Lets take an electrical dyno. The engine spins an electrical generator. The output of the generator is fed through an electronic load bank (essentially a giant electronically controlled resistor). Sensors measure how many amps the generator puts out, and how many volts. Volts X Amps = Power/Watts. 746 Watts = 1HP. No where is torque directly measured.

Here is the formula for calculating the HP of a hydraulic dyno:
"
To do the simple HP calculation all you have to do is:

• HP = (pump gpm * pressure) / 1628.3(1714 multiplied by pump efficiency of 95%)

In this calculation you have to know pump gpm. The way to get pump gpm is:

• GPM = ((pump size in cubic inches) * (Pump RPM)) / 231"

"The way this system is set up you get your HP readings first. Then you punch the HP numbers into a formula to get your Torque. Here it is:

• Torque = (HP * 5252) / Motor RPM"

Site:Making the Calculations

 

Don't get me wrong fellas. I'm not trying to convince anyone one way or the other. I'm just saying that I was taught that dyno's measures torque and calculate horsepower. If that's incorrect, then I was taught wrong.

 

That site clearly states " the way this system is set up" you get your hp readings first.

 

A dynamometer consists of an absorption (or absorber/driver) unit, and usually includes a means for measuring torque and rotational speed.


An absorbing dynamometer acts as a load that is driven by the prime mover that is under test (e.g. Pelton wheel). The dynamometer must be able to operate at any speed and load to any level of torque that the test requires.

Absorbing dynamometers are not to be confused with "inertia" dynamometers, which calculate power solely by measuring power required to accelerate a known mass drive roller and provide no variable load to the prime mover.


An Absorption dynamometer is usually equipped with some means of measuring the operating torque and speed.

The dynamometer's Power Absorption Unit absorbs the power developed by the prime mover. The power absorbed by the dynamometer is converted into heat and the heat is generally dissipated into the ambient air or transferred to cooling water which is dissipated into the air. Regenerative dynamometers, in which the prime mover drives a DC motor as a generator to create load, make excess DC power and potentially, using a DC/AC inverter, can feed AC power back into the commercial electrical power grid - where the power produced is eventually converted back into heat (as in an oven or light bulb, etc).

Absorption dynamometers can be equipped with two types of control systems to provide different main test types.

Constant Force
The dynamometer has a "braking" torque regulator, the PAU (Power Absorption Unit) is configured to provide a set braking force torque load while the prime mover is configured to operate at whatever throttle opening, fuel delivery rate or any other variable it is desired to test. The prime mover is then allowed to accelerate the engine through the desired speed or rpm range. Constant Force test routines require the PAU to be set slightly torque deficient as referenced to prime mover output to allow some rate of acceleration. Power is calculated based on torque x rpm / 5252 + calculated power required for the acceleration rate that occurred.

Constant Speed
If the dynamometer has a speed regulator (human or computer), the PAU provides a variable mount of braking force (torque) that is necessary to cause the prime mover to operate at the desired single test speed or rpm. The PAU braking load applied to the prime mover to can be manually controlled or determined by a computer. Most systems employ eddy current, oil hydraulic or DC motor produced loads because of their linear and quick load change ability.

Power is calculated based on torque x rpm / 5252.

A motoring dynamometer acts as a motor that drives the equipment under test. It must be able to drive the equipment at any speed and develop any level of torque that the test requires. In common usage, AC or DC motors are used to drive the equipment or "load" device.


In most dynamometers power (P) is not measured directly; it must be calculated from torque (τ) and angular velocity (ω) values or force (F) and linear velocity (v):


or

where
P is the power in watts
τ is the torque in newton metres
ω is the angular velocity in radians per second
F is the force in newtons
v is the linear velocity in metres per second
Division by a conversion constant may be required depending on the units of measure used.

For imperial units,


where
Php is the power in horsepower
τlb·ft is the torque in pound-feet
ωrpm is the rotational velocity in revolutions per minute
For metric units,


where
PkW is the power in kilowatts
τN·m is the torque in newton metres
ωrpm is the rotational velocity in revolutions per minute

 

you went through all that searching to find this artictle and your still wrong. hp is nothing but a calculation base on torque and engine rpm.
it doesnt matter what machine your using it has to measure torque beacuse the force being applied to the dyno is rear wheel torque.

 

All that searching? Its the first result for hydraulic dyno..

Tell me then, why can I hook a generator up to an engine, hook the generator up to a load bank and based on the known efficiency of the generator come up with how much power the engine is producing, without needing to know engine RPM or torque output?

 

you cant. the efficiency of the generater depends on the rpms of the motor for one. if that motor is turning at 1 rpm then that generator is not making any power that can be monitored. yes technically it is creating voltage but it would be such a minute amount it wouldnt even read. motors dont just make a certain amount of hp. that hp reading is calculated from the engines top torque making rpm band.


it doesnt matter that it is giving you a hp readout. its simply calculating it.

 

Jeez, what are we gonna argue about next? Get out the hair splitter, we're officially arguing for the sake of the arguement...

 

No, lets argue that a V-10 is better than most pickup diesels. I like that one.

 

pappy..... i just got a laugh outta your sig. you have superhides seat covers as a upgrade.

 

How do you like mine?

 

at least yours are custom

 

Hell yes, Marathon's are American made and they give me at least .005 more mpg and SOP is much faster as well; plus all the girls stop me and ask me where I got them.

 

Me too.

 

so now you get an impressive 3.005 mpg? lol thats way better than stock. now all you need is one of those NOS stickers. i hear they give you 20 more horses. and maybe a set of them truck ***** that hang of the reese hitch to let everyone no its a v10 lol