The scale system doesn't monitor actual weight, it monitors the height of the vehicle over the axles. As an add-on like air bags moves some of the weight handling to the add-on device, putting enough weight in the rear to max out the scale with an add-on is going to have the rear at the same height it would be maxxed out without the add-on, so the load experienced by the springs is the same.

They don't have an eco in the SD because gas turbo engines can't efficiently deliver the kind of low rpm grunt you get from a diesel that can easily get you moving when you've got a 20,000lb trailer.

You can certainly build up an eco to deliver 1000lb-ft like a TD, but it's not going to give you 800lb-ft at compressor stall to get you rolling quickly without some major compromises that affect efficiency and performance. The difference in diesels is the fuel. Diesel engines are 20% more thermally efficient, which means they extract 20% more energy from diesel than can be extracted from gasoline. Diesel lets them run a compression ratio of 18:1 in the powerstroke (Vs 10.0:1 in the 3.5eco), permitting them to extract massive grunt at low rpm out of a relatively efficient 6L engine. To do the same in a gas engine, they'd need probably over 10L of displacement (lowers mileage), or they'd have to push a LOT of boost immediately off idle (lowers mileage, increases heat), which would suffer from a lot of turbo lag Vs the powerstroke due to the size of the compressor wheel.

Can it be done with a gas engine? Yes. Will it be as efficient? Nope. You either give up the low rpm grunt, or you give up mileage. Maybe they can cull together a lot of engine technologies to get there, but then you have a system that costs quite a bit more than a turbodiesel to build and operate.

There's many good reasons why the trucking industry settled on turbodiesels long before most of us on this forum were born.

 

but if the device reduces squat would that not change how it measures the squat? 500lbs = 3" squat, 500lbs with airbags or ras = 1" of squat ??

 

I guess we can agree to disagree. Anyone that has driven an Ecoboost knows there is PLENTY of “low rpm grunt” that is as good as you can get from a diesel. Also an Ecoboost SD wouldn’t be designed to move 20,000 lbs. It would be for those those that use SDs to tow 8-15k? occasionally.

The Ecoboost in the F-150 was designed to out pull a 5.0, 5.4, and 6.2, while getting better mileage than the big 6.2. It does. Not to get better mileage than a 3.5 NA or 5.0 NA.

The 6.2 gets better mileage than the 7.3 by 1mpg usually. A 5.0 (or something similar) Eco could get better mileage than the 7.3 under light load and pull better with 800ft lb of torque as you stated.

This doesn’t mean I don’t care for the 7.3 gas. I actually really really like it and wanted one. If I was pulling very often and didn’t want a diesel, then it’s the choice. But anyone that has driven an eco and a NA engine knows that the eco is a great daily driver. Many people daily drive their SDs and tow very infrequently. But the 7.3 gas filled the hole between the 6.2 and 6.7 that I doubt an Eco will come out, but I have zero doubt that it would sell well.

A gas engine was just designed with a 15.5:1 ratio and gets 15% better mileage and performance then the previous engine. Technology is making gas engines more and more ready to take the work from diesel trucks just as diesel trucks are getting more and more clogged.

For years people said the a twin turbo gas would fail in the mighty F150 and it never happened. It is the most commonly chosen engine now. The only reason it hasn’t been given the chance in the F250 is due to Diesel engine sales. They could offer it in the F250 only and make it a max row of 15k or a little less. Most people don’t tow over that amount anyway.

Edit:

What are the positives of the Diesel engine? Power….is there another?

Even if a gas engine put out 800/800 HP/TQ, would anyone care if it got 14mpg? You no longer have to worry about DPF, EGR, DEF, 13 qt oil changes, and if the next fuel stop is going to kill you infinitely more sensitive fuel pump.

I drive a diesel and love the power. I wanted gas for everything else. I would buy an Ecoboost SD.

 

Let me try it this way:

Say you want to use the lights to limit how much weight you put on your oem springs. When that third light comes on, you stop at that point, no more weight.

If you add air bags, it will take more weight in the truck to get that third light to come on, but now some of the weight is being handled by the bags. As long as you don't go past that third light coming on, the oem springs see the same load because the rear of the truck has dropped to the same point. You can add 5psi to the bags and 150lb to the bed, or 50psi and 600lb... the oem springs don't care because they are only concerned with how much they must flex, which is determined by how much the rear drops.


Have you ever towed with a 700lb-ft or greater powerstroke? There is zero comparison. Even an eco built to the same torque needs an extra 1500-2000rpm until it hits peak torque. Do you know what that gets you? A nice view of the rear of the 30ft trailer being towed by the powerstroke getting smaller in your view.

Sounds to me like you're trying to invent another class of truck to have a second de-rated super duty. I don't see an eco as being the right move there as a smaller eco is going to burn through more fuel than a godzilla variant while towing, and likely the same mileage when not. Most of the mileage the SD trucks lose to the F150 is due to their height, weight, and tires.

 

I guess I'm still being dumb with this lol

 

The device that measures the squat still just measures the squat. A device that reduces squat does not change how the measurements are made, it only changes how much weight is required to reach a specific amount of squat.

I'm looking at this from the perspective of how the measuring device works, while you are looking at it from the perspective of how add-ons reduce squat.

Add-ons will reduce the amount of squat for a truck that has the same weight in it. Or, to view from a slightly different perspective, add-ons will allow you to put more weight in a truck to achieve the same amount of squat you had before installing the add-on.

From the perspective of the height measuring device and the leaf pack, a truck will sit higher with the add-on and no additional weight, or will sit at the same height as before with enough additional weight added. But what does not change is the relationship between the height of the truck (and what the measuring device reports) and the flex of the leaf pack. This relationship remains locked, and once that last light comes on, the oem leaf is under the same pressure as before the add-on install.

What HAS changed is the weight in the truck, as it takes more weight to squat a higher effective spring rate, which is what you have when you add more capacity via bags, RAS, Timbren, etc. Depending upon what you've installed, you can be over your rear axle capacity, but if the truck has not exceeded the squat from before the add-on install, your leaf pack is experiencing weight within it's tolerances, because the additional weight is being carried by the add-on.

Another view...

Take an unladen truck, weld some iron tubing between the axles and the frame, close to the end of the axles. The rear leafs are still compressed to the same point they were under the weight of the truck, but as the height between the axle and truck now can't change, any additional weight added to the bed goes through the tubing straight to the axle, bypassing the leaf pack. You can put 3000lb in your bed, the leaf pack still only sees the weight of the truck before you added anything to it after installing the tubing, because the frame can no longer compress the springs further. Weigh the truck, you will see the extra 3000lb on the axles, but it's bypassing the leaf pack, so as far is they are concerned, they have the weight of an empty truck on them.

 

Ok, right, so it would if Im measuring weight, tossing 500lbs in the bed, it wont read as 500lbs with the ras/airbags, etc

 

Right. A CAT scale will show the truck as being 500lb heavier, but the truck's scale will show a weight that is 500lb minus how much of that weight the add-on is supporting.

 

Have you driven a 3.5 EB? I drove one for 6 years and towed many happy miles with it, even with 3.31 gears. It had 365 HP and 425 TQ I believe.

I am currently driving a 2021 F350 6.7 3.55 diesel with 1050ft of torque and 475 HP.

I towed a 6k travel trailer with the Eco and a 7.5k travel trailer with the 6.7 diesel. Same frontal area. Towed the same 6x10 trailer over a thousand miles with each.

I went to SD for payload while camping. The Eco had enough power in every situation I have ever been in. I have only towed through the Appalachians.

The Exhaust Brake is awesome, so there is a plus for the Diesel. Yes the Eco will tow at 2500-2800 rpm’s and the diesel does it at 2100 rpm’s up the mountain. Both kept the speed limit going up. Got 9 towing the TT and 12 with the diesel. Got 13 towing the 6x10 with the Eco and 17 with the diesel. (Very mpg friendly route over 400 miles.)

A 5.0 Eco would get better mpg than the 7.3 and tow great. The mpg would be within 1 mpg of the 7.3 towing depending on terrain. But with a $3k upcharge it would take many diesel sales.

The 6 speed 6.7’s look to get 18 on the hwy and the 10 speed 6.7’s get 2-3 mpg better at constant hwy speeds. So I’m not sure if a eco in the SD would beat that but I bet it would get better mpg than the 7.3 gas.

It would blow the 6.2 away, as it did in the halfton but this 7.3 seems to have fit a nice area. But most are reporting 12.5-14-5 with them and an eco SD getting 16-18 and towing as good or better, would sell.

You seem skeptical of the eco towing prowess but those that have used it knows that it gets the job done as a weekend warrior. If you heavy tow often the 7.3 and 6.7 are for you. Would the 6.7 pull faster? I would guess so, but I accelerate about the same. Are we racing with our travel trailers?

 

I'm not skeptical of what can be done with an eco, you can build a block to be as strong as you want. As it stands, the 3.5 block is probably good for nominal 700hp as is, just beef up the crank and connecting rods and call it a day. Ford can redesign the block to handle 2500lb-ft on the daily if they want.

But that's not what the conversation is about. The conversation is about an eco being a good replacement for a diesel, and it just isn't. You can push as much power as you want with a gasoline engine, you will never meet the characteristics of a diesel while also providing the efficiency. Efficiency is the only name of the game with heavy hauling.

No, we aren't talking about racing, we are talking about why turbo gasoline engines can't be heavy haul engines.