Torque vs. Horsepower, who gets it?

[QC]

Re: Torque vs. Horsepower, who gets it?

Sorry Bert, I guess it is still analogous, but sorry this is monopolizing your thread right now. Maybe this will help . . .

This is a horsepower, fuel and torque chart from a little 150 bhp Cummins marine engine. It compares a Propeller Load Curve, the power required, vs. what is available. The relatively straight lines on the bottom of each is what the prop requires, the curvy line above is what is available in hp, torque and then the associated fuel. Oh, oh, you can double or triple every number on the chart and be able to consider a 300 or 450 hp example. The differences are not even rounding errors in regards to this discussion.

This illustration is essentially the same for gasoline and diesel except the max available curves at low RPM are not as far apart. Yes, less torque. But here's the whole flippin' point. How are you going to use that additional available power? Upshift? No, can't do that. Go climb a hill? Well I guess there are lots of little ones that we call waves, but there is no place on the water to sustain a "lug" that would allow you to utilize that extra, reserve power. Just a reminder, we are talking boats here. One gear, and no hills.

The bottom lines leave out one thing, the higher load at the point of getting the boat up on plane, and of course that ius different for every hull and why it is excluded. Regardless, I assert in the case of a displacement hull that does not come into play at all, and in the case of a semi-displacement hull (Bert's) it is minimal. So if the propeller only needs X amount to go, and the engine has more power than that is required (say at 2000 RPM) what do we get if we have more torque there? One thing . . . better acceleration. Has Bert mentioned acceleration as his concern? If I missed it sorry, but what I think he wants is more speed and less noise. For me that says turbocharger (natural muffler) or, has Bert has determined, a regular, smaller, lighter, every day, conservatively rated small block with twice as much power as he has now Great choice.

 

[g1sammons]

Re: Torque vs. Horsepower, who gets it?

Qc
This wasn't a attack rather a explnation
What I'm trying to explain is that a engine doesn't make horse power
Rather it makes torque that's it
Horse power is a measure of the torque over a period of time

Quite some time ago there Was a fella named watts
He observerd and published our standards of horsepower
He noticed that a horse could lift 550 lbs at a rate of 1 ft per second
33,000 lbs per min and so on
Now that's were the time comes into this factor
If you measure I ft off the crank then measure I reveluation you get 6.2832
Now remember that's watts said 550 ft-lbs per second or 33,000 per min
Since we are measuring rpm now we will use the 33,000 Devide it by our 6.2832 and we get 5252 rpm at which is where your h

Your hp forumla is horsepower = torque*rpm/5252
A engines produces torques you multiply that times you rpm and Devide it by 5252 and you have your hp rating

But like I said what did the engine do?

Now do you see what I'm saying

If you do the math or research you can verify all of this




This is where your rpm factor comes into play

 

[g1sammons]

Re: Torque vs. Horsepower, who gets it?

Now what the boat needs i don't know I'm strictly talking about
What engines make which is torque
Y'all know more about the boat side of this and what it needs than I ever will
But just trying to help folks understand what engines really do
I hear so many people talk about torque does this and hp does that

I'm not trying to say any one is wrong or anything like that
Just trying to explain what some of us miss understand
A simple explanation is that torque is what a engine makes and horsepower is a measure of work that the torque can do in a given amour of time
So you can't measure how fast hp will make you go when it's already a measure of what can be done
And when it comes to engines you never need more or less hp rather it should be more or lesss torque or even a torque in a broader rpm range

 

[QC]

Re: Torque vs. Horsepower, who gets it?

OMG :facepalm:

 

[scipper77]

Re: Torque vs. Horsepower, who gets it?

OMG :facepalm:

Lol.
I'd like to take this one QC but appearantly you and myself are the only ones in this thread able to understand the difference between torque and hp. Oh beck ill try again anyways.

This description does not really use the definitions of torque and hp but I think its a good view.

Think of torque as how far you can push something in one revolution. Now think of hp as that distance times the number of revolutions. If an engine has half the turque but can spin at more than twice the rpm's it will push something further in the same amount of time. Distance over time is the definition of speed (i.e. miles per hour). I don't know what is so hard to understand about torque/hp relationship. Of course QC and myself do have engineering backgrounds so maybe I am assuming we all understand things the same way.

 

[g1sammons]

Re: Torque vs. Horsepower, who gets it?

Torque is not how far you can push it rather how hard you can push it

 

[g1sammons]

Re: Torque vs. Horsepower, who gets it?

Hp is how far you can push it in a given amount of time

 

[scipper77]

Re: Torque vs. Horsepower, who gets it?

Torque is not how far you can push it rather how hard you can push it

I do not wish to argue. My whole point is that torque is only one component here. From an energy perspective a force alone does not do any work. My but is applying a force to the couch right now but believe me no work is being done. I will reluctantly stand by my previous post where I (as you point out) defined torque incorrectly. The reason I like that description is because it shows that torque does not equal hp. You can have a motor with less torque that makes more hp.

QC. If you want to delete the latest round of torque debates I will not take any offense. It just frustrates me that I understend this situation but can not describe it in a non technical way. (or I would have just posted the definitions of torque and hp in the first place).

 

[g1sammons]

Re: Torque vs. Horsepower, who gets it?

Think it's great that your both engineers
Would like you to know that I'm no dumb *** my self
And the info I'm giving you is not just some crap I'm making up
What's y'all keep telling me or everyone is you need more hp
Well I'm telling you that engines don't make hp rather it's a measure of the torque they make over a given time
Hp doesn't get anything done !
It's a measure of what got done"
So tell me where I'm wrong
If your pushing your boat with yourself meaning your legs and you want to go faster
You have to push harder. Pushing harder is what?
T o r q u e

 

[QC]

Re: Torque vs. Horsepower, who gets it?

Moved all of this over from the other thread . . . unfair to Bert, and belongs over here.

 

[g1sammons]

Re: Torque vs. Horsepower, who gets it?

Qc And the skipper
There are numerous articles on the web To support this
But if you have a force pushing you forward you will accelerate until the force pushing from wind and water is equal to the amount pushing forward the your speed will hold at a constant
Now we all know that as the rpm range goes up the hp always goes up even as torque falls
The hp rating goes up but untillnyou have more force to overcome those holding you at that speed you will not accelerate any faster
Thus is the basisbfor my argument
The force pushing you forward is torque
And in anything car boat plane your acceleration will steady when the torque be produced is met with a equal force and this cannont be overcome with hp but only more torque

 

[scipper77]

Re: Torque vs. Horsepower, who gets it?

Torque = force * distance ( a rotational force or "moment", which is a force acting at a distance.)

HP = Power

http://upload.wikimedia.org/wikipedia/en/math/0/2/2/022fd30474af9bf8c407992118eaabb2.png

I'm done here. g1sammons, I'm not trying to make you or anyone look bad. To say that a motor only produces torque is just not true. I'm not going to prove you wrong, and I have no interest in being right at this point. I was just trying to give real world examples of when torque is important in a motor and when HP is important. They are separate entities.

 

[HT32BSX115]

Re: Torque vs. Horsepower, who gets it?

6.2L specs according to Wikipedia:

• Horsepower / Torque (at start): 130 hp (97 kW) @ 3,600 rpm / 240 lb?ft (325 N?m) @ 2,000 rpm
• Horsepower / Torque (at final): 143 hp (107 kW) @ 3,600 rpm / 257 lb?ft (348 N?m) @ 2,000 rpm
• Horsepower / Torque (army): 165 hp (123 kW) @ 3,600 rpm / 330 lb?ft (447 N?m) @ 2,100 rpm

Regardless of how you define HP/torque, a 28ft boat with the above engine installed WAS/IS seriously UNDER-powered!!

He could install a 6.5L TD engine

They are available.....I think I indicated this in his first post asking about them.....
http://www.peninsulardiesel.com/WP-PENTEST/?page_id=222

But to make it produce the kind of HP required, it MUST be turbocharged AND intercooled and MUST be rebuilt with 18:1 pistons use closed cooling and have a huge raw water pump!!....... The above engine uses a modified DB-2 injection pump. Someone said earlier said that the 6.5's only come with an electronic pump? The truck engines do. No one uses them in a boat. They go to the above mechanical pump.

Also, Berts boat is SERIOUSLY OVER PROPPED if it would only turn 2600 RPM at WOT

I don't know if he tried WOT, but that's the FIRST thing I would have done.

If it rolled a cloud of smoke at WOT, and only turned 2600-2800 or maybe 3000 RPM (which I suspect) , then I would have put a lower pitch prop on it. NEXT!

The same PROP rpm rules apply REGARDLESS of what's turning it (diesel, gas, electric motors, steam engines, or chipmunks!!)

The gear ratio of his transmission also comes into play here. If it's too low or too high, you're not able to operate the propeller at it's most efficient RPM. That transmission was for a gasoline engine (SBC) which wants to run at MUCH higher RPM.


That 6.5 diesel above is coupled to a Bravo III drive that is probably a 1.36:1 ratio. Bravo III's in BIG boats connected to small or big block gas engines typically are 2.00:1 and 2.20:1 (mine is a 1.81:1 drive, but my boat is only 21ft long)


This is really NOT a HP/torque argument other than there simply wasn't "ENOUGH"!!



Cheers,


Rick

 

[g1sammons]

Re: Torque vs. Horsepower, who gets it?

Skipper
I love a good arguement
But also not trying to make anyone look bad
But the wife just said it as simple as it gets
By definition torque is a force and horse power is a unit of measurement
Horsepower is a measurement of how much work torque can do in a given amount of time
At least the horse power we are talking about
There are many other types
If horse power is a measurement of the torque at hand the horse power is not working it's a measure of work being done
Meaning it's not doing anything rather it's a measure of what's being done
The work is being done by the force which is torque
If I'm wrong I would love to know because year and years of me chassing better torque values have been wasted

 

[g1sammons]

Re: Torque vs. Horsepower, who gets it?

Just look at the specs for the 6.2 above as you notice the hp rating goes up past 2500 but
As stated top rpm for wot was 2500
The hp is greater at 3500 but the boat won't push past 2500
Tell me why
It's simple torque is the force at hand and the horse power is nothing more than a measurement of that torque for a lenth of time

 

[Luhrs28]

Re: Torque vs. Horsepower, who gets it?

I agree with what HT32 said. The boat was seriously underpowered and overpropped. That's why when it maxed out at 2500 RPM I didn't go pushing the throttle any further, 'cause I didn't want to just keep injecting more and more fuel and damage the engine.

I know I could've hauled her and changed props, but it cruised real nice at 1800 RPM so I decided to just go the rest of the summer that way and change the engine over the winter.

I checked into the 6.5 turbo. It's a lot more expensive and complicated to install, and the 6.5 also has a reputation for cracking blocks around the main bearing webs.

The 5.7 gasser is the simplest and least expensive route to decent HP. (I'd include Chrysler in there also if they were still active in the marine engine business, but they're not)

Bert

 

[joewithaboat]

Re: Torque vs. Horsepower, who gets it?

I know from living at the drag strip for 15 years and observing in dyno rooms and chassis dyno's that torque gets things moving and horse power keeps them moving. If you concentrate on the things that build torque and set the car to operate to take advantage of that, you will ultimately loose to the man that is doing the opposite. Big horse power wins races, big torque get left behind. The only time i have seen folks concentrate on torque is for towing. So if you need to get a big heavy boat on plane, fine but the hp is still going to keep it there.

I have seen people try to gear a boat to operate near peak torque, with the drive ratio and prop, to run fast. The result was a ill handling boat very sensitive to prop blow out and such. A much smaller ci motor with less torque but similar hp at a higher rpm went faster. Same boat.

All i know for sure is that they are the same at 5,252rpm
My .02

 

[QC]

Re: Torque vs. Horsepower, who gets it?

Hp doesn't get anything done !

Uh, nope . . .

So tell me where I'm wrong

First quote box ^^^^^^^^

A couple of things here . . . I am not an engineer. Our Chief Technology Officer always says that I am an engineer trapped in a salesman's body, and I say he is a salesman trapped in an engineer's body. Together we are a fairly powerful force, uh, I mean torque . . . Pah, duh, duh, chish . . .

I always post on this topic for three reasons:

1) It is so misunderstood,

2) People actually believe what they read here, and

3) There is an assumption that all applications are the same. Especially automotive and marine here. They are not!

You could argue that some of this is simply semantics. I would suggest on a written forum semantics are all we have. The fact is that good torque rise (high peak torque value vs. torque at rated RPM) make wheeled vehicles more drivable. It does not give the same advantage to marine. And high peak torque is even less important to a fixed load like a water pump or compressor, and also different for a generator drive engine.

 

[John_S]

Re: Torque vs. Horsepower, who gets it?

A couple of things here . . . I am not an engineer. Our Chief Technology Officer always says that I am an engineer trapped in a salesman's body, and I say he is a salesman trapped in an engineer's body. Together we are a fairly powerful force, uh, I mean torque . . . Pah, duh, duh, chish . . .

And you said "torque by itself is just work with an infinite amount of time to get it done."

Sounds like a couple of guys milking the job to me!

 

[Don S]

Re: Torque vs. Horsepower, who gets it?

Until one understands how Torque, HP, WOT rpm, gear ratio, and prop size all work together, then they just don't understand boats.