What do our engines flow out the exhaust?

[Allnew2Me]

I am researching a new 4" exhaust system for my truck and am seeing that all of the mufflers have a stated CFM flow, or rather 3 separate flow numbers. What does the 5. 9 flow at power? I understand that it depends on how much fuel you are burning and the individual mods, but what is a ballpark figure?

I have seen one muffler flow 1000CFM and another about the same size flow almost 1600 dues to internal baffles I suppose.

How much is needed and is too much flow (not enough back pressure) a bad thing? Thanks



I found this on the Cummins muffler site but I must be doing something wrong I can't get it to work, anyone want to take a shot?



1. To calculate exhaust flow (exhaust CFM) use:

Exhaust CFM = Disp. x RPM x E x (Temp. + 460) divided by

C x 941760

2. To calculate intake flow (intake CFM) use:

Intake CFM = Disp. x RPM x E

C x 1728

3. To calculate exhaust flow (exhaust CFM) if intake flow (intake CFM) is known, use:

Exhaust CFM = 2. 7 x intake CFM (diesel) or 3. 1 x intake CFM (gas)

Disp. = Engine displacement in cubic inches (to convert liters to cubic inches, multiply by 61. 002)

RPM = Engine speed at rated HP

E = Efficiency (. 85 for naturally aspirated, 1. 4 for turbocharged, 1. 6 for turbocharged/aftercooled and 1. 2 for engines

with scavenging blowers)

Temp. = Exhaust temperature in °F (if not known use 900° for diesel or 1200° for gas)

C = 1 for 2 cycle engines, 2 for 4 cycle engines

 

[1965LONEWOLF]

i would like to know also

 

[sfr1047]

Try using cubic inches as the displacement. 5. 9L = 360 ci

That gives 2000 rpm at 600 deg ( +460 ) about 567 CFM

And 3000 RPM at 1200 deg ( +460 ) about 1332 CFM

Those numbers seem to be in the ball park.

 

[Doubleclutch]

Why are you using a scalpel to chop down a tree? A very wise man from Wyoming... who has been making exhausts since cars started with a crank... observed that the only reason a diesel has an exhaust pipe is to keep the soot marks on the back of the truck. Youse doesn't need no stinking muffler! Unless your truck has a radio... ALL the energy expended from the turbocharger is waste!!! Diesels don't do backpressure like a gasser!!!!!!!! The turbo is SUPPOSED to add extra air. As the exhaust valve closes, the TURBO pressurizes the cylinder, not a standing wave of backpressure in the manifold. For all intents and purposes, if it weren't for the thermodynamic heat/cool issues, the exhaust could end at the turbo outlet.

Bottom line... . get either a kit exhaust, or a big muffler. Look up posts by Joe Donnelly via "search". I know he's quoted a Walker muffler number based on dyno results.

Greg