Have you reviewed the towing and hauling spec's on page 33-34 of the 2018 F-F-150 Brochure?

 

The power density isn't nearly as big a difference as you think:
The 2.7EB makes 148 ft-lb per Liter. CGI block
The 6.7L makes 140 ft-lb per Liter. CGI block
The 3.5EB makes 134 fl-lb per Liter. Al block
The 3.5EB Raptor makes 146 fl-lb per Liter. Al block.


The n/a engines are much lower:
5.0L makes 80 ft-lb / L with Al block.
6.2L makes 70 ft-lb / L with iron block


If your logic is that the smaller engine has less surface area to dissipate heat, I'd agree, but it really does not make more heat per Liter so it' heat density per Liter really isn't vastly different.


Maybe the argument is that only iron blocks are used in "heavy duty" applications (6.2L and 6.7L), but then again the 2.7EB has an iron block, too!


In fact, the power density per liter for the Raptor 3.5EB (146 fl-lb/L) is just about the same as the 2.7EB (148 ft-lb/L) and is more than the 6.7L diesel (140 ft-lb/L).


And in terms of swept area for the cylinder walls, the 2.7EB has 35 sq in, and the 3.5EB has 39 sq in, and the 6.7L has 52 sq-in. While you may be right that the 6.7L has a bit more surface area, the three EB motors have roughly the same swept area and a closely related density per swept area!


Also, cylinder wall cooling surface area is only ONE of several contributors to the overall condition of thermal transfer. There are many other things to consider such as thermal coefficient of the medium, coolant velocity, rejection surface area of the other cooler (radiator), etc, etc, etc. You cannot just look at the cooled cylinder wall and say you know the whole story. Additionally, much of the heat goes into the heads and out the exhaust. In fact, moving the turbos as close as possible to the head makes for more efficient thrust.


Maybe you could argue that the 5.0L has a greater tow rating because it's power density is so low; much less heat per liter. But then how would you explain that the 6.2L engine does not have a higher tow rating contrasted to the 6.7L engine? If the 5.0L more capable of towing due to much lower heat density, why does the 6.2L not pound out more against the 6.7? And why is it that the 3.5EB can do "more" than the 5.0L, yet have less swept area? Bottom line is this; your argument really has no decent basis because there's no clear "always works" formula that applies to any known power-density/bore/stroke/block/chassis situation.




Like it or not, there's no real decent reason I'm aware of for the 2.7EB to have such a lower tow rating versus the 5.0L. Or, if you logic is that it really cannot manage much more than 8,000 pounds, then you have to admit that the opposite is true of the other F150 engines; they are way "over-rated" (more so than the little EB).


As I said before, if the 2.7EB were rated at 10,000, and the 5.0L at 11,000, I could understand that. But there is a 25% loss of towing capacity, even though nothing else in any equation makes up for the 25% differential. power difference = 6%. Block material; goes back and forth between all engines with no direct correlation with power density, as does swept cyl area, and block material, ... etc ...


If one's argument is that the 2.7EB is not a real "towing engine", what is that based upon?
Both the 2.7EB and 6.7L diesel have these same features:
- CGI blocks
- forged cranks
- alum heads
- power density close; both above 140 ft-lb/L
- both have turbos that are mounted very near the heads (the 6.7L has a "reverse flow" system where the heads flow directly up into the engine V, where the turbo is ... In fact, the twin turbos of the 2.7 at least get to "split" the heat load by two, whereas the 6.7L has ALL heat go into ONE turbo!)
Yet every diesel owner will swear by Zeus that his diesel is the bad'est in the land due to all these features. But now someone wants to tell me that the little 2.7EB is not made to "tow"? Just what biased, one-sided, lop-sided, short-sighted, bovine-manure judgment call are you making here??????? Feature for feature, the little EB is VERY similar in construction features compared to the diesel.


This thread I started isn't a debate of why a SD can tow more than an F150; we all understand that.
This thread is about why a 6% reduction in torque results in a 25% reduction in tow rating in an F150, contrasting the 2.7EB to 5.0L engines.
It ain't the chassis, or the tranny, or the radiator, or the power density, or the swept cylinder area, or block material.



The SAE derived tow ratings are a MAX limit that the vehicle combination can sustain safely and reliably. But there is no "minimum" value applied in their requirements. The 2.7L can likely tow far more, because it's not far away from the 5.0L in terms of torque. If the vehicle chassis (frame, brakes, cooling package) can handle the 3.5EB, it can surely handle the 2.7EB.
So the power difference of 6% does not explain a 25% drop in tow rating.

The way I see it:
It's a marketing numbers game to induce folks with "tow envy" to buy a bigger rating, hence spend more $$$ on an "upgrade" engine.




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Once again, a majority of the 2.7s ride on the light duty chassis frame. The engine was designed for fuel economy and light towing. Go buy your damn 2.7 and shut up. Quit being so butt hurt. Secondly quit comparing your pop bottle engine to a diesel. They are not the same and not even used in the same category.

 

I enjoy reading your analysis. Don't always agree with your conclusions,
but you get me thinking.

I wasn't referring to swept surface area of the cylinder walls, but specifically the surface area between the engine surfaces and the coolant. There's no way I'm aware of to get actual values, but we can be certain the physically larger block has a lot more surface area to dissipate heat, particularly around the heads and exhaust ports.

Back in 2011 the V10 was dropped from the Super Duty pickups in favor of the 6.2L V8. But the V10 remained in production for the chassis/cabs, and at the time one of the engineers referred to the 6.2L not meeting the cooling benchmarks for the higher duty cycle. That's as specific as we got, and unfortunately I can't find the post at the moment.

 

Can you find a 3.5L EB in a heavy duty chassis? None have ever been made that I'm aware of.

 

Ford offers three different frames on the f150.
Light duty- a majority of the 2.7s ride on this.

standard tow frame- 2.7 if ordered with heavy duty payload package, 3.5, 5.0

​​​​max tow/hdpp frame- 3.5, 5.0

There is different frame thickness between them and different hitches too.

 

Not buying it. Makes 0 sense for Ford to have 3 frames for the F150.

 

I said the same thing too, until I seen the Ford F-150 brochure that displayed the information. Technically they make five different frames. Three for the regular f150s and two for the raptor. It's crazy *** hell. But it's true.

 

I don't see anything about that in the brochures I've found online.

 

Just to clarify I believe that standard defines a maximum towing weight for a specific powertrain/platform, but does not define a minimum. So manufacturers can be fully compliant with that standard and choose to rate certain trucks/powertrains lower for marketing or other reasons.

Probably 75% of truck buyers have never looked at a torque curve and wouldn't know what one meant if they were given one. Us FTE'ers and other enthusiasts are abnormal in this regard.

Honestly, it would be crazy to have three engines with virtually identical towing ratings in the F150. That would cause more confusion with customers than anything. The way it's laid out now is very sensible. Mid-weight towing you can choose the 5.0 or the 2.7 EB, and heavier towing you choose the 3.5 EB. That's simple, easy for the average customer to understand, and is fully compliant with the J2807 standard.

 

I can't find much detailed information in the spec sheets, but I did find this:

The spec sheet in question is attached.

 

Just tossing this out there since I have nothing to back this up, but what's the weight difference between the engines? Towing isn't always about power but balance also. If you take the same 11k trailer and put 15% tongue weight on a truck that's a few hundred lbs light up front it's gonna drive different than 1 with the heavier power plant. But the smaller cgi could be equivalent to the larger aluminum block, like I said just a thought.

 

Good thinking, but in this case I think they're all pretty similar. I never found a solid weight spec for either, most searches tend to bring up results with towing and payload figures. One site I remember a couple years ago mentioned the 2.7L EB weighed within 10 lbs of the 3.5L EB, but I can't find it for the life of me.

 

Does the 2.7 get the same rear axle? Though some were 8.x" while the other where 9.x" which would cause a drop in tow and gross rating.

Also I know the HDPP trucks have a different frame, but I have never heard of there being a special light duty chassis. Any one have a copy of that information?

 

Sort of. The "2.7L Payload Package" gets the 9.75" rear axle, the normal grade 2.7Ls get the 8.8. But the 5.0L comes with the 8.8" axle unless you get the heavy duty payload package, and it's still rated for more weight.