where can i find cfm info, cubic feet of air per minute?

Fri Jan 28, 2005 5:32 pm

i just bought me a drop in K&N. i'm still readin about intakes and exhausts n stuff. i just found out about cfm, the amount of air my engine requires per minute, (320i is me motor) and how all this is important. i can guess that i'm getting enough, but does anyone know where i can get me some specific numbers as to what i'm after??
basically, how many cubic feet of air per minute does a 320i want?
thank you for any help.

Fri Jan 28, 2005 5:39 pm

deep dude

i dont know on intake per say.. but it should give an easier breathing than the standard panel type, but some would say the original is better

Fri Jan 28, 2005 5:46 pm

i got the panel type replacement. not the cone one. also i took the horn out from the inside of my box. (damn that doesnt sound funny or anything!) i've read that air intake flow wants to be as straight and smooth as possible, a little lip or something in the flow will cause turbulent air with less power. i dont get any change in sound though. does anyone have a cone filter? how does it sound?
cheers.

Fri Jan 28, 2005 6:44 pm

I've tried the K&N 57i kit which consists of an adapter that fastens to the AFM, a filter which fastens onto the adapter with a jubilee clip and a cold air hose.
I can't say that i noticed any noise difference as the bonnet is well insulated anyway.
This setup usually gives better power gains compared to the flat panel filter. I beleive a selection of filters were tested at Bexley BMW for one of the BMW mags.
I'm now running a better adapter plate on the AFM and a bigger filter, as the K&N adapter plate was poorly designed.

Fri Jan 28, 2005 7:30 pm

If you're going to run an induction kit you need to think about shielding the filter from the engine (you don't want it sucking in hot air

) without this you would actually lose power not gain!! Ideally you want to run something like the Pipercross Viper which is completely sealed with a cold air feed, cold air = more power (ish). Another good way to allow air to flow more freely is to get the intake manifold ported and fit one of the Zone's big bore throttle bodies.. just fitted mine

Fri Jan 28, 2005 8:27 pm

The hot air issue is only a minor concern when you are stationary or in slow moving traffic.
When you are making normal progress the ram air into the engine bay plus the cold air snorkel/hose will allow sufficient cold air to the filter.
For maximum effect though the Viper arrangement is better, but power gains will be minimal.
Alternatively you could make an airbox for the filter and have the hose
connected directly to it.
I tried a remote filter and had the hose connected to the AFM instead of the filter, due to the lack of space to fit a filter behind the grill, i removed the nearside full beam light unit and modified a spare light unit housing and had the cone filter with chrome cap poking out of the hole.
It looked the business but i realised i would fall foul to MOT requirements and have just one full beam lamp.

Fri Jan 28, 2005 11:48 pm

confusion wrote:i just bought me a drop in K&N. i'm still readin about intakes and exhausts n stuff. i just found out about cfm, the amount of air my engine requires per minute, (320i is me motor) and how all this is important. i can guess that i'm getting enough, but does anyone know where i can get me some specific numbers as to what i'm after??
basically, how many cubic feet of air per minute does a 320i want?
thank you for any help.

It's more or less a mass conservation thing. Air in plus fuel in will equal exhaust out.

CFMs will be based on the bore and stroke of the motor, and the engine speed. To do some quick calcs, assume that the egine draws enough vac. to completely fill the combustion chamber with air.

So you've got pi*BoreÃƒ”šÃ‚²/4*Stroke*RPM/2*N=Cubic Feet per Minute
where N is number of cylinders, in this case 6 for the M20B20
and Bore and Stroke measurements are in FEET!

-M

Sat Jan 29, 2005 5:25 pm

damn thass some comperlacated stuff man!! i don't suppose you could do that equation for me! i've got 1995 cc 6 cylinder. 320i. can you do it form that.

MY BRAIN HURTS!

Sat Jan 29, 2005 5:54 pm

confusion wrote: damn thass some comperlacated stuff man!! i don't suppose you could do that equation for me! i've got 1995 cc 6 cylinder. 320i. can you do it form that. MY BRAIN HURTS!

Go to www.aim.com and use their web client to IM me...we'll do it live time mate!

Sat Jan 29, 2005 6:34 pm

Isnt it directionaly related to RPM?

Sat Jan 29, 2005 6:37 pm

confusion wrote: damn thass some comperlacated stuff man!! i don't suppose you could do that equation for me! i've got 1995 cc 6 cylinder. 320i. can you do it form that. MY BRAIN HURTS!

Why aren't you asking this on an E36 forum then??

A 1995 320

Sat Jan 29, 2005 7:01 pm

E30Adam wrote:
confusion wrote: damn thass some comperlacated stuff man!! i don't suppose you could do that equation for me! i've got 1995 cc 6 cylinder. 320i. can you do it form that. MY BRAIN HURTS!
Why aren't you asking this on an E36 forum then??

A 1995 320

I think he means a 1995cc engine

not the year of his motor!!