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So here’s the deal, I’m 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). I’ve done a 3k GSK, free mods, 0 plate full forward and AFC full forward with a BHAF and 4” 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. I’m 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? DV’s? Taller tires? Taller gears (3.73 - 3.54)? I would like to build a set of compounds next year, so I’m hoping to run some parts that can still be used with the compounds.
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.
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 wouldn’t mind taller tires (I figured 38’s would be about perfect for 4.10 gears and the NV4500). I’d 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
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.
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.
I’ve never checked it. Since the AFC and KDP had never been touched, I’m assuming it’s 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, there’s no smoke other than pre-boost.
What an awesome ride you have put together! If you slow down to the 55-60 mph range you will get 20mpg. It’s not very aerodynamic so a small increase in speed yields an exponential increase in drag or lost fuel economy.
Thanks Chariotdriver! It’s been a lot of work, but it’s 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, I’d get my butt run over on these Southern California freeways Maybe I’ll just have to leave it alone until I move East, where I would rarely have a need to go over 60.
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.
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.
11-20-2017, 11:38 AM
Maybe I’ll just have to leave it alone until I move East, where I would rarely have a need to go over 60.
