Let's do this:

Put a 500 lbs weight on the end of a rope, hanging from a pulley on the ceiling. The other end of the rope goes to a pulley that is powered by a fluid coupling like a torque converter.

Exerting 500 ft/lbs of torque, the weight will not move.

Exert 501ft/lbs of torque, the weight starts moving. The more torque you put into it, the faster it excellerates.

If you were to put 1000ft/lbs of torque into the pulley, the weight would accelerate straight up at 1G. 500 ft/lbs to hold against gravity, and then 500ft/lbs extra against a 500lbs weight, that's 1G.

Now, do that on the ground, with a vehicle, with an imaginary 2ft diameter (1ft radius) rear tire. The vehicle weighs 1000lbs. Put 1000ft/lbs into the rear tires, you accelerate at 1G, since we don't have to overcome gravity.

No where in there is HP.

HP is a direct function of torque vs. time (RPM). The difference between 380ft/lbs at 1500RPM and 380ft/lbs at 4000RPM is nil. The vehicle will not accelerate any faster based on what RPM the motor is revving at. It will accelerate in direct proportion to the amount of torque being applied at whatever RPM you happen to be at. A flat-torque curve motor like the diesel or the V10 will not accelerate any faster at 2000RPM in 3rd gear than 4000RPM in 3rd gear. The motor is putting out more "HP" but it isn't moving the vehicle any faster than it did at 2000RPM.

Now, you can't just look at a torque curve and have that be a direct correlation to acceleration though.

You have to take into account rotational losses from the crankshaft, tranny, etc. It takes a certain amount of torque to accelerate the crankshaft at a certain speed. That amount of torque doesn't make it to the ground.

This is the reason lots of diesels (stock) don't do so well in empty drag-races against gassers. The gasser's lighter internals help it to spin up faster. Once chipped, the diesels overcome that little bit of extra weight though

OH, and before anyone jumps on me, I kinda stuck a trick thing in there.

A component of acceleration is time. Oh, there's that stupid HP thing again

 

Well Fred,

That is about the best post I have seen penned (typed, etc) in this section of the forum. Thanks for posting it-it is basically what I have thought for some time but lacked the mental batteries to put it in words.

I make a motion that this last post of Fred's be put at the top of the V10 section as a "sticky" for everybody to read before posting here! Especially the trolls that crawl in here from time to time.

I dumped two 4x4 1/2 tons before buying my V10 F250. An '01 Chevy 5.3L with awful CSK and a 2000 Dodge Ram 1500 with a 318 that had a list of issues too long to go into now. But I had the notion that the Ford V10 was a "pig" based on listening to banter from various diesel heads I know locally. Luckily an old timer who's a customer of mine recommended "taking a 3/4t Ford V10 for a spin" before deciding on a another truck and the the rest is history. And I finally have a truck that I didn't feel compelled to dump before one year of ownership!

 

Krewat is essentially "canceling out" the time aspect. Or converting the HP back into torque at the axle shaft. Since the tire on the gasser is presumed to be the same diameter as the diesel, the "lever" on the end of the axle shaft is the same for both (half the tire height). Assuming both are rolling at the same road speed, the axle shafts must also turn at the same rpms in both situations.

- Have two equally laden trucks rolling down the road at the same speeds.
- To do that, each has to exert the same linear force at the tire to propel the truck forward.
- Since both tires are the same height, the "lever" is the same distance from the axle centerline.
- Thus, each truck has to exert the same torque on the axle shaft.

How many rpm the engine and driveshaft spin at are dependent on the gearing in the differential and the gears in the transmission.

Carried to an extreme case, suppose some engine makes only 100ft-lbs of torque but it needs to pull the same as the V10 Krewat listed. For round numbers, let's use the following:
"2002 V10 w/4.30 (340 ft/lbs) wo/OD = 1462"
That 1462ft-lbs is arrived at by multiplying the 340ft-lbs by the transmission ratio (1:1) and the axle ratio (4.30:1).
To keep pace, the 100ft-lbs engine will have to exert that same 1462 ft-lbs at the axle shaft. For the sake of simplicity, suppose it works through the same 1:1 transmission ratio and all the gearing has to be achieved in the differential. That means the rear axle must have a 14.62:1 gear set. If the V10 was spinning at ~2500rpm, then our little engine would have to spin at (14.62/4.30) times the 2500rpm which means 8500rpm from our little motor.

Working at it from the HP side, each engine produces the same power but at vastly different rpms.

HP= (Torque x RPM)/5252

V10:
HP= (340 x 2500)/5252 = 162hp

little engine:
HP= (100 x 8500)/5252 = 162hp

The shape of the torque/power curves are more important than the peak numbers. In the case of our little engine, it's a peaky bastid that probably wouldn't make a good towing engine. The power curve for an engine like that looks good in a tiny sports car but terrible in a big truck.

The gas V10 can be geared to put the same (or more)power to the ground as the diesel. It just takes more revs and uses more fuel.

Lastly, imagine you can get your truck with a constantly variable transmission (CVT) that will infinitely adjust the gear ratio to keep the engine at an rpm that matches the required load. In that case, the engine with the highest peak horsepower number always wins.