CFM Question??
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From: New Caney Texas
CFM Question?? Does anyone know how many CFM"s a mostly stock LS1 will flow through the intake at WOT?? I'm building a true ram air setup, and was just kind of curious. Any help would be greatly appreciated.
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From: New Caney Texas
Thats good news!! With my ram air scoop size of 2"1/2 inch / 13 inch. I figured at 60 mph I should have an intake charge of 745 cfm. If the engine exceeds that amount then the ram air effect is nullified. If at WOT i am only flowing 260 than I will have the ram air effect at a lower speed and I don't have to worry about the intake demand exceeding the ram air effect. How did you get those numbers??
Go to the stickies, "intake & exhaust." An LS6 flows 245 @ .550" lift, then your rockers bring it up to .582" valve lift & the LS6 flows 260 @ .600" lift. I was a bit high @ 260, it's more like 255. In either case, your between 245-260. BTW, to get 300 CFM a big cam, & a very high flowing intake is required. Most intakes won't reach 300 CFM. So, you can be sure that the 245-260CFM is pretty close for your set-up.
BTW, there was a member in the advanced tech area of this site that did a ram air test with intake pressure measurements. You may be interested in his findings.
BTW, there was a member in the advanced tech area of this site that did a ram air test with intake pressure measurements. You may be interested in his findings.
Go to the stickies, "intake & exhaust." An LS6 flows 245 @ .550" lift, then your rockers bring it up to .582" valve lift & the LS6 flows 260 @ .600" lift. I was a bit high @ 260, it's more like 255. In either case, your between 245-260. BTW, to get 300 CFM a big cam, & a very high flowing intake is required. Most intakes won't reach 300 CFM. So, you can be sure that the 245-260CFM is pretty close for your set-up.
BTW, there was a member in the advanced tech area of this site that did a ram air test with intake pressure measurements. You may be interested in his findings.
BTW, there was a member in the advanced tech area of this site that did a ram air test with intake pressure measurements. You may be interested in his findings.
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yeah that was me i think...ram air is a great mod i did run some autotap runs for you and the most mass air flow i saw with my cam only was 330grams/sec or 43.65lb/min...you can use which ever...hope this helps you some later man
330 g/s is just about 245 CFM if I use my set-up as a reference. Seems about right for a cam only.
330 g/s is just about 245 CFM if I use my set-up as a reference. Seems about right for a cam only.
EDIT: Monday
chrs1313 & I have been discussing this further through PM's. Chris has pointed out that a straight conversion of 330 g/s indicates a higher CFM rate. Chris is correct. My estimate was based on a single intake runner flow @ a time using the known single rinner flow rates of my set-up, as a reference. So, for a single runner, my estimate remains valid. However, a straight mathematical conversion of 330 g/s into CFM indicates that more than one runner is filling with air @ a time. This is the case & should have been included in my estimate. To end the long story, the CFM if chris's set-up is in the neighborhood of 542 to 591 CFM.
Here is a reference calculation for you guys to check for accuracy.
2,8316.8 cm^3 / ft^3
.00129 grams / cm^3
2,8316 x .00129 = 36.53 grams / ft^3
330 grams / sec x 60 sec / min = 19,800 grams / min (measured by MAF)
19,800 / 36.53 = 542 CFM (measured by MAF) , more than one runner pulling air @ a time.
Please, all feel free to check calculations & comment, as the goal is to be accurate. Thank-you
Last edited by LS1-450; Sep 1, 2008 at 11:17 AM.
Thread Starter
On The Tree
Joined: Apr 2008
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From: New Caney Texas
EDIT: Monday
chrs1313 & I have been discussing this further through PM's. Chris has pointed out that a straight conversion of 330 g/s indicates a higher CFM rate. Chris is correct. My estimate was based on a single intake runner flow @ a time using the known single rinner flow rates of my set-up, as a reference. So, for a single runner, my estimate remains valid. However, a straight mathematical conversion of 330 g/s into CFM indicates that more than one runner is filling with air @ a time. This is the case & should have been included in my estimate. To end the long story, the CFM if chris's set-up is in the neighborhood of 542 to 591 CFM.
Here is a reference calculation for you guys to check for accuracy.
2,8316.8 cm^3 / ft^3
.00129 grams / cm^3
2,8316 x .00129 = 36.53 grams / ft^3
330 grams / sec x 60 sec / min = 19,800 grams / min (measured by MAF)
19,800 / 36.53 = 542 CFM (measured by MAF) , more than one runner pulling air @ a time.
Please, all feel free to check calculations & comment, as the goal is to be accurate. Thank-you
chrs1313 & I have been discussing this further through PM's. Chris has pointed out that a straight conversion of 330 g/s indicates a higher CFM rate. Chris is correct. My estimate was based on a single intake runner flow @ a time using the known single rinner flow rates of my set-up, as a reference. So, for a single runner, my estimate remains valid. However, a straight mathematical conversion of 330 g/s into CFM indicates that more than one runner is filling with air @ a time. This is the case & should have been included in my estimate. To end the long story, the CFM if chris's set-up is in the neighborhood of 542 to 591 CFM.
Here is a reference calculation for you guys to check for accuracy.
2,8316.8 cm^3 / ft^3
.00129 grams / cm^3
2,8316 x .00129 = 36.53 grams / ft^3
330 grams / sec x 60 sec / min = 19,800 grams / min (measured by MAF)
19,800 / 36.53 = 542 CFM (measured by MAF) , more than one runner pulling air @ a time.
Please, all feel free to check calculations & comment, as the goal is to be accurate. Thank-you
A paper filter w/ the same surface area of a K&N filter will flow better (less pressure drop). A cloth type filter (K&N) becomes an advantage when the surface area is greater than the paper filter it replaces. This is why a large cone will outflow a stock paper filter.
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EDIT: Monday
chrs1313 & I have been discussing this further through PM's. Chris has pointed out that a straight conversion of 330 g/s indicates a higher CFM rate. Chris is correct. My estimate was based on a single intake runner flow @ a time using the known single rinner flow rates of my set-up, as a reference. So, for a single runner, my estimate remains valid. However, a straight mathematical conversion of 330 g/s into CFM indicates that more than one runner is filling with air @ a time. This is the case & should have been included in my estimate. To end the long story, the CFM if chris's set-up is in the neighborhood of 542 to 591 CFM.
Here is a reference calculation for you guys to check for accuracy.
2,8316.8 cm^3 / ft^3
.00129 grams / cm^3
2,8316 x .00129 = 36.53 grams / ft^3
330 grams / sec x 60 sec / min = 19,800 grams / min (measured by MAF)
19,800 / 36.53 = 542 CFM (measured by MAF) , more than one runner pulling air @ a time.
Please, all feel free to check calculations & comment, as the goal is to be accurate. Thank-you
chrs1313 & I have been discussing this further through PM's. Chris has pointed out that a straight conversion of 330 g/s indicates a higher CFM rate. Chris is correct. My estimate was based on a single intake runner flow @ a time using the known single rinner flow rates of my set-up, as a reference. So, for a single runner, my estimate remains valid. However, a straight mathematical conversion of 330 g/s into CFM indicates that more than one runner is filling with air @ a time. This is the case & should have been included in my estimate. To end the long story, the CFM if chris's set-up is in the neighborhood of 542 to 591 CFM.
Here is a reference calculation for you guys to check for accuracy.
2,8316.8 cm^3 / ft^3
.00129 grams / cm^3
2,8316 x .00129 = 36.53 grams / ft^3
330 grams / sec x 60 sec / min = 19,800 grams / min (measured by MAF)
19,800 / 36.53 = 542 CFM (measured by MAF) , more than one runner pulling air @ a time.
Please, all feel free to check calculations & comment, as the goal is to be accurate. Thank-you
The density of air would change, so g/cm^3 would be more or less depending upon atmospheric conditions.
FWIW doing a very basic back of the napkin calculation on an LS1's CFM flow at WOT:
346CI = 0.2 ft^3
Half of the displacement in a 4 cycle engine is covered in one crank rotation (360 degrees), or 0.1 ft^3.
0.1 ft^3 per RPM X 6,000 rpms (near redline) = 600 CFM of theoretical air consumption.
FWIW doing a very basic back of the napkin calculation on an LS1's CFM flow at WOT:
346CI = 0.2 ft^3
Half of the displacement in a 4 cycle engine is covered in one crank rotation (360 degrees), or 0.1 ft^3.
0.1 ft^3 per RPM X 6,000 rpms (near redline) = 600 CFM of theoretical air consumption.
Teching In
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density = pressure / (R * T)
Where pressure is absolute pressure (ie air pressure at sea level = 14.7 psi)
R is a constant and T is the absolute temperature (in Kelvin or Rankine).
Or to do it the easy way, just use this link and convert to your chosen units: http://www.denysschen.com/catalogue/density.asp
Teching In
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Thanks, that's what I was looking for.
I'm writing a script for ScanXL from Palmer Performance to calculate the current volumetric efficiency. So using an online converter won't help too much. I have it working, but I want to make it more accurate by including density calculations.
I'm writing a script for ScanXL from Palmer Performance to calculate the current volumetric efficiency. So using an online converter won't help too much. I have it working, but I want to make it more accurate by including density calculations.
