X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Thu, 12 Mar 2009 11:07:04 -0400 Message-ID: X-Original-Return-Path: Received: from [66.64.141.200] (HELO lucky.dts.local) by logan.com (CommuniGate Pro SMTP 5.2.13) with ESMTP id 3545142 for lml@lancaironline.net; Thu, 12 Mar 2009 10:58:43 -0400 Received-SPF: none receiver=logan.com; client-ip=66.64.141.200; envelope-from=cjensen@dts9000.com Content-class: urn:content-classes:message MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----_=_NextPart_001_01C9A323.8B98546E" X-MimeOLE: Produced By Microsoft Exchange V6.5 Subject: RE: [LML] Re: LOP vs ROP Climb: Time and Fuel Burn (LIVP) X-Original-Date: Thu, 12 Mar 2009 11:02:21 -0400 X-Original-Message-ID: <8984A39879F2F5418251CBEEC9C689B3E86968@lucky.dts.local> In-Reply-To: X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: [LML] Re: LOP vs ROP Climb: Time and Fuel Burn (LIVP) Thread-Index: AcmjH8D6Pj1tY06jQ6u9omUDqyBdnAAA1Svg From: "Chuck Jensen" X-Original-To: "Lancair Mailing List" This is a multi-part message in MIME format. ------_=_NextPart_001_01C9A323.8B98546E Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable A year or two ago, Aviation Consumer wrote an interesting article on MP = v RPM and what was the best tradeoff between friction and cylinder = pressures. The consensus, as best these things can be known, what it = was better to operate the RPM at a higher level, than low. The friction = loss associated with the higher RPM was offset by the reduced peak = pressures such that the wear and tear on the engine is less at 24 x 25 = than 24 x 24 and certainly better than 25 x 23. =20 =20 So, if you are going to reduce power, between MP or RPM, it is better to = reduce MP since higher RPM keeps PP lower, at least that was their = general conclusion, supported by engine shop experience. Thanks,=20 Chuck Jensen=20 Diversified Technologies=20 2680 Westcott Blvd=20 Knoxville, TN 37931=20 Phn: 865-539-9000 x100=20 Cell: 865-406-9001=20 Fax: 865-539-9001=20 cjensen@dts9000.com=20 -----Original Message----- From: Lancair Mailing List [mailto:lml@lancaironline.net]On Behalf Of = Colyn Case at earthlink Sent: Thursday, March 12, 2009 10:31 AM To: lml@lancaironline.net Subject: [LML] Re: LOP vs ROP Climb: Time and Fuel Burn (LIVP) Jeff, that's interesting. I wonder why you get those high temps. I wonder what is different in our engine setups. my CHT's are steady @380 in the max/max condition @140knots. It's been tested to 20,000 in that config. CHT's get better than that with less power or more speed. I have exhaust tunnel extensions which seem to make a huge difference = for cooling. also have ceramic coated exhaust. I don't know how much of a factor = that is. =20 Some will say that 2700rpm is a bad idea because of higher friction = losses. On the other hand the flame front always moves at the same speed so if = the crank is turning faster your theta pp (angle after top dead center where = peak pressure occurs) is bigger and the peak pressure is less. ....which seems good for everything. = the pulse on the crank is not as concentrated, the CHT's are lower. assuming everything else = is setup right. =20 Colyn ------_=_NextPart_001_01C9A323.8B98546E Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Re: [LML] LOP vs ROP Climb: Time and Fuel Burn (LIVP)
A year=20 or two ago, Aviation Consumer wrote an interesting article on MP v = RPM and=20 what was the best tradeoff between friction and cylinder = pressures.  The=20 consensus, as best these things can be known, what it was better to = operate the=20 RPM at a higher level, than low.  The friction loss associated with = the=20 higher RPM was offset by the reduced peak pressures such that the wear = and tear=20 on the engine is less at 24 x 25 than 24 x 24 and certainly better than = 25 x=20 23.  
 
So, if=20 you are going to reduce power, between MP or RPM, it is better to = reduce MP=20 since higher RPM keeps PP lower, at least that was their general = conclusion,=20 supported by engine shop experience.

Thanks, =
Chuck Jensen

Diversified = Technologies=20
2680 Westcott = Blvd=20
Knoxville, TN =20 37931
Phn:    865-539-9000 x100 =
Cell:    = 865-406-9001=20
Fax:    =20 865-539-9001
cjensen@dts9000.com

-----Original Message-----
From: Lancair Mailing = List=20 [mailto:lml@lancaironline.net]On Behalf Of Colyn Case at=20 earthlink
Sent: Thursday, March 12, 2009 10:31 = AM
To:=20 lml@lancaironline.net
Subject: [LML] Re: LOP vs ROP Climb: = Time and=20 Fuel Burn (LIVP)

Jeff,
that's interesting.  I wonder = why you get=20 those high temps.
I wonder what is different in our = engine=20 setups.
my CHT's are steady @380 in the = max/max condition=20 @140knots.
It's been tested to 20,000 in that=20 config.
CHT's get better than that  with = less power=20 or more speed.
I have exhaust tunnel extensions = which seem to=20 make a huge difference for cooling.
also have ceramic coated = exhaust.  I don't=20 know how much of a factor that is.
 
Some will say that 2700rpm is a bad = idea because=20 of higher friction losses.
On the other hand the flame front = always moves at=20 the same speed so if the
crank is turning faster your theta pp = (angle=20 after top dead center where peak pressure occurs) is = bigger
and the peak pressure is less.  = ....which=20 seems good for everything.  the pulse on the crank
is not as concentrated, the CHT's are = lower.  assuming everything else is setup right.
 
Colyn
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