-air.

[motzingg]

i'm assuming krob has ~30" tires, based on the numbers he listed above. going from 30"-35" is the equivalent of going from 3.55 to 4.10 gears.

with 3.55 gears on the 30" tires, 65 is at 1940 rpm, exactly what Average is saying is ideal.

i'm just going off of cummins' posted numbers saying that engine produces max torque and power-specific fuel economy around 1600-1800 rpm. How that compares to real world driving with accelerating and decelerating, I'm not making any conclusions, although 'drop like a rock' probably isn't the best way to say it.

The math looks like this, at 65 mph we are guessing (based on Average's data) that fuel economy is about 25 mpg with the 4.1 gears on 35 inch tires, or the 3.55 gears on 30 inch tires.

From Cummins' data engine speed is 1950 rpm, BSFC is .37 lb/hp/hr

Diesel fuel has a specific density of 6.95 lb/us gal.

At 65 mph, you are burning 1 gal (6.95 lbs) per 25 miles= 65mi/25mpg=18.07 lbs of fuel per hour
Using cummin's figure of .37 lb/hp/hr, the horsepower required to move the truck down the road at 65 mph is 18.07/.37= 48.8 hp, which sounds pretty reasonable to me.

With the 4.1 gears (on 30" tires) at 2240 rpm the BSFC is .39 lb/hp/hr meaning 48.8*.39=19.04 lbs of fuel /6.95 lb/gal= 2.74 gal in 65 miles- 65/2.74= 23.72 mpg = ~ 5% increase in fuel consumption.

At 1600 rpm, the math comes out to 26 mpg.

so yeah, the rpm change alone going from the recommended gearing (3.55) to the current (4.10) gearing isnt enough by itself to cause such a significant change in mileage as you're seeing, but it does suggest an improvement. 5% is well within the margin of error for sloppy calculations like this, so drive-ability is probably a bigger concern.

[KRob]

Sorry for being gone for a little while.

Truck has 265/75/16 which is 30-31 in.

I have not played at all with the pump/timing. I was going to wait until i have everything else figured out.

Truck warms up very slowly. It may after running for quite some time warm up to the bottom of the operating range of the gauge. I am using a new coolant sensor for the the truck and adapted it to the engine. So could the engine never be warming up? I have been told they just run cool. Probably couldn't hurt to put a new thermostat in there.

Air pressure good.

I don't believe a brake is dragging.

Drives straight, steers better then my Dodge, but i have not aligned it.

I may bring it on over in a month or two....I want to get the floor and sound deadening in and some more local miles before i bring it over....i would prefer to drive it because one, it needs some more miles and two, that truck (rough 6000lbs) and my trailer starts to be a heavy combo.

I also just repacked the front bearings so that might help...their wasn't a whole lot of grease still there.

The driving has not been very far runs but not start and stop either.

The Gents over on 4BT Swap seem pretty confident that 20 is what i should expect.

Thanks for the replies Average, and motzingg.

[KRob]

Well....EGT/Pyrometer gauge is in. Its not on the final install but its wired to a continues power source, i have to look and figure out where my light and power are permanently going to be wired.

After getting getting done...in the dark...started with barely any light...i went for a quick drive, which turned into an hour plus. Ended up pulling a fairly steep hill several times to see what the EGT would do. Well i can hit 1100F accelerating (foot to the floor resulting in slow acceleration) in 5th gear. So we are talking about accelerating from 50-60 while pulling a hill and only getting 1100F. Not bad in my opinion. I think there is some safe room to turn the pump up a little. So that will probably happen tomorrow morning. I think i will just turn the AFC down a turn or two so the fuel comes in a little quicker before boost comes on. My plan is to slowly adjust, nothing drastic not all at once.

I need to stay focused though because winter is already coming....and my heater is non-op, and i would like to get the floor done so that i can insulate the cab. "Wife Wench" as i call her will not be go for a ride with me when it gets cold if i don't get the cab fixed up.