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Old 10-19-2010, 02:59 AM   #1 (permalink)
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Tuning For Fuel Economy?

Hey Guys,

I've had the gears turning in my head non stop since I got into the diesel world. I have a few cross country hauling trips next year and I keep thinking about how I should go about tuning the truck. Stock it really doesn't have enough go when towing at times.

I know there are some well tuned trucks getting some pretty impressive fuel economy numbers, I just don't know what part of the tuning gets them the MPG's.

I know some timing goes a long way, how far can you go on the timing before it becomes ineffective or before you start sacrificing in other areas?

Money no object, how would you go about setting up a truck? Injectors, Turbo(s), etc?
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Old 10-19-2010, 03:11 PM   #2 (permalink)
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I'd recommend setting your timing to around 16-18 degrees to conserve the hg, if you tighten the head bolts or put some head studs in then you'd probably be better off going to 20 degrees of timing. As to how far you can go before you start seeing ill effects it would probably be the point to where you start spraying outside of the bowl. I'm not sure what the best number for fuel economy would be.

The '97 in my sig is almost perfect for fuel economy except for the 4.10 gears and the DDP3 injectors which have the wrong spray pattern. It has a mild cam, ported and polished head, 20 degrees of timing, 62/71 non-gated turbo(technically a slightly smaller turbo would be better for fuel economy), very mild pump tuning. Even with the 4.10 gears it gets 22 mpg on the highway. The biggest factors for mileage out of this build would probably be from the timing and the tires. They are 225/70/19.5 aired up to around 110 psi.

For trying to increase mpg on a budget the best and most cost effective things to do would be to increase the timing, use tall and narrow tires and air them up to the max. Also some general maintenance, use a clean air filter, a clean fuel filter, and get rid of the fuel pre-filter.
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Old 10-19-2010, 04:58 PM   #3 (permalink)
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Quote:
Originally Posted by crazyrunner33 View Post
I'd recommend setting your timing to around 16-18 degrees to conserve the hg, if you tighten the head bolts or put some head studs in then you'd probably be better off going to 20 degrees of timing. As to how far you can go before you start seeing ill effects it would probably be the point to where you start spraying outside of the bowl. I'm not sure what the best number for fuel economy would be.

The '97 in my sig is almost perfect for fuel economy except for the 4.10 gears and the DDP3 injectors which have the wrong spray pattern. It has a mild cam, ported and polished head, 20 degrees of timing, 62/71 non-gated turbo(technically a slightly smaller turbo would be better for fuel economy), very mild pump tuning. Even with the 4.10 gears it gets 22 mpg on the highway. The biggest factors for mileage out of this build would probably be from the timing and the tires. They are 225/70/19.5 aired up to around 110 psi.

For trying to increase mpg on a budget the best and most cost effective things to do would be to increase the timing, use tall and narrow tires and air them up to the max. Also some general maintenance, use a clean air filter, a clean fuel filter, and get rid of the fuel pre-filter.
22MPG on the highway with your 4.10's and injector/turbo setup is pretty reasonable!

When I eventually get around to building my perfect truck, I'll probably pull the engine and knock out everything at once. Some ARP studs are on the "to-do" list for the sake of not having to worry about it.

As far as tires, I plan on running the 19.5's on some aluminum wheels, undecided whether I want the 225s or 245's, but I think the combination of tall and skinny should really help things. The weight isn't too bad for a tall setup.

For the basic stuff, I'll probably run a nice CAI/elbow and a good free flowing exhaust.

I still have a lot to learn about turbos and injectors (all the numbers are rattling around in my head somewhere), but I figured there has to be a combination out there that can produce more power and be more efficient than stock.
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Old 10-19-2010, 05:33 PM   #4 (permalink)
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What he said, plus AFC tuning plays a considerable part.

I would think either the stock turbo, or a HE351 VGT (w/ a boost-operated pneumatic air cylinder to control the vane actuator lever) would be the best hairdriers for the job.

As for injectors, either new stock 215HP injectors (5x.010" I think?) or up to 5x.012" (maybe even a 7x.010" instead of a 5x.014" for better atomization) would be top choices for injectors. I have been told that VCO injectors have been known to get better fuel economy than SAC injectors. Just throwing that out there... something to consider.

As for timing, I think 15-16 would yield better MPG's than 19-20, but that also depends on gears/tires & injectors (timing/powerband + peak efficiency RPM = ???MPG : MPH sweetspot). Advancing timing, raises the peak HP & torque RPMs.. therefore it will affect what speed you get the best MPG's at.
If other factors [like gears, tires (rotating weight & friction), load, aerodynamics] counter-act your high timing, it will lower your MPG's overall.

Tires are lighter than rims. So smaller rims + larger tires is better than larger rims and smaller tires... for fuel economy. Rotating weight seems less crucial (to a point) than cruising RPM's, but all things factor/weigh in. If you find large rims with a very open (light) design, this won't necessarily hold true, but they might not be as strong if you're over-loading the truck and towing huge w/ big power. Just throwin examples out.

Look at Jeff Garmon's 2007 1500 singlecab shortbed w/ a 700HP compound-turbo'd 12-valve... it supposedly gets 55MPG at 55-60MPH just cruising at like 0-1PSI boost and 1300RPM.

It's so light and aerodynamic, plus has such high torque, that it's barely using any of the available torque... and that's probably the secret.

I routinely see people with 2WD SCLB 2500's saying they get 26+MPG, just mileage-hounding.. cruising as slow and low (boost) as possible.
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Old 10-20-2010, 12:26 AM   #5 (permalink)
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Quote:
Originally Posted by Algae Eater View Post
What he said, plus AFC tuning plays a considerable part.

I would think either the stock turbo, or a HE351 VGT (w/ a boost-operated pneumatic air cylinder to control the vane actuator lever) would be the best hairdriers for the job.

As for injectors, either new stock 215HP injectors (5x.010" I think?) or up to 5x.012" (maybe even a 7x.010" instead of a 5x.014" for better atomization) would be top choices for injectors. I have been told that VCO injectors have been known to get better fuel economy than SAC injectors. Just throwing that out there... something to consider.

As for timing, I think 15-16 would yield better MPG's than 19-20, but that also depends on gears/tires & injectors (timing/powerband + peak efficiency RPM = ???MPG : MPH sweetspot). Advancing timing, raises the peak HP & torque RPMs.. therefore it will affect what speed you get the best MPG's at.
If other factors [like gears, tires (rotating weight & friction), load, aerodynamics] counter-act your high timing, it will lower your MPG's overall.

Tires are lighter than rims. So smaller rims + larger tires is better than larger rims and smaller tires... for fuel economy. Rotating weight seems less crucial (to a point) than cruising RPM's, but all things factor/weigh in. If you find large rims with a very open (light) design, this won't necessarily hold true, but they might not be as strong if you're over-loading the truck and towing huge w/ big power. Just throwin examples out.

Look at Jeff Garmon's 2007 1500 singlecab shortbed w/ a 700HP compound-turbo'd 12-valve... it supposedly gets 55MPG at 55-60MPH just cruising at like 0-1PSI boost and 1300RPM.

It's so light and aerodynamic, plus has such high torque, that it's barely using any of the available torque... and that's probably the secret.

I routinely see people with 2WD SCLB 2500's saying they get 26+MPG, just mileage-hounding.. cruising as slow and low (boost) as possible.
The input is much appreciated!

The idea of a VGT turbo is interesting, they can be manually controlled? Any idea how much power they can support?

I think you hit the nail on the head here:

Quote:
As for timing, I think 15-16 would yield better MPG's than 19-20, but that also depends on gears/tires & injectors (timing/powerband + peak efficiency RPM = ???MPG : MPH sweetspot). Advancing timing, raises the peak HP & torque RPMs.. therefore it will affect what speed you get the best MPG's at.
If other factors [like gears, tires (rotating weight & friction), load, aerodynamics] counter-act your high timing, it will lower your MPG's overall.
Its pretty difficult to get everything setup just right. Its easy to make power, but harder to make it as efficient as possible.
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Old 10-20-2010, 12:06 PM   #6 (permalink)
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The input is much appreciated!
No problem, just post some pictures of that UNIMOG up here!!!
I'm dyin to see that thing from the side....

Got any more pics of that Beauty n' Beast all roll'd up into one???

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The idea of a VGT turbo is interesting, they can be manually controlled? Any idea how much power they can support?
They are manually controlled by connecting up to the lever on the side (vane actuator) that opens the vanes up.. a return spring is used to return it to the closed state.

Or Fleece Performance sells a standalone VGT controller which looks a-nice-a (said in my worst Borat voice).

Imagine compound VGT's... like a 351 or 451 under something like a 75mm S400 VGT!! Whooohooo.. Insta-spooling twins!
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Last edited by Algae Eater; 10-20-2010 at 12:33 PM.
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Old 10-20-2010, 12:47 PM   #7 (permalink)
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i've been thinkin about a vgt.........fuel pressure is another major factor. get it around 35psi on the highway and see how ya like it.
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Old 10-20-2010, 01:34 PM   #8 (permalink)
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i've been thinkin about a vgt.........fuel pressure is another major factor. get it around 35psi on the highway and see how ya like it.
From what I've heard & read.. for a stock pump, anything over 31PSI FP and the flow-rate starts to decline... The P-Pump doesn't need anything over 30PSI to deliver its maximum-set flow.

When I had my OFV replaced on the road at a Bosch pump shop, I was talking to the owner (Paul of ADS in Fresno, CA) about fuel pressure because I was setting my Raptor 100's FP on the WVO system... he said the P-Pump absolutely does not need anything over 20PSI to function at full setup capacity and if you run over 30PSI it can damage seals and really just wastes energy and adds un-necessary taxation (wear) to whatever is doin the pumping.
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Old 10-20-2010, 04:02 PM   #9 (permalink)
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haha where is this 31 psi comin from, thats the 3rd time thats been mentioned lately!! I've never had any issues with seals to tell yall the truth and I know of a ton of people running crazy pressure. I agree for the DD though, anything over 30 really isnt needed. But blowing out internal seals isnt something I would worry to much about.
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