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pitts_pilot(at)bellsouth.
Guest

Posted: Tue Sep 27, 2011 4:32 pm Post subject: % HP

Any ideas on a formula for % horsepower that works for different size 

engines?  So far Google has let me down.

Linn

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Discover

Joined: 26 Feb 2007
Posts: 429

Posted: Tue Sep 27, 2011 5:14 pm Post subject: % HP

Here ya go

  

 hp  = torque * RPM / 5252

  

 otherwise  check your POH cause it's different in each plane or

  

 see  attachments for O-360

  

  

 [quote]   ---

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pitts_pilot(at)bellsouth.
Guest

Posted: Tue Sep 27, 2011 7:36 pm Post subject: % HP

Thanks for the replies.

     

     I should have been a little more specific.  I'm looking for a     formula that computes % HP from parameters that are measurable ....      fuel flow, OAT, RPM, MP etc. so I can display the value on my EFIS.      Since the EFIS measures many parameters a formula could compute % HP     realtime.  Hard to fly and look at the graphs ......      There is a     formula from Van's (below from another email) but it doesn't seem to     be accurate for different size engines (not sure which engine really     fits), and I don't have the math skills to tweak it.  I was hoping     someone might have the magic bullet.

     Linn

     

     Van's formula:

     h=(H-((R-r)*(5.58-0.125*(M-m))/100 + 7.35*(M-m)) +     2.0*pa/1000)*sqrt((519-3.58*pa/1000)/(460+ta))

     

     h% = h/H*100

     

     where

     

     Constants:

     

     H= maximum sea level horsepower at maximum manifold pressure (from     manufacturer’s data)

     R= maximum sea level RPM at maximum manifold pressure (from     manufacturer’s data)

     M= maximum sea level manifold pressure at rated RPM (from     manufacturer’s data)

     

     For a Lycoming/Superior 320 (my case):

     

     H= 160

     R= 2700

     M= 28.6

     

     Variables (inputs)

     

     r= actual RPM

     m= actual manifold pressure

     pa= actual pressure altitude (altimeter set to 29.92 inHg)

     ta = actual air inlet temperature at pressure altitude (OAT has     practically the same value)

     

     Outputs

     

     h = calculated horsepower

     h%= calculated percent horsepower

     

     

     On 9/27/2011 9:16 PM, 923te wrote:     [quote]                            Here ya go

        

       hp = torque * RPM / 5252

        

       otherwise check your POH cause it's           different in each plane or

        

       see attachments for O-360

        

        

       [quote]         ---

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jamey

Joined: 10 Jan 2006
Posts: 124

Posted: Tue Sep 27, 2011 10:43 pm Post subject: % HP

Lean of peak %HP is determined by fuel flow.  ROP all the other atmospheric parameters apply.  A good rule of thumb for the big Continentals (IO-520/550) operated LOP is 14.9 HP per gallon per hour of fuel flow.  Probably not helpful to a carbureted Lycoming.  Drop a line to the GAMI guys and see if they have a suggestion.  There's got to be some reasonable equation for approximating out there.  Your equation doesn’t seem terrible as when I plug it into Mathematica it returns some not unreasonable looking values.  Maybe a bit high.

 

Jamey

 

 

From: owner-teamgrumman-list-server(at)matronics.com [mailto:owner-teamgrumman-list-server(at)matronics.com] On Behalf Of Linn Walters

Sent: Tuesday, September 27, 2011 8:33 PM

To: teamgrumman-list(at)matronics.com

Subject: Re: % HP

 

Thanks for the replies.



I should have been a little more specific.  I'm looking for a formula that computes % HP from parameters that are measurable ....  fuel flow, OAT, RPM, MP etc. so I can display the value on my EFIS.  Since the EFIS measures many parameters a formula could compute % HP realtime.  Hard to fly and look at the graphs ......      There is a formula from Van's (below from another email) but it doesn't seem to be accurate for different size engines (not sure which engine really fits), and I don't have the math skills to tweak it.  I was hoping someone might have the magic bullet.

Linn



Van's formula:

h=(H-((R-r)*(5.58-0.125*(M-m))/100 + 7.35*(M-m)) + 2.0*pa/1000)*sqrt((519-3.58*pa/1000)/(460+ta))



h% = h/H*100



where



Constants:



H= maximum sea level horsepower at maximum manifold pressure (from manufacturer’s data)

R= maximum sea level RPM at maximum manifold pressure (from manufacturer’s data)

M= maximum sea level manifold pressure at rated RPM (from manufacturer’s data)



For a Lycoming/Superior 320 (my case):



H= 160

R= 2700

M= 28.6



Variables (inputs)



r= actual RPM

m= actual manifold pressure

pa= actual pressure altitude (altimeter set to 29.92 inHg)

ta = actual air inlet temperature at pressure altitude (OAT has practically the same value)



Outputs



h = calculated horsepower

h%= calculated percent horsepower

On 9/27/2011 9:16 PM, 923te wrote: 

Here ya go



 



hp = torque * RPM / 5252



 



otherwise check your POH cause it's different in each plane or



 



see attachments for O-360



 



 

[quote]

---

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pitts_pilot(at)bellsouth.
Guest

Posted: Tue Sep 27, 2011 10:56 pm Post subject: % HP

Thanks Jamey.  Math is one of my weak areas.  I wish I knew what the     constants are and where they came from.  Your suggestion about GAMI     is a good one.

     Linn

     

     On 9/28/2011 2:40 AM, James Courtney wrote:     [quote]                     v\:* {behavior:url(#default#VML);} o\:* {behavior:url(#default#VML);} w\:* {behavior:url(#default#VML);} .shape {behavior:url(#default#VML);} <![endif]-->         <![endif]-->   <![endif]-->                

Lean of peak %HP is determined by fuel           flow.  ROP all the other atmospheric parameters apply.  A good           rule of thumb for the big Continentals (IO-520/550) operated           LOP is 14.9 HP per gallon per hour of fuel flow.  Probably not           helpful to a carbureted Lycoming.  Drop a line to the GAMI           guys and see if they have a suggestion.  There's got to be           some reasonable equation for approximating out there.  Your           equation doesn’t seem terrible as when I plug it into           Mathematica it returns some not unreasonable looking values.            Maybe a bit high.         

          

Jamey         

          

                                  

From:                 owner-teamgrumman-list-server(at)matronics.com (owner-teamgrumman-list-server(at)matronics.com)                 [mailto:owner-teamgrumman-list-server(at)matronics.com (owner-teamgrumman-list-server(at)matronics.com)] On                   Behalf Of Linn Walters

                 Sent: Tuesday, September 27, 2011 8:33 PM

                 To: teamgrumman-list(at)matronics.com (teamgrumman-list(at)matronics.com)

                 Subject: Re: % HP           

         

         

          

Thanks for the replies.

           

           I should have been a little more specific.  I'm looking for a           formula that computes % HP from parameters that are measurable           ....  fuel flow, OAT, RPM, MP etc. so I can display the value           on my EFIS.  Since the EFIS measures many parameters a formula           could compute % HP realtime.  Hard to fly and look at the           graphs ......                There is a formula from Van's (below from another email) but           it doesn't seem to be accurate for different size engines (not           sure which engine really fits), and I don't have the math           skills to tweak it.  I was hoping someone might have the magic           bullet.

           Linn

           

           Van's formula:

           h=(H-((R-r)*(5.58-0.125*(M-m))/100 + 7.35*(M-m)) +           2.0*pa/1000)*sqrt((519-3.58*pa/1000)/(460+ta))

           

           h% = h/H*100

           

           where

           

           Constants:

           

           H= maximum sea level horsepower at maximum manifold pressure           (from manufacturer’s data)

           R= maximum sea level RPM at maximum manifold pressure (from           manufacturer’s data)

           M= maximum sea level manifold pressure at rated RPM (from           manufacturer’s data)

           

           For a Lycoming/Superior 320 (my case):

           

           H= 160

           R= 2700

           M= 28.6

           

           Variables (inputs)

           

           r= actual RPM

           m= actual manifold pressure

           pa= actual pressure altitude (altimeter set to 29.92 inHg)

           ta = actual air inlet temperature at pressure altitude (OAT           has practically the same value)

           

           Outputs

           

           h = calculated horsepower

           h%= calculated percent horsepower

           

           

           On 9/27/2011 9:16 PM, 923te wrote:                     

Here ya go         

                    

          

                    

hp =               torque * RPM / 5252         

                    

          

                    

otherwise               check your POH cause it's different in each plane or         

                    

          

                    

see               attachments for O-360         

                    

          

                    

          

          	  Quote: 	
		                          

-----                 Original Message -----            

                        

From:                 Linn Walters (pitts_pilot(at)bellsouth.net)            

                        

To:                 grumman2 (teamgrumman-list(at)matronics.com)            

                        

Sent:                 Tuesday, September 27, 2011 7:29 PM           

                        

Subject:                 % HP           

                        

            

           

-->             TeamGrumman-List message posted by: Linn Walters <pitts_pilot(at)bellsouth.net (pitts_pilot(at)bellsouth.net)>

             

             Any ideas on a formula for % horsepower that works for             different size 

             engines?  So far Google has let me p;        Features Chat,             http://www.mnbsp;                    via the Web               href="http://forums.matronics.com">http://forums.matronics.com

             _p;         generous bsp;                    href="http://www.matronics.com/contribution">http://www.matronics.com/c=================

             

                      	
         

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		   http://www.matronics.com/Navigator?TeamGrumman-List_======================http://forums.matronics.com         - List Contribution Web generous nbsp;                        --> http://www.matronics.com/c= 	
                    

         

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