Anyone know how to analyze this?

[J0nathan225]

For my flight today I did a few ROP-LOP-ROP passes and then a LOP inflight mag check. I believe my gami spread is ~.4 not bad?

My biggest concern and maybe its because the surefly runs so smooth, but the mag side was rough and EGTs climbed to 1600+ quick.  I also got a large backfire switching back to both, which I've heard is normal with the Surefly's though. 

 

Thanks for any insight, I may op into the Savvy analysis annual subscription. 

https://apps.savvyaviation.com/my-flights/23406/f95d3be4-5558-475f-bce8-5dea0528271d

[ShuRugal]

For my flight today I did a few ROP-LOP-ROP passes and then a LOP inflight mag check. I believe my gami spread is ~.4 not bad?

My biggest concern and maybe its because the surefly runs so smooth, but the mag side was rough and EGTs climbed to 1600+ quick.  I also got a large backfire switching back to both, which I've heard is normal with the Surefly's though. 

 

Thanks for any insight, I may op into the Savvy analysis annual subscription. 

https://apps.savvyaviation.com/my-flights/23406/f95d3be4-5558-475f-bce8-5dea0528271d

If I had to hazard a guess: when the Surefly is running timing advance, you're extracting optimum power from the working gas before the exhaust valve opens.

 

When you switch to the fixed timing mag, you are no longer running as much advance, as well as running a colder spark. Both of these things result in your mixture starting to burn later, meaning that there is less time to extract power from the working gas before the exhaust valve opens.

 

With your mixture settings tuned based off where peak EGT occurs when the Surefly is running, it doesn't surprise me at all to see a huge rise in EGT when you go to the mag. Going single-mag should always increase EGT. Going from Surefly with the advance running to single mag will be a greater difference.

 

The real important question here is: what are your cylinder temperatures doing during all of this?

 

 

EDIT: got the savvy thing to work, looks like you didn't leave it in mag only mode long enough to evaluate effect on CHT. Running rough on the mag and seeing the dramatic a jump in CHT makes me think you're getting very poor ignition from the mag only, at least while running LoP.

 

Something else I noticed on the Savvy data: you have a lose CHT probe wire on the yellow trace (#2?) And the purple trace (#4?) is notably leaner than the other cylinders, which you can see by it having the highest EGT when RoP, and the lowest even LoP.

 

[carusoam]

Way to go J0hnathan....

Showing up to the discussion with data in hand!

Best regards....

-a-

Nice work, Shu!

So much detail, hard to discuss without pictures...

Let’s look at the first graph In the data collection...

See anything funny?

What is that gold box Doing there?

Is that missing EGT data or did the cylinder depart and then come back?

[carusoam]

Let’s look at the same data in a different way...

Note the detailed data inside the gold box where EGT2 is showing 800°F?

Why is it doing that?

I also included MP and FF in this chart to see what knobs you may be pulling or pushing...

Gami spread of .4 is good... smaller is better... and evenly distributed is best...

Switching between the electronic mag And the other and both has some known Delay that allows some burned fuel to go towards the muffler going lean may be helpful for that...

We have the discussion often around here on data capture rate, and waiting for the EGTs to settle before changing the switch...

can you see the two mags tested each time you did a mag test?  (Me neither... )

One day I will write a paper specific for MSers and Mooneys... 

Best regards,

-a-

 

 

[carusoam]

A close up of the inflight mag test...

where I said I didn’t see the two humps of the two mags...

Typically we are looking for identical humps... when they are not identical in height... this is a sign of the mag timing being shifted..!

 

I haven’t seen many JPI charts with electronic mags yet...

The standard mag looks pretty good... four plugs all operating similarly...

The electronic mag is working super well... burning a higher percentage of the fuel inside the cylinder Before the exhaust valve opens...

If I interpreted that correctly...

you have shown the value of the electronic mag, the engine monitor, and the power of MS, all in one picture...

Now.... Get that loose EGT tightened down...

PP thoughts only, not a mechanic...

-a-

 

 

[Ragsf15e]

I did this with a SF as well but only once because I didn’t like the BANG.  I don’t really notice a roughness lop on the old mag but I was only about 10-15 lop and my MP was ~21 which probably means I had less advance.  Were you up really high?

[carusoam]

The question of how deep LOP do you want to go...

at 21” of MP we are below 65%hp (right?)

Operating at peak is an acceptable practice...

going a few degrees LOP from there allows for complete burning of all the fuel... none ‘thrown away‘ for CHT cooling... The few degrees accounts for the oddities of the GAMI spread... depends on the accuracy of the pilot to be looking at the last cylinder to peak, or the ship’s gauge mounted downstream, or a TIT indicator...
 

going more LOP will result in cooler cylinders at the cost of slower IAS...

Going deep LOP compresses a lot of extra air for no apparent reason... less efficient, and often mis-understood as being better some how...
 

PIC gets to decide on how he wants to run his engine...

I prefer higher altitudes, and WOT, LOP by a few degrees... 

 

Getting the fancy ignition switches for the electronic mag can eliminate the ‘back fire’ during the mag test...

it occurs when it’s ignition computer gets powered off, and takes a moment to get going when the power is re-applied...

You will Probably notice this when you are switching through the R & L mags, not both... the Bendix Switch is complex... but not complex enough to handle the second of downtime...

ya know..?

Best regards,

-a-

[J0nathan225]

1 hour ago, ShuRugal said:

If I had to hazard a guess: when the Surefly is running timing advance, you're extracting optimum power from the working gas before the exhaust valve opens.

When you switch to the fixed timing mag, you are no longer running as much advance, as well as running a colder spark. Both of these things result in your mixture starting to burn later, meaning that there is less time to extract power from the working gas before the exhaust valve opens.

With your mixture settings tuned based off where peak EGT occurs when the Surefly is running, it doesn't surprise me at all to see a huge rise in EGT when you go to the mag. Going single-mag should always increase EGT. Going from Surefly with the advance running to single mag will be a greater difference.

The real important question here is: what are your cylinder temperatures doing during all of this?

Looking at the CHT graph, CHTs got cooler with just the MAG side, probably cause all the energy and flame was going out the exhaust. 

 

Gold flat line is my #2 EGT being wonky always seems to "Warmup" and work fine though.  

 

I was at 10,500MSL, density alt I didn't check guess:~12k roughly as it was 2200' on the ground at 300' MSL. 

 

Ahh what I forgot to try and do was another sweep with ram air "powerboost" on. 

 

[carusoam]

Jon,

I updated the last inflight mag test...

The FF is only 6.3..!

I assumed R & L, as R comes up first on the standard Bendix switch, tested the standard way...

How many °F LOP did you go?

The MP data looks artificially messy... as I expanded the chart to see the EGT spreads a bit better...

Thanks for sharing the data...

Got any particular flight you want us to look at... I just picked the first one...

Best regards,

-a-

[carusoam]

Electronic mags are looking more interesting by the day...

Keep an eye on any odd spark plug wear that may occur...

They spark half as often as the standard mags... but, their spark is much stronger...

Strong sparks have a tendency to ‘wear’ plug electrodes... actually knocks atoms off the surface a bit stronger than the a weaker spark...

PP thoughts only,

-a-

[carusoam]

Need help determining what your Gami spread actually is..?

Sounds like you might be unsure...

You can probably use a graph you have already... if you leaned through peak slow enough to let the EGT sensors really catch the peak...

Best regards,

-a-

[Ragsf15e]

If you were really at 6.3ff in cruise, that’s likely deep lop even at 12,500’.  You’re at like 46% power (14.85x6.3)/200.  For sure the mech mag is gonna be rough.  You’re going real slow for no gain in efficiency too.  Anthony’s plan of being just barely lop at high altitude works best.

Also, you’ll definitely want to use “power boost”/ram air up high.  Depending on how well it’s sealed , you’ll see around an inch more mp.

[J0nathan225]

I was at 55-60 % power I believe per the EDM.  I'm not 100% on how it calculates it, but it seems to take into account FF/LOP/ROP ops.  I was doing sweeps to get the data, I normally cruise at 10-20 LOPs 65% power ~8GPH I went to ~50 LOP to do the mag check.

My next flight I'll try a sweep with ram air open. I'm limited to a 50NM radius for flying, so I have nothing to do but fiddle with stuff right now.

 

thanks for the input.

[ArtVandelay]

I believe the JPI assumes ROP method to calculate HP which involves MAP, RPM and OAT. The LOP method only uses FF because 100% of the fuel is burned, where ROP there is fuel left over.

So once you go past peak, JPI displayed HP starts to become less accurate.

[Niko182]

18 hours ago, J0nathan225 said:

For my flight today I did a few ROP-LOP-ROP passes and then a LOP inflight mag check. I believe my gami spread is ~.4 not bad?

My biggest concern and maybe its because the surefly runs so smooth, but the mag side was rough and EGTs climbed to 1600+ quick.  I also got a large backfire switching back to both, which I've heard is normal with the Surefly's though. 

 

Thanks for any insight, I may op into the Savvy analysis annual subscription. 

https://apps.savvyaviation.com/my-flights/23406/f95d3be4-5558-475f-bce8-5dea0528271d

The cause of the back fire is most likely caused from the L to R switch. If you had the left mag selected on your ingnition switch during the LOP mag test, in order to jump from L to Both you need to pass R. When switching from the Mag to the Surefly, the surefly takes a fraction of a second to start up, something like a couple miliseconds. So for those couple miliseconds, the engine is off, and when the surefly reactivates, since youre at a high power, the backfire occurs. Im guessing your surefly is in place of the right Mag?

[Ragsf15e]

1 hour ago, ArtVandelay said:

I believe the JPI assumes ROP method to calculate HP which involves MAP, RPM and OAT. The LOP method only uses FF because 100% of the fuel is burned, where ROP there is fuel left over.

So once you go past peak, JPI displayed HP starts to become less accurate.

Clearly you’re right about how the ff/hp work, but my jpi seems to be pretty dang close (jpi 930).  Possibly they have updated the firmware because I just had it back there.  Possibly it’s close because I don’t go deep lop.  When I’ve checked it vs the ff, it seems to be spot on.

[Ragsf15e]

2 hours ago, J0nathan225 said:

I was at 55-60 % power I believe per the EDM.  I'm not 100% on how it calculates it, but it seems to take into account FF/LOP/ROP ops.  I was doing sweeps to get the data, I normally cruise at 10-20 LOPs 65% power ~8GPH I went to ~50 LOP to do the mag check.

My next flight I'll try a sweep with ram air open. I'm limited to a 50NM radius for flying, so I have nothing to do but fiddle with stuff right now.

 

thanks for the input.

I’d try a mag check at your normal 10-20 lop.  I bet your old mag is fine there.  At 50 lop, remember, that’s the richest cylinder.  Depending on your gami spread, leanest ones are probably barely running.  The old mag is gonna have trouble with that.

[kortopates]

1 hour ago, Ragsf15e said:

I’d try a mag check at your normal 10-20 lop.  I bet your old mag is fine there.  At 50 lop, remember, that’s the richest cylinder.  Depending on your gami spread, leanest ones are probably barely running.  The old mag is gonna have trouble with that.

A healthy ignition system will be able to handle a lot more than 50F LOP, over a 100F LOP is not unusual. A gami spread of 0.5 GPH is adequate to support 50F LOP. Doing the test near peak won't show ignition issues that will show up when properly stressed at closer to 50F LOP.  Don't mean to imply doing the test at 10-20 LOP is not useful (most carbureted engines can't even get that lean) just that it't not nearly as informative as one done at 50F LOP.  

I'll add, unless you have a min of 10 datapoints on each isolated mag (I prefer 30 sec at a 1 sec rate) with time to allow the EGTs to stabilize in between you really don't have anything to work with.

See https://resources.savvyaviation.com/resources/other-documents/flight-test-profile/ 

 

3 hours ago, J0nathan225 said:

My next flight I'll try a sweep with ram air open. I'm limited to a 50NM radius for flying, so I have nothing to do but fiddle with stuff right now.

RAM air isn't relevant to the sweeps, but doing them WOT is important.  

Edited May 20, 2020 by kortopates

[Ragsf15e]

Just now, kortopates said:

A healthy ignition system will be able to handle a lot more than 50F LOP, over a 100F LOP is not unusual. A gami spread of 0.5 GPH is adequate to support 50F LOP. Doing the test near peak won't show ignition issues that will show up when properly stressed at closer to 50F LOP.  Don't mean to imply doing the test at 10-20 LOP is not useful (most carbureted engines can't even get that lean) just that it't not nearly as informative as one done at 50F LOP.  

 

RAM air isn't relevant to the sweeps, but doing them WOT is important.  

I’m sure you’re right, especially if the gami spread is real tight.  In my case, gami spread works out 0.4 pretty consistently.  My #4 peaks first and drops quickly as I lean. If I lean all the way until #2 (richest) is at 50 lop, 4 will be 100-150 Or more and likely cold.  It definitely wouldn’t be happy on 1 mag.  Maybe that says something isn’t perfect, but she runs great at 20-40lop.

[kortopates]

2 minutes ago, Ragsf15e said:

I’m sure you’re right, especially if the gami spread is real tight.  In my case, gami spread works out 0.4 pretty consistently.  My #4 peaks first and drops quickly as I lean. If I lean all the way until #2 (richest) is at 50 lop, 4 will be 100-150 Or more and likely cold.  It definitely wouldn’t be happy on 1 mag.  Maybe that says something isn’t perfect, but she runs great at 20-40lop.

What you're describing is normal and a consistent 0.4 GPH spread is good! (You might read about a spread of zero but they don't really exist.) Running LOP, the leanest cyl bottom plug is commonly the one to start missing first, that normal, but with an adequate spread such as 0.4, we'd consider any misfire before 50F LOP on richest as premature. That said, we only need to be 50F LOP when operating at or above 75% power LOP. But that's not typical of most NA engines. So from a more practical perspective, your ignition system really only needs to be able to support the percent power levels you desire to run at. So if the altitudes you typically cruise at LOP will keep your power levels in the 70-74% range as an example, then you really only need to operate at 25F LOP for that power level and thus no point in chasing an ignition issue that you won't benefit by - which leads to my concurrence that I wouldn't be concerned if "she runs great at 20-40lop" and you have no need to operate leaner.  No point in performing maintenance that you won't benefit by and also why we don't recommend testing beyond 50F LOP.

[J0nathan225]

38 minutes ago, kortopates said:

A healthy ignition system will be able to handle a lot more than 50F LOP, over a 100F LOP is not unusual. A gami spread of 0.5 GPH is adequate to support 50F LOP. Doing the test near peak won't show ignition issues that will show up when properly stressed at closer to 50F LOP.  Don't mean to imply doing the test at 10-20 LOP is not useful (most carbureted engines can't even get that lean) just that it't not nearly as informative as one done at 50F LOP.  

I'll add, unless you have a min of 10 datapoints on each isolated mag (I prefer 30 sec at a 1 sec rate) with time to allow the EGTs to stabilize in between you really don't have anything to work with.

See https://resources.savvyaviation.com/resources/other-documents/flight-test-profile/ 

 

RAM air isn't relevant to the sweeps, but doing them WOT is important.  

I think I may still be on 2sec spread, I tried to stay there a while, but (maybe I'm misinformed) I didn't like seeing 1600+ EGTs and the roughness. 

 

for Ram air I recall noticing a difference in spread and LOP ops, from what I assume to be uneven airflow into the cyclinder?

[kortopates]

9 minutes ago, J0nathan225 said:

I think I may still be on 2sec spread, I tried to stay there a while, but (maybe I'm misinformed) I didn't like seeing 1600+ EGTs and the roughness. 

 

for Ram air I recall noticing a difference in spread and LOP ops, from what I assume to be uneven airflow into the cyclinder?

The high EGTs are only for 1/2 minute at a time and won't hurt anything yet it will provide valuable data. But you can always decrease the power with RPM to reduce the max EGTs too. BTW, contrary to some analyzer OEM's there is no redline EGT - just TIT.

The only difference in RAM air besides a a bit boost is that it bypasses the air filter but enters the induction system at the airfilter - shouldn't be responsible for any difference in mixture distribution.

P.s. that said, I would configure it identically to how you normally cruise or intend too.

Edited May 20, 2020 by kortopates

[carusoam]

8 hours ago, ArtVandelay said:

I believe the JPI assumes ROP method to calculate HP which involves MAP, RPM and OAT. The LOP method only uses FF because 100% of the fuel is burned, where ROP there is fuel left over.

So once you go past peak, JPI displayed HP starts to become less accurate.

Tell the JPI to use LOP method... fly LOP all the time...  (Setting in the menu, a couple buttons pushed at the same time to access)

Funny that JPI makes it so difficult to use...

Use the ship’s EGT gauge to roughly set mixture during the climb... while ROP...

The JPI is really good at %HP while LOP...  it may take entering a value for CR of your pistons... 

%bhp while ROP... is a look-up table to be accurate... which comes from the highly instrumented engines at Lycoming and Continental... and may not be accurately documented in the POH once translated...   

PP thoughts only, not a CFI...

Best regards,

-a-

 

[J0nathan225]

Well today was interesting. I went up to FL180, Density ALT ~20k'  -3degree C and my EDM froze and rebooted itself. That got my attention. 

[carusoam]

Just now, J0nathan225 said:

Well today was interesting. I went up to FL180, Density ALT ~20k'  -3degree C and my EDM froze and rebooted itself. That got my attention. 

In you M20E?

Go Mooney!

Now... about that JPI...?

Altitude or air density Or temperature sensitivity... not a usual problem for JPI...

Best regards,

-a-