Jump to content

Analysis?


Recommended Posts

Anyone care to speculate on what is happening with my #1 EGT? (Red trace)

Did a GAMI sweep on May 26th. Here is the link: https://savvyanalysis.com/my-flights/1006777/6596b159-77cc-4efd-b944-8816ae00849b

LOP Mag test starts at about 00:37

John-Paul at GAMI says my overall spread is .3 GPH.

I only leaned to about 40 LOP as per GAMI recommendations, and it was still running quite smoothly there. Is that an EGT probe issue or is there more going on?

EGT fluctuations seem to start once I get on the lean side of peak. If it was a bad probe, I would have thought it would be continuous.

Here is a close up of one of the sweeps:

982488022_GAMISweep.thumb.png.36981edac06bf80584f2af4afb7f0844.png

Edited by squeaky.stow
Corrected hyperlink
Link to comment
Share on other sites

0.3 is not a very tight Gami spread...

40 LOP is relatively deep LOP... it becomes a challenge to go deep LOP with the wide-ish Gami spread.

That cylinder isn’t producing a smooth run as well as the other cylinders...

  • +1 with Rich’s spark plug comment.  If champion plugs, check their resistance.
  • The red line isn’t representing the first or last to peak. So it isn’t the first to be running out of fuel...
  • What data collection rate are you using? Can you shorten it to 1sec?
  • Doesn’t look rhythmic like a sticking valve.  Sticking valves have saw tooth patterns usually...
  • Probably not a leaking intake? Altering A/F ratio for that one cylinder...

When a spark plug starts misbehaving,  excess fuel continues past the exhaust valve... its EGT begins to rise... as the fuel continues to burn in front of the EGT sensor...

Start with the logs to find out what plugs are in there... how old they are... how many hours on them... then what their resistance is...

Looks like the leaning process lasted about a minute.  Smoothly decreasing from 15gph to 9gph... EGT1 starts showing its disapproval of the event around 13gph on the ROP side... the one line is more visibly more jagged than the others...  and stops behaving well where the leaning stopped at 9gph...

The baby jar test, is a way to check the FF coming through the individual fuel injectors... a blocked FI will run leaner than its neighbors...

An inflight mag check may show strain on the ignition system, if it is a single plug going bad... a well defined mag check on the ground can help also... in this flight’s data the R and L mag check don’t seem to be very symmetrical.  Or it happened so fast, it is one peak...

For data collection, use 15 seconds or more on each R, B, L, B.... get the data collection rate down to 1sec if possible.

PP thoughts only, hoping to give some insight... but, didn’t find the obvious source....

Best regards,

-a-

Link to comment
Share on other sites

Plugs are Tempest Fine Wires with about 50 hours on them.

Data rate was set to the minimum for the EDM 830 as per GAMI instructions. 1 second, I think.

LOP mag check was done for close to 30 seconds each mag. Interestingly, the #1 EGT seems to smooth right out during the mag check.

I will definitely be having a close look at the #1 plugs and wiring.

 

Link to comment
Share on other sites

Look for a situation where the tempest loses the center electrode...  we have had a few around here over the last year or so...

A search will find a thread, some pics, and maybe a JPI graph to go with that...

Best regards,

-a-

Link to comment
Share on other sites

On 6/7/2019 at 7:52 PM, squeaky.stow said:

Plugs are Tempest Fine Wires with about 50 hours on them.

Data rate was set to the minimum for the EDM 830 as per GAMI instructions. 1 second, I think.

LOP mag check was done for close to 30 seconds each mag. Interestingly, the #1 EGT seems to smooth right out during the mag check.

I will definitely be having a close look at the #1 plugs and wiring.

 

Yes, Rich and Anthony nailed the issue being #1 misfire.

The LOP Mag test wasn't done long enough nor lean enough to show the problem. Its needs to be a minimum or 10 data points or 30 sec and should be leaned to 50F LOP providing the engine will still run smoothly but with a problem like that, it will likely get rough due to premature misfire.

Your data showed #1 didn't start misfiring the first time till ~40F LOP. Once it starts though it harder to get it to stop since the plug is burning much dirtier which is why in subsequent spreads you'll see the misfire begin much earlier as it does at 0:32.

The LOP Mag check wasn't informative. It was done at about 20+F LOP, try to target for 50 LOP if you can or just before the first sign of roughness and for a full 30 sec. (I see 4 humps fom isolating a mag, but only one was long enough.) See this for further help on how to perform the spreads and LOP mag test http://content.savvyanalysis.com/static/pdf/SavvyAnalysisFlightTestProfiles.pdf

Remember it takes both a good spread of <= 0.5 and a healthy ignition system. #1 plug (most likely bottom) probably just needs some cleaning, but also make sure they are all gapped evenly. FWIW I measured spreads of 0.5, 0.5, 0.7 and 0.8 GPH --  not seeing 0.3 in this flight data so  maybe John-Paul was looking at different data.

  • Like 1
Link to comment
Share on other sites

  • 4 weeks later...

A quick endorsement for Savvy Analysis. (Is that allowed here?)

As usual I ended up spending money trying to save money. Being too cheap to sign up for Savvy’s  analysis service, I put in a new spark plug and had the leads tested. Didn’t help, but at least I have a good spare now.

Broke down and paid for a year of analysis. Worth every penny. Paul quickly identified a probe issue and it turned out to be simply some damaged insulation on the #1 EGT. All EGTs now showing smooth and steady. 

It’s also nice to have the peace of mind that my engine data is being monitored for any trends or tell-tail signals that I would not be “savvy” enough to spot on my own. 

  • Like 2
  • Thanks 1
Link to comment
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.

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.