X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Tue, 02 Nov 2010 11:08:23 -0400 Message-ID: X-Original-Return-Path: Received: from imr-da04.mx.aol.com ([205.188.105.146] verified) by logan.com (CommuniGate Pro SMTP 5.3.10) with ESMTP id 4552069 for lml@lancaironline.net; Tue, 02 Nov 2010 10:48:32 -0400 Received-SPF: pass receiver=logan.com; client-ip=205.188.105.146; envelope-from=Sky2high@aol.com Received: from imo-ma03.mx.aol.com (imo-ma03.mx.aol.com [64.12.78.138]) by imr-da04.mx.aol.com (8.14.1/8.14.1) with ESMTP id oA2EljAg011102 for ; Tue, 2 Nov 2010 10:47:45 -0400 Received: from Sky2high@aol.com by imo-ma03.mx.aol.com (mail_out_v42.9.) id q.f64.81f7a36 (37095) for ; Tue, 2 Nov 2010 10:47:42 -0400 (EDT) Received: from magic-m16.mail.aol.com (magic-m16.mail.aol.com [172.21.188.208]) by cia-db07.mx.aol.com (v129.5) with ESMTP id MAILCIADB075-90e74cd0248e2b5; Tue, 02 Nov 2010 10:47:42 -0400 From: Sky2high@aol.com X-Original-Message-ID: <81dc2.1a14704e.3a017e8e@aol.com> X-Original-Date: Tue, 2 Nov 2010 10:47:42 EDT Subject: NA Injected Engine performance LOP X-Original-To: lml@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="part1_81dc2.1a14704e.3a017e8e_boundary" X-Mailer: AOL 9.5 sub 5400 X-AOL-IP: 24.15.17.119 X-Spam-Flag:NO X-AOL-SENDER: Sky2high@aol.com --part1_81dc2.1a14704e.3a017e8e_boundary Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Content-Language: en It is most desirable if each cylinder is producing the same power. It is= =20 even more desirable if the cylinder does not suffer from bad events such= as=20 abnormal pressures, detonation or pre-ignition. Aircraft engines are=20 interesting because each cylinder is its own engine. Assuming that each= =20 cylinder volume is the same, rings seal equally, cams produce equal valve= timing=20 and movement, all plugs produce equal spark value and timing, induction= air=20 is delivered equally, fuel is distributed equally and it is atomized=20 equally so that the flame burns the same at an equal air/fuel ratio(A/F)= =20 producing the desired power then the engine is a happy engine. =20 The burn in each cylinder should produce useful pressure against the pisto= n=20 only during a certain crank angle range. In order to accomplish that the= =20 flame must be started at the right time and burn at a proper speed. Thus= =20 the importance of spark timing and A/F. The fixed timing (say 25 DBTDC) = =20 issued by a magneto is a comprise, but it works well enough over a broad= range =20 of A/F - just not as efficient as it could be. =20 =20 High power and best power occur sufficiently ROP (EGT >100F of peak) so= =20 that some destructive events are less likely as is also true at lower pow= er=20 settings (say below 75%). That is, one can further alter the F/A at such= =20 lower power. =20 However, the mixture control affects all cylinders and if each is running= =20 at different power because of different A/F then there is a problem. I.E.= =20 reducing the mixture causes most cylinders to be 50F LOP and one is 30F RO= P=20 (bad because of cylinders pressures) will also lead to roughness because= of=20 the different power being produced. =20 Fuel flow is an indication of F/A. =20 Thus, the GAMI Lean Test. Starting at power below 75% (i.e. NA engine,= at=20 or above 6500 MSL) and quite ROP, reduce fuel flow (FF) by say .3 gph and= =20 note the EGTs of each cylinder. Continue until each cylinder has gone sa= y=20 30F LOP or until roughness but not until the engine stops. =20 Chart the FF vs EGTs and note the FF at each cylinder peak. If the =20 overall spread is greater than .3 gph, the cylinders are not producing eq= ual=20 power and they are a candidate for some adjustment before good operation= LOP=20 can be accomplished. The GAMI approach is to alter the injectors so the= FF=20 matches the air available for each cylinder, thus matched A/Fs. =20 Of course, if the spread is .3 gph or less, the engine is in good shape. =20 Other methods to achieve an acceptable spread is to alter the induction ai= r=20 (difficult because the flow may be different at different throttle=20 settings) or alter the atomization (F/A) by controlling the air going to= the=20 injector (like supercharged or turbocharged engines through the use of sh= rouded =20 injectors). =20 While ROP/LOP affect the burn speed, so does Compression Ratio (CR). =20 Thus, even greater efficiency can be obtained by optimizing the spark tim= ing to=20 better match the F/A and CR. Lower power, as measured by resultant=20 MAP/RPM, can benefit from advancing the spark ahead of the fixed value to= account=20 for slower burning. High power/CR can sometimes benefit from retarding= =20 the spark. =20 See the attached chart as an example of the benefit of operating LOP. On= e=20 must remember that low drag airplanes (Lancairs) are not penalized very=20 much by running LOP to extend range. =20 =20 Scott Krueger IO320 =20 In a message dated 11/2/2010 7:50:51 A.M. Central Daylight Time, =20 douglasbrunner@earthlink.net writes: =20 =20 Terrence,=20 LOP starts when the mixture is LOP of course! =20 Sorry, for the smart ass response. There are a number of good article on= =20 engine management and LOP operation written by John Deakin on =E2=80=9CPe= lican=E2=80=99s=20 Perch=E2=80=9D on avweb.=20 There is also an excellent course on engine management given by the GAMI= =20 folks called =E2=80=9CAdvanced Pilot Seminars=E2=80=9D - _http://www.adva= ncedpilot.com/_=20 (http://www.advancedpilot.com/) I took it and learned a lot.=20 The short answer to your question is that you want to be approximately 50= =20 deg LOP in most situations and it is best if all your cylinders are LOP= to=20 the same degree. =20 Doug Brunner=20 N241DB=20 Jeff,=20 =20 May I ask for a little more detail on when the LOP condition starts? Do= =20 all EGTs have to be LOPP, or is it when just the leanest one goes? And,= =20 how lean constitutes enough to be considered LOP?=20 =20 Thanks, =20 terrence =20 L235/I-320 --part1_81dc2.1a14704e.3a017e8e_boundary Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Content-Language: en <= FONT id=3Drole_document color=3D#000000 size=3D2 face=3DArial>
It is most desirable if each cylinder is producing the same power.&nb= sp; It=20 is even more desirable if the cylinder does not suffer from bad events suc= h=20 as abnormal pressures, detonation or pre-ignition.  Aircraft eng= ines=20 are interesting because each cylinder is its own engine.  Assuming th= at=20 each cylinder volume is the same, rings seal equally, cams produce=20 equal valve timing and movement, all plugs produce equal spark= value=20 and timing, induction air is delivered equally, fuel is distributed equall= y and=20 it is atomized equally so that the flame burns the same at an equal air/fu= el=20 ratio(A/F) producing the desired power then the engine is a happy=20 engine.
 
The burn in each cylinder should produce useful pressure against the= piston=20 only during a certain crank angle range. In order to accomplish that= the=20 flame must be started at the right time and burn at a proper speed.&n= bsp;=20 Thus the importance of spark timing and A/F. The fixed timing (say 25 DBTD= C)=20 issued by a magneto is a comprise, but it works well enough over a broad= range=20 of A/F - just not as efficient as it could be. 
 
High power and best power occur sufficiently ROP (EGT >100F of=20 peak) so that some destructive events are less likely as is also true= at=20 lower power settings (say below 75%).  That is, one can further= alter=20 the F/A at such lower power.
 
However, the mixture control affects all cylinders and if each is run= ning=20 at different power because of different A/F then there is a problem. = I.E.=20 reducing the mixture causes most cylinders to be 50F LOP and one is 30F RO= P (bad=20 because of cylinders pressures) will also lead to roughness because of the= =20 different power being produced.
 
Fuel flow is an indication of F/A.
 
Thus, the GAMI Lean Test.  Starting at power below 75% (i.e. NA= =20 engine, at or above 6500 MSL) and quite ROP, reduce fuel flow (FF) by say= .3 gph=20 and note the EGTs of each cylinder.  Continue until each cylinder has= gone=20 say 30F LOP or until roughness but not until the engine stops.
 
Chart the FF vs EGTs and note the FF at each cylinder peak.  If= the=20 overall spread is greater than .3 gph, the cylinders are not pro= ducing=20 equal power and they are a candidate for some adjustment before good= =20 operation LOP can be accomplished.  The GAMI approach is to alter the= =20 injectors so the FF matches the air available for each cyli= nder,=20 thus matched A/Fs.
 
Of course, if the spread is .3 gph or less, the engine is in good=20 shape.
 
Other methods to achieve an acceptable spread is to alter the inducti= on air=20 (difficult because the flow may be different at different throttle setting= s) or=20 alter the atomization (F/A) by controlling the air going to the injec= tor=20 (like supercharged or turbocharged engines through the use of shroude= d=20 injectors).
 
While ROP/LOP affect the burn speed, so does Compression Ratio=20 (CR).  Thus, even greater efficiency can be obtained by optimizi= ng the=20 spark timing to better match the F/A and CR.  Lower power, as measure= d by=20 resultant MAP/RPM, can benefit from advancing the spark ahead of the fixed= value=20 to account for slower burning.  High power/CR can sometimes bene= fit=20 from retarding the spark.
 
See the attached chart as an example of the benefit of operating LOP.=  =20 One must remember that low drag airplanes (Lancairs) are not penalized ver= y much=20 by running LOP to extend range. 
 
Scott Krueger
IO320
 
In a message dated 11/2/2010 7:50:51 A.M. Central Daylight Time,=20 douglasbrunner@earthlink.net writes:

Terrence,

 

LOP=20 starts when the mixture is LOP of course! 

 

Sorry,=20 for the smart ass response.  There are a number of good article on= engine=20 management and LOP operation written by John Deakin on =E2=80=9CPelican= =E2=80=99s Perch=E2=80=9D on=20 avweb.

 

There=20 is also an excellent course on engine management given by the GAMI folks= =20 called =E2=80=9CAdvanced Pilot Seminars=E2=80=9D - http://www.= advancedpilot.com/  I=20 took it and learned a lot.

 

The=20 short answer to your question is that you want to be approximately 50 de= g LOP=20 in most situations and it is best if all your cylinders are LOP to the= same=20 degree. 

 

Doug=20 Brunner

N241DB

 

 

 

Jeff,

 

May I ask for a  little more detail on when th= e LOP=20 condition starts?  Do all EGTs have to be LOPP, or is it when just= the=20 leanest one goes?  And, how lean constitutes enough to be considere= d=20 LOP?

 

Thanks,

terrence

L235/I-320

--part1_81dc2.1a14704e.3a017e8e_boundary--