That's just it though. If you operate a 302 at WOT you're going to be running 95 - 100 mph. Or 5000 - 6000 rpm in a lower gear. Not good for longevity. I think the police might take a dim view of a truck going by at 30 mph with the engine running at 5500rpm also.

You cannot reach that first statement of not sacrificing performance and running a 302 at or near WOT. The premise of operating the engine at it's most efficient BSFC range is that the power output of the engine matches the task to be performed. You mentioned earlier that it takes 9hp to run a car at highway speeds. Therefore you will need a 10-12hp engine running at 80-90% rated power to be in the most efficient operating mode. A 4500 pound truck that is that underpowered would probably be dangerous if operated on the streets.

A 302 could reasonably be expected to make 200hp. At 80% output that's 160 hp. If it take 9hp to cruise at leagal highway speeds, how fast would you be traveling at a 160hp output? Also, you want the load of moving the truck to limit the rpm of the engine, not the gearing.

 

Well then it seems to achieve this you would need to "turn off" cylinders and run two cylinders at 80% o/p at hiway speeds. Cadillac used to do this(poorly) and Chrysler does it now with the new Hemi. So it is theoritically possible? Of course this means re-writing the EEC code all together. Will it work?

 

My '78 F100 gets 21 mpg with a 300 and 3.00 gears

 

I don't think I buy the WOT routine, your engine isn't gonna last too long if your working the **** out of it. I've always heard that 2/3's power is where you should run your engine if you want it to last forever. And most of the vehicles I've had feel pretty good at about 2/3 so I tend to believe it. I would think that wind resistance is probably our worst enemy, then probably finding the right gears, which could get expensive if you miss your guess a couple of times.

 

Actually i was thinking of having this feature added to the FI when i get it. In theory, yes, theory, if you stop fuel from being injected into cylinders, you could have a variable displacement engine with a monster MPG number.

 

you would have to add solenoids to hold the exhaust valves open to eliminate compression from the cylinders you want to disable. That is how Mopar does the Hemi. If you do not do this, it'll sound like it is missing. That will not sound cool.

 

Plus you have to spend the energy to compress the air charge without the benefit of a power stroke from that cycle. Vibration would be a B too.

 

you don't need to compress it if you leave the valve open.

 

Amen to everything you said.
I bought my 79 Bronco to wheel and play with.
I wouldn't want to drive anything else other than that or my 77 F-100 that I use as a DD( this is my good gas mileage truck, I didn't want any 4 cyl.)

 

I hope you make it Terran. It is definitely a sightly goal for yourself. I think you could do it.

My 73 f100 with a 400 gets about 16-18 mpg highway. I could probably push at least 20 or more if I had a tonneu cover and tweaked the 400 just right. Gotta love the 2V and that ol' motorcraft 2100 2bbl.

And for those of you who will ask... No I have no idea what gears are in her. I just got the truck about 2 months ago.

"Weight of foot - distance to floorboard + cubic inches = bad gas mileage no matter how you put it"

__________________
1973 F-100 Ranger
w/ '79 F-150 Ranger XLT cab and decals
400 2-v
automatic trans
power steering

 

MBB and Rebel, nobody is trying to force YOU into increasing your fuel mileage. Some people are doing it as a hobby, some are doing it to see if they can, and some are doing it because at 8mpg and 3+ dollars a gallon it's eating into our profits. Personally the latter is my case, and I'm not shooting for Magic numbers, but I'd really like to see 12-14 mpg, and that is why we're in this thread, throwing around ideas.

 

12-14mpg is possible. I'm pulling that down right now with a 390, 4BBL, C6, 3.00 open rear gears in a supercab F-150.

 

ya i would hope so, I just picked up the 74 today and brought it home, I was happy to find it has a 3.55 rear in it, which is what I think I want. Have to replace some brake lines tomorrow then I'll register it and fill the tank and see how it does the way it is.

 

Speaking of rear gears, i have a "06" right now meaning i have a 2.75 in the rear. Sombody told me swapping to 3.75 would make a pretty big improvement.

 

gears are a tough call, the higher the gear the slower your engine turns, but it only helps until the engine isn't powerful enough to turn the gears. I would think you would be much better off with the 2.75 if your shooting for better mileage. But that isn't always the case, if your 302 is working too hard with the 2.75's you might want to try 3.00, but I wouldn't jump all the way to 3.75

The only reason I'm not shooting for a higher gear than 3.55 is because I also have to tow a heavy load. I also have a 460 which is pushing about twice the HP you are.

PS. if your close to Cape Cod, Mass. I'll lend you a 3.00 to try if your running a 9 inch. I have one in my 70 ragtop.