Flymac

Engine slightly Rough/Stumble when LOP?

Recommended Posts

I highly prefer to fly LOP, usually cruise 6500-9500', currently 30Hrs post OH, IO-360, finewire plugs ~100 Hrs, new harness at overhaul.  After breakin used my JPI data to swap around some injectors to get my GAMI spread back in line, and have it at 0.4-0.5 GPH spread, so quite happy with that.  Just took my first big trip with the plane post overhaul, but engine does not seem to be entirely happy running LOP despite the nice(low) GAMI spread...when I transition to running LOP, the engine just seems to run a bit "rumbly"...not quite full stumbles or skips, but its like you can tell its just not entirely happy for some reason.  Just feels by sound its not smooth running...

This is without going extremely deep LOP or such, only 30-40deg LOP, and different that kind of the roughness you get when going too deep LOP where perhaps the GAMI spread gets worse and power disparity between the cylinders.  One leg at 8500 it just seemed too unhappy to continue LOP, but next leg at 6500 seemed alittle smoother, both where same GAMI spread when transitioned.

Any ideas/suggestions why the engine would be running like this, even with a pretty good GAMI spread?  I forgot a LOP mag check before landing from the trip was only other idea currently.

Share this post


Link to post
Share on other sites

*Members that donate $10 or more do not see advertisements*

Some thoughts...

1) can you post some JPI data?

2) When swapping FIs, did you clean them with the  usual solvent and or ultra sonic cleaner..?

These would be ideas to follow-up if there is a FI challenge...

Were the FIs numbered, or randomly placed back in position?

PP thoughts only, not a mechanic...

Best regards,

-a-

Share this post


Link to post
Share on other sites
33 minutes ago, Flymac said:

I highly prefer to fly LOP, usually cruise 6500-9500', currently 30Hrs post OH, IO-360, finewire plugs ~100 Hrs, new harness at overhaul.  After breakin used my JPI data to swap around some injectors to get my GAMI spread back in line, and have it at 0.4-0.5 GPH spread, so quite happy with that.  Just took my first big trip with the plane post overhaul, but engine does not seem to be entirely happy running LOP despite the nice(low) GAMI spread...when I transition to running LOP, the engine just seems to run a bit "rumbly"...not quite full stumbles or skips, but its like you can tell its just not entirely happy for some reason.  Just feels by sound its not smooth running... This is without going extremely deep LOP or such, only 30-40deg LOP, and different that kind of the roughness you get when going too deep LOP where perhaps the GAMI spread gets worse and power disparity between the cylinders.  One leg at 8500 it just seemed too unhappy to continue LOP, but next leg at 6500 seemed alittle smoother, both where same GAMI spread when transitioned.

At 9,500 ft, 40ºLOP may be too far LOP.

  • Like 4

Share this post


Link to post
Share on other sites

I did try different RPM/MP settings...essentially varying between 2400 to 2550 RPM...my default is/was WOT during the trip, I tried backing that off some with varying RPM, but it didnt seem to have any affect.  I just had the prop balanced down to 0.02 as well, so I believe what I'm feeling/hearing is truly this slight stumble-ish behavior of the engine.

-When we were swapping injectors around, I believe my mechanic cleaned them with spray/cleaner, no ultrasonic.  we started at ~1.2GPH spread post-OH so definitely worked our way forward

The JPI EZTrends is still a bit boggling to me how to change the scales, get FF together with the temps..etc...attempting to post...

This is 5500Ft running LOP, ~8.8GPH...slightly rumbly as I have described..but was happier than trying at 8500

image.thumb.png.3d6fa13a5bf6164af5986b2337008bed.png 

 

This was at 8500Ft trying LOP when it was just too unhappy to continue LOP...same WOT, ~2400, was still about 9GPH...as you can see still being 9gph not trying to get excessively deep LOP, just enough to peak all cylinders, still which were still all within ~0.4gph

image.thumb.png.95507c6645d614cb8e6dcc0032fdf896.png

 

 

  • Like 1

Share this post


Link to post
Share on other sites

Something to consider...

Using Savvy, the free parts at first....

You can upload entire flights of data...

Then compare before and after data...

Some of the most interesting data occurs during the run-up...

The Savvy site also has some good advice on best ways for collecting data...

PP thoughts...

-a-

  • Like 2

Share this post


Link to post
Share on other sites

Focus on the red and green lines... E1and E2.. they don’t seem well behaved...

typical good behavior of all lines... usually no intersections... these guys are crossing each other in a defined manor...

two cylinders are similar to each other, as is the other two cylinders... usually all four are doing more or less the same thing...

Good luck with the next steps...

-a-

 

Share this post


Link to post
Share on other sites
On 3/16/2019 at 10:37 PM, carusoam said:

Focus on the red and green lines... E1and E2.. they don’t seem well behaved...

typical good behavior of all lines... usually no intersections... these guys are crossing each other in a defined manor...

two cylinders are similar to each other, as is the other two cylinders... usually all four are doing more or less the same thing...

Good luck with the next steps...

-a-

 

Help me understand your feedback alittle more if you could, and thanks for taking a look...you noted E1/E2, red/green which match up so I dont think a typo, but I dont see these crossing each other, or otherwise why you believe their ill behaved?  If I have exhaust temps crossing each other, especially at this small scale, I would actually take this as a good thing that their running so close/consistent together (not take I care vs having the fuel mixtures close rather than temps)..but just want to understand your feedback.

It does seem #1 is a tad lean to begin with as I dont get much rise out of it compared to the others...will have to see if I could possibly richen it up with another injector swap...

Share this post


Link to post
Share on other sites

Blue and yellow are paired together in behavior...

Red and green are paired together in behavior...

They usually all behave the same...

usually the lines don’t cross at all...Some May be higher than the others, but the separation is always there...

Two lines climb more than the other two...

 

What you probably want to do... is start with a standard... Savvy has a couple Of standard procedures that are easy to follow...

 

If you don’t use a standard... you would have to explain all the steps you took for people to understand what the engine was doing when...

In An ordinary flight there are about a dozen details that can be picked up...

1) Start and warm up...

2) leaning for taxi...

3) run-up... (perform a good timed run-up) don’t rush

4) Max power T/O

5) Make note if you lean in the climb, what method you use...

6) Level off for cruise....

7) Leaning in cruise...

8) Descent... any enrichening... or power adjustments...

9) Land, taxi, shut-down

10) any inflight mag checks?

11) any anomalies prior to engine start... all EGT and CHT numbers should be close to each other... before start...

12) try to not add a bunch of other things to the flight... the data gets really messy and hard to follow after that... if you change altitudes or  re-lean... make a note of the time, then share your notes...

Compare to the Savvy site, or compare to previous flights to made

Essentially each cylinder is like a small identical engine to the other three cylinders....

From the one graph you have posted... something is making two cylinders work slightly differently than the other two cylinders... hence the lines crossing each other...

PP thoughts only, not an expert chartist... or mechanic...

Best regards,

-a-

Sorry, I can be more descriptive than that... :)

Share this post


Link to post
Share on other sites

Really specific this time...

Lets look at the last graph... 8500’, LOP leaning...

What is the change in EGT for each cylinder from before leaning to after...

E1, the red line... is not behaving the same way as his friends...

He starts warmer than everyone else, and barely raises for leaning....

E4, the yellow line rises so much, he crosses over E1...

 

At the end of the graph, is that going rich?  

The opposite effect is undoing itself... the redline returns to the original level, barely moving...

 

yellow and blue change a lot.

red and green are not changing very much...

 

Well balanced FF to all cylinders generally produces identical graph lines... with a little separation between lines...

 

These don’t look so well balanced... at least not from the graphs that have been supplied...

So if you are feeling some roughness.... you now have a picture that describes something funky is actually happening...

 

a dirty FI would be hot from the beginning, and get hotter while leaning... E1 is hot from the beginning, but barely budges while leaning...

 

 

There is a test that can be performed to determine how well balanced your FIs are... it is called the baby food jar test.  A timed flow test into four different identical jars...

This may identify which two are flowing more than the other two...

 

What comes to mind... it Might not be a FI problem...?

It might be nearing time to send some data to Savvy... or Gami to get some detailed help...

 

Did that describe enough detail about what I am seeing?

Got any previous flight data to share?

We have an MSer that might be able to point you in a better direction, than I can...  see if he has a minute... @kortopates 

Best regards,

-a-

Share this post


Link to post
Share on other sites
15 hours ago, Cruiser said:

what is the sample frequency set to on the JPI ?

2 seconds

Share this post


Link to post
Share on other sites

I'm in agreement with @carusoam. And I'd guess you might have an ignition issue? A LOP inflight Mag check would be in order. It may be a couple of weak plugs?

Also as Anthony said as well, upload your data to SavvyAnalysis and post the link, not the screen shots. That way the collective here can evaluate all the data instead of just looking at what you choose to post.

  • Like 1

Share this post


Link to post
Share on other sites

I've posted my file (was a download all) to Savvy...it says I can share a link for individual flights, but I only see a link to share them all it seems. The 2 focus flight might be #26 and #32, and as described below.  I agree on a in flight LOP Mag check, it was my absolute intention before landing, just forgot, certainly hope no ignition issues being a brand new harness and new fine wires with only ~100 hrs.

https://www.savvyanalysis.com/my-flights/1006233/db30367a-f41b-4a94-9f8b-e99500b43dc6

#32 Was pretty much all LOP, 5500, a climb at 1:06 to 7500, then right back to LOP rest of flight, was the slight rumbley/stumble as described...

#26 Was the "failed attemp" flight of 8500 trying LOP 2 times that was just a tab too rumbly to accept after trying for ~5 min or so, 8500ft...at 29 min and 54min were first 2 LOP attempts for a few minutes

  • Like 1

Share this post


Link to post
Share on other sites

Mac,

i clicked on the link...

it is one file...

each flight is identified by date and time...

The most recent ones have locations start and end of the flight... five recent flights in March...

i don’t see any numbers to identify the flights... there might be a column I am not seeing...?

19 flights filtered from 21... The note says...

But, the data is readily viewable...

Expect LOP at higher altitudes is going to be challenging in the thinner air... the better your air/fuel ratios are balanced in each cylinder... the better the LOP results will be... the fuel ratio balance is described using the Gami spread... or FF difference between first and last to peak...

when doing a run-up... Let 15 seconds or more elapse on each mag position... R, B, L, B.... this allows for the system (engine) to stabilize while collecting data points... each data point takes 2 seconds... and that is after the engine stabilizes which takes a few seconds itself...  watch the monitor... for motion of the segments... single mag they go high and stay... both, they come back down and stay...

If you are just waiting to hear things change...and change the switch...you haven’t waited for any stability... and you didn't collect any valuable data...

Precision takes time...

So let’s pick a specific flight by date and time and give it a look...

Note: you have great data in the file... in Savvy, you can select EGTs and FF and see them graphed...

 

PP thoughts while hanging around MS...

Best regards,

-a-

Share this post


Link to post
Share on other sites

I get this view/web when I click the link...but maybe its different to others, see the "Misc" column is the Flight numbers I was referring to in the notes above.  Thank you much for taking the time to check it out and all your feedback!

image.thumb.png.53d0076b17767fdc074a38d1b0cacb50.png

Share this post


Link to post
Share on other sites

I can’t get that column to appear... there is a button to select or deselect columns....

It showed briefly once, then I lost it again... :)

a bunch of + signs show up on the left side instead...

pick a flight, any flight...  use the date time method for ID...

-a-

figured it out... I am width limited... so hitting the + goes to a second row... or I need to deselect something else to have it all show up on a single line...

Share this post


Link to post
Share on other sites

I've looked at flights 26 and 32 in detail and the only thing I see is that I'm not convinced that your GAMI spread is as close as you say it is. I would recommend going out for a flight and running the Savvy Test Profile. On the Savvy page where you see your flight, click on Learn More in the top right corner, then Flight Test Profile. Go out and fly that profile just as it's explained and then upload the flight. The data shows a GAMI spread of .5 on some and .3 on others which should be fine. But you're moving from ROP to LOP very quickly and I'm not sure the JPI is actually capturing all the data. The reason I think this is that cylinders 1,2 and 4 seem to all be about 40 degrees LOP, #3 is only about 16 degrees LOP. 

The problem also might be ignition, which will be exposed with the Savvy mag check in the Flight Test Profile as well.

Best of luck with it. There's nothing quite as good as the range of a Mooney flying LOP.

  • Like 1

Share this post


Link to post
Share on other sites

I was reviewing the data... looking for signatures of the usual items...

But, without knowledge of what the pilot was actually doing... it can get dicey....

I see plenty of FF early into the run...minutes after start-up...

My IO550 taxis using 2gph, after it starts using about 3-4gph...

The next time, for me, FF changes is for the run-up...

 

Things get hard to follow right after that... 

 

What I was seeing, but gave up on... there are some EGTs that are separating from the pack... but without a well defined run-up to calibrate the data from... it is too challenging to make further judgements...

 

Flight #32...

Briefly, cause it’s late...

2) Start-up... check.  Things start warming up..

3) 1.3gph taxi... 4 minutes into the run...

4) 5 minute mark... FF is 19.2,  no rpm data?, that is a lot of FF unless you are in the T/O run... no?  Fast taxi? Egt1 starts to separate from the pack...

5) 11 minute mark looks like a run-up signature, but it occurs too quickly to see the defined pair of EGT peaks... FF hits 15.2 gph...

6) 14 minute mark looks like run-up complete idling at the hold short line? 8.7gph...taxi into place?

7) T/O run... 14:30... 

8) 

 

Next steps...

1) review the Savvy site... regarding collecting data... and what their sample run-up and leaning looks like...

2) you have some good data collecting and sharing skills...

3) just need to get to the level of collecting a good set of data...

4) The good thing to know... it is really obvious where you adjusted the mixture in the flight... you can see the FF change and the EGTs shift...

5) Go really slow in the run-up collect some good data points, hang on both for a while to allow the EGTs to come down and the JPI to actually collect data... everything takes longer than expected in this step...

6) Since you are trying to find and issue... it is worthwhile to take it slow...

 

Sorry I couldn’t get any more out of the existing data...

If you want, we can go step by step through the details... you have to supply the steps... what you did at this minute mark... that minute mark... the next minute mark...

each time you move the throttle or mixture knob... deserves a note... (best for sharing the flight details without mis-interpretation...)

Real life has response times that are pretty long... this science is very much removed from instantaneous... :)

PP thoughts not a CFI or mechanic...

How far away is the runway to the hangar?  It appears really close?

Best regards,

-a-

 

Share this post


Link to post
Share on other sites

Following up with more data after getting to do the detailed Savvy inflight test today finally, and the LOP mag test I had originally forgotten to do before my last flight and posting all of the original data...

Runup to usual 1900RPM, 30 Sec Both, 30 Left, 30 Both, 30 Right...if we're able to nitpick 30 seconds worth of data and only 20 degrees...I see here that L mag E2/Green is alittle cool compared to others...until on R mag, where in general all EGTs are much closer together..apart from E4/Yellow.  What this means...not sure! Ha.

I have the dual mag, so the balance between the 2 overall EGT temps is in line as expected...possibly clean plugs on #2/#4 is all I get here...

image.thumb.png.8e0dfb01f8b4b63d1c87cb22eec666d7.png

 

LOP/ROP sweeps, 7500 0 Deg C, LOP Mag Check

The JPI data taking the time to do the seeps much much slower revealed a spread of closer to 0.6-0.8 Gami spread...so maybe that is part of my issue vs all by prior data, even with pretty slow sweeps, was showing 0.5gph spread every time..  

-Funny E4 on this one is much higher on that others on the L mag vs the R mag on the runup above....

-LOP order is consistent...E4/Yellow and E3/Blue still rising significantly and crossing others

jimage.thumb.png.5fb9f051baada373b102c02a737bd124.png

 

  • Like 1

Share this post


Link to post
Share on other sites

Nice notes on the graph!

left mag vs right mag shows something interesting... they should be more similar... do you have all the same plugs in each cylinder or a mix of fine and regular plugs...

Do you see anything interesting with the mag drop during the run-up... one mag is behaving differently than the other? What is the mag rpm drop each time?

Looks like there may be a timing difference, one of the mags may have slipped a timing setting...

running on a single mag, raises the EGTs... having the timing delayed raises the EGTs on that mag...

It looks like, running on one mag there are higher EGTs than the other... possible timing difference between the mags...

Yellow E4 continues to stand out as more different than the rest... on the L mag... the spread of EGTs is really large on the L mag vs the R mag...

Check to see which spark plugs you have related each position in the cylinder... it is possible that the E4 related to the L mag is a high resistance champion spark plug...

check your logs to see what spark plugs have been used, and any notes what cylinder and mag got which plug.  High resistance mags have a tendency to raise EGTs as the fuel doesn’t burn very well in the cylinder...   slight odd feeling probably comes from that... a mechanic can check the resistance of the plugs.

 

Leaving a note for Mr. @kortopates to see the interesting JPI graph if he can...

 

PP guesses only, not a mechanic at all... 

-a-

Share this post


Link to post
Share on other sites

Did you do an inflight Mag check as recommended by Savvy? The mag check on the ground is not very telling of anything.

Share this post


Link to post
Share on other sites
6 hours ago, gsxrpilot said:

Did you do an inflight Mag check as recommended by Savvy? The mag check on the ground is not very telling of anything.

Yep, see 2nd graph i had posted above right after the ground mag check graph

Share this post


Link to post
Share on other sites
On 3/16/2019 at 5:43 PM, KLRDMD said:

At 9,500 ft, 40ºLOP may be too far LOP.

Remember that the Lycoming recommended leaning procedure is to lean to loss of power (or roughness for a carbureted engine) and then enrich back to smooth operation.  If it's rough it may be that you're just too lean.

 

Share this post


Link to post
Share on other sites
4 minutes ago, EricJ said:

Remember that the Lycoming recommended leaning procedure is to lean to loss of power (or roughness for a carbureted engine) and then enrich back to smooth operation.  If it's rough it may be that you're just too lean.

 

Lycoming's recommendation really isn't very good. Savvy, APS, Deakin, et.al. are all much better and more accurate.

  • Like 1

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.