just curious....who here has driven a motor with say 425HP @ 2200RPM and 1450lbs tq at say 1200RPM?

and who here has driven say a 500HP motor with lets say 1100lbs of torque?

I've driven both with similar loads, once up to speed 425HP and 1450lbs of tq beats 500HP and 1100lbs of torque to the top of the hill any day of the week.

 

If shaft is turning there is tq. If force is appylied there's tq. An engine isn't going to be turning with out tq.
A man some years ago smarter than me said hmmm tq is force in a twisting motion. Alittle while later he thought wow great how can I measure it. He grabbed a 1 breaker foot bar and socket and applied his body weight to bar on a bolt and so it was 165 ftlb was applied. The bolt didn't break non the less tq/force was there. That's just the way it is.

 

His last post in the thread from earlier today.
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Texas450
Senior User
Garage is empty, add now </td> <td width="100%"> </td> <td nowrap="nowrap" valign="top"> Join Date: Aug 2010
Posts: 212



</td> </tr> </tbody></table> Update since 9-1-10
Miles 71051
Saved $9236.63
Paid 25k for the truck not to bad

He put those miles on his truck since August 2010. For that kind of savings, wouldn't you at least consider an EGR delete? Some states are more strict on emissions than others. Being he's running an F450, I doubt many DOT guys could figure out if the EGR has been disconnected or not. I don't know of a single one that will climb under your truck (an F450 or so) for an inspection. I just had one done last week.

 

I am certainly not going to come on here and tell you that you didn't do something you say you did. But if you have the time, I would love for you to explain to me how it was possible. I'll start you off with some example numbers:

Let's start with the 500 HP truck. Assume it has 1048 engine ft. lbs., a 4.10 rear end, and 33 inch tires. Going 60 mph, the wheels are turning 611 rpm.

Now in 4th gear the engine is turning 2505 rpm, and it's producing the full 1048 ft. lbs.

(2505 x 1048) / 5252 = 500 HP at the crank.

That's 4297 ft/lbs at the rear axle, turning 611 rpm.

(4297 x 611) / 5252 = 500 HP at the rear wheels.

Now pluck out the 500 HP motor, and drop in the 425 HP motor. The truck is still going 60 mph, with the same load, so you will have the same rear-wheel torque and the same rear-wheel speed. You can change the rear-end gearing and/or the tranny gearing all you want.

What do you change, in order to still get 500 HP at the rear wheels?

 

If there is no load applied, there is no torque. If you have an engine running on an engine stand, but the crank is not connected to anything, there is zero torque. Of course there are torque forces inside on the crank, in-between the crankshaft throws, but after the flywheel, if you don't have anything connected to it, the torque is zero.

Start to engage a clutch to drive a load, and you start to develop torque.

 

I drove tractor trailers for 10 years before switching to heavy equipment. The last two engines I was running were the 425hp Cat and the 444 HP Cummings. Now a days most of them are running 650 HP up this way.

 

funny you say that, the 2 engines I was referring to where the 425HP 3406B and the NTC 444HP Cummins.

The cat made more torque 1450ish the cummins made less....we had 2 and they where both turned up to about ~490 HP but they only put out 1200lbs of torque.

so basically the NTC 444 was like driving a V10....rev it to get to the HP and life wasn't to bad.....miss a gear and its over, get in behind a swift truck because you didn't have the torque to pull back out of the hole you fell in to.

With the CAT's..whole different story. miss a gear...so what, you could pick it back up whenever you felt like it.

yeha. HP is great...but when you need to get/keep a load moving EASILY....torque is a larger piece of the pie.

 

Yup, I found the Cat liked to be pulled down low on the hills. Let the rpm come right down and it would get down to a point where it would just lock in and pull like a mule. The 444 was a smoother more refined engine, but for pulling in the hills the 425 Cat was a beast. We were hauling molten sulfur in "B" trains running around 125,000 lbs loaded.

 

Indulge me. Got put a torque wrench on the crank on the engine on that engine stand. Set it ti click at 1 lb. Now turn it. Click. Keep adding until you don't get a click. It takes tq to lift them pistons, turn that cam, open close those intake valves. Just turning the crank. If your cruising at 1500 rpm then the engine is inputting x amout of tq to the transmission. The transmission outputs y tq to the rearend. The tranny is turning the the drive shaft. Takes tq to do it.

 

I'll raise the B.S. flag on that one. Bill was the ONLY one to make the towing statement. Go look in nearly every V10 towing/mpg/vs. thread and find many, many instances of "should have bought a psd" or "is not a diesel" or some B.S. to that effect. You guys have the soot in your eyes and continue to blow smoke up everyones a$$es 90% of the time. You must remember, about 50% of us gas owners went there because of a diesel. Personally, I wont ever look to Ford diesel again. Failure after failure you can expect with them. I have friends with dodges with over 400k on the clock and mine couldn't make it to 38k without several engine changes.


Arrogant aren't we?? How about the F650 that come standard with the 6.8L? Think that might be a problem? Hell, a PSD isn't even available in that truck, only 6.7L Cummins. One might say that the PSD might be "Medium duty" or even "Light duty" then????? Who knows........

 

Should have gotten a 7.3!

 

Yes, but when the engine is running on the stand with nothing connected to it, all of those torque values are inside of the engine, on the crankshaft between the individual cylinders, and on the crank between the cylinders and the flywheel. There's no torque on the output end of the shaft, which has nothing connected to it.

Envisioning this means getting your mind around the concept that you can have torque in part of a shaft, but no torque in other parts of the same shaft.

For instance, suppose you seriously overload an engine and wind up breaking the crankshaft. Where does it break? Somewhere between the pistons and the flywheel, right? It doesn't break in front of all of the pistons, where it's only driving the fan belt, as there is almost no load there, and thus almost no torque.

Yes it does, but in this example there is a load, and that's what I have been trying to say, you cannot have torque if you do not have any load.

 

youre not lookin at the big"ger" picture. you obviously understand your physics, however, youre overlookin the "range" at which the larger motor produces the 500 hp. if i could pull up two dyno charts with ease i would. . .but the semi motor, with and BECAUSE OF its massive available torque, produces an enormous amount of its 500 available hp, FROM IDLE TO REDLINE (just bein lazy with caps vs bold, not yelling). that bein said, my 500/1000 (yes wheel numbers measured by the rollers, not the rear axle) has to "make its way" to 500 hp via rpm. because, while my 1000 lb/ft of torque is a lot, im still pushin it through a 5.9. what this means in the real world, is, the 500 hp semi motor, BECAUSE OF ITS GREATER TORQUE OUTPUT, has 500 hp for a much longer time, giving it the ABILITY TO TOW MORE. a dyno chart of both would prove my point. you'd see the hp "curve" would hardly be a "curve". . .more like a flat line of available close-to-if-not-max hp from idle to redline, whereas mine starts much lower, and peaks at the 500 mark. thanks to its buddy, massive torque. meanwhile, the 5.9 works its ***** off just to reach that 500 hp mark with a load behind it, then, uhoh time to upshift and start all over again.

edit: in a nutshell; torque values, in conjunction with hp, are in an indicator of how much power is available, and where.

 

OK 89F2urd, I see the point you are making, and it is a good one. Believe me, I am not anti-diesel or anything like that. As I have said, I would rather tow with my 7.3 than with my significantly more powerful GMC, exactly because of the qualities you are talking about.

Now can we talk about your rear-wheel torque number for a second? I'd like to understand why it's only 1000 ft. lbs.

 

i actually just edited my above post for clarity on a few things, that was one of them. the rollers dont measure the torque placed on the axle by the wheels (at least on the dyno's ya drive onto), it only measures the torque that it sees in relation to the input data before and during the run (i.e. vehicle information and engine rpm). so, while the torque calculatoins you gave may be correct and the torque on the axle is 4000+ at 611 (which seems correct at such low rpm), the dyno reads the torque applied in relation to engine rpm, with the trans in 1:1 gear (1:1 crankshaft/output shaft of trans speed). it may even be so that it performs your very calculation on its own, spitting out the numbers in correlation with the engine speed itself (basically a conversion). but the entire test is based off engine speed, not axle speed. i could rig the speed sensors up to the axle instead of the crank and take the numbers that way and could then (perhaps) put 500/4000 rahp/tq in my sig.