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Date: Tue, 25 Aug 2009 15:49:24 -0400
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From:  <troneill@charter.net>
Subject: Re: [LML] Re: Plenum pressure and Injector performance LOP
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Thanks fr the procedure, Grayhawk.
I've run EGTs to lean of peak at low power settings, and didn't understand why so much spread in them... aside from them being in the bottom of the heads in the primer portsw (no ports in top on my heads)... but will now try this procedure and record the spreads.

terrence (aka Redhand)


---- 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
> 
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