cfm requirements
Thread Starter
6th Gear Member
Joined: Oct 2006
Posts: 6,417
From: Cork, Ireland
cfm requirements
Hi all,
i'm about to put together a little calculator (a windows application), that will be free.
Mainly for my own use, but can be distributed once finished (it will be a while as I only get to it when bored).
So the question is, how would you calculate required cfm.
The most common one in use is:
cfm = (RPM * CID) / 3456
with that I believe however that if dual plane manifold is in use this value should be increased by about 10% maybe (at least I read that somehwere).
If someone would buy a vacuum secondary carb (which effectively is a variable cfm size carb, this value could be further increased without having driveability problems).
Maybe I should take into consideration if the boosters are straight-leg/downleg or annular in case it's a holley based carb ..?!
any ideas, what would you want to see?
I was thinking
cfm = (RPM * CID) / 3456
add 10% if vacuum secondary is used
add 10% if dual plane manifold is used
....
PS: this calculator will include 1/8mile-weight-time-hp calculations, rpm/gear/axle/speed calculations and others
to be an allround thingie for what people might need occasionally
i'm about to put together a little calculator (a windows application), that will be free.
Mainly for my own use, but can be distributed once finished (it will be a while as I only get to it when bored).
So the question is, how would you calculate required cfm.
The most common one in use is:
cfm = (RPM * CID) / 3456
with that I believe however that if dual plane manifold is in use this value should be increased by about 10% maybe (at least I read that somehwere).
If someone would buy a vacuum secondary carb (which effectively is a variable cfm size carb, this value could be further increased without having driveability problems).
Maybe I should take into consideration if the boosters are straight-leg/downleg or annular in case it's a holley based carb ..?!
any ideas, what would you want to see?
I was thinking
cfm = (RPM * CID) / 3456
add 10% if vacuum secondary is used
add 10% if dual plane manifold is used
....
PS: this calculator will include 1/8mile-weight-time-hp calculations, rpm/gear/axle/speed calculations and others
to be an allround thingie for what people might need occasionally
6th Gear Member
Joined: Apr 2007
Posts: 10,468
From: California
Thread Starter
6th Gear Member
Joined: Oct 2006
Posts: 6,417
From: Cork, Ireland
just read through it. Thanks a million :-)
I'll use that since they know what they're talking about (that video with the plug reader was quite impressive) ...
I might add basic info to it and will reference to their site in it, so people can read.
Kalli
I'll use that since they know what they're talking about (that video with the plug reader was quite impressive) ...
I might add basic info to it and will reference to their site in it, so people can read.
Kalli
1st Gear Member
Joined: Jun 2007
Posts: 66
From: Colorado
Sounds like an interesting program.
You can also back into CFM using horsepowerd as a given amount of air is needed to go with the amount of gas needed for the power. You'd have to assume running close to perfect mixture, but these days, who can afford to do otherwise!
According to your sig, you and I found nearly the same set of parts for our 302s. What method did you use to figure your carb? I cheated and just called Holley. It all works very well.
Good luck with your program!
Brian
You can also back into CFM using horsepowerd as a given amount of air is needed to go with the amount of gas needed for the power. You'd have to assume running close to perfect mixture, but these days, who can afford to do otherwise!
According to your sig, you and I found nearly the same set of parts for our 302s. What method did you use to figure your carb? I cheated and just called Holley. It all works very well.
Good luck with your program!
Brian
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