Old HP thread...

[JoshPeters]

OK, I've been searching for an hour... about 4 different ways...

I can't find it.

There was a thread that I am looking for was a discussion about HP being a calculation and Torque being the true force. IF I remember right (big if) it was written/posted by Hohn... .



Anyone know where it went? I've searched threads going back to 03... . I know it's not that old...



Thanks in advance

Josh

 

[Vaughn MacKenzie]

I remember that discussion, I think it ensued in more than one thread :-laf

I think it's the reverse though, HP is measured and torque calculated, that's why dynos always give you a HP value, but in order to get a torque reading they have to hook up the tach sensor. The dyno software needs the engine RPM since that is needed to calculate torque (N = Speed in this equation):

HPx5252
N

Torque is a measure of twisting force, can't detect that with a dyno like you can HP. That's why you have to calculate it.

 

[Vaughn MacKenzie]

One other thing, a Mustang type (loading) dyno does use sensors to measure the amount of torque applied to the roller, but the software uses this value (which doesn't correlate with anything other than to serve as map values in the dyno software) and the drum speed to calculate (measure) HP. While it does see the torque being applied by your rear tires, the dyno has no clue how much torque your engine is making, unless it's being fed its RPM and using that to calculate its torque.

Bottom line is basically this- you don't have to know the torque of a vehicle to get HP, but you have to have the HP to calculate torque.

Vaughn

 

[JoshPeters]

Ya it's been a while since I read it so I wanted to read it again.



If I remember right it was HP is a calculation of how much work was being done, torque is an actual force that can be measured... .



but really... . I don't remember...

 

[CJ Johansson]

It's all just math. For HP, you need torque & RPM:

HP = torque x RPM x constant

The constant is based on the torque measurement. If torque is in lb-ft, the conversion constant is 1/5252 so you use:

HP = (Torque x RPM)/5252

Now, if you know HP & RPM, you can calculate Torque:

T = (HP x 5252)/RPM

Torque is an actual force and is measurable, HP is a calculated value. Torque is a rotational force defined as force (in force units) applied at some distance (in distance units). So, lb-ft torque is simply a force in lbs applied at a distance in feet. N-m is a force in Newtons applied at a distance in meters for you metric types (this uses a different constant, not 5252).

After *WAY* too many years of college physics,

-cj

 

[JoshPeters]

Thanks for the formula...



it was more than that... It was a discussion of the theory involved.

 

[nickleinonen]

I Finally Figured out this RPM tourqe stuff! - Rotory Modeler - Powered by FusionBB

 

[JoshPeters]

LOL

Awesome!

 

[ToolManTimTaylor]

https://www.turbodieselregister.com...discussions/17395-horsepower-toeque-math.html



Here ya go It was made back in 2001

 

[JoshPeters]

Thanks Toolman...



That's not it...

The calculations were all in conversation. It was a very lengthy article with lots of Theory and discussion involved.



I could have sworn it was posted by Hohn... I think it was in General Diesel... but I'm not sure...

 

[obert]

Wow, CJ! Reallty hit the nail on the head, there.

Both HP and TQ can be calculated. HP is the "rate" of tourque, it was explained to me.



When I first got my truck, a coworker wondered why I wanted 235Hp truck when his gasser had 300. He didn't get that the diesel had mucho more power but at half the RPM, making the smaller HP number.

 

[Vaughn MacKenzie]

Wow, CJ! Reallty hit the nail on the head, there.

Both HP and TQ can be calculated. HP is the "rate" of tourque, it was explained to me

That basically dawned on me after posting last night. Both HP and torque can be calculated, but torque can be measured directly.



BUT-



The torque that is measured directly on a loading dyno (not a Dynojet) is the torque produced at the rear wheels, NOT what the engine is producing. Because torque is the product of force and radius, gearing and tire diameter greatly influence this value, so the torque your engine is producing is much different than that at the rear wheels.



That is why engine torque has to be calculated, there is no way to measure it directly- you'd have to remove your transmission and hook directly to the crankshaft :-laf

 

[JoshPeters]

Ugh... this discussion is exactly what this thread talked about...



I want to find it! 2 hours of searching... . still no luck...

 

[obert]

... ... The torque that is measured directly on a loading dyno (not a Dynojet) is the torque produced at the rear wheels, NOT what the engine is producing. Because torque is the product of force and radius, gearing and tire diameter greatly influence this value, so the torque your engine is producing is much different than that at the rear wheels.



That is why engine torque has to be calculated, there is no way to measure it directly- you'd have to remove your transmission and hook directly to the crankshaft :-laf

Aaaaaahhh! I was thinking more about the values in of themselves, not as appied to a dyno sheet. I got on a dyno once, and found GOBS of calculations to convert to Flywheel HP, but putting the TQ in resulted in numbers I know were wrong. Only physics I've had is from high-skool, calculating tourque thrugh the drivetrian would fry my mind.

 

[GIT-R-DONE]

Found a few here, maybe help you out:



https://www.turbodieselregister.com...mbers-only/123688-hp-vs-tq-one-more-time.html



https://www.turbodieselregister.com/forums/general-diesel-topics/116600-poll-torque-important.html



https://www.turbodieselregister.com...31595-ultimate-diesel-drag-racing-engine.html



Help any?