Torque or Horsepower????

brycter · Oct 1, 2009

When we install a turbo on a sled do we feel torque or horse power? Everybody talks about horse power but shouldn't we talk about torque? because torque is what the turbo brings out of the motor.

What is you take on this?

RKT · Oct 1, 2009

brycter said:
When we install a turbo on a sled do we feel torque or horse power? Everybody talks about horse power but shouldn't we talk about torque? because torque is what the turbo brings out of the motor.

What is you take on this?

Torque is measured .. HP is calculated..

This question is one that get asked a lot..

IMO, the answer is quite simple..

You can not have HP without Torque.. It is impossible.. HP is calculated FROM TORQUE.. So, to state that one is felt more or is more important than the other does not make much sense.. They are both related, both connected... And neither is more important NOR more "felt" than the other..

HP is what ultimately gets you up the hill.. If you are clutched for peak torque, you will go lower on the hill, slower in the race and have a much harder time clutching the sled..

I wrote a tech article a while back addressing this very topic.

ALL are welcome to view it..

Keep in mind, this is all my opinion based on MY experieinces and knowledge in the field..

Here is the link to the article: http://www.2strokeheads.com/torque%20vs%20hp.htm

Kelsey

brycter · Oct 1, 2009

Good post kelesy. thanks for your imput. and a great read!

For a turbo to build more hp it has to create more torque first. A turbo is quite frankly a torque multiplier and then the rest will follow. The more boost the more torque the more hp. a boost level of 6 psi will increase torque by approx 40% over a astperated motor. At 10 psi of boost it should increase by approx 50%-54%. That is alot better when on the hill on on a long pull

Please correct me if i am wrong or if my words don't make sense. I would just like to get some knowledge out there about this topic. I think this is some of the basic that poeple need to understand.

brycter · Oct 1, 2009

Can you ever have a situation when torque falls or levels off and hp still rises?

gus bohne · Oct 2, 2009

Spin the object at any desired rpm and apply load, the resistance to to deceleration is measured as torque.

Can hp break a driveshaft ? No, torque is the twist force that is directly measureable .
Can hp be measured directly ? No, hp is a mythical mathmatic function.

Why do I say its mythical ?

When fulton designed and produced the steam engine , there became a need to (quantify ) the work that the powerplant could do.

At the time the best comparison was the powerplant they were hoping to replace,,,,,(the horse).

to compare, they developed a formula ( mythical as it may be ) to make a direct comparison.

Its nice to have big gaol, but to me, hp is a poster, of a cute chick.
Torque is what we harness to produce WORK.
Without torque there is no work as the spinning crank will stop quickly as there is no energy to maintain its velocity.

Note, I stated quickly,, any spinning objest has a quantity of inertia, stored inertai will be what is providing the resisitance to decellaeration if no torque is present..

2 cups of coffe

Gus
JMHO

And yes, as long as rpm rises faster than torque falls, the mythical hp fiqure will maintain or possiby e rise slightly before crumbling miserably.

DaveB · Oct 2, 2009

brycter said:
Can you ever have a situation when torque falls or levels off and hp still rises?

[T] = {5250 * [HP]} / [RPM]

200 hp @ 7700rpm = 136.36 tq
210 hp @ 8200rpm = 134.45 tq

winter brew · Oct 2, 2009

Good responses from RKT and Gus. A dyno cannot measure HP, it measures nothing but torque and is converted to HP. Then depending on which of many possible correction factors you can change the HP by quite a bit.

DaveB · Oct 2, 2009

I understand that TQ is measurable and has a unit of ft*lbs. But if HP is only calculated, then why do dyno runs continue past the reasonable TQ peak?

HP is the measure of WORK and CAN be measured. The unit Horse Power is a ficticious thing, but if you go to the actual measurement of work, which is a force applied over a time, the units are ft*lbs/sec or in metric, Watts or joules/sec.

Edit: I haven't taken a physics class in 25 yrs....so I might be out in left field....LOL

HPJUNKIE · Oct 2, 2009

I've always thought of it this way. TQ accelerates you & HP makes you go fast.....

RKT · Oct 2, 2009

Torque is the entity that does work to the crank train... Like stated above, HP is calculated from the torque...

My goal here is to NOT get into a huge Physics debate and keep it very simple.. Once the equations pop out..people generally lose interest..
In any case...The area under the toque curve or the "shape" of the curve is whatreally dictates the engine's personality and performance ..

If you have a very wide and flat TQ curve, then you have an engine that is very linear in its power delivery and will not be to sensitive to rpm fluctuations.. These are the good engines.. If you have an engine that has a big PEAK TQ number but ....before and after this peak point is very steep in the curve's profile.. you have an engine that makes big peak HP but is very sensitive to rpm drift.. These engines usually hit very hard and usually fall off just as hard..

As far as turbo's making "X"% of torque multiplication at "X" boost.. With all due respect, this is simply WAAAY too general and simply not a correct assessment IMO.
There are way too many variables in play to state that any turbo can and will produce "X%" torque @ "X" Boost..

Kelsey

winter4ever · Oct 2, 2009

Not trying to stir the pot here, just adding my own thoughts but it seams (to me) that hp and torque are two seperate units, where hp is independent of rpm, or torque is dependent of rpm and hp.
sure the function can be re wrote as
hp= (torque*Rpm)5252
torque=(hp*5252)/rpm
rpm=(torque*5252)/hp

So just for kicks someone has two 5 hp motors, which is a given. (One horsepower is defined as a force that can lift 550 pounds 1 foot per second, or 5.5 pounds 100 feet, or any combo of that force). One engine makes 5hp at 3000rpms, the makes 5 hp at 5000rpms, then the will have 8.7 foot pounds and 5.2 foot pounds of torque respectivley. even though the torque is different by definition they should be able to to the same work at their peak rpms.

gus bohne · Oct 2, 2009

Winter, I hope you realize you have it backward ?
torque is INdependent of rpm
HP is soley dependant on rpm, for if there is no RPM there is NO hp.

like I stated in my first post, as long as torque falls SLOWER than rpm rise you will see a mathmatic increase in hp until the torque is falling faster than the rpm is rising.

hence the dyno runs PAST torque peak, on most IN PHASE pipes , the torque and hp peak very closely if not together. In this scenario, the hp will typical drop like a rock within just afew hundred rpms past the peak.

with out of phase pipes, you can get a torque peak as much as 1000 rpm below hp peak.

Why ?
the pipes pulse is less focused to specific window and more spread for a wider effective operating range. this typically will show long overrevs well past the torque PEAK but still not falling like a cliff drop..LOL

Gus

winter4ever · Oct 2, 2009

Yeah I worded that poorley. I meant hp is independent in the function, not for a particular motor, because of course hp is going to be different at any given rpm for any particular motor. I guess i just dont understand how torque can be independent for any given motor. simply because hp is a calculable force, and torque is a function of the hp based on the rpm... kinda fun to talk about though:beer;

winter brew · Oct 2, 2009

How about watts?...wouldn't that be much simpler? :beer;

winter4ever · Oct 2, 2009

winter brew said:
How about watts?...wouldn't that be much simpler? :beer;

watts and hp are directly convertable, so that makes sense. watts and hp are a measure of work being done. torque is a derivative of hp and rpm, as I understand it.

DaveB · Oct 2, 2009

Didn't somebody mention watts and joules once already?

winter brew · Oct 2, 2009

DaveB said:
Didn't somebody mention watts and joules once already?

Ya, but it didn't take off...it needed a little push.

CBX · Oct 2, 2009

brycter said:
When we install a turbo on a sled do we feel torque or horse power? Everybody talks about horse power but shouldn't we talk about torque? because torque is what the turbo brings out of the motor.

What is you take on this?

Great topic!

Torque = Force
Horsepower = Rate of work

Torque is King. Ride in or a Drive a 500 Hp Corvette and then do the same in a 500 Hp Duramax or Dodge Cummins.

Then load them equally. The corvette wont be impressive once loaded equally to the truck.

Is it a fair comparison, No. But both have 500 right. Lets assume 500 at the wheels even.

Now take a 500 hp at the wheels Kenworth. Even with the theoretical gearing to get the corvette or the pickup to do equal work of the Kenworth it still wont happen.

Torque is king. As far as vehicles are concernd, Horsepower tends to create speed. Torque creates " the muscle" if you will.

CBX · Oct 2, 2009

brycter said:
When we install a turbo on a sled do we feel torque or horse power? Everybody talks about horse power but shouldn't we talk about torque? because torque is what the turbo brings out of the motor.

What is you take on this?

On a snowmobile I think the added Horsepower will be mostly felt when a turbo is added. Even though the torque is most definetly increased, Turbo sleds create a violent acceleration. Its not the "torque feel" that say A big 425hp John deere makes when its yanking something through a field.

Mainly due to operating RPM being above 5252. Well, I guess other factors too.

I think the level of horsepower determines the grin factor when riding. :beer;

CBX · Oct 2, 2009

brycter said:
Good post kelesy. thanks for your imput. and a great read!

For a turbo to build more hp it has to create more torque first. A turbo is quite frankly a torque multiplier and then the rest will follow. The more boost the more torque the more hp. a boost level of 6 psi will increase torque by approx 40% over a astperated motor. At 10 psi of boost it should increase by approx 50%-54%. That is alot better when on the hill on on a long pull

Please correct me if i am wrong or if my words don't make sense. I would just like to get some knowledge out there about this topic. I think this is some of the basic that poeple need to understand.

Yes, but turbochargers and boost are a function of horsepower and drive energy.

What happens once above torque peak? Only horsepower is left through function of RPM.

What your saying Brycter is true below torque peak, but not above. At that point additional power is provided by an increase mass air flow and fuel charge through additional compressor speed and/or drive ratio from exhaust energy, not a function of increased torque.

By the way Brycter, Thanks for starting this great topic! tech topics teach the most by far.

Torque or Horsepower????

Well-known member

Well-known member

Well-known member

Well-known member

Premium Member

Active member

Well-known member

Premium Member

Premium Member

Well-known member

Well-known member

Well-known member

Similar threads