I need help with fuel economy

so in the steam release of automation i tried my hand at making a pickup truck in the year 1985 and i first made a 10.85 liter V8 as a bit of a joke since it only got 6 miles to the gallon (but produced 527 HP, might be a good chassis for heavy duty industrial vehicles) but the i toned it down to a 3 liter inline 6 making a little over 120 horsepower, and i only get 8 miles to the gallon, how can i fix this without making the truck being barely able to carry anything more than feathers or not costing your granddads gold tooth and not changing the tech year, or is the truck just simply too heavy for fuel economy?

Make sure the gearing is high enough, and the cooling airflow slider is set low enough.

(btw i rechecked the stats, the I6 isnt 8 mpg its 6 mpg, and idk what the V8 since i cannot load the truck anymore) thanks daffyflyer, that got me one more on the MPG and took a second off the 0-60, ut still not really efficient enough, i should get at least 12 from the I6 im hoping

The first thing I would try is reducing compression or ignition timing and leaning out the fuel mixture. Running rich is the major fuel-waster per horsepower, I think. You’ll lose some power, but gain a LOT of economy in exchange.

i’ll try that, i just hope i dont lose so much power that it can barely move itself

The fuel economy of the engine by itself is rated by force and time, not MPG. If you have 2 engines with identical bench efficiency ratings, but one is 120 HP and the other is 150 HP, they will have different efficiencies once applied inside a vehicle. You may find that building a BIGGER, more powerful straight-6 with a little less aggressive fuel mixture will actually be much more efficient.

Real world example: the 1st generation Hyundai Tucson was powered by either a 130 HP 2.0L inline-4 or 175 HP 2.7L V6. Comparing the two engines, each mated to a FWD automatic, netted very similar efficiency results. The V6 was ONLY one MPG shy of the I4. However, the performance difference was absolutely ridiculous. The 4’s were absolutely gutless, lost performance very quickly as weight (cargo or passenger) was added, and was not rated to tow in the US. On the flip side, the V6 was smooth, responsive, didn’t care as much about weight, and was rated to tow 2000 pounds IN ADDITION to a full load of passengers (Yes, I crunched the numbers. Several times.)

It’s very possible that this is your problem. 3.0L is SMALL for a pickup engine in 1985. Remember, the I-6s used by Ford from the 60’s to the 90’s were primarily 3.9L and 4.9L displacements. Similarly, Chevy would have used a 4.8L in the mid 80’s. The 1980’s truck body is similar in size and weight to those, not the Toyota and Nissan competitors that started showing up with smaller engines.

Edit: Yup, that’s going to be your problem. I quickly whipped up a 1985 truck based on an existing engine for one of my companies. It’s a 3.9L straight-6, 3v SOHC, with a 4 bbl carb. 192 HP, mated to a 4-speed manual RWD with open diff. 15.8 MPG.

Thanks vicvictory, it’s actually working, got it to 9 mpg and improving :slight_smile:

You mind uploading the specific model and engine so i can look at it? Should be found in your automation folder in your steam apps.

I also hope that the engine you made is running with low cam profile and has a high stroke vs bore size. Reliability might suffer. If you keep it in acceptable levels it will be fine, combined with low cam you will not rev particularity high anyway.

i shall try that next then

120hp from a 3 liter engine is really pretty horrendous, even for the '80s.

I’d shoot for at least 50-60hp/liter. Modern engines often exceed 100hp/liter.

This doesn’t really effect efficient per-say, but with the HP that low I suspect something in the way your engine is designed is really sub optimal. Generally you want advanced timing and high compression, and a lean air:fuel ratio.

[quote=“Tyler”]120hp from a 3 liter engine is really pretty horrendous, even for the '80s.

I’d shoot for at least 50-60hp/liter. Modern engines often exceed 100hp/liter.

This doesn’t really effect efficient per-say, but with the HP that low I suspect something in the way your engine is designed is really sub optimal. Generally you want advanced timing and high compression, and a lean air:fuel ratio.[/quote]

Actually low HP in the 3-4L range was quite common in the 80s, the 1st edition of the Ford 3.8L had only 112ish horsepower, once fuel injection came along it went up to 140hp which was the same as the 3.0L. Both these engines were in the Ford Taurus and both had the same/similar HP ratings but the 3.8 had vastly higher torque ratings. These engines were OHV too, no SOHC or DOHC for them. The 2.8L I had in my Ranger had 115HP, also OHV but with a hiddeous 2BBL computer controlled carburetor.

Yup. Even in 1992 when my parents bought their Grand Prix, the 3.3L OHV V6 was putting out only 140-ish. And that was actually with an early MPFI system.

My 1.4L turbo DOHC gets close to that now. And it’s tuned for economy… there are other 1.4L turbos out there cranking at least 20% more out of them.

Cars were a LOT lighter back in the 80’s so didn’t need as much power. I remember our old Subaru wagon (1.8L OHV boxer 4, about 80 hp) wasn’t a barn-burner, but it also wasn’t slow either. The fact that the car weighed less than a ton helped… whereas my “subcompact” now is pushing close to 3000 lbs.

Just to show that’s it’s possible…

This has many options that hurt MPG btw… AWD, better than minimum interior, entertainment, and safety. Engine is a 2997cc I6 with two barrel carbs. 1985 tech level and everything is 0 quality.

i.imgur.com/4T9uVlN.jpg

If I strip the interior down and go RWD can get it to almost 18mpg.

That is actually quite comparable to mid-80s pickup trucks at 16 mpg. The power output is just about spot-on, too.

EDIT: If it were the big block 460 or even the small block 351, the mpg would be much lower and the hp would be much higher.

I actually made a fuel injected model that goes a good bit better…something like 21mpg, and ~240hp. That one had some quality sliders boosted a bit, though. Sort of a standard “premium” engine.

There’s never a replacement for displacement. Here’s 15.5 mpg from a '83 pickup using offroad tires, a 4 speed auto, and a 548ci big block. no sliders used. This one has a manual locking live rear axle and extra ground clearance for off roading. This is a attempt at a period correct build, so it has a restrictive, emissions compliant, exhaust with a 3 way cat, low compression hypereutectic pistons and a low end torque oriented cam profile. Even with all that it can still do 0-60 in under 10 seconds, it can run with a '91 chevy c1500 454ss with better tires.