X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Tue, 25 Aug 2009 15:49:09 -0400 Message-ID: X-Original-Return-Path: Received: from imr-ma01.mx.aol.com ([64.12.206.39] verified) by logan.com (CommuniGate Pro SMTP 5.2.16) with ESMTP id 3823803 for lml@lancaironline.net; Tue, 25 Aug 2009 08:13:56 -0400 Received-SPF: pass receiver=logan.com; client-ip=64.12.206.39; envelope-from=Sky2high@aol.com Received: from imo-da02.mx.aol.com (imo-da02.mx.aol.com [205.188.169.200]) by imr-ma01.mx.aol.com (8.14.1/8.14.1) with ESMTP id n7PCDF3R022801 for ; Tue, 25 Aug 2009 08:13:15 -0400 Received: from Sky2high@aol.com by imo-da02.mx.aol.com (mail_out_v42.5.) id q.c5b.4e8ffc62 (39955) for ; Tue, 25 Aug 2009 08:13:11 -0400 (EDT) From: Sky2high@aol.com X-Original-Message-ID: X-Original-Date: Tue, 25 Aug 2009 08:13:11 EDT Subject: Re: [LML] Re: Plenum pressure and Injector performance LOP X-Original-To: lml@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="-----------------------------1251202391" X-Mailer: AOL 9.1 sub 5006 X-Spam-Flag:NO X-AOL-SENDER: Sky2high@aol.com -------------------------------1251202391 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Tim, Ahh, thanks for the write-up. If the fuel and air are controlled, then one must look at timing. The setup is one mag, one Plasma ignition. Let's assume the magneto is fixed at 25 DBTDC. For High CRs (over 8.5:1), Klaus suggests retarding the Plasma pickup by 5 degrees. At high power settings (measured by MAP and RPM), the Plasma may actually lag the mag firing. At low power settings, the Plasma will precede the mag. This does have an effect on timing (time of reaching max cylinder pressure), but it should be the same for all cylinders. However, while the mag timing remains fixed, the Plasma is driven off MAP, RPM and data from the timing pickup device (for a 6 cylinder, it should be the crank/flywheel sensor). Does your friend have the optional Plasma Display installed? If so, it can be illuminating. MAP and RPM should be pretty close to what the engine monitor shows and the display should not be jumping around too much. Neither should the timing. On my engine (9:1, Dual Plasma), the Plasma MAP and RPM read a bit lower than my engine monitor display (I trust my engine monitor - RPM checked against external sensor during prop balance) and I must assume the timing is accurate. At take-off power (from 700 MSL), I see 22 DBTDC. At ROP best power cruise, 3500 to 6000 MSL, I see around 25 DBTDC and at higher altitudes (less power) I will see more advance taking place. Hmmmmm, I have not checked if there is a change in timing in level flight when switching from best power to best economy - The MAP and RPM being constant?........... Hmmmmm..... I did have some excitement once when timing data from the sensors was bad (loose plug) and the engine ran rather rough. Fixed timing from a mag/Plasma setup might cover that up somewhat. Of course, in the case your referenced, Slick mags are capable of dropping sparks (too weak) and that would show up more in a high CR environment. A note: I have recently heard that many Lancair flyers with big 6-cyl engines have removed the Plasma system (either dual or mixed) because "it wasn't working right." I don't know what that means exactly. For me, the dual system works great on my IO 320. Scott Krueger AKA Grayhawk In a message dated 8/25/2009 5:18:39 A.M. Central Daylight Time, Tim@5000feet.com writes: That is all good stuff. I just did all that on my own plane. We're all talking Fuel Injected engines, that's for sure. I just did this write-up of my own experience doing the lean test and all: http://www.myrv10.com/N104CD/upgrades/20090822/index.html The problem is, there is one guy in particular who's a friend of mine and I flew his plane, and analyzed his GAMI curves and his are probably better than mine (and mine are < .2) and yet he still can't get even all the way TO peak without it stumbling. So I'm trying to learn what other effects to worry about. Timing, Compression, Exhaust, and whatever else. My compression is 8.5:1, his is 10:1. We have different exhaust, but both are supposed to be good at exhaust scavenging and good flowing. Timing he's got to check and verify yet. The interesting thing is, there are a few other people I'm talking to who have plenums and circular inlets by coincidence and they're all having the same problem...stumbling as they get to 13gph or so...and considering I know the one guys injectors are flowed well and peak together, I'm getting curious as to how much of an effect things like Plenum air pressures and the like will have on injector performance. Looking for the things OTHER than the gph spread in the EGT peaks that could cause things not to run at peak EGT or leaner. I sure hear you though....LOP can definitely be faster than ROP when you start dropping off extra fuel stops from the equation!!! Tim Sky2high@aol.com wrote: > Listen up Grasshopper, > > 1. If the engine is carbureted, you may be out of luck as there is no > way to control the F/A ratio in each cylinder. However, you can try > step 3 for informational purposes if you have the equipment listed in > step 2. > > 2. You must have an engine monitor and sensors that display (or record) > EGT for each Cyl and the fuel flow. > > 3. Injected engines must perform the GAMI lean test before a "next > step." At 75% power (that means at or above 6500 MSL, 7500 if using ram > air and KIAS is less than 190, or higher), WOT (necessary to control air > distribution when running LOP) . > a. Starting sufficiently ROP, lean in small steps (less than .3 gph) > and record the EGT for each step for Cyl 1. Continue past peak EGT for > that Cyl for about 50F degrees LOP or until ugly roughness. > b. repeat "a" for each cylinder. > c. Check the gph for each cyl peak EGT. If the spread in .3 gph or > less, you are done and you should be able to run LOP 20F, 30F, 40F > depending on the spread). > > 4. If the spread is GT .3 gph, you must fix the A/F ratio. A cheap > way to start is to provide equal air pressure to each injector - a wee > plenum distribution to each shrouded injector) and repeat the Lean Test. > > 5. if the lean test shows the proper spread, go fly LOP (less than 75% > power)................... > > 6. If the lean test fails (GT .3 gph spread), consider different sized > injector nozzles (either GAMI or others) for the rich/lean cyls. > > Grayhawk can fly a 320 at 8500 MSL, ROP, 9.5 gph and see 195 KTAS or > LOP, 7.5 gph and 186 KTAS (all things being equal) thus eliminating a > fuel stop at 3.5 hours cause he could go another hour. 195 x 3.5 = 683, > 186 x 4.5 = 837, 837/195 = 4.3 + 1 (re-fuel stop time) = 5.3 Duh! > > Grayhawk > > In a message dated 8/24/2009 2:40:57 P.M. Central Daylight Time, > Tim@5000feet.com writes: > > Hey guys, I am remembering a long time ago reading about > how the air pressure surrounding the injector can affect how > well the injector works. If I'm not mistaken, turbocharged > engines even use some pressure manifold around the injector > to accommodate for the increased Manifold Pressure. > > What gets me curious is that I'm having a discussion with some > folks right now who are all having problems running Lean of Peak > and their engines stumble before they get to peak EGT. Between > the group, there are a variety of ignitions such as 2 mags > or 1 lightspeed and one mag, and varieties such as 8.5:1, > 9:1, and 10:1 compression ratios, but the one constant is that > they all have what is purported to be a more effective cowl... > the Sam James cowl with a plenum. So I'm wondering if the > knowledge base some of you have would provide any insight > to the issue. I originally was worried that the 10:1 pistons > might make LOP operation harder to accomplish, but perhaps > there is just too much air pressure on the outside of the > injector? The cowl is known to often have too little exit > area, so it could be that the pressure differential is > even too high between the top and bottom half of the > cowl. > > Any insight you can give? > Thanks, > Tim > > -- > For archives and unsub > http://mail.lancaironline.net:81/lists/lml/List.html > > > ------------------------------------------------------------------------ -- For archives and unsub http://mail.lancaironline.net:81/lists/lml/List.html -------------------------------1251202391 Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable
Tim,
 
Ahh, thanks for the write-up.  If the fuel and air are controlle= d,=20 then one must look at timing.  The setup is one mag, one Plasma=20 ignition.  Let's assume the magneto is fixed at 25 DBTDC.  For= High=20 CRs (over 8.5:1), Klaus suggests retarding the Plasma pickup by 5 degrees.=  =20 At high power settings (measured by MAP and RPM), the Plasma may actually= lag=20 the mag firing.  At low power settings, the Plasma will precede the= =20 mag.  This does have an effect on timing (time of reaching max=20 cylinder pressure), but it should be the same for all cylinders. = ;=20 However, while the mag timing remains fixed, the Plasma is driven off= MAP,=20 RPM and data from the timing pickup device (for a 6 cylinder, it shou= ld be=20 the crank/flywheel sensor). 
 
Does your friend have the optional Plasma Display installed? If so,= it can=20 be illuminating.  MAP and RPM should be pretty close to what the engi= ne=20 monitor shows and the display should not be jumping around too much. = =20 Neither should the timing.  On my engine (9:1, Dual Plasma), the Plas= ma MAP=20 and RPM read a bit lower than my engine monitor display (I trust my= engine=20 monitor - RPM checked against external sensor during prop=20 balance) and I must assume the timing is accurate.  At take= -off=20 power (from 700 MSL), I see 22 DBTDC.  At ROP best power cruise, 3500= to=20 6000 MSL, I see around 25 DBTDC and at higher altitudes (less power) I wil= l see=20 more advance taking place.  Hmmmmm, I have not checked if there is a= change=20 in timing in level flight when switching from best power to best econ= omy -=20 The MAP and RPM being constant?........... Hmmmmm.....
 
I did have some excitement once when timing data from the sensors was= bad=20 (loose plug) and the engine ran rather rough.   Fixed timin= g=20 from a mag/Plasma setup might cover that up somewhat.  Of= course,=20 in the case your referenced, Slick mags are capable of dropping sparks (to= o=20 weak) and that would show up more in a high CR environment.
 
A note:  I have recently heard that many Lancair flyers with big= 6-cyl=20 engines have removed the Plasma system (either dual or mixed) because= "it=20 wasn't working right."  I don't know what that means exactly. = For me,=20 the dual system works great on my IO 320.
 
Scott Krueger AKA Grayhawk
 
In a message dated 8/25/2009 5:18:39 A.M. Central Daylight Time,=20 Tim@5000feet.com writes:
That is=20 all good stuff.  I just did all that on my own plane.  We'reall=20 talking Fuel Injected engines, that's for sure.  I just did=20 this
write-up of my own experience doing the lean test and=20 all:
http://www.myrv10.com/N104CD/upgrades/20090822/index.html
The=20 problem is, there is one guy in particular who's a friend
of mine and= I=20 flew his plane, and analyzed his GAMI curves
and his are probably bet= ter=20 than mine (and mine are < .2)
and yet he still can't get even all= the=20 way TO peak without
it stumbling.  So I'm trying to learn what= other=20 effects
to worry about.  Timing, Compression, Exhaust, and=20 whatever
else.  My compression is 8.5:1, his is 10:1.  We= have=20 different
exhaust, but both are supposed to be good at exhaust=20 scavenging
and good flowing.  Timing he's got to check and verif= y=20 yet.
The interesting thing is, there are a few other people I'm
ta= lking=20 to who have plenums and circular inlets by
coincidence and they're al= l=20 having the same problem...stumbling
as they get to 13gph or so...and= =20 considering I know the one
guys injectors are flowed well and peak=20 together, I'm getting
curious as to how much of an effect things like= =20 Plenum air
pressures and the like will have on injector=20 performance.
Looking for the things OTHER than the gph spread in the<= BR>EGT=20 peaks that could cause things not to run at peak EGT or
leaner.
I=20 sure hear you though....LOP can definitely be faster than
ROP when yo= u=20 start dropping off extra fuel stops from=20 the
equation!!!
Tim

Sky2high@aol.com wrote:
> Listen= up=20 Grasshopper,
> 
> 1.  If the engine is carbureted= , you=20 may be out of luck as there is no
> way to control the F/A ratio= in=20 each cylinder.  However, you can try
> step 3 for informatio= nal=20 purposes if you have the equipment listed in
> step 2.
>&n= bsp;=20
> 2. You must have an engine monitor and sensors that display (or= =20 record)
> EGT for each Cyl and the fuel flow.
> 
&= gt;=20 3.  Injected engines must perform the GAMI lean test before a "next= =20
> step."  At 75% power (that means at or above 6500 MSL, 750= 0 if=20 using ram
> air and KIAS is less than 190, or higher), WOT (neces= sary=20 to control air
> distribution when running LOP) .
> = =20    a. Starting sufficiently ROP, lean in small steps (less tha= n .3=20 gph)
> and record the EGT for each step for Cyl 1.  Continue= past=20 peak EGT for
> that Cyl for about 50F degrees LOP or until ugly= =20 roughness.
>     b. repeat "a" for each=20 cylinder.
>     c. Check the gph for each cyl peak= =20 EGT.  If the spread in .3 gph or
> less, you are done and yo= u=20 should be able to run LOP 20F, 30F, 40F
> depending on the=20 spread).
> 
> 4.  If the spread is GT .3 gph,&nbs= p; you=20 must fix the A/F ratio.  A cheap
> way to start is to provid= e=20 equal air pressure to each injector - a wee
> plenum distribution= to=20 each shrouded injector) and repeat the Lean Test.
> 
>= =20 5.  if the lean test shows the proper spread, go fly LOP (less than= 75%=20
> power)...................
> 
> 6. If the lean= test=20 fails (GT .3 gph spread), consider different sized
> injector noz= zles=20 (either GAMI or others) for the rich/lean cyls.
> 
>= =20 Grayhawk can fly a 320 at 8500 MSL, ROP, 9.5 gph and see 195 KTAS or >=20 LOP, 7.5 gph and 186 KTAS (all things being equal) thus eliminating a >=20 fuel stop at 3.5 hours cause he could go another hour. 195 x 3.5 =3D 683= ,=20
> 186 x 4.5 =3D 837, 837/195 =3D 4.3 + 1 (re-fuel stop time) =3D= 5.3 =20 Duh!
> 
> Grayhawk
> 
> In a message= dated=20 8/24/2009 2:40:57 P.M. Central Daylight Time,
> Tim@5000feet.com= =20 writes:
>
>     Hey guys, I am remembering= a long=20 time ago reading about
>     how the air pressure= =20 surrounding the injector can affect how
>     well= the=20 injector works.  If I'm not mistaken, turbocharged
> =20    engines even use some pressure manifold around the=20 injector
>     to accommodate for the increased Man= ifold=20 Pressure.
>
>     What gets me curious is th= at I'm=20 having a discussion with some
>     folks right now= who=20 are all having problems running Lean of Peak
>    = and=20 their engines stumble before they get to peak EGT. Between
> = =20    the group, there are a variety of ignitions such as 2=20 mags
>     or 1 lightspeed and one mag, and varieti= es=20 such as 8.5:1,
>     9:1, and 10:1 compression rati= os,=20 but the one constant is that
>     they all have wh= at is=20 purported to be a more effective cowl...
>     the= Sam=20 James cowl with a plenum.  So I'm wondering if the
> =20    knowledge base some of you have would provide any=20 insight
>     to the issue. I originally was worrie= d that=20 the 10:1 pistons
>     might make LOP operation har= der to=20 accomplish, but perhaps
>     there is just too muc= h air=20 pressure on the outside of the
>     injector? = ; The=20 cowl is known to often have too little exit
>    = area,=20 so it could be that the pressure differential is
>   &nb= sp;=20 even too high between the top and bottom half of the
> =20    cowl.
>
>     Any insight you= can=20 give?
>     Thanks,
>    =20 Tim
>
>     --
>     Fo= r=20 archives and unsub
>    =20 http://mail.lancaironline.net:81/lists/lml/List.html
>
> >=20 ------------------------------------------------------------------------=

--
For=20 archives and unsub=20 http://mail.lancaironline.net:81/lists/lml/List.html

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