My 99 truck was rated stock at 275 HP @4250 RPM'S and 410 lb. ft. torque at 2650 RPM'S.
I hear V-10 owners talking about on the forums about not being afraid to run the tach up to 5,000 on the big grades for towing with the V-10.

I have an H.P. and torque curve from the manufacturer of my Hypertech Power Programmer measuring both on a factory dyno. It shows max torque, at about 2750 rpm's, of about 215 lb ft and 150 lb ft at 4500 rpm's.
The H.P. curve shows a max of 210 @ 4000 rpm @ 205 h.p. @ 3500 and on a decline.

If the H.P. starts declining slightly after it's peak of 4,000 & torque has declined down to 150 lb ft at 4500, why would increasing rpm create more power.

This especially seems strange to me when I thought torque is what moves you up the grade. These numbers are from a dyno, but the peaks seem to occur at about the same points as reported in the Ford literature.

Thanks for your help in explaining thsi. LIKENIT

 

The '99 pre-PI V10 was known to run out of breath - so much so that sometimes downshifting actually slowed you DOWN under big loads.

I think the key is downshifting.

When you are going up a hill, say in 3rd gear (1:1 in a 4-speed auto), the transmission is passing power straight through to the rear, which, say it's a 3.73, multiplies the torque by 3.73. If you downshift to 2nd, and that gear is, say, 2.5:1 (just an example), you are multiplying the engine's torque by 2.5 in the transmission.

So, DOWNSHIFTING and running at a higher RPM does make a big difference in the amount of torque to the ground.

This is one spot where a V10 can put more torque to the ground than a diesel because it can rev all the way to 5000RPM (in a lower gear) while a diesel can't.

 

Thanks!

Are you saying that even though my engine is decreasing in torque produced after 2650 rpm, my transmission is making up for it? I know what you mean about it running out of breath. Thats why the theory does not seem to apply to mine. I wonder at what RPM I would be better to just hold it there. It seems to me that somewhere between 3500 and 4000 I'm reaching a point of diminishing returns,
Are you also saying the 2000 and later do no have the running out of breath problem. Fortunately, I have a Gear Vendors Unit, so I can split my gears, which helps a lot.

LIKENIT

 

2001 is when the PI (Power Improved) heads came out. It increased horsepower to 310 and torque to 425 ft lbs.

 

What kind of mileage do you get with a gear splitter?

 

I am pleased with my mileage. If i run around town (small town) on short trips, I'm usually between 10-11. When the truck was relatively new, I made 2 trips 220 miles non-stop on 4 lane. Had the cruise set at 70 and no wind with 2 people aboard.
I was running in over-overdrive turning about 1850 rpm. I got 17.3 twice. Once, I had an opportunity to hold at 60 other than a few small towns for 140 miles and got 18.2. These are actually reads, not trip computer. I always completely fill when I check. I have tonurse the last 5 gallons in, as italways trips the pump with about 5 gallons left to go.
The last few years I have not been able to do better than between 15-16 on similar trips.
Towing, I used to be around 8.5 to 9.5 towing a 5th wheel with a CGVW of 17,000. I try to hold at 60 and am easy on the foot. I now have a new 5th wheel with a GCVW of around 21,000 to 21,500 from actual wgts on scales. I have usually been between 8-9, with lows of 7.3 and a high of 9.4. I just made a 90 mile trip that came out at 6.4 which is way out of my normal range in the past. I'm still trying to figure that one out. Can't wait until my next tow after the 3 weeks we will be at our present spot. We are fulltimers.
I love the Gear Vendors. It not only aids in towing, but puts some fun back in driving with a "Slush" box.
LIKENIT

 

To help you answer you question I would have you Google up Horsepower and Torque. During your search you find the difference between the two. HP is a measure of torque output over time. You also need to learn how HP is determined. HP = trq x rpm / 5252. HP is a mathematical figure. Torque is for real.

During your reading adventure I'm sure the light bulb will go off over your head like it did for all us here who already know that stuff. Once it goes off...beware...your search for more knowledge on the subject will not cease.

Oh and put simply; More torque makes you quicker, more horsepower makes you faster.

 

Monsta,

Thanks for the suggestion. I want to go quickly as fast as I can under 60 up steep hills with a big load. I have not been able to comprehend how running at rpm's that are causing a decline in max H.P. & torque would be advantageous.

LIKENIT

 

Well listen HP peak on the V10 is stated to be 4250. Anything over that and you're wasting your (its?) breath.

BTW, the torque will always decline as the revs rise; to certain point (based on engine design parameters and about a jillion other things).

Here's anothe rHP / TRQ analogy.

Look at this guys. He embodies torque.



These guys show HP. They have the ability to do work (run) over a long period of time. Notice how different their bodies are from the torque dude? Almost like diesel vs gas, huh?





You don't need cubes (per se) to get HP. Just look at my next motorcycle

.

190HP out of 1352cc! That's 1.4 liters (rounded up)! Imagine if our V10 with it's 6.8L of displacement had that kind of output! We'd have 921.5HP! Holy crap! How does that kinda of power come out of 1.352 liters? REVS. The things revs to TWICE our redline.

So revs make HP. So go read to find out how torque is actually produced. I wouldn't want to spoil all the fun. And keep your RPMs below 4300 when pulling anything else is kinda a waste. Where it can become important is the shift. If you need to go above the HP peak so that when it shifts it will be in an optimum RPM well...that's what that "extra" part of the rev range is for.

 

And can take twice as much gear.

By the way, don't start talking out loud about torque and HP after you find the real truth.

People won't believe you.

--

What's worse? Get into the part where motor spinup (rotational weight) becomes crutial and you can't describe that with the terms "HP" or "torque".

More confusion? Some (many?) chassis dynos rely on timing how fast your vehicle can spin up (accelerate) a drum that has a fixed weight. "HP" becomes a measurement of "work" by describing how fast an engine (and drivetrain) can spin up that weight.

While the actual mathematical definition of "HP" is torque-vs-speed. Like Monsta said, HP=torque*RPM/5252 (Horsepower equals torque times RPM divided by 5252).

So, the term "HP" used by the manufacturers is not the same "HP" that many chassis dynos produce. Likewise, the "torque" from a chassis dyno is interpolated by taking the measured "HP", multipying by 5252 and dividing by engine RPM.

Now, there are two types of dynos - ones that do the "fixed weight" thing, and the other type that actually "brakes" the rear wheels and figures out the actual TORQUE and basically interpolates HP.

In the "fixed weight" setup, HP will increase whenever you lighten up a spinning component - driveshaft, wheels, tires, flywheel, mechanical fan, water pump, etc.

In the "brake" type setup, those things won't be as noticable in terms of "HP". If at all.

--

So, some people consider "HP" to be a measurement of acceleration.

It's not. But on certain dynos, "HP" does mean acceleration.

On others, it's just a term to describe the speed AND torque of the rear wheels.

An elusive distinction, to say the least.

 

Awww man I didn't want to get into torque yet.

 

No, 2000 is when the PI heads came out!!!!

 

Thanks again for all the help. I'm a bit attention deficet disorder and have had some mini-strokes, so I sometimes find it hard to comprehend this stuff. I need a Ram upgrade in my memory and more torque and H.P.
From what all of you have said, it sounds like I should not push beyond about 4000 rpm because that is the point where my H.P. curve is starting to drop. It also looks like the new V-10 hits a point of diminishing returns at 4750 RPM.
The other question I've had was where do you try to run for the best mpg based on torque and h.p.?

Thanks, LIKENIT

 

Holy crap - this ***** is getting deep. Some of y'all take your 'hobbies' too far or have way too much time on your hands... but the rest of us really appreicate it. At least I know I do. Sometimes I can sit and read stuff like this for hours and still be unclear, so it's nice to see some of the analogies to put it in perspective.

 

I personally get the best mileage when I run at about 60-65mph. I'm turning at about 1900 rpms at this speed. I tried once at 55mph and noticed that my mileage went down a little even though it didn't downshift nearly as much which confuses the hell out of me. Whats your take on the Krewat?