Would MAG IRAN and new plugs result in better fuel efficiency

WannFly

WannFly

Final Approach
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recently got MAGs' IRAN-ed and new plugs and noticing something different during ground ops and flight as well, for a change, noticing something good.

i lean quite aggressively during taxi ops, JPI shows close to 2 GPH burn, sometimes less, i know the exact mixture position for that, been doing that for a while. after i got the plan back, put the mixture in the same place, JPI shows 3.2-3.5 GPH burn, i kept pulling the red knob back till i say 2 GPH and happily taxied around without any engine flutter, but the mixture knob is way out, almost uncomfortably out. same in cruise, even at 1000 AGL, i know my 100 ROP mixture knob position, now to get to 100 ROP, i have to lean further. temps have been cooler, so technically i need richer mixture, not leaner.

does equal plug firing or a better timing of the MAG have anything to do with it? nothing else was done firewall forward other than changing the carb heat hose.

i happy i am burning less fuel, but curious to understand what made the diff
 
I assume they were re-timed to the engine accurately with correct test equipment when they were reinstalled?

If so, timing being right can help fuel economy.

Could also indicate they were timed wrong. Ha.

You get to decide. :)
 
Wait, if you are pulling the mixture to the same fuel flow, the fact that the knob is in a different place just means it was adjusted differently on the engine, you're not more efficient if you were burning 2gph and are still 2 gph. It';s just the knob that's different.

One of us is missing something. Not sure which one. ;)
 
Salty said:
Wait, if you are pulling the mixture to the same fuel flow, the fact that the knob is in a different place just means it was adjusted differently on the engine, you're not more efficient if you were burning 2gph and are still 2 gph. It';s just the knob that's different.

One of us is missing something. Not sure which one. ;)
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the knob wasnt touched....
 
WannFly said:
bad @denverpilot :p
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I wasn’t really kidding. LOL.

If the timing changed, mechanic had better have written down where it was and where they moved it to.

Learned that lesson about maintenance long ago. The regs don’t say they have to document it that way. It’ll bite you in the ass when not done that way. LOL.
 
denverpilot said:
I wasn’t really kidding. LOL.

If the timing changed, mechanic had better have written down where it was and where they moved it to.

Learned that lesson about maintenance long ago. The regs don’t say they have to document it that way. It’ll bite you in the ass when not done that way. LOL.
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ha, i dont have anything written timing wise, i know they ensured it was timed right after the mags came back
 
Salty said:
How does burning the same GPH show more efficiency?
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that is true.. guess my question then is why do i have to close the mixture more to get same GPH
 
WannFly said:
that is true.. guess my question then is why do i have to close the mixture more to get same GPH
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Are you sure your A&P didn't have to unhook the mixture to get to something? He may have had to mess with it to do the carb heat hose.
 
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Is the mixture bottoming out before the knob/level hits the stop? Is there a little play in the "full on" position?
 
Salty said:
Are you sure your A&P didn't have to unhook the mixture to get to something? He may have had to mess with it to do the carb heat hose.
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checked with A&P, they didnt touch anything to do with the mixture cable / knob

Salty said:
Is the mixture bottoming out before the knob/level hits the stop? Is there a little play in the "full on" position?
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nope. everything is working as before, no play in full on position. the only difference now i have to pull the knob than before to get the same GPH
 
WannFly said:
checked with A&P, they didnt touch anything to do with the mixture cable / knob



nope. everything is working as before, no play in full on position. the only difference now i have to pull the knob than before to get the same GPH
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Actually, you want a little play in full on. What I mean is, if it's pushed all the way in, does it stop a little before the knob actually hits the physical stop?
 
Salty said:
Actually, you want a little play in full on. What I mean is, if it's pushed all the way in, does it stop a little before the knob actually hits the physical stop?
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i will have to check on that and report back...
 
To answer your question in the title, yes it can. But, in your example in the post, 2 gph is 2 gph, no savings there.
 
WannFly said:
i will have to check on that and report back...
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It guarantees you are at full rich when pushed all the way in. If the knob bottoms out, you may not be going full rich at the other side.

84FB7D6F-30B8-42E0-A054-A87A7B648925.jpeg
 
Salty said:
It guarantees you are at full rich when pushed all the way in. If the knob bottoms out, you may not be going full rich at the other side.

View attachment 77760
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Good point, I just went to the hangar but didn’t take a pic, should have. I will take a pic tomorrow
 
But, in your case, maybe you are bottoming too soon, making it stick out further during normal ops
 
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