Clogged injector?

[Shadrach]

8 minutes ago, Godfather said:

Mooney owns the STC now. My JPI flashes at me on every single takeoff. They are unwilling to bump the “unsafe” limit. 

29gph is better, but still sub optimal!  Good luck and you keep us posted woth regard to your exchanges with GAMI.

[carusoam]

3 hours ago, Shadrach said:

So the STC specifies exact full rich FF, not a minimum? 27.2gph max for a 310hp engine is absolutely sub-optimal at full power. If I had that upgrade, my hangar fairy would figure out a way to bump FF.  I’ve heard of the pixie hole and the tendency for #5 to run hot. However, the fact that it’s 380° on the take off run  with OAT of 25 - 35° Suggests this is a F/A issue, not a cooling issue.   It is likely magnified by the cold weather given that a 310hp engine on a standard day can make considerably more than 310hp on a 25° high-pressure day and limited to 27.2gph.    No wonder it looks lean across the board. Who owns the STC?  

So we have an engine set up on the lean side for a standard day, running in cold dense air, with a possible F/A issue on the one cylinder that is known to lack adequate cooling airflow?

 

Oops... I skipped a few posts trying to write the following down...  short on time...  back later...  

 

 

The STC has a range of FF, measured in pounds per hour.  Translated into gph, the highest level is the 27.2 gph I stated...

Mooney purchased the STC from its author...

Yes, I think you have the basics down.

See if we can get additional data from the GodFather...  fuel flow and complete graphs the way Savvy would like...

Best regards,

-a-

[carusoam]

Back, and reading...

I see the FF is increased to 29gph... a definite improvement over the 27.2...

Somebody documented using 30gph... unfortunately not on an STC or service letter anywhere to be official enough...

 

Another thing to be familiar with.... Might be interesting, but not very helpful for this one cylinder specific looking issue...

The ships EGT is a seventh EGT probe that is mounted on one side of the engine at the location of the 3 into one pipe.  Where three exhaust streams flow into one pipe.  It sees three peaks of hot exhaust gasses in the same time the single exhaust headers see one.

This location is further downstream, but the three waves of heat give a higher average EGT...  

this seventh EGT probe is the ship's EGT probe that feeds the blue box on an individual panel mounted EGT gauge, or white box on the G1000.

On the JPI900 on the GF's plane is there a seventh EGT probe, and is it presented as the one piece of data to lean with?

It would be kind of strange that JPI locks in specific ranges based on POH facts, but would accidently leave out the POH fact regarding the actual controlling EGT sensor that Mooney is actually using... I don’t see an E7 in the data... it might accidently get labeled TIT as some TN’d engines need that seventh data point for leaning the turbo safely...

And of course, I’m only a PP trying to lend a hand... I am not a mechanic or sound enough in my technical writing skills to be accurate...

Best regards,

-a-

 

[Godfather]

1 hour ago, carusoam said:

Back, and reading...

I see the FF is increased to 29gph... a definite improvement over the 27.2...

Somebody documented using 30gph... unfortunately not on an STC or service letter anywhere to be official enough...

 

Another thing to be familiar with.... Might be interesting, but not very helpful for this one cylinder specific looking issue...

The ships EGT is a seventh EGT probe that is mounted on one side of the engine at the location of the 3 into one pipe.  Where three exhaust streams flow into one pipe.  It sees three peaks of hot exhaust gasses in the same time the single exhaust headers see one.

This location is further downstream, but the three waves of heat give a higher average EGT...  

this seventh EGT probe is the ship's EGT probe that feeds the blue box on an individual panel mounted EGT gauge, or white box on the G1000.

On the JPI900 on the GF's plane is there a seventh EGT probe, and is it presented as the one piece of data to lean with?

It would be kind of strange that JPI locks in specific ranges based on POH facts, but would accidently leave out the POH fact regarding the actual controlling EGT sensor that Mooney is actually using... I don’t see an E7 in the data... it might accidently get labeled TIT as some TN’d engines need that seventh data point for leaning the turbo safely...

And of course, I’m only a PP trying to lend a hand... I am not a mechanic or sound enough in my technical writing skills to be accurate...

Best regards,

-a-

 

JPI will not even allow 27.2 forcing the 26.7 quoted earlier in the STC. 

The pilot side ship EGT was not added to the system when the exhaust was completely rebuilt during the overhaul. TIT would be a required probe.

[carusoam]

^^^  Interesting....  The Os with a G1000...  ship's EGT gauge is actually mislabeled... I believe it gets labeled as a TIT... this way it’s identical to the Acclaim. One system that functions as two...

All based on fuzzy memory I think somebody told me recently. I don't have a G1000 to Check...

Best regards,

-a-

[Shadrach]

Wow...this reads like something I’d expect from a manufacturer back in 1972. It is a  simple task (relatively speaking) to fit useful instrumentation to an air cooled engine. Having the “collective” EGT for one bank of cylinders on a normally aspirated aircraft seems like the answer to a question no one asked. 

Who was the original STC holder?

[carusoam]

For the STC for the 310hp IO550... I Always defer to @StevenL757 for the author's name and historical details...

Some days my memory isn't as strong as I’d like...

The STC no... SA02193CH  owner at the time was Midwest Mooney Sales in Flora IL

As for the EGT instrument in all Os... That is factory original going back to 1994...  in that year JPIs may not have been standard issued... A single CHT and Single calibrated EGT were....

My seventh EGT sensor is not wired to my JPI. It’s wiring details and location have gotten forgotten a couple of times before getting refreshed again...

its function is derived by Continental who was pointing out the ability to run LOP.  Doing it from a single sensor in the collector pipe makes a small amount of sense as it is less sensitive to a single EGT that may peak early or late.  The POH has actual LOP charts for operation.  

Looks like Mooney added JPIs, Then went G1000 after that...

Pilots hadn’t been that demanding or talkative about engine analysis, prior...

prior, They didn't even calibrate the EGT sensor with actual numbers... or mention LOP..?

Best regards,

-a-

 

[DonMuncy]

11 hours ago, carusoam said:

They didn't even calibrate the EGT sensor with actual numbers...

It is my understanding the aircraft manufacturers back then intentionally omitted the real numbers on the EGT, as "the real EGT values were irrelevant; only the distance from peak."

[carusoam]

Don,

1) Today, the raw EGT values aren’t much more relevant than they were back in the day...

2) They became more relevant when the factory located the sensor in the exact same spot on every plane... that same reading gains actual value for comparison between cylinders and other planes...

3) The IO550 uses the ship’s gauge for leaning in the climb. It is still a relative number.  200 - 300 ROP... 

4) The big Deal here... the pilot doesn't search out Peak while at high power in the climb. He just stays ROP using the calibrated gauge.

5) The larger the NA engine, the more excess fuel is being dumped through the cylinders in the climb... continuous adjustment is ideal... 

6) With a TC’d engine you probably won't see much advantage to this, because your MP doesn't change much on you during the climb... 

7) The most relevant EGT number is called TIT... where the actual temperature is important to the health of the turbine.  Too hot and the blades soften and stretch under the centrifical load.  Really hot, can lead to blade erosion.   Super hot, the blade tips contact the Case...

8) If There is a hell in the airplane World it has to be in the exhaust system.  It’s a nasty environment in there... high pressure, extra hot and oxidizing... the crappy environment starts at the exhaust valve and goes all the way to the turbo’s exit restriction... things get better after the pressure is relieved and adiabatic cooling immediately takes place..

9) For the hardware... the actual temperature matters.  Keep in mind that our best measuring techniques are averages of the peaks that are flowing through the system....

10) our equipment's safety limits are based on these actual funky measuring experiences... A  TIT of 1650°F being displayed... is made up of many peaks and valleys in temp being delivered per second... the same temp has been proven safe to operate at.

Fortunately the materials of construction are not that sensitive to micro second bursts of thermal  energy...

11) A different challenge can occur if we were to change the method of measuring the EGT... a complexity that wouldn't gain us much more benefit...

PP thoughts only, not an instrumentation guru...

Best regards,

-a-