I found these lower priced plastic air filter boxes on Donaldsons website. ($104.00 for a 6") THEY say that these are more durable than most metal filters.
Donaldson FPG medium duty air filters
I called them and the tech guy said you need to know the engines CFM requirement before determining which air filter will work. Anyone know how to figure this out? My engine will be a 3.5 Nissan with 7psi of boost. Thanks
Full Version: Airflow Requirements
You will need a Kestrel Wind Speed instrument, you can but it for about $65-75, it measures air speed in Feet Per Minute (FPM). You need to measure the opening that that air is being sucked through, usually the intake tube.
Then convert the measurement into square feet (sq.ft.). For square or retanglular openings to get the area (multiply the height by the width) in inches, then convert inches into(sq.ft.) by dividing the # in inches by 144. (144 is the are of one square foot in inches)
Example: 10"H X 12"W=120 square inches
Convert the area to (sq.ft.): 120"/144=0.8333 (sq.ft.) round up to 0.84(sq.ft.)
To measure a round opening measure the diameter of the opening in inches.
Now divide the diameter by 2 to get the radius (d/2=R)
Multiple ® by itself. exampe: 8/2=4 4x4=16
Multiple the last # you get by 3.1416 to get the area in square inches
Convert the opening size to (sq.ft.) by dividing the area(last # you have after multiplying 3.1416) by 144
Now take the meter and put it up against the opening. Start the car and rev it about 3/4 throttle, it shouldn't take long to get a reading, usually a couple seconds.
Now take you final # from your calculation and multiply it by the # you got on the meter in Feet per second (FPM), that should give you a pretty accuarate use of (CFM) that you motor makes, I usually add about 100-150(CFM) for full throttle.
Now that's not to technical now is it.
Then convert the measurement into square feet (sq.ft.). For square or retanglular openings to get the area (multiply the height by the width) in inches, then convert inches into(sq.ft.) by dividing the # in inches by 144. (144 is the are of one square foot in inches)
Example: 10"H X 12"W=120 square inches
Convert the area to (sq.ft.): 120"/144=0.8333 (sq.ft.) round up to 0.84(sq.ft.)
To measure a round opening measure the diameter of the opening in inches.
Now divide the diameter by 2 to get the radius (d/2=R)
Multiple ® by itself. exampe: 8/2=4 4x4=16
Multiple the last # you get by 3.1416 to get the area in square inches
Convert the opening size to (sq.ft.) by dividing the area(last # you have after multiplying 3.1416) by 144
Now take the meter and put it up against the opening. Start the car and rev it about 3/4 throttle, it shouldn't take long to get a reading, usually a couple seconds.
Now take you final # from your calculation and multiply it by the # you got on the meter in Feet per second (FPM), that should give you a pretty accuarate use of (CFM) that you motor makes, I usually add about 100-150(CFM) for full throttle.
Now that's not to technical now is it.
QUOTE
You will need a Kestrel Wind Speed instrument, you can but it for about $65-75, it measures air speed in Feet Per Minute (FPM). You need to measure the opening that that air is being sucked through, usually the intake tube.
Then convert the measurement into square feet (sq.ft.). For square or retanglular openings to get the area (multiply the height by the width) in inches, then convert inches into(sq.ft.) by dividing the # in inches by 144. (144 is the are of one square foot in inches)
Example: 10"H X 12"W=120 square inches
Convert the area to (sq.ft.): 120"/144=0.8333 (sq.ft.) round up to 0.84(sq.ft.)
To measure a round opening measure the diameter of the opening in inches.
Now divide the diameter by 2 to get the radius (d/2=R)
Multiple ® by itself. exampe: 8/2=4 4x4=16
Multiple the last # you get by 3.1416 to get the area in square inches
Convert the opening size to (sq.ft.) by dividing the area(last # you have after multiplying 3.1416) by 144
Now take the meter and put it up against the opening. Start the car and rev it about 3/4 throttle, it shouldn't take long to get a reading, usually a couple seconds.
Now take you final # from your calculation and multiply it by the # you got on the meter in Feet per second (FPM), that should give you a pretty accuarate use of (CFM) that you motor makes, I usually add about 100-150(CFM) for full throttle.
Now that's not to technical now is it.
Then convert the measurement into square feet (sq.ft.). For square or retanglular openings to get the area (multiply the height by the width) in inches, then convert inches into(sq.ft.) by dividing the # in inches by 144. (144 is the are of one square foot in inches)
Example: 10"H X 12"W=120 square inches
Convert the area to (sq.ft.): 120"/144=0.8333 (sq.ft.) round up to 0.84(sq.ft.)
To measure a round opening measure the diameter of the opening in inches.
Now divide the diameter by 2 to get the radius (d/2=R)
Multiple ® by itself. exampe: 8/2=4 4x4=16
Multiple the last # you get by 3.1416 to get the area in square inches
Convert the opening size to (sq.ft.) by dividing the area(last # you have after multiplying 3.1416) by 144
Now take the meter and put it up against the opening. Start the car and rev it about 3/4 throttle, it shouldn't take long to get a reading, usually a couple seconds.
Now take you final # from your calculation and multiply it by the # you got on the meter in Feet per second (FPM), that should give you a pretty accuarate use of (CFM) that you motor makes, I usually add about 100-150(CFM) for full throttle.
Now that's not to technical now is it.
Holy
Plastic is light.
Buy the biggest one that will fit and be done with it.
Buy the biggest one that will fit and be done with it.
CFM = (CID/1728) x (RPM/2) x VE
1 cubic inch = 16.4 cubic centimeters
2457cc / 16.4 = 149.81cid
This is how you get CFM unboosted.
Pressure ratio = 14.7 + boost pressure / 14.7
Cfm boosted = cfm unboosted x pressure ratio
This is what you are looking for.
Lb/min = cfm boosted x .07
You would use this for a compressor map.
Do a search I did a write up on this, and expanded how to do it. If you can not figure it out, I’ll help.
1 cubic inch = 16.4 cubic centimeters
2457cc / 16.4 = 149.81cid
This is how you get CFM unboosted.
Pressure ratio = 14.7 + boost pressure / 14.7
Cfm boosted = cfm unboosted x pressure ratio
This is what you are looking for.
Lb/min = cfm boosted x .07
You would use this for a compressor map.
Do a search I did a write up on this, and expanded how to do it. If you can not figure it out, I’ll help.
Tell me the fill in's and I'll do the math.
Let my try 
Cubic inches on the 3.5 is 213.58.
For pressure 14.7 + 7psi / 14.7 = 1.476
CFM = (213.58 / 1728 =.12360) x (6200 / 2 =3100) x100% = 383.16
CFM unboosted x 1.476 = 565.64 CFM boosted
(Even though redline is 6700, peak HP on my last motor was around 6000 rpm + or -, so I went towards the high side)
Peak HP at 5800 would be 529.05 CFM
Did I do that right??
Cubic inches on the 3.5 is 213.58.
For pressure 14.7 + 7psi / 14.7 = 1.476
CFM = (213.58 / 1728 =.12360) x (6200 / 2 =3100) x100% = 383.16
CFM unboosted x 1.476 = 565.64 CFM boosted
(Even though redline is 6700, peak HP on my last motor was around 6000 rpm + or -, so I went towards the high side)
Peak HP at 5800 would be 529.05 CFM
Did I do that right??
I got a little different answer, but it is very small.
This will work for you, I hope it helps?
Now you can take that answer, and finish the math to figure out what compressor wheel you could run.
LB/min = cfm boosted x .07
If you have a map that has LB/min you could use this, or an old Ray jay map used CFM.
This will work for you, I hope it helps?
Now you can take that answer, and finish the math to figure out what compressor wheel you could run.
LB/min = cfm boosted x .07
If you have a map that has LB/min you could use this, or an old Ray jay map used CFM.
One more thing, look at peak torque. This is where your VE is the highest
What?
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