formula

[Irish_Alley]

i think im working on a formula but need approval to see if it all checks out.


you need 1.5 cfm per hp for your carb. you need 2.2 cfm per hp for your exhaust.


so lets say you have a 600 cfm carb the max hp it can produce is 600/1.5=400 (this is the MAX that carb can produce at any given RPM)

so now you need to support that 400 HP. 400 x 2.2=880 cfm out of your tail pipe. so a good section of exhaust pipe can support 115cfm/per square inch

and according to this chart on exhaust pipe cfm a 400 hp motor will only need 3.14" single pipe & 2.5 for dual pipes



Now these formulas are for MAX HP not what you might make just the MAX you can make

Engine size / 2 x Redline RPM / 12 / 12 / 12= Carb CFM

Carb cfm/1.5=Max Hp

(Max Hp x 1.5= Carb CFM)

Max Hp x 2.2 = Exhaust CFM

(Exhaust CFM / 2.2 = Max Hp)




http://www.exhaustvideos.com/faq/how-to-calculate-muffler-size-pipe-diameter/

[Irish_Alley]

so if a 350 redlines at 5000 can only use a 506 cfm carb (or a tad bigger)
(Engine size / 2 x Redline RPM / 12 / 12 / 12= Carb CFM)

550 cfm carb / 1.5 = 366hp
(Carb cfm/1.5=Max Hp)

366 x 2.2=805.2
(Max Hp x 2.2 = Exhaust CFM)

[Irish_Alley]

another note
the mentioned 366 hp 350 mentioned above is putting 45.7 hp per cylinder.
and with the above mentioned formula every hp needs 2.2 cfm for exhaust the exhaust manifold/header pipe would have to flow 100.54 cfms

and each pipe would have to be 1.6"