What do you guys think about this GAMI spread

[bradp]

Hi All,

Wondering what you think about this GAMI spread?  It's an old data pull from my JPI, but the pattern is persistent on more recent flights.  The behavior of my #1 has never quite been in line with the others.  Peaks later and doesn't fall off quite as much as the other three.  Cyl #1 is acting "richer", but the spread FF / "Gami" spread is 0.3, which is pretty good for stock injectors. 

Since this went to all fine wires, still the same pattern.

Swapped EGT probes, still the same pattern.

We did a high voltage lead test at annual.  I've been thinking about ignition harness replacement as I'm getting "engine noise" through the headset and some of the shielding is fraying.  IA says don't worry so much about it and likes the look of the leads. 

I've done a few LOP in flight mag checks s... but the only one I have handy is not reflective of the new fine wires.  I'll have to pull some more data from the JPI next time I visit her to see if it follows the same pattern. 

It's one of those things that bothers me a little bit because it's not in line with the others. 

My hunch is that it's a mag / lead issue, but just a hunch. 

What do you guys think?

-Brad

 

 

 

[carusoam]

Time to break out the baby food jars and a stop watch...

This is where your mechanic puts each fuel injector into a jar and runs the fuel pump to see what is going on.  It would help to have one of those glass labware devices with CCs calibrated on the side. ...Volumetric Cylinder...

could be dirt in the injectors slowing them down.

could be a different injector flowing more than the others.

could be the reason gami has a balanced injector business!

There is probably a procedure for this written by the oracle of all things Mooney at KGGG (?)...

Thinking out loud, Brad.  But your Gami spread is quite large.  A perfect spread, the cylinders all peak at the same FF.  A mild spread they all peak within a few tenths of a gallon of each other.  Your chart doesn't show many data points to tell what the FF is as they peak.

EGT1 shows that FI1 will fill the baby jar faster than the others. Followed by 2.  3&4 seem to be similar to each other...

if one were to peak early and another were to peak late, that is an indication that two FIs have been swapped and need to be put back.

one thing I notice is that the speed at which you are leaning is faster than the JPI is recording data.  You may want to slow things down near the peak.  You already know the FF where the peak begins and ends.  Check the data rate on your JPI. It may be set on six seconds.  It can be sped up to 2 seconds or better...  know that TCs and laws of physics get in the way of Leaning quickly.  Make sure you are using quick response TCs too.

Best regards,

-a-

[Browncbr1]

Gami spread looks really good.  Your #1 could be higher because of the probe location or less than optimal fire.  Have you rotated plugs?  Is the probe located any closer to the flange than on the other pipes?

[bradp]

1 hour ago, Browncbr1 said:

Gami spread looks really good.  Your #1 could be higher because of the probe location or less than optimal fire.  Have you rotated plugs?  Is the probe located any closer to the flange than on the other pipes?

I've rotated spark plugs, no change. I used to have champion on top and tempest fine wires on the bottom, but have gone to all fine wires.    I haven't measured the distance from flange to EGT probe.  Good idea. 

I was thinking weak spark is high on the list of potentials - in flight mag check may help with that.  The ignition noise is almost making me jump to the ignition harness upfront, but I want to trouble shoot that separately (i.e. Make sure p lead shielding grounds look good).  

Some more data to collect, perhaps.  

I ran the savvy Gami spread tool for several flights and was getting 0.3-0.4 on most of them.  Anthony makes a good point about leaning slowly.  I have a quadrant, which makes adjustments a bit imprecise, and I've never wanted to spend too much time at peak when leaning. 

Baby bottle test about a month after that flight I posted a picture of.

-B

[carusoam]

Advantage...mixture knob with precision twist control. 

Since FF is measured in 0.1 increments, all the extra precision of the mixture control kind of gets lost.

if possible lean using the FF indicator, spending enough seconds to catch a data point at each Leaning step.

While experimenting it does make sense to continue to avoid the red box.  Use a proper altitude to help out...

0.3 isn't bad at all.

0.1 is pretty smooth if you are leaning deeply.

See how deep LOP you can go.  My old engine was set up nicely.  It could go 90°F LOP at lower altitudes until it just stopped running after that.... at higher altitudes 40° LOP was possible.  

This is a demonstration of smooth LOP power.  Some of it is made possible by the curvy intake tubes of the IO550.  It is a technical achievement for demonstration.  It isn't a good way to travel long distances.... low power, slow, cool CHTs....

Best regards,

-a-

 

[Zucke]

On 12/29/2016 at 5:25 AM, bradp said:

Hi All,

Wondering what you think about this GAMI spread?  It's an old data pull from my JPI, but the pattern is persistent on more recent flights.  The behavior of my #1 has never quite been in line with the others.  Peaks later and doesn't fall off quite as much as the other three.  Cyl #1 is acting "richer", but the spread FF / "Gami" spread is 0.3, which is pretty good for stock injectors. 

Since this went to all fine wires, still the same pattern.

Swapped EGT probes, still the same pattern.

We did a high voltage lead test at annual.  I've been thinking about ignition harness replacement as I'm getting "engine noise" through the headset and some of the shielding is fraying.  IA says don't worry so much about it and likes the look of the leads. 

I've done a few LOP in flight mag checks s... but the only one I have handy is not reflective of the new fine wires.  I'll have to pull some more data from the JPI next time I visit her to see if it follows the same pattern. 

It's one of those things that bothers me a little bit because it's not in line with the others. 

My hunch is that it's a mag / lead issue, but just a hunch. 

What do you guys think?

-Brad

 

 

 

Hi Brad

Your #1 cylinder seems a littlebit richer, but there is nothing you should  worry about.

The reason #1 EGT ist higher just indicates, that this EGT-probe is sitting in a place where exhaustgases hit it more directly, then the others.

The EGT is NOT an actual temperature :-)

 

Best regards Zucke

[Cruiser]

Enjoy the Mooney economy. The M20J can consistently get 15 mpg at 150 KTAS. 

As others have mentioned ^^ the EGT is a reference temp and not a concern. Your GAMI spread is acceptable. 

Go flying. 

[LANCECASPER]

7 hours ago, Zucke said:

Hi Brad

Your #1 cylinder seems a littlebit richer, but there is nothing you should  worry about.

The reason #1 EGT ist higher just indicates, that this EGT-probe is sitting in a place where exhaustgases hit it more directly, then the others.

The EGT is NOT an actual temperature :-)

 

Best regards Zucke

 

6 minutes ago, Cruiser said:

Enjoy the Mooney economy. The M20J can consistently get 15 mpg at 150 KTAS. 

As others have mentioned ^^ the EGT is a reference temp and not a concern. Your GAMI spread is acceptable. 

Go flying. 

His post is almost 4 years old. It would be interesting to hear about any updates to this.

[kmyfm20s]

.3 GAMI spread is pretty good! It would be fun to hear a follow up. I would have preferred to see the end of the sample segment on the down slope of the curve instead of at the peak of #1. The fuel jars look pretty even so I would look for an induction leak next. The o-rings where the induction tubes go into the plenum crack over time and go unnoticed. Air, spark and gas:) 

[Zucke]

Hey Bred.

Could you describe this engine noise?

Does it disappear, when one mag turned off?

- Zucke

[carusoam]

Welcome aboard Zucke...

In terms of time frame...

This situation occurred a few years ago... Dec 2016.
 

Are you fighting a similar challenge?

Standby, Brad will probably be back later...

Best regards,

-a-

[Zucke]

2 minutes ago, carusoam said:

Welcome aboard Zucke...

In terms of time frame...

This situation occurred a few years ago... Dec 2016.
 

Are you fighting a similar challenge?

Standby, Brad will probably be back later...

Best regards,

-a-

Thank you.

No actualy Im just a studentpilot, but I read a lot about GA pistonengines.

And thought I can help with some problems...It is a pity if someone is throwing money at a problem, while a good diagnosis could reveal just a minor problem.

Best regards

-Zucke

[carusoam]

Stick around Zucke,  there will be plenty of more opportunities... in real time...

If you search on words found in the phrase...

download your JPI data... you will find a few opportunities for problem solving...

dental camera pics... you will see what happens to valves when they start to stick...

MS has a few thousand members... whenever something fails, somebody will want to ask a question....

We have a few really good mechanics around here that spend some times discussing tech details.

You might find the threads regarding electronic ignition interesting... not everything has to be 1930s technology... 

Enjoy!

Let us know if you have any additional questions.

I’m only a PP, not a CFI or mechanic...

Best regards,

-a-