No announcement yet.

Injector size vs Horsepower

This is a sticky topic.
  • Filter
  • Time
  • Show
Clear All
new posts

  • Injector size vs Horsepower

    If you want to know how much HP an injector can support,here is the formula for figuring that out.

    ((Injector flow rate in lb/hr X # of injectors) / Break Specific Fuel Consumption) X Maximum duty cycle of injector

    so, if you have a 44 lb/hr injector on a V8 that will make a .5 BSFC and you want a maximum of 85% duty cycle (this in how long the injector is spraying fuel per cycle. 85% is a good baseline) here is the results;

    44 X 8 = 352, 352 / .50 = 704, 704 x .85 = 598.4 HP.

    Our injector flow values are based on a 43.5 psi fuel pressure. If you change the fuel pressure, you will need to know the new flow rate to make the formula work.

    Formula for injector flow vs. pressure;

    (Square Root (new pressure / old pressure)) X old pressure

    New pressure = 60, old pressure = 43.5 with 44 lb/hr injectors;

    60 / 43.5 = 1.378, sqrt 1.378 = 1.174, 1.174 X 44 lb/hr = 51.7 lb/hr

    This new flow rate would allow the following HP calculation;

    ((51.7 X 8) / .5) X .85 = 703 HP

  • #2
    The injector calculation doesn't look correct. Let's take the pro flow as a base. There claim is its rated for up to 450hp with 29lb injectors. So how do we check this. Fist the power 450 X .5 . You get 225 which is the total amount you need to support 450hp. You then divide 225 by the number of cylinders you have. So 225lbph / 8 is 28.1. So 8 29lb injectors is slightly more than need for 450hp.


    • #3
      It's just "general" basic math. So it's not 100% foolproof.

      Pro-Flo 2 #35030 comes with 29 lb/hr injectors..... It's rated up to 350 HP.
      This system has a unique 2 barrel throttle body that flows 250 CFM less then the other throttle bodies.

      The systems are dyno tested. So Edelbrocks systems are accurate for the HP ratings.....Most use Edelbrock heads, and camshafts on the "published" dyno charts.
      Posting Green

      All my posts are made from 80% post consumer waste recycled pixels :-)