Honda CBX 1350 Fuel Injected - Speakers UP!!

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Syscrush
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Re: Honda CBX 1350 Fuel Injected - Speakers UP!!

Post by Syscrush »

Mouse wrote:I'm off on a tangent but;
Are you saying that the drum type Dyno measures how quickly the drum is accelerated then multiplies/divides that with some (imaginary?) constants to get HP and Torque numbers? :think:
None of the constants are imaginary, but some aren't constants. :D The moment of inertia of the drum is known to a high degree of accuracy and it is a constant. The drag from bearings and wind could be estimated, but I don't know if they include that in their calculations or not. If it is, the bearing drag is probably pretty constant, and the wind drag would depend on the speed of the rotating drum.

Either way, at any moment with the information about the speed at which the drum is spinning (which changes during a run) and the moment of inertia of the drum (which is constant), it is easy to calculate the energy stored in the spinning drum. Power is defined as the rate of change of energy (which is also equivalent to the rate at which work is done - the "work" in physics has a specific definition, not work in the general sense), so by measuring how quickly the drum is accelerated, you're measuring how quickly the energy of spinning drum is changing, which is equal to the power being applied to the drum.

If the dyno gets a tach signal from the bike, then it can calculate engine RPM at the same time that it's making its calculations of the drum speed. With the power and engine RPM, engine torque (after driveline losses) can be calculated. If it does not get that tach signal, then the dyno can plot power vs drum RPM or drum MPH equivalent at the perimeter. Some dynos will let you say that this bike turns X RPM at Y MPH in the gear I'm using for this run. That ratio is a constant for a given run, but could vary from bike to bike, or from run to run (if you wanted to compare results in 4th gear vs 5th gear, for example). With that ratio, the dyno can calculate the engine RPM from the drum speed and calculate engine torque from hp. This is what rperacing was referring to when he talked about changing the "RPM - roller speed relationship". This changes the dyno's engine torque calculation, because it changes the dyno's estimation of engine RPM.


This is all for a simple inertial dyno where the only load is the inertia of the drum. There are more sophisticated systems that can vary the load based on a bunch of different parameters by using a brake or eddy current system which can be controlled by the computer in the dyno or by the operator. In that case, there would be some kind of model or input used to add the drag from the additional load to all of the calculations and there may be some measurements of torque applied to the dyno as part of the hp & engine torque applications.


Does that make sense? Should this be split into a different thread?
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Re: Honda CBX 1350 Fuel Injected - Speakers UP!!

Post by rperacing »

Not at all. Great quality contributions. Learned something!

But you are correct, it was getting a bit too religious at the SOHC forum so I ducked out :laughing-rollingyellow:

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Re: Honda CBX 1350 Fuel Injected - Speakers UP!!

Post by Mouse »

Syscrush wrote:Does that make sense?
After a few read thru's, I think I've got a handle on about 1/2 of it. I'll need to do some reading and some think time with the rest.
I did say it was a tangent, and you have given me a bit to chew on, so no need at this time for a separate thread. :-)
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Re: Honda CBX 1350 Fuel Injected - Speakers UP!!

Post by EMS »

Consider this: No device, no matter how it is designed, can measure horsepower by itself. If you prevent the device to get rpm/speed input, the device cannot indicate horsepower, because horsepower has speed in the unit.
Torque has force and lever. And that can be measured without speed. If you disconnect the speed input in the measuring device (dynamometer), you still would get a torque reading. You just don't know at which rpm the torque value is. You would never get a horsepower reading if rpm is not used as an input parameter.

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Re: Honda CBX 1350 Fuel Injected - Speakers UP!!

Post by Syscrush »

EMS wrote:Consider this: No device, no matter how it is designed, can measure horsepower by itself. If you prevent the device to get rpm/speed input, the device cannot indicate horsepower, because horsepower has speed in the unit.
Torque has force and lever. And that can be measured without speed. If you disconnect the speed input in the measuring device (dynamometer), you still would get a torque reading. You just don't know at which rpm the torque value is. You would never get a horsepower reading if rpm is not used as an input parameter.
With all respect, that's not true. You can measure the horsepower of a jet dragster - which has no torque to the wheels, only thrust - by measuring its acceleration (assuming you know its weight and its coefficient of drag). You can measure the power output of a battery or capacitor by measuring voltage and current across a resistor - again no torque involved.

Power = rate of change of energy. Any mechanism for measuring the energy output of a device at different times can measure power.
Last edited by Syscrush on Sat Oct 22, 2016 10:18 am, edited 1 time in total.
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Re: Honda CBX 1350 Fuel Injected - Speakers UP!!

Post by Mouse »

:think:
Maybe we do need a separate thread;
EMS wrote: Torque has force and lever. And that can be measured without speed. If you disconnect the speed input in the measuring device (dynamometer), you still would get a torque reading. You just don't know at which rpm the torque value is.
You lost me with that last sentence.
Being that Torque is the force needed to turn an object, Is not the Torque value always gotten at the moment you break inertia ie. at zero rpm?
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Re: Honda CBX 1350 Fuel Injected - Speakers UP!!

Post by Syscrush »

Mouse wrote::think:
You lost me with that last sentence.
Being that Torque is the force needed to turn an object, Is not the Torque value always gotten at the moment you break inertia ie. at zero rpm?
Imagine you have an engine on a stand, and it has a clutch but no transmission. The output side of the clutch has a lever going from the clutch plates to a bathroom scale. As you let out the clutch so it's still slipping but applying enough resistance to keep the engine revs from increasing despite having the engine at wide-open throttle, you take a reading from the bathroom scale. Knowing the length of the lever and the force applied to the scale, you'd know the torque but not the RPM.

This is called a brake type dyno. Here's an awful diagram:

Image
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Re: Honda CBX 1350 Fuel Injected - Speakers UP!!

Post by EMS »

Syscrush wrote:
EMS wrote:Consider this: No device, no matter how it is designed, can measure horsepower by itself. If you prevent the device to get rpm/speed input, the device cannot indicate horsepower, because horsepower has speed in the unit.
Torque has force and lever. And that can be measured without speed. If you disconnect the speed input in the measuring device (dynamometer), you still would get a torque reading. You just don't know at which rpm the torque value is. You would never get a horsepower reading if rpm is not used as an input parameter.
With all respect, that's not true. You can measure the horsepower of a jet dragster - which has no torque to the wheels, only thrust - by measuring its acceleration (assuming you know its weight and its coefficient of drag). You can measure the power output of a battery or capacitor by measuring voltage and current across a resistor - again no torque involved.

Power = rate of change of energy. Any mechanism for measuring the energy output of a device at different times can measure power.
Phil: I will not try to hammer anything home here anymore, but all of the things you refer to include m/sec in their unit somewhere. Acceleration is m/sec². Distance over time is necessary to determine power flow.
Watt is Nm/sec. And if you refer to the power output of a battery or capacitor and use W= V x A, you need to look how Ampère is defined. Again you will find "per second" in it.

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Re: Honda CBX 1350 Fuel Injected - Speakers UP!!

Post by Syscrush »

EMS wrote:Phil: I will not try to hammer anything home here anymore, but all of the things you refer to include m/sec in their unit somewhere. Acceleration is m/sec². Distance over time is necessary to determine power flow.
Watt is Nm/sec. And if you refer to the power output of a battery or capacitor and use W= V x A, you need to look how Ampère is defined. Again you will find "per second" in it.
I agree 100% that time or speed are inherent in the definition of power, and not part of the definition of torque.

I may have misinterpreted this:
If you disconnect the speed input in the measuring device (dynamometer), you still would get a torque reading.
If we're talking about an inertial dyno, and we disconnect the engine speed input, we get hp but no torque reading. If we disconnect the drum/wheel speed input, we get no reading of any kind. This is what I meant when I disagreed.

But on a brake, water, or eddy current dyno, you can get a torque reading but no hp as you said. Perhaps that's what you were referring to. I think that most engine dynos work the way you describe, while most motorcycle chassis dynos are the inertial type.
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Re: Honda CBX 1350 Fuel Injected - Speakers UP!!

Post by wyly »

:shock: this all rocket science to me...

here's what I know right or wrong...

horsepower - how fast you hit the wall
torque - how far you take the wall with you...

torque matters more than HP imo... :D
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Re: Honda CBX 1350 Fuel Injected - Speakers UP!!

Post by Syscrush »

wyly wrote:here's what I know right or wrong...
It's wrong. :lol:
torque matters more than HP imo... :D
That explains why Harleys are better than CBX's, then, eh? :laughing-rolling:
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Re: Honda CBX 1350 Fuel Injected - Speakers UP!!

Post by Mouse »

Mouse wrote::think:
Maybe we do need a separate thread;
EMS wrote: Torque has force and lever. And that can be measured without speed. If you disconnect the speed input in the measuring device (dynamometer), you still would get a torque reading. You just don't know at which rpm the torque value is.
You lost me with that last sentence.
Being that Torque is the force needed to turn an object, Is not the Torque value always gotten at the moment you break inertia ie. at zero rpm?
Ok.... so two hrs after I wrote this I was driving out to the nearby forestry reserve to harvest firewood and the light bulb in my head turned on. I suddenly realized that I was looking at what EMS wrote wrong way round.
My question... "is not the Torque value always gotten at the moment you break inertia ie. at Zero RPM" is correct only if you are measuring the force being applied to an object at the object the moment before that object begins to turn . That means that what EMS wrote is correct for reciprocating engines.
If you disconnect the RPM input device on some Dyno's you find out the max Torque value, you just won't know at what RPM that engine makes max torque.
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Re: Honda CBX 1350 Fuel Injected - Speakers UP!!

Post by Mouse »

wyly wrote: horsepower - how fast you hit the wall
torque - how far you take the wall with you...
Here's what I was told, way back when, by a muscle car guy.
"Torque is what gets you off the line
Horse Power is what makes you move fast."

:D
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Re: Honda CBX 1350 Fuel Injected - Speakers UP!!

Post by Syscrush »

Mouse wrote: If you disconnect the RPM input device on some Dyno's you find out the max Torque value, you just won't know at what RPM that engine makes max torque.
It depends on the dyno. For a brake type engine dyno, this is correct. For a chassis dyno, it's incorrect.
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Re: Honda CBX 1350 Fuel Injected - Speakers UP!!

Post by Syscrush »

Mouse wrote:Here's what I was told, way back when, by a muscle car guy.
"Torque is what gets you off the line
Horse Power is what makes you move fast."

:D
Next time ask a mechanical engineer or a physicist and see what answer you get. :D
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