Likes Likes:  0
Results 1 to 3 of 3

Thread: P-Ponk engines and JPI engine monitor constants

  1. #1
    windknot54's Avatar
    Join Date
    Jun 2014
    Bend, OR
    Post Thanks / Like

    P-Ponk engines and JPI engine monitor constants

    When installed my new 0-470-50, I added a JPI EDM-830 engine monitor. The EDM-830 calculates percent horsepower based on the MAP, RPM, altitude, and OAT.

    During the setup process, you need to enter a couple of constants that the EDM-830 uses to calculate the percent horsepower (%HP). Of particular interest are: 1) the engine horsepower (hp); and 2) the ‘horsepower constant’ (HPC).

    Lacking the results of a dynamometer test, the choice of the horsepower value for the 0-470-50 could be a bit subjective. The P-Ponk STC states 235 hp; Steve Knopp claims between 265 hp and 275 hp. I had a discussion with the JPI technical representative about the significance of this value, but I never received a satisfactory (or comprehendible) answer.

    The horsepower constant has a clear and obvious impact on the %HP. For any particular power setting: increase the value of the HPC and the %HP increases, decrease the value of the HPC and the %HP decreases.

    I asked the Knopps for information they might have on the 0-470-50 performance at altitude. Their response was that they believed the engine performed similarly to the IO-520-A, which has the same bore and stroke, and compression ratio. So, I have been working with the attached IO-520-A performance chart from Continental.

    I’ve been flying around at various power settings and testing out the effects of the various constants. I can't fly lower than 5,000 around my place, so my testing has been at 5,000' and 7,500'. After all my experimenting, I have ended up using hp=275 and HPC=126 – a least for the moment.

    I know many of you will be saying – “What’s the point? It’s all meaningless”. You’re probably right, but I’m an engineer and I love this stuff.

    I would be interested in hearing anyone else’s choices on these constants and your experience.

    Name:  I0-520-A performance curves.jpg
Views: 1477
Size:  123.9 KB
    Thanks JohnnyR thanked for this post

  2. #2
    hotrod180's Avatar
    Join Date
    May 2008
    Port Townsend, WA
    Post Thanks / Like
    Percent-of-power gauge:

    $ - $$ - $$$ - $WOW!

    THis is applicable to the fuel flow gauge also.
    Cessna Skywagon-- accept no substitute!

  3. #3
    skywagon8a's Avatar
    Join Date
    Mar 2008
    SE Mass
    Post Thanks / Like
    Since you do not know the horsepower, can you back into your question by comparing the specific fuel consumption to the fuel flow with the resultant answer being your horsepower? Isn't there an engineering calculation for this approach?

Similar Threads

  1. Engine Monitor
    By Rice farmer in forum Cafe Supercub
    Replies: 43
    Last Post: 04-04-2016, 10:25 PM
  2. EI CGR-30P engine monitor
    By Monte in forum Modifications
    Replies: 6
    Last Post: 06-03-2014, 07:37 AM
  3. EXP Engines-Subaru EJ-22 Engine
    By J5Ron in forum Experimental Cubs
    Replies: 10
    Last Post: 09-29-2008, 08:40 AM



Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts