Help me understand Dyno's. this makes no sense.

[skip68]

Not sure if time is a factor.  How ever long it takes to hit redline.   You'd think time it takes to hit redline is part of the equation. 
But some engines can be a dog down low and more powerful up top.  That could make more power than another engine but take longer to get there right?   I better quit because I'm getting lost again.   

[cdr]

Not sure if time is a factor.  How ever long it takes to hit redline.   You'd think time it takes to hit redline is part of the equation. 
But some engines can be a dog down low and more powerful up top.  That could make more power than another engine but take longer to get there right?   I better quit because I'm getting lost again.   

time & weight & Rpm of the rollers is how they calculate HP on an inertia dyno.

[skip68]

Ok, then an inertia dyno would be closest to the carnival ring the bell with the hammer test.   

[flyinlow]

At peak HP your drive train/accessory load is 28 HP.  (180-152)

So your R1 is sitting there idling 1000rpm.  It is making just enough power to overcome the engine friction and pumping losses at 1000rpm .Plus the power to turn the water pump, oil pump , alternator and the friction of the gears/bearings of the trans , input shaft ( I think they call it a counter shaft on a bike)  with no load on it because the trans is in neutral. So you put the R1 on it's center stand ( if it has one) put the trans in first gear and let the clutch out and the rear wheel spins about 10mph with almost no load on it. At this point the drive train loss is very small probable a fraction of a HP  or it would bog the idling engine down. The engine probably slowed very slightly unless the fuel injections idle speed motor compensates...

Next your put on your best riding gear ,find a test track and wind it up to 186mph (300KPH limit speed unless you cut the wire) . Don't sit up from behind the fairing or you will learn about the cube rule of parasitic drag.
The wind drag and tire friction will be loading the drivetrain to the max. The gears in the trans which are cut with a slight angle to reduce noise , the teeth are engaging sliding past each other and disengaging under max. torgue load and producing a lot of side trust and friction. The chain and sprockets are making a lot more friction as well. That tennis ball contact patch is heating up as it contacts the road and tries to put the power to the pavement . It does not do it 100% success rate, it slipping slightly. ......or you can use a dyno to simulate a similar load.

I can push my Goldwing around in the garage , so the drivetrain does not take much power at low speeds and loads.

Yea dyno numbers are great for rating how changes add/subtract .   Since you have an R1 ,you already know about that power to weight thing.

Changing sprocket sizes will not make your R1 engine make more HP, but it might go quicker in the 1/4 mile.   

[skip68]

  
I've known about wind drag for 25+ years.    
Anything over 130mph on this bike and my last R1 I need to be tucking in.  On my Busa it was around the 150mph mark.   I usually sit up around 140 to help slow me down for turns. 
Goldwing?   I've looked at those lately.  Talk about luxury.   
My wife has ridden twice on this bike and doesn't want to anymore.  Can't blame her.  I was considering a fjr but I'd rather just keep this for the fun factor and get something like the Goldwing for two up.   All I've ever ridden for street is super sports and the last 3 I've had I've told my wife "this is my last fast bike"      This time I'm pretty sure it's it as I really want something that's comfortable and we can take small trips with.   At almost 48 I think I've peaked far as skills.   Probably peaked 10 years ago and just can't admit it.   

[Paul G]

I dont know. My brain hurts now Skip. Thanks for that.

[skip68]

     
Where's our local scientist?   
Let me take this one step deeper into the insanity.   
Does un-sprung weight (the wheel) tires play a role?
Some have mentioned tires and here's my thoughts. 
As the tire (tires) spin faster and faster they get skinnier and taller. 
The forces are in a sense throwing the tire outward.  Does that also take more power the faster it goes?   Chad's a scientist, where is he.     

[cdr]

   
Where's our local scientist?   
Let me take this one step deeper into the insanity.   
Does un-sprung weight (the wheel) tires play a role?
Some have mentioned tires and here's my thoughts. 
As the tire (tires) spin faster and faster they get skinnier and taller. 
The forces are in a sense throwing the tire outward.  Does that also take more power the faster it goes?   Chad's a scientist, where is he.     

on an inertia dyno it can have a larger effect.

[flyinlow]

 
I've known about wind drag for 25+ years.    
Anything over 130mph on this bike and my last R1 I need to be tucking in.  On my Busa it was around the 150mph mark.   I usually sit up around 140 to help slow me down for turns. 
Goldwing?   I've looked at those lately.  Talk about luxury.   
My wife has ridden twice on this bike and doesn't want to anymore.  Can't blame her.  I was considering a fjr but I'd rather just keep this for the fun factor and get something like the Goldwing for two up.   All I've ever ridden for street is super sports and the last 3 I've had I've told my wife "this is my last fast bike"      This time I'm pretty sure it's it as I really want something that's comfortable and we can take small trips with.   At almost 48 I think I've peaked far as skills.   Probably peaked 10 years ago and just can't admit it.   

Yea I here you and I am 10 years farther down the road. The Wing's nice ,but it's kind of an old man's motorcycle.  I need a Ninja 14  to balance it out.

[cdr]

hey Skip this is a long read but a lot of good info
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=8&cad=rja&uact=8&ved=0ahUKEwiymL-em6_KAhVD4iYKHRSrBFQQFghCMAc&url=http%3A%2F%2Fwww.factorypro.com%2Fdyno%2Ftrue1.html&usg=AFQjCNGnJoBaXP5-Jzh-IuCHFVAWKpM2gA

[skip68]

Thanks cdr.    Looks like I'm making even less power now then I thought.    
Interesting read for sure. 

[John_Kunkel]

That's crazy but they all do seem to cross at 5252 more or less.  This is way above me. 

http://trust-me-im-an-engineer.kinja.com/why-do-horsepower-and-torque-cross-at-5-252-rpm-1650651680

[flyinlow]

So a Cummins Ram makes 0 HP.....hmmmm. I always knew real trucks have 2 spark plugs per cylinder.  

The CFM 56's at work idle above 5252rpm...how do I measure HP?

My head hurts too.

[cdr]

So a Cummins Ram makes 0 HP.....hmmmm. I always knew real trucks have 2 spark plugs per cylinder.  

The CFM 56's at work idle above 5252rpm...how do I measure HP?

My head hurts too.

it is still tq x rpm / 5252 =            1000 x 2500 / 5252 = 476 hp

Torque & thrust are two different things

[skip68]

Thank you John.     That is excellent.  This is all pure science.   

[flyinlow]

Just being a wise guy by picking two engines whose normal rpm range does not include 5252.

[Homerr]

On a stand my bike can idle in 6th gear with the wheel spinning of course and using very little effort.    So how the hell is it using about 28HP to do this?   Obviously this doesn't require 28HP from the crank to the tire.  I've also seen this math used in cars where we're talking about HP losses through transmission.  
...

At peak HP your drive train/accessory load is 28 HP.  (180-152)

So your R1 is sitting there idling 1000rpm.  It is making just enough power to overcome the engine friction and pumping losses at 1000rpm .Plus the power to turn the water pump, oil pump , alternator and the friction of the gears/bearings of the trans , input shaft ( I think they call it a counter shaft on a bike)  with no load on it because the trans is in neutral. So you put the R1 on it's center stand ( if it has one) put the trans in first gear and let the clutch out and the rear wheel spins about 10mph with almost no load on it. At this point the drive train loss is very small probable a fraction of a HP  or it would bog the idling engine down. The engine probably slowed very slightly unless the fuel injections idle speed motor compensates...

...

I think flyinlow did a great job capturing a lot of what is going on.  I'd also mention at high rpm the oil in the engine/trans is almost acting like wind resistance at high speed making HP more and more difficult to achieve.  Over time heat will build up as well and change output numbers.

... 
With that theory, a transmission should only require X amount of power to operate regardless of what engine it's bolted to.  
Take a 440 and a 383.  Both engines should see the same amount of loss through the transmission if you used the same transmission testing both motors.   Right    

     If the 383 dyno'd at say 350HP, then dyno'd at 275HP on a chassis dyno that's a 75HP loss.  
Now take the 440 and say it dyno'd at 500HP, put it in the same chassis the 383 was in and it should dyno with the same 75HP loss at 425HP.   Correct?    Or would there be less loss because the more powerful 440 takes less energy to spin the drive train?
... 

Rotational mass is different on 383 vs. 440 so they would not both lose 75hp.  The 440 would have higher loss...90hp?  (Just suggesting that number as a comparison, it's not real.)


This tool might be interesting to play with - reverse-engineer your Cd (drag), etc. from the intended ecomodder use.

http://ecomodder.com/forum/tool-aero-rolling-resistance.php

[c00nhunterjoe]

This entire discussion is another reason why when you tell me how much hp your car makes on the dyno, i usually answer with what the mph was in the 1/4 and what the d/a was on that run. The 2nd method is far more accurate and doesnt lie, nor can it be manipulated to achieve the desired numbers.

[cdr]

This entire discussion is another reason why when you tell me how much hp your car makes on the dyno, i usually answer with what the mph was in the 1/4 and what the d/a was on that run. The 2nd method is far more accurate and doesnt lie, nor can it be manipulated to achieve the desired numbers.

                                               

[Paul G]

How much power does it take to spin a driveline at 5000 RPM and maintain that speed? The amount of power needed should be a constant correct? So it should make no difference how much power the prime mover makes. It will take the same amount of power to do that amount of work.

[ws23rt]

I don't have a clue how the on board sensors in my Challenger come up with the data they provide but at 70mph on level ground the horse power indicator reads 45hp.
So that obviously is a total of all the drags on the engine.----drive train resistance, rolling resistance, aero drag, etc.

[skip68]

Sounds right to me.   But if you've read all my posts you may not take my word.   

[flyinlow]

How much power does it take to spin a driveline at 5000 RPM and maintain that speed? The amount of power needed should be a constant correct? So it should make no difference how much power the prime mover makes. It will take the same amount of power to do that amount of work.

Legal notice: do not  do this!

If you put your car on jackstands under the rear axle so the drive shaft angle would be close to normal and put your car in drive and ran it up to 5000rpm and showed lets say 120mph ( I don,t know what you rear axle is and I am ignoring your OD) It would not take much power to spin the drivetrain a steady 5000rpm (driveshaft speed) , It would be the same power if it was a 318 or 440. A 318 might have a 904 trans and 8 1/4 axle which are slightly easier to turn. Your torque converter would not slip much because of the light load.

Now put your car back on the ground and drive on a flat road with no headwind at 120 mph. It will take a lot more power, Most will be going to overcoming parasitic drag , some induced drag ( your car is shaped like a crappy wing and makes some lift) and higher rolling friction. Some of the extra power required will be spent over coming the increase in drive train friction operating under a heavier load to propel the car at a higher speed. Your torque converter will be slipping a few hundred rpm at this point.

Two identical '68 Chargers /727/8 3/4 axle ,same gear ratio. Both going 120mph .One has a 318 ,one has a 440. The 440 car is slightly heavier , but to go a steady 120mph the power required would be about the same.
\
Now you floor both cars. The 318 was probably pretty much floored already and has very little power left to add, The 440 has a lot more left  to accelerate with ,but as it does the extra load on the drive train from the higher torgue load from the engine during accelertion ,burns up some of the extra power the 440 has over the 318.

Drive train friction and loss is a function of the load on it.

[1974dodgecharger]

theres too many smart people on this board...just spit me a number it can be 100HP I don't care Im going for a drive.....