kawi600

Im getting about 10mpg city on this truck. Trying to track down whats doing it and have had no luck so far.
The shop I work with suggested a pump rebuild, but I think my problems started with the head gasket when I did the .020 gasket + .015 deck to relieve the valves and optimize for boost. I sure know the compression loss isnt helping my low end power.

Anyone with a similar 12v setup that knows what their city mileage is?

sewman

What headgasket are you running?I have the 0.20 marine which lowered the compression along with DD4 which really brought my truck down.
What do you get on the road?Probably alot better?I think in town @ lower rpm you need to set your timing to 16.

John_P

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kawi:

I think you got my P.M., but I get 15-16 MPG in town with my 1996 Dodge CTD 12 valve IF I take it easy on the throttle! My truck is WAY up on H.P. and still gets better mileage in town than my 2006 does! Go figure.............................

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John_P

13FOX

I got an additional .050 of combustion space with 5x18's now and get 15-17 in town. Highway I've gotten 22 hand cal a few times. Mostly around 20-21 though.

John_P

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kawi:

Like DTR Member 13FOX,........the MPG that I gave you on my 96' is also with
the 5X18 Injectors just like he is using. Those are not small injectors, so any of the "naysayers" here that may not believe it now will see that two DTR members are getting pretty good mileage with a fairly large injector.

kawi600

Well, I have to ask whats -different- in these setups.. Im getting 10city 15highway mpg. 4.10's.. marine .020 gasket wirth .015 deck. hamilton street cam. DTT trans with 75k on it. 33" BFG AT tires inflated to 55psi.
something weird is going on... sure looks close to what some of you run with much better mileage.

think lowering the timing would help economy in town? Most of the time I drive like grandma in this truck, since people drive so crazy here. Its how my driving record stays so clean, lol.
youd think going easy on the skinny pedal would help but it doesnt do much.

John_P

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kawi:

I agree that your situation is baffling. I would recommend trying to change your timing as you noted to see if it helps you at all. FWIW,.....I am at 22 degrees right now. On my 96' I found that going above 25 degrees hurt not only my mileage, but my power also.

patdaly

Kawi, I think you said you had checked your fuel pressure, right?

kawi600

Im not so convinced that timing is going to help. Some of you folks that posted probably run higher timing and still show decent economy.
Wonder if the cam is doing anything? Usually you trade off some low end compression for top end gain with overlap, right? Suppose this would be a hamilton question.. theyre pretty good about support questions and stuff I hear.

Argh.. its got me going in circles. Just cant figure out what to do with it

kujo

i can see you burning more fuel at lower rpm with a bigger combustion chamber and cam, that stuff will help when on the boost but you need more fuel when the turbo isnt helping cylender pressure than you would with stock compression.. you may actually benefit from more timing since your fuel still has the same flash point its not lighting as easy as before unless under boost..

just my 2 cents, im alot newer to the cummins than most on here so what do i know..

yellowrosefarm

Early 98 3500 4x4 auto, stock everything except B/W turbo, 4.10 gears. 10-13 around town empty, 10-13 highway pulling 24' gooseneck, 1 time high of 18 highway empty, usually 15-16. More would be great but it's still a lot better than the 5-6 my old Ford 460 got.

13FOX

My pump is benched timed at 18.5* right now. Kinda low for what I have under the hood. Now my head has been worked over by Extrude Hone and I have a custom intake which has greatly improved breathability for the engine. On the highway I pull right at 5psi at 70mph. XCLR8 (Mike) will verify that. I do run Amsoil in everything but the engine and trans.

kawi600

Not sure what to do with this thing. I made an appointment to service the injector pump.. need some other work done too anyhow.
I know the head gasket isnt helping, but that would be a pretty expensive fix, just to find out for sure. Maybe if I ever look into a ported cyl head Ill do that.