Okay, first of all, the informaition I was using was not from the early 80s, I could not dig up much that far back. On the fuel economy, the oldest I could find was 1985, from the EPAs website. You're right about small increases; there's a company that's right now working on finalizing a way to use a seperate ethanol tank, seperate ethanol injectors, and a high compression, turbo engine to improve gas mileage. Their theory is that most of the time the small engine would not need to put out much power, therefore it will not recieve much boost, and it runs like a conventional gas engine. When the driver puts the pedal down, to accelerate or get more power, the turbo boost comes up, and the seperate injectors inject pure ethanol to raise the octane of the mix so it will withstand the high compression/high boost and get more power. Yes, they are getting better mileage with a smaller engine, using improved technology to provide the horsepower the vehicle needs. Anyone wanting to see this information for yourself, look at the July issue of car and driver, Csaba Csere's column.

To some extent, mileage can be improved in manners such as this, but the CEO of the company even admitted it may save as much as 25%, due to the increased efficiency of higher compression and the smaller engine.

The problem is that accelerating that much mass still takes lots of power, and systems like this are designed to combat cars like the Volkswagen Rabbit diesel, not your favorite half ton truck. I suspect the fuel economy benefit on a large vehicle would be much more modest.

By the way, the best tank my '03 ever got with the 4.2L V6/auto tranny was 19 on the highway, worst was 12 on the highway...2 weeks before I got rid of it. Have a friend with a Jeep Liberty and a friend with an Explorer sport Trac, and both get within 1 MPG of my F150. The Jeep has a 3.7 and the 'splorer has the 4.0.

Gas mileage has MUCH more to do with it than engine size and power. Simply changing the engine will NOT yield useful fuel gains.

BTW...not taking offense to any of this...this is a fun discussion

 

Tom, I have to agree with you on this post, overall mileage is much more than just a small engine, while it does help. We also need to get the thermal efficiency up as well. I know that Ford was working on Ceramic coated pistons in the late 70's, to allow a much higher operating temp , IE no coolant. I wonder how that worked out in the long run. I can imagine several drawbacks to it just thinking about the idea.

Of course, once you hit the hills, then less weight is also a good thing. But you can also only go so low here, and still have a workable/usable truck.

On my own daily driver work truck, a 1997 UD (nissan) cab over 2600 (26k) 6.5L Turbo, Intercooled 200hp diesel backed up by a manual six speed, the radiator is very small, not very thick and about a third the size of a 6.0 / 7.3 radiator. I get up to 11 mpg, but never less than 9mpg, so the thermal efficency must be fairly high on this engine design. Of course I don't come close to 80k, but I am at least three gears short on the top end compared to the mid eighties Frieghtliners that we had. I pretty much am maxed out at 70mph (redline) That has to affect mileage somewhat.

Interesting things on FTE, I enjoy the discussion!

David

 

according to my calculations, the difference in the weight of the 2 trucks is 9.3%. the difference in the fuel economy was 9.4%. so, the technology for fuel economy in the 80s was better than now. i suspect the 1985 supercab had a 300 6?

interesting discussion fellas

 

Yeah, I noticed the same thing with heavy duty diesels. I have a couple uncles that drive tractor trailers for a living, and they average between 5-6 MPG loaded. An 80,000 lb truck gets 1/3rd the EPA mileage of the average 4-6,000 lb truck.

It's pretty common knowledge that you lose lots of energy through the auto tranny, which most commercial diesels don't use. The heavy duty autoshift units are, the way I understand it, automated manuals, thus there still is not much power loss.

The other reason, IMHO, is because diesels are inherently about 30% more efficient than gas engines. Diesel engines run at twice the compression ratio which improves efficiency and reduces excess heat loss. In Afghanistan I drove a little Toyota pickup with a diesel. This thing would NOT hold its temperature on cold days if it were idling. Less loss to heat equals better mileage. Modern gas engines can only push compression so high while still using 87 octane fuel. The modern 5.4 has a 9.8 compression ratio, which is higher than any previous domestic truck engine I can think of.

Honestly I think one of the biggest problems with modern trucks is how the autobox is the ONLY tranny offered in many models. I can not even GET the truck I have with a manual, as there is simply no market for it. Sure, the slushbox is nice, but when you figure every bit of heat that has to be dissipated by the radiator and cooler lines is energy that SHOULD be going towards moving your truck, I think they should be less common.

Another problem in the US is the federal restrictions on diesel engines. Because of the clean air acts, virtually every diesel model offered in Europe and the rest of the world that gets better mileage is illegal to be sold here. Those diesels that will pass modern emissions standards have such expensive emissions components that it makes no financial sense to spend the extra money on them. Think of the less pollution that would be in the air if the US embraced diesels back in the 90s like europe did...how many MILLIONS of gallons of petrolium would that save? BUT...like every technology out today, nothing is the final answer. Diesels have lots of issues, particularly in the cold weather, and many people will simply not buy them.

So, you have a market saturated with heavy, gas powered, auto-trannied trucks that suck down gas like there's no tomorrow. Make a truck that is radically different, and nobody will buy it. Right now, people want their big, comfy, gasoline powered, automatic transmission trucks. To spend millions designing anything else would be suicide for any of the major automakers. Design one with a manual tranny as the only model offered, everyone would flock to the other manufacturers with the autoboxes. Seems that there's only so much the auto makers can do to improve things when these are what's selling.

All things considered...I'm very proud of the 21.5 MPG highway!

 

Ok I don't want to start this one again

I had the 302 EFI / AOD combo along with 3.55 gears, stock height 4x4, stock size, fully inflated tires. Truck was runing solo / unloaded, I did not push it up hills. Up to 70mph indicated on the flats. I drove over to Spokane from the Seattle area, with my son, I bought the 86 Bronco, then he drove the Bronco back while I tooled along in the F150. The Bronco only returned about 15-16 mpg with the same engine and trans and gear ratio, although it had a 4" lift, and 33" 12.50 tires, inflation unknown.

Maybe that day at 22.8 mpg overall was a fluke, as it was 99.9% freeway driving. I normally only run 14 to 16 mpg in combination driving. The AOD didn't hurt me at all in the case of the trip, as it has a 100% lockup in 4th gear. Same mileage on the freeway as a manual

I would have prefered the 300/6 over the 302 but it was not available in the 80-86 body style with EFI. 87's and later have the EFI 300/6, although to me, I don't care for the 87 and later body styles. Personal preference though, nothing wrong with the 87 and later trucks.

David

Now of course I am Ford truckless, so I guess I am a bit grumpy. Hopefully soon I will find what I am looking for.

 

Your uncles trucks are running about 425hp to 500hp I would guess, with a 10spd Road Ranger? 3.70 rear end gears? How far off am I on this? Please feel free to correct, I am taking a WAG here based on previous experience.

As to the second paragraph. Yup, you hit it right on the head of the nail, it really would take a rethink of the whole situation, it could happen, but I am not so sure that is in the works right now.

And no Tom, I can't fault 21.5 mpg either for what you have. Sure beats 14 or 15 that the old carb's larger V-8 seemed to get on the hiway.

David

 

Not sure about the specs of their trucks, I haven't talked with them in awhile. I've been looking into getting into that industry in the next 6 months, when I get out of the military and that was part of the research I've been doing.

We'll see how things go in the next 10 years. What with gas prices where they are and rising, you have to wonder whether or not the public mindset is going to change. My personal peeve is when people blame the "big, greedy auto industry" for their MPG woes. They'll build what people will buy, and that's never gonna change. Thanks for the replies!

 

hey man if your going to get a hot rod motor, why would you be that worried about mpg. I am looking at hp not mpg

 

If you are looking for a hot rod...why are you looking at a fullsize truck?

 

but heres the part you forgot.....my current truck has 300 hp.....those 300 I6 motors had somewhere in the neighborhood of 150 i think....so you forget the 100% increase in hp....

 

I regularly get 18+ in combination (more local than highway BTW) driving with a 89 302 4x4 with a five speed manual, Friends of mine who had similar trucks with automatics didn't come close to this.

 

You are getting excellent mileage for mostly city driving. I ran 14-16 mpg mixed. However, I was talking hiway mileage differences.

Times are changing, there are several new cars with current state of the art automatics that are rated at the same or even higher mileage thsn the same engine with a manual. It is only a matter of time before the same technology comes to trucks.

My old F150 certainly did get great mileage for what it was, automatic or not. It could be the way I drove it, but there is no getting around that modern automatics, even if not state of the art, do every bit or very close to the same as a manual transmission, at least in strictly hiway driving. This is and always has been the strong point of the AOD as it is a features 100% lockup in top gear (4th)

Will the AOD get the same mileage as a stick in less than strictly hiway driving, such as a mix or all city, I doubt it. I was only comparing strict hiway driving mileage.

The old three speed automatics with open torque converters however, always got worse mileage reguardless of either hiway or city driving. It was the nature of the beast. We are almost twenty five years past those designs, time to let them rest in the land of where fuel was 50 cents a gallon...

Not that the C6 is stil not a great heavy duty trans, it is just at least one gear too short, if not in truth, two gears two short.

My two cents worth - David

 

And the one thing that you forget, is that if you use all of that horsepower, you will use more fuel. With the current engine designs that we have, it takes X pounds of fuel to get X horsepower.

However, you don't need all of the horsepower that you engine produces to move it down the freeway at 70 mph, so you don't use X pounds of fuel to get X horsepower. If you were to use all of your horsepower for some reason, trust me that you would use about twice the fuel that the 150hp engine uses, of course I am assuming that we are comparing EFI engines here, A carb to a EFI engine throws a whole different twist into the comparison.

Where the smaller displacement enigne shines is that at normal hiway speeds, when you do not have the need for 300hp, the smaller, more highly stressed engine will return better mileage. This is a function of a throttled Gasoline engine that it is less efficient the slower the engine runs (more throttle plate closure) as you still have to maintain the stoichmetric ratio and the pumping losses go up.

While the 300/6 is most efficient at speeds up to around 90 mph, if we were talking German Autobaugn thing here, your 300 hp, larger displacement engine would be most efficient at say 150 miles per hour. That is where I feel the waste is. I don't have any problem with horespower generation, what I have is why waste it when you can't use it?

So it has to to do with the need to maintain a paticular stoichmetric ratio. You cannot get around this. Period. It is a law of Physics in the case of gasoline. Do you understand what the stoicmetric ratio is? An how it is important in a spark fired Gasoline engine? The major thing(s) that are going to change that is to reduce the size of the enigne, increase the thermal efficiency of the engine or increase the BTU's available in the fuel.

Diesel fuel has approx 10% more BTU's per gallon, so diesels, X diesel horsepower for X gasoline horsepower will get 10% better mileage, but unlike a throttled gasoline engine, a diesel is more efficient at low/idle speeds, therefore actual fuel savings in normal driving, where you do not have the need for 300hp, will run up to 50% or so greater with the diesel engine.

Volkswagon did spend quite a bit of time on a unthrottled Gasoline engine AKA like a diesel from the late 70's to mid 80's, just to come up with some weird driving issues, that might be tamed with todays computers. However, barring something like this, or as previously mentiond a small highly tuned turbo engine, you are left with improving efficiency in one of the more traditional ways.

I hope this helps, David

 

BMW currently has several motors that do not use throttle plates, but use variable valve lift to control intake. They realize fuel economy, power and drive-ability gains (Valvetronic) with this system.
I don't know how much better we can expect our fuel economy to get. My '79 F150 4x4 400/4 speed/3.50 regular cab got 11-13 mpg (12 MPG avg.). 157 hp/ 287 ft. lbs.(factory), weight about 4800 lbs. My '07 SCrew 4x4 5.4/3.73 has averaged 17.5 since new, and I have tanks that have been in the 18-19 MPG range. Same roads, same loads. Considering the additional weight of all the options my old truck didn't have (A/C, PW, auto tranny, etc), I think it does very well. Even my '78 SC w/300 I6/3 speed manual 4x2 never saw above 17 on the highway, and averaged 15. The GVWR on that was 6200 lbs, not much more than what the '07 weighs empty. Not to mention the 140hp vs 300hp. Things have improved a lot!

 

I agree with just about everything posted in the past 12 hours here.

I just get real pissed when you have trolls expecting a new design full size truck to get 30+ MPG. There are certainly ways to make things more efficient, but IMHO there's no way to make a 6,000 lb truck get similar gas mileage to a sedan.

Those who think they should need a crash course in basic, high school physics.