Calculate HP from airflow! - Help Needed!
I need some help on this one.
Well basically it is exactly how the title says! .... How one can be able to calculate HP from airflow? Example: From my calcualtions (based on a HONDA D15) I was able to determine aiflow of apprximately 15.68lb/min. (ie. {91cid x 0.5(4-stroke) x 6750rpm x 0.85VE}/1728 = 151CFM @ 1 Pressure Ratio) Desired Pressure Ratio is 1.4762 (=7PSI) [={14.7+7}/14.7] Therefore Airflow would be 151CFM X 1.4762PR = 223CFM Convert 223CFM to LB/MIN @ 112 degrees F = (223 x 0.070318) = 15.68 LB/MIN So far so good..... the only question mark that may do some substantial difference is Volumetric Efficiency @ 1PR (I assume that 85% is suitable for now..correct me if I am wrong) Now here comes what I am not understanding: If I know airflow ie.(15.68lb/min therefore 940.80lb/hr {15.68 x 60}) I also know the ideal AIR TO FUEL RATIO (ie 14.7 air : 1 fuel) Now I can identify how much ideal fuel is required for 940.8lb/hr of air (ie 940.8lb/hr / 14.7 = 64lb/hr of fuel) Now I know that I should ideally inject 64lb/hr of fuel @ 6750RPM I also know a rough approximation of how much fuel consumes 1 horsepower (ie Brake Specific Fuel Consumption - BSFC) which it seems to vary from 0.50lb/hr - 0.65lb/hr. Now I can calculate how much Power I will be able to make with 64lb/hr (ie 64lb/hr / .55 = 116HP) I will be able to make only 116HP ???.... I AM DOING SOMETHING TERRIBLY WRONG! Can someone enlighten me up!!! Nevertheless... the research continues!!! Thanks!! |
Re: Calculate HP from airflow! - Help Needed!
Its easy..
D-Series + 10 Pounds ____________ Will turn you out. |
Re: Calculate HP from airflow! - Help Needed!
Originally Posted by imburne
Its easy..
hell yeah!!!! D-Series + 10 Pounds ____________ Will turn you out. |
Re: Calculate HP from airflow! - Help Needed!
Can't say how it works on other platforms but for most people with a decent tune and a 4g63. 1lb/min will make somewhere in the vicinity of 10.5hp. Its just a ballpark, there are so many variables.
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Re: Calculate HP from airflow! - Help Needed!
Originally Posted by aero
there are so many variables.
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Re: Calculate HP from airflow! - Help Needed!
Originally Posted by borg_jos
I need some help on this one.
Well basically it is exactly how the title says! .... How one can be able to calculate HP from airflow? Example: From my calcualtions (based on a HONDA D15) I was able to determine aiflow of apprximately 15.68lb/min. (ie. {91cid x 0.5(4-stroke) x 6750rpm x 0.85VE}/1728 = 151CFM @ 1 Pressure Ratio) Desired Pressure Ratio is 1.4762 (=7PSI) [={14.7+7}/14.7] Therefore Airflow would be 151CFM X 1.4762PR = 223CFM Convert 223CFM to LB/MIN @ 112 degrees F = (223 x 0.070318) = 15.68 LB/MIN So far so good..... the only question mark that may do some substantial difference is Volumetric Efficiency @ 1PR (I assume that 85% is suitable for now..correct me if I am wrong) Now here comes what I am not understanding: If I know airflow ie.(15.68lb/min therefore 940.80lb/hr {15.68 x 60}) I also know the ideal AIR TO FUEL RATIO (ie 14.7 air : 1 fuel) Now I can identify how much ideal fuel is required for 940.8lb/hr of air (ie 940.8lb/hr / 14.7 = 64lb/hr of fuel) Now I know that I should ideally inject 64lb/hr of fuel @ 6750RPM I also know a rough approximation of how much fuel consumes 1 horsepower (ie Brake Specific Fuel Consumption - BSFC) which it seems to vary from 0.50lb/hr - 0.65lb/hr. Now I can calculate how much Power I will be able to make with 64lb/hr (ie 64lb/hr / .55 = 116HP) I will be able to make only 116HP ???.... I AM DOING SOMETHING TERRIBLY WRONG! Can someone enlighten me up!!! Nevertheless... the research continues!!! Thanks!! |
Re: Calculate HP from airflow! - Help Needed!
Its just the long version. Stealthmode couldn't make all that rhyme though so it got broken down to what I posted above.
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Re: Calculate HP from airflow! - Help Needed!
What is the problem??
You took stock airflow numbers, at atmospheric pressure, and got ~ stock hp numbers... :1 if you take and change the variables to what it could be boosted (higher air flow and pressure), you will get... wait for it..... Different numbers. :X |
Re: Calculate HP from airflow! - Help Needed!
10lb/min = 100hp ish.
Calculating any further is not worth your time. |
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