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1% hp gain for each 44.6 Degrees temp drops

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    #1

    1% hp gain for each 44.6 Degrees temp drops

    * means degrees btw

    A 7*C (12.6* Fahrenheit) drop in temp equates to 1% increase in HP
    A 7*C (12.6* Fahrenheit) increase in temp equates to 1% lose in HP

    That means, on a 130hp engine, when you drop intake temps by 12.6 degrees Fahrenheit, you will gain 1% hp (1.3hp)

    Calculation taken from A. Graham Bell's 4 stroke performance tuning book 3rd edition 2006...page 8 third paragraph

    This info is taken from someone who literally wrote SEVERAL books on tuning and performance...hardback books I might add. I suggest you pick up his forced induction book AND his 4 stroke performance hardbacks...you will NOT waste your money.

    *corrected formulas as I posted actual temperatures and NOT CHANGE in temps...apologies...44.6 is incorrect...12.6 is correct for CHANGE in temps
    Last edited by bcjammerx; 10-03-2009, 05:23 AM.
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    #2
    Good Info...

    Interfooler here i come!!!!

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      #3
      Physics is my favorite
      IF, implies a possibility.

      Comment

        #4
        I love this book...it gives some very clear info...but does assume you already have some knowledge. But if you don't you won't be lost.

        I'm sure you could find this info on the net...but case in point...you WILL find wrong info...and if you don't know what is correct you can be dupped as I was.

        It gives air pressure charts at sea level as xx temp and air density...etc.

        along with how humidity coupled with temperature effect air intake...and I'm only at page 9...it's just nice to have that kind of info laid out nicely by someone who knows what they are talking about.

        I love how he even says,
        "From what I hear, some of the stuff getting on to computer screens is pretty questionable,; on the other hand there is information that is quite accurate, providing you are tuning a small-block Chev V8!"

        The same is true of engine books I've bought. LOT of good info...on chevy v8's...doesn't help me out...this book IS FOR 4 cylinder engines. Great stuff.
        ____

        Comment

          #5
          Just because he wrote a book, doesn't mean anything. I guarantee the 3*-5* per 1% number is more accurate.
          The OFFICIAL how to add me to your ignore list thread!

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            #6
            thats really good to know!!

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              #7
              Won't the amount of moisture in the air also have a factor on the number? For example on more humid conditions, will the percent of added horsepower be any different then with less humid conditions?
              I would think the more wet the air is, it would not compress as much as dry air and also the fuel would not be able to atomize as good as if the air were more dry. If the air is more humid, less oxygen would be able to fit in the cylinder because moisture is taking up space where oxygen could be. So the optimal type of air would be cool and dry.
              It's kinda hard to explain what I'm saying but hopefully you understand. Just pondering a little bit lol.
              Last edited by AbsurdNY; 10-01-2009, 02:53 PM.


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                #8
                Originally posted by AbsurdNY View Post
                Won't the amount of moisture in the air also have a factor on the number? For example on more humid conditions, will the percent of added horsepower be any different then with less humid conditions?
                I would think the more wet the air is, it would not compress as much as dry air and also the fuel would not be able to atomize as good as if the air were more dry. If the air is more humid, less oxygen would be able to fit in the cylinder because moisture is taking up space where oxygen could be. So the optimal type of air would be cool and dry.
                It's kinda hard to explain what I'm saying but hopefully you understand. Just pondering a little bit lol.
                Yes, humidity plays a part, more for the second reason.

                The water takes the place of the air, and thus requires a leaner mixture of fuel.
                The OFFICIAL how to add me to your ignore list thread!

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                  #9
                  Originally posted by bcjammerx View Post
                  * means degrees btw

                  A 7*C (44.6* Fahrenheit) drop in temp equates to 1% increase in HP
                  A 7*C (44.6* Fahrenheit) increase in temp equates to 1% lose in HP

                  That means, on a 130hp engine, when you drop intake temps by 44.6 degrees Fahrenheit, you will gain 1% hp (1.3hp)

                  Calculation taken from A. Graham Bell's 4 stroke performance tuning book 3rd edition 2006...page 8 third paragraph

                  Why post? It's a good figure to have floating around...plus I had at one time said that 10 degree drop equaled 1%hp increase...and that spec was based on internet searching...and that info was wrong. This info is taken from someone who literally wrote SEVERAL books on tuning and performance...hardback books I might add. I suggest you pick up his forced induction book AND his 4 stroke performance hardbacks...you will NOT waste your money.
                  FWIW, a 7 degree celsius change in temp is equal to a 12.6 degree change in fahrenheit temp (a degree C = (9/5) a degree F). Your 44.6 number comes from the conversion formula which includes the offset of 32 degrees (F = (9/5)C + 32)...that offset doesn't come into play when you're just talking about a change in temp.

                  If the temp goes from 0 degrees C to 7 degrees C, it went from 32 degrees F to 44.6 degrees F (0C=32F, 7C=44.6F) for a change of 12.6 degrees. So it does actually look like the info you previously had from the internet was a fair approximation.
                  Last edited by Grin0048; 10-02-2009, 01:31 AM.

                  Comment

                    #10
                    ^^^^ Yep. Well said Grin0048.

                    Comment

                      #11
                      Originally posted by Grin0048 View Post
                      FWIW, a 7 degree celsius change in temp is equal to a 12.6 degree change in fahrenheit temp (a degree C = (9/5) a degree F). Your 44.6 number comes from the conversion formula which includes the offset of 32 degrees (F = (9/5)C + 32)...that offset doesn't come into play when you're just talking about a change in temp.

                      If the temp goes from 0 degrees C to 7 degrees C, it went from 32 degrees F to 44.6 degrees F (0C=32F, 7C=44.6F) for a change of 12.6 degrees. So it does actually look like the info you previously had from the internet was a fair approximation.
                      I knew something was wrong with the math, but with the kids hollering around me, I couldn't quite figure it out. Good catch!

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                        #12
                        gotcha...12.6 I will change to
                        Last edited by bcjammerx; 10-03-2009, 05:21 AM.
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