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!!

 

Its easy..






D-Series
+ 10 Pounds
____________
Will turn you out.

 

 

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.

 

like he said there is to many variables to even try to do the math.

 

the ---- did you just say

 

Its just the long version. Stealthmode couldn't make all that rhyme though so it got broken down to what I posted above.

 

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.

 

10lb/min = 100hp ish.

Calculating any further is not worth your time.