One of these things is not like the other ones.

[bradp]

I didn't want to title this another LOP question, but that's kind of what it is. Ran LOP today with a gami spread of as close to zero as possible without a vernier type throttle. However, as the picture explains, the a/f ratio ceases to be matched as I continue to lean.

The plane just came back from annual and I had an exhaust leak repaired and an induction leak repaired (on two different cylinders).

I'm thinking that I just need to rotate the stock fuel injectors , but I was a little curious about this effect and wanted to get the group opinion.

Also one more reason I want to get my hail pocked DeeDee fixed up.

Sent from my iPhone using Tapatalk

[Cruiser]

First, most people lean way too fast and the JPI will not give accurate information when that happens. So if you are seeing one thing and then it seems to change or continue to change on its own, you are probably leaning too fast.

 

Second, It seems unlikely you are at GAMI zero and then have an imbalance as shown in the image above. Remember GAMI spreads are based on peak EGT fuel flows, or the difference in FF between the cylinders when each one peaks EGT.

 

I would try again at 5000 MSL or higher in cruise configuration, then lean slowly. no more than 10°F per second.

[Shadrach]

I didn't want to title this another LOP question, but that's kind of what it is. Ran LOP today with a gami spread of as close to zero as possible without a vernier type throttle. However, as the picture explains, the a/f ratio ceases to be matched as I continue to lean.

The plane just came back from annual and I had an exhaust leak repaired and an induction leak repaired (on two different cylinders).

I'm thinking that I just need to rotate the stock fuel injectors , but I was a little curious about this effect and wanted to get the group opinion.

Also one more reason I want to get my hail pocked DeeDee fixed up.

Sent from my iPhone using Tapatalk

 

That panel pic does not tell us anything about your GAMI spread. I see CHT and fuel flow. It looks like cyl#4 is 6 degrees LOP

[bradp]

I'm flying again today so I'll get a bit more information. However, I was going about as slow as I could go with the quadrant type mixture control. Given this limitation I was seeing all 4 cylinders peaking at what surprised me to be almost exactly the same time. I agree it suggests 1 is a lot richer than the other cylinders. I'll see if I can get a video. -B

Sent from my iPhone using Tapatalk

[Bob - S50]

That looks pretty good to me.  Your readings look almost the same as mine.

 

#4 on ours is the hottest so I use if for leaning during the climb.  It's also the leanest so it peaks first.

 

#1 is the last to peak (richest) so I usually lean without the lean find feature.  I just watch the #1 EGT and wait for it to peak and then decline.  When I do use the lean find function, I usually see a spread of 20 to 30 degrees between the leanest and the richest.  Since I want to operate 10-30 LOP and the engine is still running smoothly, it's good enough for me.

[mike_elliott]

I didn't want to title this another LOP question, but that's kind of what it is. Ran LOP today with a gami spread of as close to zero as possible without a vernier type throttle. However, as the picture explains, the a/f ratio ceases to be matched as I continue to lean.

The plane just came back from annual and I had an exhaust leak repaired and an induction leak repaired (on two different cylinders).

I'm thinking that I just need to rotate the stock fuel injectors , but I was a little curious about this effect and wanted to get the group opinion.

Also one more reason I want to get my hail pocked DeeDee fixed up.

Sent from my iPhone using Tapatalk

I *think* you mean to say your EGTs are not matched as you continue to lean, not the Air/fuel ratio. 

write down what the FF is as each cylinder reaches peak EGT., then switch the injectors that have the highest FF and the lowest FF (please torque properly or get ready to crack a head) if they are not very close together.

Disclaimer

  This is not an owner authorized maintenance procedure and if done improperly, could cause catastrophic results.

[pinerunner]

I wouldn't worry about it ..much, but I would continue to investigate it. The EGTs are measured after the burned fuel air mixture comes out of course and are much cooler than that same gaseous mixture was at the top of the power stroke. As much as anything the EGT's reflect how the exhaust manifold is being cooled and where the probes were placed; therefore the caveat that one shouldn't get too hung up on the actual temperatures or go to heroic lengths trying to get them matched. Its much more important to have the cooling of the cylinders right. 

 

I'm attaching one of my early GAMI spread files done with my then-new UBG-16. When I changed the FF slowly you can see the tops of the peaks are sometimes a bit different which might account for an otherwise well-matched GAMI  spread yielding a different value for the degrees LOP.  You can also see why I'm thinking about GAMI injectors since my not so good GAMI spread is maybe just good enough to do LOP. I've tried swapping injectors but no joy yet (who remembers what no joy means?). 

DCYGamiSpread.pdf

[bradp]

Thanks for the advice everyone. I think that I need to download the data off the EDM as this video shows the gami spread tight but cyl 1 is definitely running a bit richer than everyone else. I was running LOP fine at 6500 ft and during descent. Just something different I've noticed since having induction / exhaust leaks repaired.

https://youtu.be/yVzfnU3swgY

I'll post a comparison video if I (ehem) have some injectors swapped.

Just to confirm proper torque value is 60-in lbs from the lycoming cleaning injector SI. However there seems to be some variances regarding whether to rotate the "a" stamp downward depending on the part number of the injector. LW-18265 appears to be the correct part number - 60 in lbs plus up to 180-deg rotation.

Thanks - Brad

Sent from my iPhone using Tapatalk