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Benefits of improving GAMI spread


Bartman

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After my last annual my injectors must have been cleaned and placed back in random order. That was the worst my bird ever ran in over 10 years of flying LOP.  My GAMI spread went from my usual 0.2 up to 0.6 and my #3 EGT was -40 before #4 would go LOP which made the engine slightly rough by the time I got to -10 LOP.  We swapped #3 and #4 injectors which were the first and last to go LOP and my GAMI spread is the best it has ever been.  I'm getting 0.0 to 0.1 GAMI spread and she runs great with a smooth loss of power going deeper LOP and basically smooth all the way to mixture cutoff. Several times this past week at 8K -11K all four cylinders have gone LOP basically simultaneously so I have been running at peak to -5 LOP.  I am very pleased with the results of something that basically didn't even cost me anything and no bad effects on CHTs.  As a matter of fact while my TAS is still the same while ROP, I gained 1-2 Kts while LOP due to more power being produced by the leanest cylinder while at the same setting on the last to lean.

Thank you to the MS community because I learned to do this by being a member of this forum. If you have the same problem I described, I highly recommend swapping some injectors. 

Edited by Bartman
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Our IO-360 engines typically run great LOP if the induction system is tight and the ignition system is in good shape. Swapping injectors to fine-tune is the final step and you did great getting to a 0.0 GAMI spread. Now don't let a mechanic take the injectors out for any reason unless your spread changes! They don't need cleaning if you stay at 0.0.

Sent from my LG-US996 using Tapatalk

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1 hour ago, KSMooniac said:

Our IO-360 engines typically run great LOP if the induction system is tight and the ignition system is in good shape. Swapping injectors to fine-tune is the final step and you did great getting to a 0.0 GAMI spread. Now don't let a mechanic take the injectors out for any reason unless your spread changes! They don't need cleaning if you stay at 0.0.

Sent from my LG-US996 using Tapatalk
 

I very much second that when it comes to injectors. If it ain't broke don't fix it.

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I was thinking of putting a code on the FI's body... paint or etch or something.

This way, when you have the perfect Gami spread, it doesn't get away.

swapping the low and the high FI only works because they were all nicely balanced at one time. And have gotten mixed up after maintenance.

having six cylinders makes the variations even more of a challenge...

Best regards,

-a-

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I flew 2 more hours since last post and I can say this is the best 1TF has ever run LOP since I have owned her. I discussed with my IA and he knows either so not touch the injectiors, or if he cleans them  do one at a time and place back in the same spot. He flies LOP too and understands fully the reasoning. 

I didn't fly LOP the first year and for all I know the last guy had her set up this way, and I got lucky by swapping a couple of injectors with and educated guess and got back wherein I started and didn't even know it. 

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The other day I flew my first "GAMI Spread Test" flight and found a spread of 1gph. I probably should fly the pattern again to make sure I didn't mess it up, but if it is 1 gph is that wide/large enough to think about doing something? (stock injectors TCM IO-550G)

Robert

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Robert there is a lot of info on doing the GAMI test, both at SL and at altitude. I would check everything for leaks (air and fuel) before anything else.

1.0 spread is too much for the IO550...... it has tuned induction and is balanced from the factory. You should be getting much better, <.5 gph spread is acceptable.

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My first IO550 would lean smoothly until it stopped running altogether... 90°+ F LOP @5000’

It's Gami spread was .1 gph.  I was under the impression that they were factory stock as there was no log entry or sales info for them in the logs.

It isn't very hard to run the test.

What you get out of the test is good information.

If you find bad news.  You can always make improvements.

Win win situation.

Best regards,

-a-

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