Honda CBX 1350 Fuel Injected - Speakers UP!!

CBXs, new bikes, old bikes, cars, trucks, general chat, off topic, this is the place to post it.
EMS
ICOA Member
ICOA Member
Posts: 10151
Joined: Wed Mar 05, 2003 7:55 am
Location: North East OH, ICOA 3904

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

Post by EMS »

Captain wrote: the torque and HP lines cross at 5252 RPM
.

Captain
That is only true for torque measured in lbs-ft, not for Nm.
Because hp is a calculated figure from torque, speed and the circular frequency, when you use lbs-ft instead of Nm, the hp and torque number come out as the same value.
Of course, it also depends on what the scale for hp and torque is. Some diagrams that use one side for plotting torque and the other for hp and if the scale is different, the curves do not cross at 5252 rpm.

Captain
New Member & Happy To Be Here
New Member & Happy To Be Here
Posts: 7
Joined: Fri Sep 12, 2014 5:39 am
Location: Auckland
Location: Auckland

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

Post by Captain »

Very true and my apologies for not picking up this error.
As a form of explanation for this, when looking at the HP line (imperial system) I immediately assumed (should never assume) that the torque line displayed would be in the same imperial format . It wasn't and is in Nm (metric) and not ft/lb. The Hp equivalent in metric form is Kw and should have been used in this case.
It is misleading to use two different scales on the same graph and they should be displayed either or.

Captain

User avatar
rperacing
New Member & Happy To Be Here
New Member & Happy To Be Here
Posts: 21
Joined: Mon Oct 10, 2016 12:31 am
Location: Sydney
Location: Sydney

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

Post by rperacing »

Captain wrote:Just a small question but with some big reamifications.

The very first thing I ever look at when presented with a Dyno graph is verify that the torque and HP lines cross at 5252 RPM
In order for it to be a valid. In the graph posted earlier in this thread this not the case (the lines are crossing at 7000 RPM)
Please explain why this is ?
For those that are unaware of the importance of this 5252 RPM figure, it is the factor that is fixed in order to calculate HP from a torque figure. Torque is the only thing measured by a Dyno and the HP is a calculation.
If anyone requires verification of this fact and the 5252 RPM requirement, google it for yourselves.

Captain
Thanks for your remark but it is not true, although a lot of people believe so...

Hp= Tq * RPM / 5252

Your first mistake is that torque is in ftlb, not Nm as in the graph
Second mistake is that even if the graph was in ftlb, the lines would only cross at 5252 rpm if the vertical scales of Hp and Tq coincide (y axis)

An example of this is the same graph, modified to verify the above conditions:
Image

If you convert the torque values you will see that they match perfectly. Every dyno respects this equation because it is based on it.

I have to admit though you had my head spinning for a little bit :D

:text-thankyouyellow:
Paulo

User avatar
rperacing
New Member & Happy To Be Here
New Member & Happy To Be Here
Posts: 21
Joined: Mon Oct 10, 2016 12:31 am
Location: Sydney
Location: Sydney

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

Post by rperacing »

Sorry didn't see there was a second page in the thread.

Well said EMS!

*Edit: As you know the overwhelming majority of motorcycle manufacturers quote their bikes in Hp and Nm, hence why we tend to follow suit.*

:text-thankyouyellow:
Paulo

Mouse
ICOA Member
ICOA Member
Posts: 569
Joined: Fri Jun 12, 2015 9:56 am
Location: Canmore Alberta Canada
Location: Canmore Alberta Canada

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

Post by Mouse »

Some days the things being discussed on this forum leave me :shock:
Can anyone recommend well written reading material that talks/teaches about what you have been disgussing?
Thx
Canadian Amateur Radio Call sign VE6 VES

User avatar
wyly
ICOA Member
ICOA Member
Posts: 1727
Joined: Tue Oct 30, 2007 4:20 pm
Location: calgary alberta canada
Location: Calgary Canada

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

Post by wyly »

yeah I'm intrigued by EFI but it's technology above my pay grade...and quite likely my budget as well :(
CBX a work in progress, still improving...GS1150EFE completed and awaiting modifications.....RD350, remnants in boxes scattered throughout the garage

User avatar
rperacing
New Member & Happy To Be Here
New Member & Happy To Be Here
Posts: 21
Joined: Mon Oct 10, 2016 12:31 am
Location: Sydney
Location: Sydney

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

Post by rperacing »

Mouse wrote:Some days the things being discussed on this forum leave me :shock:
Can anyone recommend well written reading material that talks/teaches about what you have been disgussing?
Thx
If you are serious about it, this website has everything you will ever need:
https://hpacademy.com/

Wonderful resource.
:twocents-02cents:

Mouse
ICOA Member
ICOA Member
Posts: 569
Joined: Fri Jun 12, 2015 9:56 am
Location: Canmore Alberta Canada
Location: Canmore Alberta Canada

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

Post by Mouse »

rperacing wrote: If you are serious about it, this website has everything you will ever need:
https://hpacademy.com/

Wonderful resource.
:twocents-02cents:
Bookmarked!
Thx :-)
Canadian Amateur Radio Call sign VE6 VES

letxbruce
ICOA Member
ICOA Member
Posts: 33
Joined: Wed Dec 02, 2009 10:54 pm
Location: Right Here!
Location: Right Here!

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

Post by letxbruce »

Because the torque in the graph is shown as Newton Meters instead of Ft Lbs.

Bruce

User avatar
Syscrush
ICOA Member
ICOA Member
Posts: 1714
Joined: Fri Sep 14, 2012 2:29 pm
Location: Toronto, ON
Location: Toronto, ON

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

Post by Syscrush »

Mouse wrote:Some days the things being discussed on this forum leave me :shock:
Can anyone recommend well written reading material that talks/teaches about what you have been disgussing?
Thx
This is not motorcycle centric, but quite interesting while being very technical and informative - the Engineering Explained YouTube channel:

https://m.youtube.com/user/EngineeringE ... dd&view=50

Happy watching!

Then there's Ash on Bikes, some very technical discussion of the dynamics of motorcycles, especially engines:

http://ashonbikes.com

And Tony Foale has written and experimented a tremendous amount on motorcycle suspension and handling:

http://www.tonyfoale.com/Articles/
Phil in Toronto
A cool guy deserves a cool bike, a dork needs a cool bike...
Pics of Perry, my '79.

Mouse
ICOA Member
ICOA Member
Posts: 569
Joined: Fri Jun 12, 2015 9:56 am
Location: Canmore Alberta Canada
Location: Canmore Alberta Canada

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

Post by Mouse »

Syscrush wrote:
Mouse wrote:Some days the things being discussed on this forum leave me :shock:
Can anyone recommend well written reading material that talks/teaches about what you have been disgussing?
Thx
This is not motorcycle centric, but quite interesting while being very technical and informative - the Engineering Explained YouTube channel:

https://m.youtube.com/user/EngineeringE ... dd&view=50

Happy watching!

Then there's Ash on Bikes, some very technical discussion of the dynamics of motorcycles, especially engines:

http://ashonbikes.com

And Tony Foale has written and experimented a tremendous amount on motorcycle suspension and handling:

http://www.tonyfoale.com/Articles/


:text-thankyouyellow:
Canadian Amateur Radio Call sign VE6 VES

User avatar
Syscrush
ICOA Member
ICOA Member
Posts: 1714
Joined: Fri Sep 14, 2012 2:29 pm
Location: Toronto, ON
Location: Toronto, ON

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

Post by Syscrush »

EMS wrote:Because hp is a calculated figure from torque, speed and the circular frequency, when you use lbs-ft instead of Nm, the hp and torque number come out as the same value.
I don't want to derail this thread, but I do want to push back against this idea a bit because it's a bit of "common knowledge" that's just not correct. You can calculate torque from power and rotational speed or you can calculate power from torque and rotational speed. You could even calculate rotational speed from power and torque but I don't think that there are real applications to that.

Here's an example: if you measure the coefficient of drag of a motorcycle then run it wide-open on the salt flats until it reaches its terminal velocity, you can come up with a pretty good calculation of its power. If you note the engine speed at that terminal velocity, you have the rotational speed and can calculate the torque of the engine at that speed.

On a drum-type dyno, you're measuring the acceleration of a mass with a known moment of inertia - the calculation of torque from that acceleration is exactly equivalent to the calculation of power from the increased kinetic energy - there's no difference. One is not more intrinsic or primal to how engines work, or what power and torque are.

On an old brake-type dyno where there was an arm of a known length actuated through a clutch and pushing on a load cell (or spring/dial), you could certainly claim that you were measuring torque and calculating hp, but on a modern dyno, you'd be more correct to say that you're measuring voltages from a number of sources and taking a bunch of known quantities to calculate time, speed, torque, and hp all together.

Note that you can run a bike or a car on a dyno without hooking up the tach signal and get an engine hp vs wheel mph graph, but you can't get an engine torque vs wheel mph graph - this should demonstrate that hp does not have to be calculated from torque.
Phil in Toronto
A cool guy deserves a cool bike, a dork needs a cool bike...
Pics of Perry, my '79.

User avatar
rperacing
New Member & Happy To Be Here
New Member & Happy To Be Here
Posts: 21
Joined: Mon Oct 10, 2016 12:31 am
Location: Sydney
Location: Sydney

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

Post by rperacing »

Syscrush wrote:
EMS wrote:Because hp is a calculated figure from torque, speed and the circular frequency, when you use lbs-ft instead of Nm, the hp and torque number come out as the same value.
I don't want to derail this thread, but I do want to push back against this idea a bit because it's a bit of "common knowledge" that's just not correct. You can calculate torque from power and rotational speed or you can calculate power from torque and rotational speed. You could even calculate rotational speed from power and torque but I don't think that there are real applications to that.

Here's an example: if you measure the coefficient of drag of a motorcycle then run it wide-open on the salt flats until it reaches its terminal velocity, you can come up with a pretty good calculation of its power. If you note the engine speed at that terminal velocity, you have the rotational speed and can calculate the torque of the engine at that speed.

On a drum-type dyno, you're measuring the acceleration of a mass with a known moment of inertia - the calculation of torque from that acceleration is exactly equivalent to the calculation of power from the increased kinetic energy - there's no difference. One is not more intrinsic or primal to how engines work, or what power and torque are.

On an old brake-type dyno where there was an arm of a known length actuated through a clutch and pushing on a load cell (or spring/dial), you could certainly claim that you were measuring torque and calculating hp, but on a modern dyno, you'd be more correct to say that you're measuring voltages from a number of sources and taking a bunch of known quantities to calculate time, speed, torque, and hp all together.

Note that you can run a bike or a car on a dyno without hooking up the tach signal and get an engine hp vs wheel mph graph, but you can't get an engine torque vs wheel mph graph - this should demonstrate that hp does not have to be calculated from torque.
Thanks for that. I always found that information confusing as operating a dyno shows otherwise.

I wrote this on the SOHC forums today lol:

"Example: Same bike, same dyno, same gear, same everything
1st - You set the RPM - roller speed relationship for example 5000rpm = 100km/h
2nd - You change your RPM - roller speed to 4500=100km/h

Result - The HP will be exactly the same but the torque changes (as does the rpm of course). #2 will show more torque.

I cannot explain it because mathematically I agree with you. But this is experience. I can post dynos if you want

Bottom line, I can mess up the torque reading, but not the hp reading - go figure."

Now I know I am not insane. Thank you for putting it so eloquently. Mind if I quote you on the other forum?
:text-thankyouyellow:

User avatar
Syscrush
ICOA Member
ICOA Member
Posts: 1714
Joined: Fri Sep 14, 2012 2:29 pm
Location: Toronto, ON
Location: Toronto, ON

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

Post by Syscrush »

rperacing wrote:Now I know I am not insane. Thank you for putting it so eloquently. Mind if I quote you on the other forum?
By all means. Is this the SOHC4 Honda forum? I used to be pretty active there before I abandoned my CB550 for the CBX.

I find it surprising how the hp-torque relationship takes on a borderline religious element at times - these discussions can spiral out of control when people take them personally/emotionally. But there's no reason for it, it's literally Physics 101 stuff - which is not to say that first year university physics is basic, simple, or obvious, but rather that this stuff is not at all mysterious.
Phil in Toronto
A cool guy deserves a cool bike, a dork needs a cool bike...
Pics of Perry, my '79.

Mouse
ICOA Member
ICOA Member
Posts: 569
Joined: Fri Jun 12, 2015 9:56 am
Location: Canmore Alberta Canada
Location: Canmore Alberta Canada

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

Post by Mouse »

I'm off on a tangent but;
Syscrush wrote: On a drum-type dyno, you're measuring the acceleration of a mass with a known moment of inertia - the calculation of torque from that acceleration is exactly equivalent to the calculation of power from the increased kinetic energy - there's no difference. One is not more intrinsic or primal to how engines work, or what power and torque are.
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:
Canadian Amateur Radio Call sign VE6 VES

Post Reply

Return to “Daily Discussion: By, For & About CBXers”