Looking for a source for the new 3.5L naturally aspirated (NA) torque curve.
Lots of sources of torque curves for 3.5L EB and 3.7L NA.

Why was the 3.7L NA replaced with the 3.5L NA?
Is there that much difference in MPG between the two engines?

 

Probably did it for parts commonization

 

Here's the only one I could find. It's from a Ford of Canada publication touting the 2.0L EcoBoost engine in the '11 Explorer. Peak numbers are a bit different, so I imagine the F150's engine is a bit different than this.




SOURCE.

Probably not a huge difference, but I'm sure it's there. My '15 is a full 692 lbs lighter than my '13 was, and with the same engine and lower gears it's easily the snappiest truck I've ever driven. With the lighter body it makes sense that the 3.5L N/A would be more than adequate for most folks.

 

Just guessing, but I would imagine that the 3.5L NA is the same block as the 3.5L Ecoboost. Would make a lot of sense to me. And with the 6-bolt mains, the NA would be almost bullet proof.

 

GlueGuy
Agree, since the 3.5L EB & 3.5L NA both share the same bore & stroke specifications.

Would conclude that the 3.5L EB is a souped up version of the 3.5L NA.

Do not believe the 3.5L NA is getting enough credit.

Believe it is interesting to compare the 3.5L NA to the 5.0L NA.
The 3.5L NA torque curve is nearly flat in the 2000-3000 rpm range
& peaks at 4250 rpm.
The 5.0L NA torque curve has no flat rpm ranges. The 5.0L NA has a totally positive linear slope torque curve from 1000 rpm to 3850 rpm at peak torque, then decreases with negative slope.

At 65 mph in 6th gear OD with stock tires, the 3.5L NA engine speed is 1814 rpm with default 3.55 rear end ratio. The engine develops 197 lb-ft of SAE net torque, based on the torque curve furnished by TOM and curve fit adjusted to meet the current F150 peak torque specification, 253 lb-ft @ 4250 rpm.

At 65 mph in 6th gear OD with stock tires, the 5.0L NA engine speed is 1692 rpm with default 3.31 rear end ratio. At that engine speed the 5.0L NA develops 173 lb-ft of net torque, 24 lb-ft less than the 3.5L NA.

The 3.5L NA develops 12% more net torque at crusing highway speed
than the 5.0L NA.

Engine speed is easy to calculate.
MPH road speed x 1min/60 sec x tire rotations/mile x trans gear ratio x rear end ratio = engine speed, RPM.
Tire rotations/mile is published by each tire manufactures for size of tire and easy to find on Tire Rack.com for most tires.
Stock tires for the F150 are 245/70/17.

The only experiece of towing a heavy load with a light duty truck was back in 1992
when towed a 26 ft boat with a flybridge & two stern drive engines from SOCAL to Portland, Oregon. Used my 5.8L/C6 , three speed trans in a Ford Bronco as the towing vehicle with 105" wheel base.
The weight of the boat & trailer was approximately 8000#.
Barely made the trip. Used 2nd gear most of the time at 45 mph with engine speed ~ 2785 rpm with 31x10.5x15 tires. On the 10 mile, 8% down grade from CA state line into Medford, Oregon used 1 st gear all the way down the hill
with ground speed < 25 mph.
Travel a 10 mile up hill, 6% grade almost every day. The Semi Trucks will run you off the road, if traveling < 45 mph.

If traveling 45 mph in 3rd gear, 1.52:1 ratio, with a 3.5L NA ,
engine speed ~ 2767 rpm, which is the middle of the torque curve flat rpm range.
The engine develops 214 lb-ft of net torque.

If traveling 45 mph in 3rd gear with a 5.0L NA ,
engine speed ~ 2580 rpm.
The engine develops 245 lb-ft of net torque, only 14.5% more torque than the 3.5L NA.

The 2015/16, 5.0L even with the upgrade to 387 lb-ft peak torque compared to 2012-2014 with 380 lb-ft of peak torque is not the same 5.OL EFI engine found in the 1986-1996 Ford Bronco/F150.
That engine had a completely different torque curve using a compression ratio of 9.0
compared the 10.5 for the current generation.
engine speed, rpm torque , lb-ft
1000 230
1500 250
2000 265
2400 270 peak rating
2500 270
3000 270
4000 240
This data is published by FoMoCo & posted on this forum

OEM Tire size for that vintage was 235/75/15, according to Tire Rack.
At 45 mph road speed the engine speed is 2928 rmp in 2nd gea,r using the C6 , 3 speed trans and OEM 3.73 rear end.

At that engine speed the engine develops 270 lb-ft torque, operating in the flat region of the torque curve, compared to 245 lb-ft for the current 5.0L operating on the slope of the torque curve with both vehicles traveling @ 45 mph ground speed.
The older generation 5.0L developed 10% greater torque than the current 5.0L NA
at low up hill ground speed towing a heavy load.

Bottom line is in my opinion,the 3.5L NA has a better shaped torque curve for a truck application than the current 5.0L NA and even develops more torque than the 5.0L NA at highway speed.

Believe the 3.5L NA has more merit than it is being given and should not be discounted as a viable engine option.

 

I'd completely agree with that.

 

Tom:

Along the lines of what has already been posted, are there data available on one chart so that we could compare the horsepower and torque between
1. the 3.5 ECO,
2. the 3.5 NA, and
3. the 3.7 NA on one chart?

I for one am curious about the three, as I am shopping for a truck for (mainly) highway trips. My secondary use would be occasional brush/trash hauling, lawn care shopping, and light car towing (under 5000 lb gross) to car shows using a Featherlight trailer. I would travel mostly undulating terrain with the occasional low mountain range (east coast) to get from here to there.

For the above, I hope that one of the above powerplants would be able to do both types of jobs. Good highway mileage would be a goal when just traveling, but also decent power to do the secondary jobs when the truck is needed for that is very important too. I am assuming 2WD, the 6-speed in current use, and a 3.73 rear end would work, but perhaps there should be some comment regarding best-use ratios too.

So how do each of the three engines stack up when compared to each other? I have been reading posts but have not yet found one that asks this question. Please feel free to move this post if it merits being its own topic.

Thanks in advance,
Ronald

 

Hi Ronald, welcome to FTE!

I'll interpolate some numbers from that chart when I get home and plot them against one I already have of the other engines.

 

Just for fun I did a build on their website crew cab 4x4 3.5 N/A 5 1/2 ft bed 3.73 electric lock diff (just cause I am not a fan of open diff anymore) max payload was 1549lbs and max towing is 7100lbs. Now I can't remember my 99 F150 specs but I think even with this 3.5 N/A seems at least on paper a decent engine for the average person who may tow a smaller boat or camper. Gets the same mpg as the 2.7EB will just not as powerful.

Think they dropped the 3.7 in favor for the 2.7. Didn't they just detune the 5.0 a bit to make the 3.5EB seem more desirable?

 

Here ya go @rds289k
DISCLAIMER: All values for the 3.5 N/A engine are from my interpretation of the graph I posted earlier. It's a different application, so I'm sure there is some variance from the actual numbers. I believe it's very close though.

Special thanks to @Robbgt for compiling most of the data.


Torque:



Horsepower:

 

There's no doubt that the 3.5L NA would be all the engine that I really needed. The ecoboost sure if fun though.

 

Test drove a regular cab XL with hand crank windows, 6.5 ft box equipped with 3.5L NA, today
The truck is quite nimble with great zero to 25 mph acceleration, empty.
Could drop another 50# with full size spare tire.
This RCS was the only short box in all of SoCal.

Note: The truck incorporated a one section aluminum material drive shaft with center located slip joint.

 

I test drove the 3.5 NA supercab and was very pleased with performance. I've owned several SVT Lightnings and this new truck did not tend to **** me off on power. Yep, it's a nice setup and probably a long runner.

MY QUESTION IS.....

Are the internals the same, likely forged, as the 3.5 boosted version.

THAT would be sweet!!

 

That has been discussed elsewhere on the forum, and it appears to be fact; the 3.5L NA is the same block/internals as the 3.5L EB.