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  #81  
Old 05-28-2009, 09:25 AM
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logansc logansc is offline
 
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Charlie/Kevin: Thanks for taking the time to respond, that is certainly useful "ballpark" information. Normally aspirated piston engine BSFC's don't change much with engine size, but do change with compression ratio. Being lean on takeoff with an experimental engine is a possibility worth monitoring, I think. Wouldn't expect it with a factory new engine, but with an experimental engine presumably it is possible to be lean at takeoff power due to a too small main jet or inappropriate installed injector sizes for the demands of the engine. That is what flight test is all about, of course, but I am just looking for a rough number that I shouldn't be too far away from on my first takeoff.

I think figures you two are suggesting are probably about right, which equates to takeoff full power fuel flows in the neighborhood of 24-26 gph. If I see significantly less than that passing through 100 knots (full rpm), I will likely terminate full power and perhaps shorten my initial flight. You can fix too rich in the air, but not too lean!

Again, thanks for the help!

Regards,


Lee...
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  #82  
Old 05-28-2009, 09:56 AM
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f1rocket f1rocket is offline
 
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Lee,

I typically saw 24-28 GPH at full rich, WOT during takeoff.

During first flight, it is possible to have an instrumention error when everything is working just fine. Test your fuel pump on the ground per the plans and my website to make sure you can flow enough fuel. If that checks out, you should be good to go.
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  #83  
Old 05-31-2009, 10:46 AM
BillOrcutt BillOrcutt is offline
 
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The "big pull" is very important in turbo applications, where a 6-cyl ROP fuel flow of 25-27 gph is reduced to 17 gph, LOP. If done too slowly, TIT's get way too hot, and take some time to recover......hence, the value of the quicker "big pull" which minimizes time at the high TIT. For nomally aspirated LOP ops, the fuel savings are generally about 2 gph (from 9 GPH down to 7 GPH on our 4 cyl engines). Balanced fuel injectors are a MUST, either GAMI's or AirFlow Performance. Do the "GAMI lean test" to check yours, to be sure the "delta" between first and last cylinder to peak is .5 gph or less. This will insure smooth LOP ops, which can be done at any altitude. This will also help you insure that all cylinders are at least 50 LOP, just outside the "red box." The speed drops off rapidly as we go LOP, but a speed loss of 5 KIAS is normal at 50 LOP. Go further lean, and the speed loss is much greater. Hence, 50 LOP is ideal - - - as long as all cyls are matched. Other benefits of LOP ops besides fuel savings, include low lead build-up in plugs, longer cyl life due to reduced internal cylinder pressures, and no carbon monoxide production when LOP.
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  #84  
Old 06-03-2009, 01:52 AM
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Here are the results after changing the restrictor on cylinder #4. Note how the cylinders are all peaking much closer. I'll get a chance to verify the flow rate at best power/speed and at 75 rop this weekend. Also going to look at # 3 and may put put a smaller restrictor in it.



Quote:
Originally Posted by Webb View Post
Here are the graphed results that Kevin is using some of the other data in another post regarding fuel flow and power. Best IAS was at 9.2 gal/hr when #4 was 75 LOP but the others were approximately at 90 ROP. I'm hoping to see the flow rate drop to around 8.8 when all cylinders will be close to 75 LOP.

I'll post again after replacing the #4 restrictor to verify the change.

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Last edited by Webb : 06-03-2009 at 02:00 AM.
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  #85  
Old 01-30-2011, 12:46 PM
vjdslk vjdslk is offline
 
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Location: Rocklin, CA
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Question LOP Ops - Deakin's "big pull"

A friend of mine just forwarded me this article from ECI regarding rapid leaning. I would like to hear other's thoughts and practices.

http://www.eci.aero/pdf/93-6-7.pdf

Thanks!

Jon D.
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  #86  
Old 01-30-2011, 05:18 PM
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Russ McCutcheon Russ McCutcheon is offline
 
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Quote:
Originally Posted by vjdslk View Post
A friend of mine just forwarded me this article from ECI regarding rapid leaning. I would like to hear other's thoughts and practices.

http://www.eci.aero/pdf/93-6-7.pdf

Thanks!

Jon D.
Interesting read, I’m not sure I buy there theory, just how fast is rapid? They don’t say. I cruse at about 55% power and after establishing 55% cruse above 3500 feet I slowly pull the mixture tell the engine starts to run ruff then slowly push it back in tell its smooth, at this point I am LOP on all four cylinders, I boar scope them every year and have none of the problems they are describing. My “Big pull” takes about 5 or 6 seconds.
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  #87  
Old 01-30-2011, 05:53 PM
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erich weaver erich weaver is offline
 
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The article provides so little information it is essentially useless for anything except inspiring fear. There are many many people going LOP using "the big pull" with no I'll effects and lots of good effects. If it makes you squirm, use the other method of leaning gradually by adjusting every 1000 to keep EGTs at takeoff temps.

Erich
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  #88  
Old 01-31-2011, 08:59 AM
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airguy airguy is offline
 
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Quote:
Originally Posted by erich weaver View Post
The article provides so little information it is essentially useless for anything except inspiring fear. There are many many people going LOP using "the big pull" with no I'll effects and lots of good effects. If it makes you squirm, use the other method of leaning gradually by adjusting every 1000 to keep EGTs at takeoff temps.

Erich
Agreed. While I like ECI in general, this article (with absolutely zero test datapoints) is nothing short of useless.

I'm an engineer, I want data - not fearmongering. Gimme RPM, MAP, CHT/EGT, fuel flow, oil temp, airflow conditions since it was a teststand (velocity, temperature, pressure), fuel type, ignition type, ignition timing, and then put that on a graph versus time for the event that occured - THEN we can proceed to properly analyze what happened. This article doesn't even say if the engine was carburated or injected, for goodness sake! Completely worthless!
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  #89  
Old 01-31-2011, 11:17 AM
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John Clark John Clark is offline
 
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Location: Santa Barbara, CA
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Default Note the date...

..on ECI's letter. The "information" is 18 years old. Also very weak science, an issue with one engine on a test stand that could have been caused by a number of conditions.

John Clark ATP, CFI
FAA FAAST Team Member
EAA Flight Advisor
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  #90  
Old 02-01-2011, 01:12 AM
bignose bignose is offline
 
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Location: Sao Paulo, Brasil
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Question Where is the Red Box ?

Now, most important to know, where is really the so tamed Red Box to be avoided ?

To know the right thing to do, we should first know what NOT to do under no sircumstances, right ?

Lycoming recomends Peak under 75% and that's it ! So, where is the Edge?

That's the question... Where is RED BOX ?

Last edited by bignose : 02-01-2011 at 01:16 AM.
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