Return-Path: Sender: (Marvin Kaye) To: lml@lancaironline.net Date: Mon, 22 Mar 2004 07:20:59 -0500 Message-ID: X-Original-Return-Path: Received: from imf20aec.mail.bellsouth.net ([205.152.59.68] verified) by logan.com (CommuniGate Pro SMTP 4.1.8) with ESMTP id 3112122 for lml@lancaironline.net; Sun, 21 Mar 2004 22:50:04 -0500 Received: from P4DESKTOP ([65.80.109.243]) by imf20aec.mail.bellsouth.net (InterMail vM.5.01.06.08 201-253-122-130-108-20031117) with SMTP id <20040322035004.KCDR1709.imf20aec.mail.bellsouth.net@P4DESKTOP> for ; Sun, 21 Mar 2004 22:50:04 -0500 From: "Douglas W. Johnson, MD" X-Original-To: "'Lancair Mailing List'" Subject: RE: [LML] Re: SCFM X-Original-Date: Sun, 21 Mar 2004 22:51:28 -0500 X-Original-Message-ID: <00dd01c40fc0$f525f720$0f01a8c0@P4DESKTOP> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_00DE_01C40F97.0C4FEF20" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook CWS, Build 9.0.2416 (9.0.2910.0) Importance: Normal X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1165 In-Reply-To: This is a multi-part message in MIME format. ------=_NextPart_000_00DE_01C40F97.0C4FEF20 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Based upon these discussions I had with Brent 6 yrs ago, I have been flying behind a K&E 1560 reusable filter for the last 600hrs in my TSIO-550B2B. It is rated at 530cfpm, and seems to work well in the space I had already committed to for the original WIX filter. Doug Johnson -----Original Message----- From: Lancair Mailing List [mailto:lml@lancaironline.net]On Behalf Of Brent Regan Sent: Sunday, March 21, 2004 10:13 PM To: Lancair Mailing List Subject: [LML] Re: SCFM Art asks: <<<< Question for Brent Regan Brent Can you give me the formula's to figure CFM required for a TSIO 550 and SCFM rating for a K & N filter? >>>> Calculating the Standard Cubic Foot per Minute (SCFM) is, at best, an approximation. The basic strategy is to take the displacement of the engine (550 cubic inches in the case of the Continental) and multiply it how many "displacements" the engine uses in a minute to get the volumetric needs of the engine. Remember that in a 4 stroke engine it takes two revolutions to get one displacement so divide the RPM by two and multiply by RPM to get the (theoretical) cubic inch per minute flow through the engine. Divide this by 1,728 (cubic inches per cubic foot) to get Cubic Feet per Minute (CFM). This assumes the engine has no net restriction on airflow. There are a lot of things that effect the air flow throughout the engine. Well designed "tuned" intake and exhaust runners improve flow. So do superchargers (this includes turbochargers) and a well designed cam. Filters, bends, friction, valves and throttle plates all reduce flow. The net effect of all these factors is defined at the Volumetric Efficiency, which is the ratio of the actual flow versus the theoretical flow. Altitude and temperature have an effect as related to standard atmospheric conditions. The wide open throttle (WOT) volumetric efficiency varies with the engine and installation but a conservative (and easy) figure to use for a naturally aspirated engine is 1.0 and a turbocharged engine is 1.1. The volumetric efficiency of my TIO-540 at 350 Hp is 1.043. I know this because I measured it on a calibrated dynamometer. The airflow requirement of the TSIO-550 would therefore be 275 cuin/revolution x 2700 RPM /1728 cuin/cuft x 1.10 = 472 CFM. The density of air at standard conditions is 0.07647 Lb/cuft. The mass flow requirements of the engine at WOT and standard conditions is therefore 472 CFM x 0.07647 Lb/CFM = 36 pounds per minute. For a given power setting the mass flow through the engine must remain the same. For a turbocharged engine at a fixed power output the CFM flow through the filter increases with altitude because the density of the air is decreasing. For the same TSIO-550 at 75% power you need about 27 pounds of air per minute to feed the fire. At FL250 every cubic foot contains 0.0343 lbs of air so you need to flow about 780 CFM through the filter. The air pressure at FL250 is about 150 inches of water. A dirty 400 SCFM filter may cost you 8 inches of water or better than 5% power. Filter flow ratings are available from the manufacturer. Be sure you get the pressure drop across the filter at rated flow so you can do an accurate comparison between filters. Regards Brent Regan ------=_NextPart_000_00DE_01C40F97.0C4FEF20 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable
Based=20 upon these discussions I had with Brent 6 yrs ago, I have been flying = behind a=20 K&E 1560 reusable filter for the last 600hrs in my = TSIO-550B2B.  It is=20 rated at 530cfpm, and seems to work well in the space I had already = committed to=20 for the original WIX filter.
Doug=20 Johnson
-----Original Message-----
From: Lancair Mailing = List=20 [mailto:lml@lancaironline.net]On Behalf Of Brent = Regan
Sent:=20 Sunday, March 21, 2004 10:13 PM
To: Lancair Mailing=20 List
Subject: [LML] Re: SCFM

Art asks:

<<<<
Question for Brent Regan
Brent
Can you give me the = formula's=20 to figure CFM required
for a TSIO 550 and SCFM rating for a K & = N=20 filter?
>>>>

Calculating the=20 Standard Cubic Foot per Minute (SCFM) is, at best, an approximation. = The basic=20 strategy is to take the displacement of the engine (550 cubic inches = in the=20 case of the Continental) and multiply it how many "displacements" the = engine=20 uses in a minute to get the volumetric needs of the engine. Remember = that in a=20 4 stroke engine it takes two revolutions to get one displacement so = divide the=20 RPM by two and multiply by RPM to get the (theoretical) cubic inch per = minute=20 flow through the engine.  Divide this by 1,728 (cubic inches per = cubic=20 foot) to get  Cubic Feet per Minute (CFM).  This assumes the = engine=20 has no net restriction on airflow.  There are a lot of things = that=20 effect  the air flow throughout the engine.  Well designed = "tuned"=20 intake and exhaust runners improve flow. So do superchargers (this = includes=20 turbochargers) and a well designed cam. Filters, bends, friction, = valves and=20 throttle plates all reduce flow. The net = effect of=20 all  these factors is defined at the Volumetric Efficiency, which = is the=20 ratio of the actual flow versus the theoretical flow. Altitude and temperature have an effect as related to = standard=20 atmospheric conditions.

The wide open throttle (WOT) = volumetric=20 efficiency varies with the engine and installation but a conservative = (and=20 easy) figure to use for a naturally aspirated engine is 1.0 and a = turbocharged=20 engine is 1.1.  The volumetric efficiency of my TIO-540 at 350 Hp = is=20 1.043. I know this because I measured it on a calibrated=20 dynamometer.

The airflow requirement of the TSIO-550 would = therefore be=20 275 cuin/revolution x 2700 RPM /1728 cuin/cuft x 1.10 =3D 472 CFM. The = density=20 of air at standard conditions is 0.07647 Lb/cuft. The mass flow = requirements=20 of the engine at WOT and  standard conditions is therefore 472 = CFM x=20 0.07647 Lb/CFM =3D 36 pounds per minute. For a given power setting the = mass flow=20 through the engine must remain the same. For a turbocharged engine at = a fixed=20 power output the CFM flow through the filter increases with altitude = because=20 the density of the air is decreasing.

For the same TSIO-550 at = 75%=20 power you need about 27 pounds of air per minute to feed the fire. At = FL250=20 every cubic foot contains 0.0343 lbs of air so you need to flow about = 780 CFM=20 through the filter. The air pressure at FL250 is about 150 inches of=20 water.  A dirty 400 SCFM filter may cost you 8 inches of water or = better=20 than 5% power.

Filter flow ratings are available from the=20 manufacturer. Be sure you get the pressure drop across the filter at = rated=20 flow so you can do an accurate comparison between=20 filters.

Regards
Brent=20 Regan



 
------=_NextPart_000_00DE_01C40F97.0C4FEF20--