A very insightful post Eric. To expand on this line of thinking, the motors are further handicapped by the gearing and the shift points in the automatic transmissions. I looked into this once, and although I don't recall the exact numbers, The 5.4 in the F150 is indeed handicapped by it's transmisssion compared to the competition. Going to lower differential gears helps.

When one considers how well the 5.4 Trucks handle real work and towing, despite the trannies, it becomes clear that there's really nothing wrong with the motors. 5.4's in some Superduty, manual transmission applications, perform quite well, and get fairly good gas milege.

 

Sure happy to know.....you know where you are.......A FORD site.....enjoy all FTE offers about Ford trucks...

 

I have no actual test data to prove this, and I know that OHV engine like higher revs, but I have to believe that running an engine constantly at 3000-4000 rpm will wear it out faster than running it at 2000-3000 rpm.

For any set period of time, say 1 hour, at 4000 rpms, don't the pistons travel twice as far as at 2000 rpms? Doesn't the crank turn within its bearing twice as many times? Doesn't the waterpump turn more? Etc., etc.

So while I can agree that modern engines are not "hurt" by running higher rpms, I have a hard time believing that they last as long running those high rpms.

Therefore, I see it as a major compromise to stick 4.10 or 4.30 gears into a truck just to get the motor to rev high enough to put out some power.

Look at the 5R110. Why even bother putting a 5 speed into a gasser truck? The 5th gear is on the low end. Final drive is the same as the 4R100. If you are going to pull any load, especially with the 5.4, you are going to have to lock out O/D. So you never really get to use the extra gear.

Ditto the new GM 6 speed auto. The 6th gear is an even lower O/D. With any load, you won't be able to go beyond 4th if you want to keep the engine revs up and put out any power.

I am sure that there are flaws in my "big picture" logic. The devil is in the details.

 

Depends on the stroke. Besides, the 5.4/6.8 may have the longest stroke of its competitors, which is more of a concern when talking about piston speed (engine wear)than where the cams are placed . (you're correct about accessories, however)

They are all OHV (I know what you meant) but as far as OH(C) "liking" higher revs" I will respectfully disagree when talking about the RPM range these trucks operate at.

OHC may be able to rev higher more safely than a pushrod motor but at <7,000 RPM it's kinda a moot point. (witness the LSx motors and the hemi)



My V10 runs 4.30's......I actually want higher numerical gears in the future....
Factor in that I've never read of any car/truck having a shortened life span due to a few hundred more RPM's at cruising speed and I'd rather have the added performance lower gearing (higher numerical) makes.





Considering the majority of us tow a small percentage of the time, a steep OD is beneficial when the truck is empty.


At the risk of being redundant, Ford actually jumped the gun with their small bore, OHC design. They must have thought it would be the only way to meet tightening emissions in the future.....technology stayed ahead of the curve........the bores are back over 4" and the pushrod motors are still making clean, high HP.

 

I was comparing engine to engine. In any given engine, twice the rpm equals twice the piston travel. It has to, doesn't it?

I haven't read it about it either, and I doubt that you ever will. I have no idea how much the higher revs shorten lifespan . . if at all.

And is can be a lot more than a few 100 rpms. In O/D, my 4.6 runs 2000 rpm at 70 mph. With O/D off, it runs 2800 rpm at 66-68 mph, and it still does not tow very well. Max torque is not reached until 3500 rpm. So it is more like 1000 rpm difference.

No doubt, but my point is that an engine putting out max torque in the 2000-3000 rpm range would be more useful for towing and theoretically, should last longer because you could pull in O/D.

As far as MPGs, that can be taken care of with a super high O/D, like in the GM 6 speed.

Diesels have a well-earned reputation for longevity. At least part of that must be because diesels are so low reving.

 

Well what I'm talking about is how the transmission gearing effects seat of the pants feel. If your transmission has, say a 2.72:1 first gear, as oppossed to, say a 3.30 1st gear, and it also has slightly higher second or possibly third gears, spread farther apart, the truck is going to feel less "peppy" and more "doggy", even if the power to weigh to ratios are relatively favorable, and the engine produces good usable power over a fairly wide RPM range.

What may be needed with such a good tourqey motor, is more lower (1 through 3, or 4) gears in the tranny, at slightly lower ratios, with quicker shifting between them, and perhaps a steep OD gear(s). I don't think with modern OD transmisssions increased engine wear is a significant factor. Even with relatively low differential gearing your not roaring down the highway at 3500+ rpm in OD.

 

That's true but the stroke also has a lot to do with piston travel. If the stroke is longer, then the piston travel is more. For example, the piston travels twice as far per revolution if you have a 4 inch stroke than if you have a 2 inch stroke.

 

Agreed.

But whatever the stroke of your engine, the pistons are traveling twice as far at 4000 rpm as they are at 2000 rpm.

But I think that your point is that a long stroke motor at 2000 rpm might have even more total piston travel than a short stroke motor at 4000 rpm.

Isn't more torque produced by lengthening the stroke? If so, then you could be right, getting more torque out of an engine at lower rpms by increasing stroke could result in the same, or even longer piston travel. So no wear benefits from lower rpms.

 

Yep. Increased stroke means more cubic inches and more torque at a lower speed. As they say when towing "there is not replacement for displacement".

 

Right, right.......sorry about that. Of course if you're comparing the same motors the piston speed increases with RPM....I was still stuck on comparing the 5.4 with the competition.


USUALLY the 3rd gear is a 1 to 1 on a 4 speed OD automatic, the OD is USUALLY .75-.60 to 1. So yes, @ 3,000 RPM in OD you'd be aprox @ 3,750-4200 dropping to 3rd. (25%-40% higher revs)

But I thought we were talking rear gear ratios...........4.10's are 10% lower (higher numerically) than 3.73's. So the difference @ 3,000 rpm would be 300 RPM's.

 

More stroke(longer arm) = more leverage on the crank= more torque. The thing with Fords is in theory they should have lots of torque with some looong strokes but the bore is tiny which keeps the displacement lower.

 

If I could get anything out of it, I'd love to sell my dog of a truck and get a Dodge with the 360. Even has the D44 up front.

I think Im going to wait and drop in a 514 though. It might have enough power for me. I'll probably have to go with a supercharger on top of that.

 

Does anyone have a link to graph(s) of the torque/HP curves for Ford's engines?

Ford claims that most of the torque for the 5.4 is available at 1000 rpm. I'd like to see that.

GM has graphs for all of its engines available at its corporate website.

See:

http://www.media.gm.com/us/powertrai..._Silverado.pdf

 

im glad you'll be happy..i know i will cause i wont have to listen to just one more person cry about there "weak" 5.4!

 

Well, I like my 2002 5.4 F150. It might not be as fast as a Chevy or Dodge, but I haven't had to race anyone, but I have had to haul and tow. For that, I don't think you could find a better engine. Just about a month ago, we picked up a new (to us) milling machine weighing about 2500 lbs. on a 1500 lb. trailer. Total tow weight give or take was 4000 lbs. It was kind of tippy because the mill is about 6 feet tall, and we couldn't get it back very far on the trailer so we had a pretty high tongue weight, but the truck pulled it great. I think a lot of people test drive Ford, Chevy, and Dodge, and say the 5.4 is "underpowered" in comparison. Well, do some work with a 5.4 and you just might change your mind. My truck has more than enough power to merge with traffic in the Twin Cities with me (245 lbs.) and 750 lbs. of steel in the box.

As far as stroke and wear, I think you would have to worry about bearings more than cylinder wear. I've heard about a few 300's with a 4" stroke that had 150,000-200,000 miles on them that had the heads off them, and you could still see hone marks on the cylinder walls. The only thing that would wear more would be your rings because the piston is still traveling in the same stroke, whether it's 2" or 4", so any point on the cylinder wall still only sees the piston once a revolution. It's the piston that's traveling twice as far on a 4" stroke vs. a 2" stroke, so I would think that would be the thing to wear more.