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Quest for 20+ MPG

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Old 11-20-2017, 11:38 AM
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Quest for 20+ MPG

Dodge... itís NOT a Ram


So hereís the deal, Iím getting 17MPG combined/hand calculated in my 73 Crewcab with a 1995 running gear. I have 2nd Gen 4.10 axles, NV4500, NP241DHD and a 160hp P-pump motor with HX35 (it was originally an auto). Iíve done a 3k GSK, free mods, 0 plate full forward and AFC full forward with a BHAF and 4Ē straight pipe. The truck is running 35/12.50R16 tires. Is there anything that I can do to get this thing at or over 20MPG running empty? I know the aerodynamics are terrible, and I usually run about 62-70MPH with the windows down (no AC). I will average towing 6-10k lbs, and occasionally 16k lbs in the future. Iím planning on a timing bump (15-16*) as soon as I get some head studs. Should I be looking at some 5x12 - 5x14 injectors? A different fuel plate? Benching the pump? A different pump? DVís? Taller tires? Taller gears (3.73 - 3.54)? I would like to build a set of compounds next year, so Iím hoping to run some parts that can still be used with the compounds.
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Old 11-20-2017, 01:06 PM
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17 with 4.10 gears and a lift crew cab with 35's is pretty good.
You could get a mile or two more by going to 3.54s, but you would loose some low end grunt that those 35s steal. Slightly taller and narrower tires sometime help MPGs as it drops the cruising RPM.

I can get about 18 MPG with my '85 crew cab with 6 inch lift 37 and 4.10s.
I think the VE pumped motor get a bit better fuel mileage than the P-pumps.

I can get OVER 20 MPG with my other '85 crew cab with 3.07 gears and 32 inch tires, that also has a VE pumped 12V.

I get under to 20 MPG on my '91.0 with 3.54 gears and the old 33's I ran.

I would leave the 4.10 alone with those tires and towing. Timing might help a bit.

I don't use my 1st gens for towing anything really, I have the '95 dually for that.
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Old 11-20-2017, 07:57 PM
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Thanks for the reply. I had a feeling from lots of reading on this site that the VE pumps are better for mileage, and P-pumps are better for higher power levels. I wouldnít mind taller tires (I figured 38ís would be about perfect for 4.10 gears and the NV4500). Iíd really like to be between 1700 and 2100 RPM at 55 MPH in 4th gear, for towing up longer grades. Only have about 5k miles on the tires I have though. I have more to add to this, but my Boxer let one rip and I need to move to the other side of the house

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Old 11-20-2017, 08:02 PM
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Only thing that ever helped me hit 20 and over was shaving about 5 lbs off my right foot
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Old 11-27-2017, 05:31 PM
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What timing advance is your pump set to? For highway driving, about 16 degrees advance is good. That's not going to get you to 20MPG if you're currently at 17 though.
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Old 11-27-2017, 07:36 PM
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Originally Posted by Midnite View Post
What timing advance is your pump set to? For highway driving, about 16 degrees advance is good. That's not going to get you to 20MPG if you're currently at 17 though.
Iíve never checked it. Since the AFC and KDP had never been touched, Iím assuming itís stock. 12.5* if I remember correct. Also, still running stock injectors. I think they come out to 5x9.5 ?? No matter what I do to the AFC, thereís no smoke other than pre-boost.
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Old 11-29-2017, 09:29 PM
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What an awesome ride you have put together! If you slow down to the 55-60 mph range you will get 20mpg. Itís not very aerodynamic so a small increase in speed yields an exponential increase in drag or lost fuel economy.
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Old 12-05-2017, 11:13 AM
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Thanks Chariotdriver! Itís been a lot of work, but itís worth it and I love driving it daily. Still a long ways to go. I wish I could do 55-60, but unless I follow a Prius in the fast lane, Iíd get my butt run over on these Southern California freeways Maybe Iíll just have to leave it alone until I move East, where I would rarely have a need to go over 60.
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Old 02-02-2018, 12:40 AM
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Before I tore my ‘90 down, it was a stock, non-intercooled with 3.07, standard 3spd. No OD, and 35” Tire’s. It got me 12mpg and took about 35 sec. to get to 60 mph.
Added an intercooler, Smaller turbo housing, 4” exhaust, K&N air filter, turned the fuel screw up 1-1/2 turns. Didn’t matter if I was empty or pulling a 10k trailer, It doubled the fuel mileage. Trimmed 15 or so seconds off my 0-60 time too. 24 mpg all the time! Thought my Fuel guage was broke at first, but nope. Trying to get 30 mpg when I put it all back together with no smoke.
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Old 03-25-2018, 06:56 PM
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73crewcab, nice truck. I would make a sleeper out of that second seat, if you remove the seat will a double mattress fit? Look at my sig for my setup and mileage. I don't think you can get here from where you are now. Perhaps your zero plate and AFC are pumping unburned fuel. It really hurts to pay CA fuel prices and get low mileage.
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