Join Date: Feb 2009
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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 15-16º would yield better MPG's than 19-20º, 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.
98' 12v QCLB 4x4 216k, S363/68/.83 + S478/87/1.1, Steed T4 manifold + JGS gate, Levi's Blankets, A1 studs, Goerend, 5x18 SAC, 042DV, 2095, 4GSK, TerraG 295/17's on 4thGen 6-spokes
Last edited by Algae Eater; 10-19-2010 at 06:44 PM.