Engine analyzer interpretation

Lance F

Lance F

En-Route
PoA Supporter
Joined
Apr 9, 2005
Messages
2,897
Location
GA
Display Name
Display name:
Lance F
I posted this on the red board too, but I'm concerned and am looking for advise anywhere I might get it. Thanks

A review of my engine analyzer data after my first post annual flight shows an anomoly. Cylinder 1 CHT has always been lowest (or tied with #2 for lowest) and #1 EGT has always been highest by 10 or 20 dF. On this flight, however, #1 CHT was highest - 390 dF - and its EGT was lowest. It stayed like this until I went to low power settings for landing at which point the #1 CHT and EGT went back to their "normal" relationship to the other 3.
This has been a very sweet running high mid-time engine ~1500 hrs, since I got the airplane in July of last year. I'd welcome any interpretation of this situation and can provide more data if that would be helpful.
 
Since 390F is a perfectly good CHT, I wouldn't worry much unless this is a radical jump from its usual reading. Just how much higher than usual was it, and how much lower than usual was the EGT? And did any of the other cylinders' temps change significantly?
 
Lance,

What kind of engine monitor?

It could all be normal like Ron suggests.

I've had several probes go bad on the JPI. I lost a couple after the exhaust system was changed out.

Here are some possibilities:

The probes work on resistance. On the JPI, there's usually a splice in the engine compartment, where the probes connect to the harness. Ring terminals are used. If the wires are not secure in the ring terminal, or the ring terminal is not clean with good contact, you'll see a change in reading.

It's possible that the probe wires were swapped if the shop disconnected them. Verify that the correct probe goes to the correct wire in the harness.

Probe depth is a factor on the cylinder EGT. Make sure that the probe depth didn't change.

Also, if you use bayonnet probes rather than plug gasket probes, one of them might not be secure. Are all your spark plugs tight?

Finally, how's the engine baffling? Is it back where it's supposed to be?

In the end, it may be all OK. The temp reading doesn't seem out of line, my CHTs run to 390-400 and EGTs run to 1600-1650. I have a turbocharged engine.
 
I was getting some bad readings on my engine analyzer and the mechanic checked and cleaned some connections. It's worked fine since then. Maybe your mechanic saw something he did not like and removed and cleaned it. Maybe a couple of wires got crossed when it was reinstalled.

1500 hours. I know you run yours LOP with stock injectors. Have you had any problems? How many hours were on the engine when you started running it LOP? I'm asking because I have an 81 201. I have had other pilots tell me it's the smoothest running Mooney they have ever flown in. I have 275 hrs SMOH.
 
Here's what I posted on AOPA, pretty much what others have said:

Are you sure everything was put back right? The baffling in particular. Also, is there a chance any wire were swapped. I look for the simple things first. After my annual, my DME was out. Before going to the shop, I checked and just reconnected the antenna on the belly plate.
 
Analyzer is a JPI800 installed May this year. The #1 CHT probe for the JPI is the spark plug gasket type because the "certified" probe sits in the good spot inside the CH...sigh. On this flight #1 CHT was 30 to 35 dF hotter than I would expect it to be and the #1 EGT was ~20 dF less than I would expect based on many, many hours of previous data. I've got records of something like 100 flights and #1 CHT has NEVER been hottest until this one.

New spark plugs were put in so the #1 CHT probe was disturbed. No other CHT probes were disturbed and none of the EGT probes were disturbed. No engine baffling was touched.

I know that 390 dF is within the spec, but it is a lot higher than I am used to seeing, especially on the best cooled cylinder in the engine.

We will very carefully recheck all connections, baffling and such. (but I'm not optimistic that will be it )
 
Did the sparkplug gasket probe go back on the same plug? There is a big difference. I didn't like that setup and bought the piggy back sensor so I could double with the factory probe.

I agree, #1 is seldom the hottest on an IO-360.
 
First, a gasket probe will usually read about 20 F higher on the top plug and 30-40 F higher on the lower plug than a probe in the CHT boss. Was a plug replaced? If it were a different heat range, it might influence the temp at the gasket. BTW despite what Ron said, I think 390 is a bit hot for a CHT during cruise, mostly because it seems a lot more likely to go above 400 during a climb. Of course if you take into account the "extra" temp from the plug gasket location, it could indeed be just fine. Depending on how much the #1 CHT has increased of late, the "problem" could be a change in the baffling, a hotter plug, or an exhaust leak that's torching the probe.

You also might have a lean cylinder, but I wouldn't expect the EGT to have decreased if that were the case although the absolute EGT's don't really mean that much. More important is the differences in where the EGT peaks in terms of fuel flow relative to the other cylinders.

BTW you can get a probe from JPI that allows the factory CHT probe to co-exist with the analyzer probe. That way all CHT's will be measured at the same point.
 
wsuffa said:
...
It's possible that the probe wires were swapped if the shop disconnected them. Verify that the correct probe goes to the correct wire in the harness.
...
Click to expand...

This one gets my vote, based purely upon my electronic troubleshooting principles- "where did you mess with it last."

Symtoms suggest this, anyway.
 
SCCutler said:
This one gets my vote, based purely upon my electronic troubleshooting principles- "where did you mess with it last."

Symtoms suggest this, anyway.
Click to expand...

If the EGT was swapped with a CHT, it would be made obvious by the 1400+ F CHT and the >400 F EGT. It is possible that two CHT's were swapped, but that's unlikely since they wouldn't have had any reason to mess with other CHT probes (could have happend though). And if they simply reversed the two wires for the one CHT, the monitor would be indicating a bad probe. One other possibility is that one of the probe wires have become shorted to the engine ground, as might happen if they misplaced the sleeve covering the connections between the probe and the cable to the monitor (the probe wires are only about 10 inches long).
 
I wonder if it's possible that one of the spark plugs in cylinder 1 is either damgaged, not fireing or loose. You could try an inflight mag check to see if it reveals a bad plug. 390 in cruise seems high. What were your power and mixture settings at the time? I think what another poster said about cleaned and switching the injectors may also account for the difference.
 
More data...#1 cylinder is the only one with a gasket type probe, impossible to switch with anything else. The connector for this probe is still neatly tucked in its Nomex sleeve, so I'm certain nothing is loose. The FI nozzles were removed, but this was done one at a time, so each nozzle was where it has always been.

I just got back from the hanger where I pulled the cowlings. All baffling is exactly where it should be. There is nothing blocking anything.

My thinking (my hope actually) is with Pete's idea. We put in all new spark plugs, so maybe the problem lies there. The plan tomorrow is to replace the plugs in #1 with 2 of the older ones that were just removed (after careful cleaning and gapping, of course) and then take a test flight.

I'm crossing my fingers that I happened to get a bad plug.

Thanks for all the ideas!
 
Lance F said:
I'm crossing my fingers that I happened to get a bad plug.

Thanks for all the ideas!
Click to expand...

That would be my next step. You might also check the plug wire, too.
 
Lance F said:
More data...#1 cylinder is the only one with a gasket type probe, impossible to switch with anything else. The connector for this probe is still neatly tucked in its Nomex sleeve, so I'm certain nothing is loose.
Click to expand...

The probe wires could still be loose since they were no doubt "disturbed". That said, loose probe wires give widely varying readings, not a consistently high reading IME.

The FI nozzles were removed, but this was done one at a time, so each nozzle was where it has always been.
Click to expand...

It's also possible (albeit not very likely) that the nozzle became partiall plugged by the cleaning process.

BTW did you verify that the CHT gasket probe didn't move from top to bottom (or vice versa).
 
Thanks again for everyone's ideas. A&P and I checked everything imaginable yesterday. No loose or switched connections. Pulled the plugs on #1 and saw that the bottom one showed a hint of oil, but it is a 1500 hrs engine. Cleaned and gapped a couple of the used plugs that were taken out at the annual last week and installed them. I had one suggestion of a induction leak, so we pulled off the intake tube. The gasket looked OK, but put a new one on.

I flew the plane, but could not repeat the tests I did last wek because of low ceilings around here. I shot 3 approaches for practice and then downloaded the engine monitor data. Under full TO power #1 again shot up to be the highest CHT; however, after backing off for my approaches it dropped down to the second lowest to #2 which is OK.

I guess I'll just fly it normally for a while, monitor everything closely and see what happens.
 
You must log in or register to reply here.
Back
Top