X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Sun, 23 Oct 2005 18:47:40 -0400 Message-ID: X-Original-Return-Path: Received: from imo-d05.mx.aol.com ([205.188.157.37] verified) by logan.com (CommuniGate Pro SMTP 5.0c6) with ESMTP id 781165 for lml@lancaironline.net; Sun, 23 Oct 2005 18:46:03 -0400 Received-SPF: pass receiver=logan.com; client-ip=205.188.157.37; envelope-from=Sky2high@aol.com Received: from Sky2high@aol.com by imo-d05.mx.aol.com (mail_out_v38_r6.3.) id q.db.3092a2a6 (57293) for ; Sun, 23 Oct 2005 18:45:14 -0400 (EDT) From: Sky2high@aol.com X-Original-Message-ID: X-Original-Date: Sun, 23 Oct 2005 18:45:14 EDT Subject: Re: [LML] Re: Advanced Ignition Timing and EIs on normally aspirated engines. X-Original-To: lml@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="-----------------------------1130107514" X-Mailer: 9.0 Security Edition for Windows sub 5009 X-Spam-Flag: NO -------------------------------1130107514 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit In a message dated 10/23/2005 4:49:54 P.M. Central Standard Time, walter@advancedpilot.com writes: Pick any power where the thetaPP is at 16dATDC, and ANY change in timing, advancing or retarding will decrease HP output. The problem is that to do this, you really need a closed loop system that MEASURES the thetaPP and adjusts the timing accordingly. This is only marginally successful when you calculate the thetaPP. I only now of one system that is capable of measuring the thetaPP in real time and adjusting the timing on the fly--PRISM. Computer mapping is only a guess. If one maps for anything other than thetaPP and peak pressure, there are potential problems. Walter, Thanks for the response and additional details. I agree completely that a closed loop system could be the best way to handle this. I am investigating O2 exhaust sensors since now there are ones that can survive in a leaded environment. Disallowing for any bias on your part, PRISM may not be the only answer since all thru history we have been able to manage engines by indirect measurements that imply other conditions (i.e. F/A ratio via EGT). A predetermined map utilized by an EI computer may do an adequate job as indirectly measured by increased airspeed and decreased fuel consumption whilst the engine remains within reasonable operating limits, LASAR notwithstanding. Even utilizing an engine map, one can make a best guess at ignition timing, fuel flow, etc. by using direct measurements of such things as barometric pressure, temperature, mass air flow, MAP, RPM, other temperatures (depending on how the engine is cooled), exhaust O2 content, etc. and then refine the control of efficient combustion producing elements with cylinder pressure, the so called theta PP. Sometimes I am just amazed that my water cooled twin cylinder motorcycle engine (110 ci, 4" bore, 4.4" stroke), utilizing two iridium plugs per cylinder, 12 port electronic fuel injection, 9:1 CR, 3 valves and a 3D mapped computer that manages the 107 HP (@5000 RPM) engine with refinements from coolant temperature (startup), Baro, MAP, RPM, induction air temp, and O2 feedback. Works at any altitude with a road. Why aren't our aircraft engines so controlled? Ahhh, don't answer that - it was a rhetorical question. I am patiently waiting for a better system. The only problem is that I am rapidly aging to TBO whilst waiting. Arrrrrgghh. Scott Krueger AKA Grayhawk Lancair N92EX IO320 SB 89/96 Aurora, IL (KARR) -------------------------------1130107514 Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable

In a message dated 10/23/2005 4:49:54 P.M. Central Standard Time,=20 walter@advancedpilot.com writes:

<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>Pick any=20 power where the thetaPP is at
16dATDC, and ANY change in timing, advan= cing=20 or retarding will decrease
HP output. The problem is that to do=20 this, you really need a closed
loop system that MEASURES the thetaPP a= nd=20 adjusts the timing
accordingly. This is only marginally successf= ul=20 when you calculate the
thetaPP. I only now of one system that is= =20 capable of measuring the
thetaPP in real time and adjusting the timing= on=20 the fly--PRISM.
Computer mapping is only a guess. If one m= aps=20 for anything other than
thetaPP and peak pressure, there are potential= =20 problems.

Walter,

Thanks for the response and additional details.

I agree completely that a closed loop system could be the best way to=20 handle this. I am investigating O2 exhaust sensors since now there are= =20 ones that can survive in a leaded environment.

Disallowing for any bias on your part, PRISM may not be the only answer= =20 since all thru history we have been able to manage engines by indirect=20 measurements that imply other conditions (i.e. F/A ratio via EGT). A=20 predetermined map utilized by an EI computer may do an adequate job as=20 indirectly measured by increased airspeed and decreased fuel consumption whi= lst=20 the engine remains within reasonable operating limits, LASAR=20 notwithstanding.

Even utilizing an engine map, one can make a best guess at ignition tim= ing,=20 fuel flow, etc. by using direct measurements of such things as barometric=20 pressure, temperature, mass air flow, MAP, RPM, other temperatures (dependin= g on=20 how the engine is cooled), exhaust O2 content, etc. and then refine the cont= rol=20 of efficient combustion producing elements with cylinder pressure,= the=20 so called theta PP.

Sometimes I am just amazed that my water cooled twin cylinder=20 motorcycle engine (110 ci, 4" bore, 4.4" stroke), utilizing two=20 iridium plugs per cylinder, 12 port electronic fuel injection, 9:1 CR,=20= 3=20 valves and a 3D mapped computer that manages the 107 HP (@5000=20 RPM) engine with refinements from coolant temperature (startup), Baro,=20= MAP,=20 RPM, induction air temp, and O2 feedback. Works at any altitude w= ith=20 a road. Why aren't our aircraft engines so controlled? Ahhh, don= 't=20 answer that - it was a rhetorical question.

I am patiently waiting for a better system. The only problem is t= hat=20 I am rapidly aging to TBO whilst waiting. Arrrrrgghh.

Scott Krueger=20 AKA Grayhawk
Lancair N92EX IO320 SB 89/96
Aurora, IL=20 (KARR)

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