Just how much is your power adder helping you?

Track Times and Triumphs

  1. Morbid Intentions

    Morbid Intentions Well-Known LVC Member

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    Oct 10, 2007
    so over the course of my involvement with different automotive sites I've really been a big part of the "street and strip" sections the most.... a couple months ago I came up with a rough estimate theory and an early stage mathematical breakdown of just how much a power adder would be helping you at a given elevation and posted it on the mustang site I moderate (I thought I would share this with you guys)... because as we all know, N/A cars suffer the most the higher you go... but just how much more do they suffer on a BHP scale? that is the question I found myself asking when I started this little mini breakdown

    turbocharged/supercharged elevation equation... simple steps


    figure out your TOTAL PSI @ sea level
    (atmospheric pressure + boost pressure = TOTAL PSI)


    Figure out your CORRECTED PSI for your elevation and add it to your boost pressure

    (2,000ft = -1.1PSI)


    Divide TOTAL sea level PSI into CORRECTED PSI


    your final product will be a percentage... you need to minus this percentage from 100% and this is your total percentage of BHP lost at given elevation through a forced induction application

    now that you have your percentage of power lost through your turbocharged application you need to find out what a N/A car would lose at the same BHP

    so take your total PSI @ elevation and divide it into atmospheric pressure (considering there is no boost pressure)

    this percentage again, you need to minus from 100% and this is your total percentage of BHP lost at given elevation through a N/A application

    now that you have percentages lost from both N/A and F/I application... now you have to figure out the difference in your given BHP between the two

    this is how much of a help your forced induction is helping you at your elevation compared to other N/A cars


    bone stock 2003 SVT cobra @ 6,000ft

    stock PSI = 8PSI


    14.7PSI + 8PSI = 22.7PSI

    22.7 TOTAL PSI @ sea level for terminator

    now factor in elevation


    14.7PSI - 3.3PSI = 11.4PSI

    @ 6,000ft atmospheric pressure is 11.4PSI

    now that we have corrected atmospheric pressure.... let's do the math

    a terminator loses 15% of it's power @ 6,000ft... 15% of it's power is 59BHP, making a terminator into a 331BHP car @ 6,000ft

    now let's equate for a naturally aspirated car for comparison to see just how much it's supercharger is helping it at elevation

    math time...

    seeing as a naturally aspirated engine with the same power output makes 304BHP and the terminator actually makes 331BHP @ 6,000ft we can conclude that 8PSI of boost pressure is helping the terminator make 27BHP @ 6,000ft... a small margin... but as boost pressure and elevation increases, so does this figure

    (I know a terminator is under rated from the factory... I was just using the factory BHP numbers as a simple guide for now... this same principle can be used on and horsepower number [RWHP/BHP].. and even your torque if you wish)

    again... just like DA factoring, it should be taken with a grain of salt and used as a rough estimate guide

    and as everyone knows... bottle fed setups suffer the least, so if you are running gas then this doesn't apply to you at all

    EDIT: one of the big reasons I came up with this is because when they tested the ecoboost MKS against all of the european V8 sedans @ 12,000ft and the MKS came in second place... I knew it was a staged BS comparison @ 12,000ft.... at sea level there is good chance the MKS would be dead last, I just needed the math and facts together to show the people that didn't understand why
  2. RedLinCoupe

    RedLinCoupe Active LVC Member

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    Mar 10, 2009
    Hmmmm, interesting. I skimmed a little bit it sounds accurate. I grew up racing in Denver CO (5280ft, or 1 mile) and i know that boosted cars dont loose as much performance at high elevations.

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