Calculate HP from airflow! - Help Needed!
#1
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 0.07031 = 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!!
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 0.07031 = 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!!
#4
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.
#6
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 0.07031 = 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!!
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 0.07031 = 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!!
#8
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.
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.
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