X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from elasmtp-spurfowl.atl.sa.earthlink.net ([209.86.89.66] verified) by logan.com (CommuniGate Pro SMTP 6.0.4) with ESMTP id 6185649 for lml@lancaironline.net; Sun, 07 Apr 2013 18:56:36 -0400 Received-SPF: none receiver=logan.com; client-ip=209.86.89.66; envelope-from=colyncase@earthlink.net DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=dk20050327; d=earthlink.net; b=JorA3D10f8Lp7XLPPOqsJ7Zt8AvCL6ZFoxy/Fmjgc8KEuYKnPmrdGBJIKRSebInz; h=Received:From:Mime-Version:Content-Type:Subject:Date:In-Reply-To:To:References:Message-Id:X-Mailer:X-ELNK-Trace:X-Originating-IP; Received: from [72.92.131.242] (helo=[192.168.1.24]) by elasmtp-spurfowl.atl.sa.earthlink.net with esmtpa (Exim 4.67) (envelope-from ) id 1UOyVH-0003cl-2A for lml@lancaironline.net; Sun, 07 Apr 2013 18:56:03 -0400 From: Colyn Case Mime-Version: 1.0 (Apple Message framework v1085) Content-Type: multipart/alternative; boundary=Apple-Mail-265-521105790 Subject: Re: [LML] 31" / 2300 vs 28" / 2500 Date: Sun, 7 Apr 2013 18:56:02 -0400 In-Reply-To: To: "Lancair Mailing List" References: Message-Id: <9DBFF544-0EA4-4619-9BFF-8AF4EF2769DD@earthlink.net> X-Mailer: Apple Mail (2.1085) X-ELNK-Trace: 63d5d3452847f8b1d6dd28457998182d7e972de0d01da94062712b761d12b13edd2def900bff17ef350badd9bab72f9c350badd9bab72f9c350badd9bab72f9c X-Originating-IP: 72.92.131.242 --Apple-Mail-265-521105790 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=us-ascii In cruise I run 2500 rpm and enough MP so that I can get 17.8 gph FF = without getting over 1650 dF on the TIT. ...which comes out to 31" - 32" inches. If you were happier with a lower = power setting, lower rpm might be more efficient for the prop. I = haven't done the math on that. At takeoff MP I never run less than 2750rpm because as you lower the rpm = you are moving the max intra cylinder pressure closer to top dead center = and higher max pressure. I won't come back (to 2500) on the rpm until the MP is down to 32" or = less. re: the rpm argument, I think it seldom plays in the wear equation. = High pressures break almost everything. High temps soften cylinders. = Bad torqueing concentrates stress. Valves break because the guide or = the seat is incorrect. Bad metallurgy will fail at any rpm. Corrosion = will destroy a cam. but how many times does a well-oiled engine fail = because it has two many revolutions on a connecting rod journal? It's = been said "It's not how hard you run it, it's how you run it hard." = I haven't seen any convincing evidence to the contrary, although I am = definitely not an expert. For a more definitive treatment, read John Deakin's two series on engine = management below in the short term. If you haven't been to APS yet, you should go. ...not just to know = where to put the knobs. You will have a much clearer understanding of = your engine. Registration for that is here. The live course is given occasionally = in Ada. The online course is available immediately. (No they don't pay me. It's just that when you ask a question the = answer always starts with "Well here's the data on that....." So nice = in a world where the answer is more often "I feel...." or "I think..." = or "For decades we have...." or "I'm sorry that question is not listed = on my script..." ) http://www.advancedpilot.com/=20 Deakin's series on engine management in general can be found here: (read = them in order by "part xx") = http://www.google.com/search?client=3Dsafari&rls=3Den&q=3Dwhere+should+I+r= un+my+engine+Pelican's+perch+part&ie=3DUTF-8&oe=3DUTF-8 His series on running a turbo charged engine is here:=20 = http://www.google.com/search?client=3Dsafari&rls=3Den&q=3Dthose+fire+breat= hing+turbos+Deakin&ie=3DUTF-8&oe=3DUTF-8 Colyn On Apr 7, 2013, at 3:06 PM, Dico Reijers wrote: Hi All, I am wondering what the school of thought is on engine power settings... = I see some people run a high MP and lower RPM and some run a low MP = and higher RPM... at the end of the day, it amounts to the same power = percentage... but I'm wondering which is better? I would think that a = lower RPM would be less wear on the engine --- but I am very far from an = expert.... Thoughts? -dr --=20 Regards, Dico Reijers InternetWorks Ltd. 300 University Avenue Charlottetown PE, C1A 4M4 902-892-4671 (T) 888-368-9484 (F) www.internetworks.ca www.apartmentspei.com --Apple-Mail-265-521105790 Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=us-ascii In = cruise I run 2500 rpm and enough MP so that I can get 17.8 gph FF =  without getting over 1650 dF on the TIT.
...which comes out to = 31" - 32" inches. If you were happier with a lower power setting, lower = rpm might be more efficient for the prop.  I haven't done the math = on that.

At takeoff MP I never run less than = 2750rpm because as you lower the rpm you are moving the max intra = cylinder pressure closer to top dead center and higher max = pressure.
I won't come back (to 2500) on the rpm until the MP = is down to 32" or less.

re: the rpm argument, I = think it seldom plays in the wear equation.  High pressures break = almost everything.   High temps soften cylinders.   Bad = torqueing concentrates stress.  Valves break because the guide or = the seat is incorrect. Bad metallurgy will fail at any rpm. =  Corrosion will destroy a cam.   but how many times does a = well-oiled engine fail because it has two many revolutions on a = connecting rod journal?   It's been said "It's not how hard you run = it, it's how you run it hard."     I haven't seen any = convincing evidence to the contrary, although I am definitely not an = expert.

For a more definitive treatment, read = John Deakin's two series on engine management below in the short = term.
If you haven't been to APS yet, you should go.   = ...not just to know where to put the knobs.  You will have a much = clearer understanding of your engine.
Registration for that is = here.   The live course is given occasionally in Ada.  The = online course is available immediately.
(No they don't pay me. =   It's just that when you ask a question the answer always starts = with "Well here's the data on that....."   So nice in a world where = the answer is more often "I feel...." or "I think..." or "For decades we = have...." or "I'm sorry that question is not listed on my script..." = )


Deakin's series on engine management in = general can be found here: (read them in order by "part = xx")


His series on running a turbo = charged engine is here: 


=
Colyn


On = Apr 7, 2013, at 3:06 PM, Dico Reijers wrote:

Hi All,

I am wondering what = the school of thought is on engine power settings...   I see = some people run a high MP and lower RPM and some run a low MP and higher = RPM... at the end of the day, it amounts to the same power percentage... = but I'm wondering which is better?  I would think that a lower RPM = would be less wear on the engine --- but I am very far from an = expert....

Thoughts?

-dr



-- =
Regards,

Dico Reijers

InternetWorks Ltd.
300 = University Avenue
Charlottetown
PE, C1A 4M4

902-892-4671 = (T)
888-368-9484 (F)

www.internetworks.ca
www.apartmentspei.com

= --Apple-Mail-265-521105790--