X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Mon, 28 Nov 2011 16:51:14 -0500 Message-ID: X-Original-Return-Path: Received: from imr-ma01.mx.aol.com ([64.12.206.39] verified) by logan.com (CommuniGate Pro SMTP 5.4.2) with ESMTP id 5262117 for lml@lancaironline.net; Mon, 28 Nov 2011 11:34:53 -0500 Received-SPF: pass receiver=logan.com; client-ip=64.12.206.39; envelope-from=Sky2high@aol.com Received: from mtaomg-ma05.r1000.mx.aol.com (mtaomg-ma05.r1000.mx.aol.com [172.29.41.12]) by imr-ma01.mx.aol.com (8.14.1/8.14.1) with ESMTP id pASGYCXB020334 for ; Mon, 28 Nov 2011 11:34:12 -0500 Received: from core-mtb004a.r1000.mail.aol.com (core-mtb004.r1000.mail.aol.com [172.29.234.205]) by mtaomg-ma05.r1000.mx.aol.com (OMAG/Core Interface) with ESMTP id 16027E0000A5 for ; Mon, 28 Nov 2011 11:34:12 -0500 (EST) From: Sky2high@aol.com X-Original-Message-ID: <57c3f.66d2aca6.3c051203@aol.com> X-Original-Date: Mon, 28 Nov 2011 11:34:11 -0500 (EST) Subject: Re: [LML] Re: E-Mag/P-Mag X-Original-To: lml@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="part1_57c3f.66d2aca6.3c051203_boundary" X-Mailer: AOL 9.6 sub 168 X-Originating-IP: [24.1.9.48] x-aol-global-disposition: G X-AOL-SCOLL-SCORE: 0:2:449772736:93952408 X-AOL-SCOLL-URL_COUNT: 0 x-aol-sid: 3039ac1d290c4ed3b80448bf --part1_57c3f.66d2aca6.3c051203_boundary Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Chris, Besides the two plugs being backup, the flame front is more effective with 2 ignition sources. Some dual EI's that communicate with each other change the timing slightly if one of them has ceased operating. As can be seen from my experience, 25 DBTDC (both mag and single EI) cover a broad range of cruise flight conditions and the EI is producing a better and more reliable spark. This is probably why there is a more modest cruise performance improvement from only one EI. At high altitudes or low power, the mag is lagging the advanced EI spark and the flame fronts are started differently or the mag is already firing into an already started combustion event. This still improves the power delivered from a better timed fire. To experience your question, turn off one of your mags in cruise. You know what happens at the pre flight mag check - RPM drops and RPM is a component of power. The loss of power is related to the entire combustion event timing not matching the twin flame front condition. Scott In a message dated 11/28/2011 9:53:59 A.M. Central Standard Time, chris_zavatson@yahoo.com writes: Gary, Scott, A little off-thread, but... Do our Lycoming cylinders require that each spark plug fires to properly propagate the combustion event throughout the entire cylinder? On those planes that have one mag and one EI (and while the EI has advanced its spark), does the mag contribute or can it even still fire? Chris Zavatson N91CZ 360std _www.N91CZ.net_ (http://www.n91cz.net/) On Nov 26, 2011, at 3:12 PM, _Sky2high@aol.com_ (mailto:Sky2high@aol.com) wrote: Gary and Chris, Here is detailed info from my most recent long trip (ARR-EDC-PLK-ARR). Perhaps you can deduce more as the RPM was in the 2480 to 2500 range for all legs. ARR->EDC 820 NM 4.7 hrs block to block. Flown at 6500 MSL to avoid higher headwinds at higher altitudes and LOP (economy) to eliminate a fuel stop. Conditions were constant for the entire trip and all four data points are very similar. OAT 19C, Dalt 7500, KIAS 168, KTAS 187, 24.8" MAP, 2480 RPM, 7.4 GPH and 24.5 DBTDC. Actual flight time was 4.3 hours and I put 32.1 gallons at EDC having been left with a reserve of 9.9 gals. EDC->PLK 440 NM 2.4 hours block to block. Flown at 9500 MSL to use the winds and ROP (best power) to go fast. OAT 16C, Dalt 11000, KIAS 163, KTAS 190 (Ahhh, over PGO GS 208 Kts), 22.1" MAP, 2490 RPM, 8.5 GPH and 27 DBTDC. PLK-> ARR 380 NM 2.2 hours block to block. Flown at 7500 MSL and ROP. OAT 18C, Dalt 8700, KIAS 171, KTAS 194, 24.1" MAP, 2500 RPM, 9.8 GPH and 25 DBTDC. Scott Krueger IO 320, 9:1 CR, unfiltered ram air, dual Plasma III EI, Hartzell CS prop, uh, a few drag reducers.... In a message dated 11/26/2011 9:23:27 A.M. Central Standard Time, _casey.gary@yahoo.com_ (mailto:casey.gary@yahoo.com) writes: Scott, Thanks for the information. I took your numbers and did a crude reqression analysis and came up with the following: The advance increases by 2.2 degrees per thousand rpm above 1700 and 0.85 degrees per inche of manifold pressure below 28. Just gives a rough idea of how it works. Gary From Scott: Restricting my comments to Lycoming engines (320, 360), one would note that 25 DBTDC is the fixed timing delivered by standard magnetos and that timing is adequate for a wide range of engine operations. My injected 320 engine has a 9:1 CR and uses a base timing of 20 DBTDC. Normal ROP cruise settings in the 4000 to 9000 MSL range and 2500 RPM (say 21 to 25 MAP), the timing is between 24 and 26 DBTDC. At takeoff and low altitude race power settings (2760 -2600 RPM, WOT, 28-30 MAP), the timing is about 22-23 DBTDC. At leaned idle/taxi power (<10" MAP, <1100 RPM) the timing is about 34-35 DBTDC. At altitudes 10000- 14000 MSL, 2500 RPM, WOT and LOP the timings are generally 29-31 DBTDC. Scott Krueger --part1_57c3f.66d2aca6.3c051203_boundary Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable
Chris,
 
Besides the two plugs being backup, the flame front is more effective = with=20 2 ignition sources.  Some dual EI's that communicate with each ot= her=20 change the timing slightly if one of them has ceased operating.  = As=20 can be seen from my experience,  25 DBTDC (both mag and single EI)&nbs= p;=20 cover a broad range of cruise flight conditions and the EI is producing a b= etter=20 and more reliable spark. This is probably why there is a more mod= est=20 cruise performance improvement from only one EI.  At high altitud= es or=20 low power, the mag is lagging the advanced EI spark and the flame fron= ts=20 are started differently or the mag is already firing into an already starte= d=20 combustion event.  This still improves the power delivered from a bett= er=20 timed fire.
 
To experience your question, turn off one of your mags in cruise. = ; You=20 know what happens at the pre flight mag check - RPM drops and RPM= is a=20 component of power.  The loss of power is related to the entire combus= tion=20 event timing not matching the twin flame front condition.
 
Scott
 
In a message dated 11/28/2011 9:53:59 A.M. Central Standard Time,=20 chris_zavatson@yahoo.com writes:
=
Gary, Scott,
A little off-thread, but... 
Do our Lyco= ming=20 cylinders require that each spark plug fires to properly <= SPAN=20 style=3D"RIGHT: auto" id=3Dmisspell-1>propagate the combustion event throughout t= he=20 entire cylinder?  On those planes that have one mag and one EI (and while the EI has advanced its spark), does the mag contrib= ute or=20 can it even still fire?
 
Chris Zavatson
N91CZ
360std

On Nov 26, 2011, at 3:12 PM, Sky2high@aol.com wrote:

Gary and Chris,
 
Here is detailed info from my most recent long trip (ARR-EDC-PLK-ARR).  Perhaps you can deduce more as the = RPM was=20 in the 2480 to 2500 range for all legs.
 
ARR->EDC 820 NM 4.7 h= rs block=20 to block.  Flown at 6500 MSL to=20 avoid higher headwinds at higher altitudes and LOP (economy) to=20 eliminate a fuel stop.  Conditions were constant for the entire tr= ip=20 and all four data points are very similar. OAT 19C, Dalt 7500, KIAS 168, KTAS 187, 24.8" MAP, 2480 RPM, 7.4 GPH and 24.5 DBTDC.  Actual flight time was 4.3 hours and I= put=20 32.1 gallons at EDC hav= ing been=20 left with a reserve of 9.9 gals.
 
EDC->PLK 440 NM 2.4 hours block to block.  Flown at= 9500=20 MSL to use the winds and ROP (best power) to go fast. = OAT=20 16C,  Dalt 11000, KIAS = 163,=20 KTAS 190 (Ahhh, over PGO GS 208 Kts), 22.1" MAP, 2490 RPM, 8.5 GPH and 27 DBTDC. 
 
PLK-> ARR 380 NM 2.2= hours=20 block to block.  Flown at 7500 MSL and ROP. =20 OAT 18C, Dalt 8700, KIAS 171= , KTAS 194, 24.1" MAP, 2500 RPM, 9.8= GPH and 25 DBTDC.
 
Scott Krueger
IO 320, 9:1 CR, unfiltered ram air, dual Plasma III EI, Hartzell CS prop, uh, a few drag=20 reducers.... 
 
 
 
In a message dated 11/26/2011 9:23:27 A.M. Central Standard Time, = casey.gary@yahoo.com writes= :
Scott,
Thanks for the information.  I took your numbers and did a = crude=20 reqression analysis and ca= me up=20 with the following:  The advance increases by 2.2 degrees per=20 thousand rpm above 1700 and 0.85 degrees per inche of manifold pressure below 28.  Just g= ives a=20 rough idea of how it works.
Gary
 
From Scott:
Restricting my comments to Lycoming engines (320, 360), one would note that = 25=20 DBTDC is the fixed timing = delivered=20 by standard magnetos and that timing is adequate for a wide range of= =20 engine operations. My injected 320 engine has a 9:1 CR and uses a bas= e=20 timing of 20 DBTDC. Normal= ROP cruise settings in the 4000 = to 9000=20 MSL range and 2500 RPM (sa= y 21 to=20 25 MAP), the timing is between 24 and 26 DBTDC. At takeoff and low altitude race power set= tings=20 (2760 -2600 RPM, WOT, 28-30 MAP), the timing is about 22-23 DBTDC. At leaned idle/taxi power= (<10"=20 MAP, <1100 RPM) the timing is about 34-35 DBTDC. At altitudes 10000- 14000 MSL, 2500 RPM, WOT and LOP the timings are genera= lly=20 29-31 DBTDC.
Scott Krueger=20
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