X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Thu, 12 May 2005 01:57:54 -0400 Message-ID: X-Original-Return-Path: Received: from [68.89.254.181] (HELO sdf1.mail.taturbo.com) by logan.com (CommuniGate Pro SMTP 4.3c5) with ESMTP id 940812 for lml@lancaironline.net; Wed, 11 May 2005 23:08:01 -0400 Received-SPF: none receiver=logan.com; client-ip=68.89.254.181; envelope-from=gwbraly@gami.com content-class: urn:content-classes:message MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----_=_NextPart_001_01C5569F.DFD9DAF4" X-MimeOLE: Produced By Microsoft Exchange V6.0.6487.1 Subject: RE: [LML] Re: Plasma III on Hi Compression Engines - Firewall Install Notes X-Original-Date: Wed, 11 May 2005 22:08:30 -0500 X-Original-Message-ID: X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: [LML] Re: Plasma III on Hi Compression Engines - Firewall Install Notes Thread-Index: AcVUxYcc9p3bd8sCTy2X1J4r/wWcugB13xbA From: "George Braly" X-Original-To: "Lancair Mailing List" This is a multi-part message in MIME format. ------_=_NextPart_001_01C5569F.DFD9DAF4 Content-Type: text/plain; charset="Windows-1252" Content-Transfer-Encoding: quoted-printable Craig, =20 Sorry for the delay in responding. =20 Yes. =20 =20 Yes. =20 At high MP, Max Brake Torque on these big bore engines happens with = peak combustion pressures at around 15 to 16d ATDC. =20 There is a broad range of spark advance for which the torque is within = + - 1 to 2 % of MBT. =20 However, that range of spark advance covers an operating spread of peak = cylinder pressures that ranges from benign to RTTSPB (ready to turn = spark plugs ballistic ). =20 So, to pull a Willy Clinton on you, the answer to your question all = depends on the meaning of the word =93best=94.=20 =20 If =93best=94 means =93the difference between 600 and 605 ft-lbs of = torque, I may not want to be part of the discussion! =20 If best means what is the best possible combination of engine operating = parameters for very high continuous torque and reasonable engine = durability - - then we have a lot to talk about. =20 The recent data that came out of the trial in Texas suggests that the = six cylinder 300+ Hp Lycoming crankshafts are rather marginal in design. = From data we have developed at our test stand, the crankshaft = torsional issues get to be rather excited if one tries to push the peak = cylinder pressures to the 15-16d ATDC range - - even if that would make = more torque. =20 =20 I put those two pieces of information together and reach the conclusion = that if there are ways to operate the engine at high power but minimize = the peak torsionals, then that method ought to be used.=20 =20 I=92m not sure I answered your question. If not, let me try again. =20 Regards, George =20 =20 _____ =20 From: Lancair Mailing List [mailto:lml@lancaironline.net] On Behalf Of = Craig Berland Sent: Monday, May 09, 2005 1:32 PM To: Lancair Mailing List Subject: [LML] Re: Plasma III on Hi Compression Engines - Firewall = Install Notes =20 "I would not be comfortable with the timing set at 25d BTDC for a 10:1 CR experimental version of the 8.7:1 Lycoming engine. = George" =20 George, is 25 deg BTDC over advanced? Or is the engine not = structurally capable of carrying the added torque? What is best timing = (that is timing to produce peak torque)? =20 Craig Berland =20 --- Incoming mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.859 / Virus Database: 585 - Release Date: 2/14/2005 --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.859 / Virus Database: 585 - Release Date: 2/14/2005 =20 ------_=_NextPart_001_01C5569F.DFD9DAF4 Content-Type: text/html; charset="Windows-1252" Content-Transfer-Encoding: quoted-printable

Craig,

 

Sorry for the delay in = responding.

 

Yes.  =

 

Yes.

 

At high MP,  Max Brake Torque = on these big bore engines happens with peak combustion pressures at around = 15 to 16d  ATDC.

 

There is a broad range of spark = advance for which the torque is within  + - 1 to 2 % of  = MBT.

 

However,  that range of spark = advance covers an operating spread of peak cylinder pressures that ranges from = benign to  RTTSPB  (ready to turn spark plugs ballistic = ).

 

So, to pull a  Willy Clinton = on you,  the answer to your question all depends on the meaning of the word  “best”.

 

If  “best” = means  “the difference between 600 and 605 ft-lbs of torque,  I may not want to = be part of the discussion!

 

If best means what is the best = possible combination of  engine operating parameters for  very high = continuous torque and reasonable engine durability - - then we have a lot to talk = about.

 

The recent data that came out of = the trial in Texas suggests that the six cylinder 300+ Hp Lycoming crankshafts are rather = marginal in design.  From data we have developed at our test stand,  = the crankshaft torsional issues get to be rather excited if one tries to = push the peak cylinder pressures to the 15-16d ATDC range - - even if that would make = more torque. 

 

I put those two pieces of = information together and reach the conclusion that if there are ways to operate the = engine at high power but minimize the peak torsionals,  then that method = ought to be used.

 

I’m not sure I answered your question.  If not, let me try again.

 

Regards,  = George

 

 

From: = Lancair Mailing List = [mailto:lml@lancaironline.net] On Behalf Of Craig Berland
Sent: Monday, May 09, = 2005 1:32 PM
To: Lancair Mailing List
Subject: [LML] Re: Plasma = III on Hi Compression Engines - Firewall Install = Notes

 

"I would not be comfortable with the = timing set at 25d
BTDC for a 10:1 CR experimental = version of the 8.7:1 Lycoming engine. = George"

 

George,  is 25 deg BTDC over advanced?  Or is the = engine not structurally capable of carrying the added torque?  What is best = timing (that is timing to produce peak torque)?

 

Craig Berland

 


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