Is this a problem spark plug showing in the EDM data?

[Matt Ward]

Hey guys,

I flew from KCPR back to KBJC today on a great flight.  I flew a bit LOP at 8.5GPH.  I just downloaded the data and noticed something peculiar I figured I'd ask you guys about. You can see my JPI EDM 700 data here: https://apps.savvyaviation.com/flights/3944849/324f4290-bd33-43be-9b6c-aceebef72f2d

The taxi portion of the flight was about 7 minutes in to 11 minutes in.

During that low power portion of the flight you can see that EGT is running a bit higher than the other cylinders.  During the run-up (11 to 13 minutes approx), things stabilized.  Then during cruise, EGT 3 ran a little lower than the rest.

Of note, during my flight yesterday up to KCPR from KBJC while running 100 ROP at about 10.5GPH, EGT 3 ran a little cooler in cruise but didn't show the same taxi behavior, seen here: https://apps.savvyaviation.com/flights/3944848/778265ae-8327-4186-9153-124dd3630949

What do you guys make of this?  Is this an early indication of something I should be concerned about?

Thanks!

[carusoam]

What is the peculiarity you are referring to, Matt?

When wondering about plugs...

It really helps when you do a run-up with a method that allows for collecting data...

See if you can point out what you did during your run-up... on the graph...

If you can’t see it on your graph... chances are we won’t be able to see it either....

Know you data collection rate...

Know how long it takes to collect data...

Adjust your run-up to include these details...

Or, we do the best we can with what we have.... lots of guesswork included... 
 

Best regards,

-a-

[carusoam]

From your data....

I don’t see Rmag, both, Lmag, both in the EGTs....

are you familiar how long your hardware takes to do what you are asking for?

Done so quickly, the two separate peaks blended into one, hiding anything like a single plug not working...

Keep in mind, you have much instrument power in your hands compared to the standard school airplane... the run-up is a valuable test where you can get really good engine information...

Or you can go through the motions of the school taught run-up... both mags work, some change in rpm, not a lot.... I’m good to go....  their planes have dedicated mechanics looking after the machines... your plane has you.... 

Best regards,

-a-

[Ragsf15e]

Absolute values of egt aren’t really helpful.  They don’t even need to be real consistent between cylinders.  They are obviously helpful for finding peak egt and setting fuel flow in cruise.

Not all your cylinders are running with exactly the same fuel/air mixture at the same time.  Some are richer or leaner than others.  I know my #4 is slightly leaner than the others, so if I’m LOP, it’s generally cooler egt than the others.  Conversly, if I run ROP, #4 egt will be hotter than the others.  
 

[Matt Ward]

Thanks for that.  It's interesting you say that about not see L R Both.  I actually do it twice, meaning B-R-L-B-R-L-B, pasted below.  I have the data sampling set at 2 but maybe I didn't leave it on each mag long enough.  Or, maybe I did and there is another problem?

 

Regarding the taxi, this is what I'm wondering about:

 

Then during cruise, 

Regarding what I * think * was my mag check:

[carusoam]

Without MP, RPM, and FF data...

You may have to add some detailed narrative....

like...

see the mark I put on the run-up here... the EGTs on the Lmag are much higher than on the Rmag just before it...

See the dromedary humps... that’s where I did the inflight mag check... both look pretty uniform....

-a-

 

[Matt Ward]

So @carusoam, I think you're pointing to my 2000 RPM Prop Cycle.  I * think * the mag check is just before that, as seen in the mag check view on Savvy.

[carusoam]

The graphs get more challenging to read each time the pilot changes an engine control...

Without knowing when the pilot changed things... MP, mixture, rpm.... it appears the engine may be doing this on its own....

I went through this with another MSer a few days ago... there are about 20 times we change the controls in each ‘standard’ flight...

As far as EGT data goes... See Rag’s note...

Best regards,

-a-

 

[Matt Ward]

Thanks.  I understand absolute values of EGT don't matter.  My concern is about deviation from typical.  I've not seen the EGT 3 separate like that from the other cylinders in any other flight, during taxi operations.  It always runs a little lower in cruise, which if that was my only issue I wouldn't have raised it.  The CHT is in-line with expectations, the primary anomaly I was concerned about was the low power deviation from normal (to a hotter EGT).

But now you've got me wondering about my mag check...

 

[carusoam]

Looks like you did the flight school Mag check... based on sound and instrument deflection...

Your JPI doesn’t work near that quickly... because EGT instruments don’t react that quickly...

Nobody teaches this in flight school....

Unless you hire somebody like an MSer to be your CFI or flight partner...

Best regards,

-a-

[carusoam]

See if you can find a flight in your database that accidentally captured more data...

Our engines are designed to fly at high levels of power...

What they do on the ground is generally mis-behave.... in comparison... 

 

Lets collect some good data on a flight... skip all the noisy activities...

This will help you define what works for you and your equipment...

 

Next most important thing.... post graphs in a standard format...

This helps to keep from losing reader interest... if it is too hard to understand what you did, some helpful people will move to the next post....

Best regards,

-a-

[Matt Ward]

Point taken!  I'll give it a good 20-30 seconds or so next time.  That's what Mike Busch recommends for the inflight mag check based on my data rate.

[carusoam]

20 seconds on each switch position... watch the display... when the lines stabilize count a few more seconds to catch all the data...

This is 90s technology... not like the latest Pentium PC chip in there....  

Still the delay is the speed of which heat can transfer from the outside of the TC armor to the inside.... and back a few times over...

Mike Busch is good.... but he is not looking at your instrument like you can...

Hmmmm.... that makes you potentially better than MB! For your engine... 

Best regards,

-a-

[carusoam]

So....

We can use the aged JPI 700 to determine....

• Any spark plugs not working.... even if they only skip a beat every now and then... 
• Any differences in mag timing... even if it is a few degrees one way or the other....
• Any differences in FF in a single injector... even if there isn’t a FF meter....

It really helps to upgrade to a JPI 730 to collect FF, rpm and MP data too....

PP thoughts only, not a mechanic...

Best regards,

-a-

[Matt Ward]

So @carusoam, I think I got a little bit of good data this AM, on purpose even!  Unfortunately I had to fly shorter than I wanted because I inadvertently flooded my engine.  I think it was partially due to my new fuel pump (thanks Aeromotors!) providing a little more fuel than I am used to and I need to tweak my technique.  Anyways, I took your advice and prolonged my run-up mag check.  In Savvy, using the mag check view, it *seems* to look ok to me.  The original issue I was looking for (the odd EGT on one cylinder) seems to be gone and I'm chalking that up to a fouled plug.  I'm trying to lean more aggressively on the ground now.

Anyways, here is what my mag check looked this today.

https://apps.savvyaviation.com/flights/3956956/40b6abbd-6292-4a47-802f-c0ffbc09b622

Cheers!

[gsxrpilot]

That mag check looks fine to me.

[carusoam]

Now that’s a well defined dromedary mag check! 

If you get further interested...

Each of the lines, and what they do... are not usually random...

As in, often they will behave the same way on different flights...

Spark plugs drift in performance over time.... Especially the champion ones...

So...  the highest peak may always be the same plug...a little more resistance, a weaker spark.... more fuel burning past the exhaust valve...  As the resistance changes... so will the peaks...

 

Thanks for sharing the data...

Best regards,

-a-

[kortopates]

The above mag check does look good and with even mag timing. But a ground mag check is very limiting since its rarely done lean enough. The real test is the LOP Mag check done in the air at 50F LOP if possible along with the gami sweeps just prior to the mag test.

The mag check should be a min of 30 sec; especially with your 2 sec timing (10 data points is an absolute minimum with more even better). See this for details  https://resources.savvyaviation.com/resources/other-documents/flight-test-profile/

[carusoam]

Great added details, Paul!

Thanks for supplying the real expertise.

-a-

[Matt Ward]

Thanks for the help everyone.  Today I did an in-flight mag check at about 25 LOP, or, about 8.5GPH.  It's the typical BOTH-R-BOTH-L check.  I was a little surprised to see the uniformity, but there it is!  Not too much roughness during the check - slightly perceptible but not enough to frighten you.

https://apps.savvyaviation.com/flights/3958638/5dea8109-dc64-4bb7-8407-0bce62aee974

[gsxrpilot]

I was there. Thanks for the ride @Matt Ward. That is a sweet flying E. And one of the smoothest running IO360's I've ever seen. You've got a really nice airplane.

[carusoam]

Wow!

It’s running soooo well...

He needed a qualified, independent, MSer to verify his story... 
 

It might have soundEd too good to be true...  

 

There is Enough data that the curves even have shape to them...

The rise on a single mag is pretty sharp...

The fall on both mags is also pretty sharp at the top....

a softer curve occurs as the state of the mags is held... As nature occurs... a natural stability in action...

The egts didn’t quite plateau they probably were still rising... the tools are much more accurate than the process needs... (a really good sign)

Nice work Matt!

Thanks for collecting and sharing the data...

Best regards,

-a-