The torque's non existing influence on cutting speed.

[SmokinDodge]

Hopefully it's not a NV4500.

01 with the 5600 with 4.10's. That should be the definition of "Torque"

 

[peter399]

Wow. Coming back after 24 hours I find 80 replies in my thread. Not bad!
Maybe it will end up like the "Prince of saws" thread.

It's true that for chainsaws that lacks gearbox it's a bit tricky since you can't change the ratio during operation.
But: Two saws, same hp, one "torquier" than the other having a race. Rpm drops. What happens? Well, the torquier engine continues cutting...... because????? Answer: It now has more POWER = Horsepowers than the non torquier engine. Power is the physical unit that performs the work. Torque is not. The engine torque gives you an idea of the engine's character (rpm at peak power) The higher the engine torque the lower the rpm at it's max power.

So, here comes the big truth:
What you want for highest cutting capacity, car/bike acceleration is:
As big surface as possible in the graph with power on the Y-axis and rpm on the X-axis. (Intergral of power curve from rpm1 to rpm2). So the engine rated at the highest power will always win when it's operated in the correct power band.

My intentions with this thread was to kill untrue statesment like the one I mentioned: My saw cuts fast because it has a lot of torque. NO, it's because it has much power.

/Peter

 

[blis]

.........

But: Two saws, same hp, one "torquier" than the other having a race. Rpm drops. What happens? Well, the torquier engine continues cutting...... because????? Answer: It now has more POWER = Horsepowers than the non torquier engine. Power is the physical unit that performs the work. Torque is not. The engine torque gives you an idea of the engine's character (rpm at peak power) The higher the engine torque the lower the rpm at it's max power.

..........

/Peter

that isnt necesarily true, torquer engine may have its peak power higher than not so torquey saw....

 

[deezulsmoke]

01 with the 5600 with 4.10's. That should be the definition of "Torque"

Oh I soooooo agree :hmm3grin2orange: My little inline six cylinder is only pushing around 425 hp with 850 ft-lbs of torque.

 

[peter399]

that isnt necesarily true, torquer engine may have its peak power higher than not so torquey saw....

Only if it also has more peak power.

/Peter

 

[chowdozer]

Wow. Coming back after 24 hours I find 80 replies in my thread. Not bad!
Maybe it will end up like the "Prince of saws" thread.

It's true that for chainsaws that lacks gearbox it's a bit tricky since you can't change the ratio during operation.
But: Two saws, same hp, one "torquier" than the other having a race. Rpm drops. What happens? Well, the torquier engine continues cutting...... because????? Answer: It now has more POWER = Horsepowers than the non torquier engine. Power is the physical unit that performs the work. Torque is not. The engine torque gives you an idea of the engine's character (rpm at peak power) The higher the engine torque the lower the rpm at it's max power.

So, here comes the big truth:
What you want for highest cutting capacity, car/bike acceleration is:
As big surface as possible in the graph with power on the Y-axis and rpm on the X-axis. (Intergral of power curve from rpm1 to rpm2). So the engine rated at the highest power will always win when it's operated in the correct power band.

My intentions with this thread was to kill untrue statesment like the one I mentioned: My saw cuts fast because it has a lot of torque. NO, it's because it has much power.

/Peter

That I know of, no one one here has ever claimed their saw cuts fast because it has torque. Maybe you could point out some examples?

 

[timberwolf]

Yes, my saw cuts fast, because it has lots of torque at a high RPM.


----------------------------------------------------------
Man only hears what he wants and dismisses the rest.

 

[chowdozer]

Yes, my saw cuts fast, because it has lots of torque at a high RPM.


----------------------------------------------------------
Man only hears what he wants and dismisses the rest.

Hey Timberwolf,

 

[Freakingstang]

Only if it also has more peak power.

/Peter

No. Why are you stuck on this?


I'll try to give a real world example.

The motor in one of my mustangs produce only 312 RWHP (rear wheel HP), but almost 350 lb/ft of TORQUE (at the rear wheels)

Why is it faster than my buddies car that makes 320 HP, but only 305 lb/ft of torque?

He has more power, but a shallower torque band, or power curve. Why is his torque output so low?

Granted, his setup isn't ideal, as it he run nitrous on it, and the tuning is completely differant, as the engine build is too. Without nitrous, the thing is a pig. You can't stereotype all engines and power curves. Torque is what starts the work being done, and HP is what keeps the work being done.

I'll stick by by statements on here that the 7900 is a torquier saw than other saws in the same class :help:

Show me some dyno sheets of a bunch of saws and will figure it out instead of just thinking about it. Just because torque and HP meet at 5250, it doesn't have any affect on total HP or torque produced.

 

[timberwolf]

Steve, take his engine, put in a 500lb lighter car with a more areodynamic shape, and it may be faster.

Three things, peek torque, peek HP, and net HP.

If we take the moving car as an example the real work being done is moving the car at the maximum speed, this has no direct relationship to peek torque, and is very unlikely to have any relation to the peek HP the engine on its own shows on a dyno, but it is directly related to the net HP.

That is the point in a car where the hp curve reaches equilibrium with rolling and air resistance. So at that point if the car slows, the engine will gain power and work to accelerate the car back to that speed, also friction would go down to assist that, if the car was to speed up, the engine would start to produce less hp and air resistance would go up, so again it would return to that equilibrium.

Samething with a saw. WOT RPM is the point where the engine HP and friction/acceleration losses meet, this point is well beyond max HP. In the cut RPM is where the engine is loaded idealy to the maximum HP point, this is above peek torque. The trick is to find the balance, the highest net HP, higher RPM = more HP and greater chain speed, which has the potential to do the most work, however system losses are also higher and climbing fast.

This is where torque is very importaint.

Take a saw cutting up in the 13k range, if HP is increased by torque alone, the saw will cut faster, by being able to push harder, set rakers lower..., this will increase bar friction but as a direct relatiopnship, and will not affect losses due to chain acceleration. Now take the same saw and make the same HP gain, but this time do it by increasing RPM. In this case both friction and acceleration losses go up on the square and even though the engine is putting out more power, it may gain little, nothing or even show a loss when net HP is evaluated.

 

[Monkeyhanger]

I'll try to give a real world example.

The motor in one of my mustangs produce only 312 RWHP (rear wheel HP), but almost 350 lb/ft of TORQUE (at the rear wheels)

Why is it faster than my buddies car that makes 320 HP, but only 305 lb/ft of torque?

He has more power, but a shallower torque band, or power curve. Why is his torque output so low?

Hi,

that reminds me of the situation comparing my motorbike with my son-in-laws bike. I have a GSF600 inline-4 78HP@10500 54Nm@9500 220kg and he has a SV650 V-twin 71HP@9000 62Nm@7400 193kg.

On the roads he has better accelleration and "pulling power" when overtaking. I have a slightly higher top speed. Generally however his bike is faster (with rider they weigh the same ). I have to change gears all the time to keep up, I think that is what you might call the result of a narrow powerband.

His "torquier" bike wipes the floor with my higher HP bike (I know they are only small engines) on everything but topspeed and even there it's only maybe 5 to 10 kmh difference depending on whose bike was most recently serviced...

Bye

 

[Woodie]

The engine torque gives you an idea of the engine's character (rpm at peak power) The higher the engine torque the lower the rpm at it's max power.

There is a basic misunderstanding you have here, and that is the fact that your "power" is nothing more than an artificially derived unit of measure. The fact that you don't understand this is made even more clear by the last line of your above quote. There is no ONE torque number for an engine, torque is measured along the usable RPM range for an engine...this is the torque curve. A dynamometer cannot "measure" horsepower, but it CAN measure torque. It measures it at given speeds, then it DERIVES the horsepower. TORQUE is measured, HP is derived.

Think of it this way...torque comes first, HP comes second, and you only get HP by measuring torque, recording the speed, and punching them in to a calculator.

 

[Woodie]

Yes, my saw cuts fast, because it has lots of torque at a high RPM.

This is the clearest example yet of the whole concept.

 

[timberwolf]

for post 92

 

[ShoerFast]

Hi,

that reminds me of the situation comparing my motorbike with my son-in-laws bike. I have a GSF600 inline-4 78HP@10500 54Nm@9500 220kg and he has a SV650 V-twin 71HP@9000 62Nm@7400 193kg.

On the roads he has better accelleration and "pulling power" when overtaking. I have a slightly higher top speed. Generally however his bike is faster (with rider they weigh the same ). I have to change gears all the time to keep up, I think that is what you might call the result of a narrow powerband.

His "torquier" bike wipes the floor with my higher HP bike (I know they are only small engines) on everything but topspeed and even there it's only maybe 5 to 10 kmh difference depending on whose bike was most recently serviced...

Bye

Simple design changes can have a lot to do with how an engine performs, ignition timing, combustion chamber shape, degrees and angle of effective power stroke, duration and timing of exhaust, duration and timing of intake, even the the way an engine handles a loads that effects the effective cylinder pressures to the type of fuel burned .

There is a chance that the "V" twin is designed to hold longer exhaust duration, more effective - longer power stroke durations , allowing the engine to get more out of each time it fires and more work out of the heat increase of heaver loads.

It seems that engines designed for higher rpm's change gears a lot, while engines designed for heaver loads change lanes!

 

[ShoerFast]

There is a basic misunderstanding you have here, and that is the fact that your "power" is nothing more than an artificially derived unit of measure. The fact that you don't understand this is made even more clear by the last line of your above quote. There is no ONE torque number for an engine, torque is measured along the usable RPM range for an engine...this is the torque curve. A dynamometer cannot "measure" horsepower, but it CAN measure torque. It measures it at given speeds, then it DERIVES the horsepower. TORQUE is measured, HP is derived.

Think of it this way...torque comes first, HP comes second, and you only get HP by measuring torque, recording the speed, and punching them in to a calculator.

Yes and combining the two! But a dyno can do the math, this problem is nothing new, how many cups of truck stop coffee were poured over this question?

The S.A.E and may other organizations standardized test, on of the better is adding the term and the word of the day, "Brake Horsepower" or :

abbr. bhp or b.hp. The actual or useful horsepower of an engine, usually determined from the force exerted on a friction brake or dynamometer connected to the drive shaft.

 

[Luke]

Thanks Wood Newbie

I normally don't post much, but if I got started on this I might not stop. Its all torque. How high of an RPM can you make your torque so that you can get the most "work" (physics definition) done is the challenge.

 

[ShoerFast]

Anyone ever see those rip-off air filter gizmos called the Volcano?

Or watch there rip-offomomercial?

In there commercial, it shows a car running on a Clayton dyno, I ran a lot of cars on Clayton's, so I caught this!

They show this car pulling like 115 BHP @ 55 mph (or something, the hp was not important) then simply twist in there air-gizmo and wahla, reran the car and it has an instant 135 hp,,,,,,, at 65mph!

What happened, they fallowed two different tests, the first one, they tighten the dyno till the speed topped @ 55mph, in the second test, they cheated, giving a 10mph difference, and showed the gain, (you can also see the MPH gauge). Oldest dyno trick in the books.

I would bet any amount of beer that run the same test, same speed, before and after , the Volcano - gizmo took away power?

 

[paulkx5]

I like both:biggrinbounce2: For me it just depends on the application. If its speed I'm after, give me big HP and lots or RPM, and a lot of gears. Heavy / slow work to be done, give me killer torque at a low RPM (turbo diesel please).

Wait, maybe I am conflicted, sometimes I have a hard time trying to decide whether to ride the CR250, or the KX500.

 

[Jim Mesthene]

... a dyno can do the math

Not really. A dyno measures torque. Then the operator applies his favorite mathematical formula to translate it into horsepower.