Relation between CFM and HP

[brandoracing]

Hi guys.
Yesterday I talk with one of my friend and talking about the relationship of CFM and HP.
I think is depends from the pressure test.
But for example,@28" where is the correct relation?
Is also to know and develop the correct size of a piece.
for example,this carburettor runner,enough for XXX hp?
And,this head,for a turbo engine,can support XXX hp for each cylinder?

[Hotz]

My friend Brando, there is an excel spreadsheet forum here that makes this calculation if I remember, unfortunately I do not remember where this.

I think it was Jhon Holm who shared. (excuse me! how I not think in English many things are lost).

If you do not know, this is a place with lots of information.
http://speedtalk.com/forum/index.php

[storm]

There are websites that have HP calculators, do a search for CFM to HP calculator and you can go from there.

From memory one of the well known Pontiac modification engines shops has one (Buttler performance maybe?).

[c.watson]

CFM @ max lift and 28"wc x 0.257 gets you close, depends on transmission losses,hope this helps.
Clive

[saltfever]

Thank you Mr. Watson. I would like to look into that a little bit more. Could you suggest other sources or information about the HP/CFM subject?

[Hotz]

Here calculator!

http://users.erols.com/srweiss/calcafhp.htm

http://www.wallaceracing.com/calcafhp.php

small Talk Theory:

http://www.speedtalk.com/forum/viewtopi ... =1&t=28602


Brando holiday

[1960FL]

CFM @ max lift and 28"wc x 0.257 gets you close, depends on transmission losses,hope this helps.
Clive

This formula X the number of cylinders is used to provide the HP Potential based solely on intake flow it is meant to be used based on the flow of the entire intake tract Head + Manifold + Carb + Air intake and is based on Crank HP. The details surrounding this one example can be found in Harold Bettes's book Engine Airflow in Practice and Theory. http://www.amazon.com/Engine-Airflow-HP ... 1557885370 He also has many other formulas and concepts toward HP estimation.

Remember just because your intake port can flow 300 CFM does not mean your engine will make 76 HP per cylinder. but conversely if you said you wanted to build a small block Chevy that made 800HP at the crank you could perform the inverse and say 800/8 = 100, 100/.257 = 390 thus your intake track will need to flow at least 390CFM per cylinder to reach this goal and that is only part of equation. Remember this is based on naturally aspirated combustion.

Rick

[saltfever]

. . . The details surrounding this one example can be found in Harold Bettes's book Engine Airflow in Practice and Theory. http://www.amazon.com/Engine-Airflow-HP ... 1557885370 He also has many other formulas and concepts toward HP estimation. Rick

Thanks Rick. That is the information I was looking for. I forgot I had Betts' book. Great book! I want to understand it rather than just filling out a calculator field.

[brandoracing]

very interest post! I had the book of Bettes. All of this is awesome for naturally aspirated engine\heads.
But for we turbo guys?
I remember an incredible interesting topic on this forum,a guy very expert says the minimus difference of cfm from N\A and turbos,because CFM as an volumetric measure,in a turbos change the density.
So,I have interest to talk with they of this.