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  #11  
Old 12-30-2021, 06:50 AM
Camillo Camillo is offline
 
Join Date: Sep 2006
Location: Roma, Italy
Posts: 531
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Thank-you for your answers.
I had a very hard work season. Shortly I will get back to the hangar and investigate, starting with downloading engine monitor data.
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RV4 IO-320, Catto 3-blade, Christen, I-BILT
Flight time: 20 hour
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  #12  
Old 01-03-2022, 04:30 AM
Camillo Camillo is offline
 
Join Date: Sep 2006
Location: Roma, Italy
Posts: 531
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Hallo to everyone.
Yesterday I made some fix/checks on the plane.
I checked the exhaust and intake tubes and they are all tight.
I checked the fuel line and it seems that they are OK. The line is covered with firesleeve and shielded in a couple of positions. See photos:





Then I checked the idle mixture. The RPMs rise was 30/40 instead of 50. When leaning, the RPMs went to 1.030/1.040 before dropping.

I enriched slighlty turning less than a turn (three "notches"). The RPMs rose to 1.050/1.060. I came back one notch (so 2 notches enriched) and obtained the 1.050 rise.

I didn't fly, yet. However, minimum on the ground is perfectly round (600 RPMs).

Could that slight difference be the culprit for the engine coughing in flight while idle in a hot day?



I downloaded the Dynon EMS logs and uploaded to savyaviation website.

This is the first flight when the issue occurred (2021_09_25_14.36Z):
https://apps.savvyaviation.com/my-fl...5-4cc3d944dd25
Problem started a few seconds before minute 26.30.
At 24.03 engine was idled.
From 25.27 RPM dramatically went down (approx. slightly low 1.000 RPMs), even if MAP was left unchanged.
At 26.30, after the engine "hiccup", I gave power and made a 360° close to the runway.
At 28.30 I landed.

I noticed that just before the RPM drop pitch raised by 5° (from 5° to 10°). Maybe the airflow disturbed the idle...

This is the relevant part of this flight. Note that the first circled area is when the problem started and the second one is the final part of flight, where RPMs normalized. It is strange that for same MAP RPMs changes very much.


And this is the second one, in the same day (2021_09_25_10.29Z):
https://apps.savvyaviation.com/my-fl...5-4cc3d944dd25
Here I can say that at minute 18.22 I switched on the fuel pump, while reducing power and entering downwind. On 19.22 I think I had the engine coughing and I thaught it could go off. After a few second I switched off the pump but engine continued to go high and low on RPMs. Then I landed.

RPM seems to be well over 1.000. However, I had the clear sensation of a close to quit engine while in flight.

Thanks.
Camillo
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RV4 IO-320, Catto 3-blade, Christen, I-BILT
Flight time: 20 hour
Status: flight
www.rv4.it

ROME, Italy
---
RV9A O-320 D1A, Hartzell C/S prop, slider, I-PRCA
Flight time: 350 hours
Status: SOLD
http://nuke.rv9.it

Last edited by Camillo : 01-03-2022 at 06:07 AM.
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  #13  
Old 01-03-2022, 08:01 AM
thinkn9a thinkn9a is offline
 
Join Date: Nov 2007
Location: Mississippi
Posts: 321
Default Did you use the Precision Airmotive SIL RS-67

The service letter goes through setting idle and mixture.

I’m just wondering as I am not sure about the numbers,…you seem to indicate it goes to over 1000 RPM when leaning mixture from idle,… yet idle is 600 or 700.

Also looks like you haven’t flown all that much and mixture has been a question,…. How are the plugs looking?

The folks at Saavy should be able to give you some ideas on what to go look for.
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  #14  
Old 01-03-2022, 08:17 AM
Camillo Camillo is offline
 
Join Date: Sep 2006
Location: Roma, Italy
Posts: 531
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Thank-you.
Idle RPM is 700.
Engine manual says to perform the test at 1.000 RPM.
RPM increase was 30-40 RPM. So, within limits. While I was there I adjusted it to 1.050. However, I suspect the issue was not dued to the idle mixture setting.
No, I didn't check for spark plugs. I have to.

Precision document at the end says:
If the system is set in accordance with this letter (prior to extended engine runs or flights), and the mixture does not meet the criteria after flight (especially in warm weather), vapor formation may be indicated. See the publications referenced in paragraph D for further information. If no other discrepancies are found, the servo should be removed and sent to an approved repair facility for evaluation".

The issue rose in a very hot day, with a hot engine. So, vapor formation may be a more possibile cause...?
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RV4 IO-320, Catto 3-blade, Christen, I-BILT
Flight time: 20 hour
Status: flight
www.rv4.it

ROME, Italy
---
RV9A O-320 D1A, Hartzell C/S prop, slider, I-PRCA
Flight time: 350 hours
Status: SOLD
http://nuke.rv9.it

Last edited by Camillo : 01-03-2022 at 08:25 AM.
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  #15  
Old 01-03-2022, 08:40 AM
mahlon_r mahlon_r is offline
 
Join Date: Jan 2005
Posts: 1,070
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When the problem is occurring, does manually leaning the engine fix it? If so, it is going too rich. If it doesn't, it may be too lean or the problem is not fuel related. If it shows too rich, check the raw fuel pressure and if the raw fuel pressure is staying within normal parameters, then the center body seal in the servo may be sticking. To test start at idle with engine running well. Increase rpm from idle to say 1500rpm without going past 1500rpm and note the fuel flow. The continue up to full power and then retard the throttle to 1500 RPM, again without going past 1500rpm. and note the fuel flow. This reading should be very similar to the reading you had on the way to power. If it is substantially different the servo needs to be removed and sent in for repair.
If the raw fuel pressure is out of limits high, it will cause the engine to run way too rich and want to quit.
Does the engine monitor show one cylinder with very low egt as compared to the others when it is happening? If so that would indicate the cylinder with low or no egt isn't functioning and causing the roughness. the Trouble shoot that cylinder for not firing, too rich/lean, ignition, compression.
Happy New Year,
Mahlon
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  #16  
Old 01-03-2022, 09:22 AM
Camillo Camillo is offline
 
Join Date: Sep 2006
Location: Roma, Italy
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I haven't tried to manually lean while making the issue. I will try during the next flight at a safe altitude.

What do you mean for "raw" fuel pressure? Without aux fuel pump? I will try this method.

I only have EGT on cylinder #3...

Thanks.
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RV4 IO-320, Catto 3-blade, Christen, I-BILT
Flight time: 20 hour
Status: flight
www.rv4.it

ROME, Italy
---
RV9A O-320 D1A, Hartzell C/S prop, slider, I-PRCA
Flight time: 350 hours
Status: SOLD
http://nuke.rv9.it
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  #17  
Old 01-03-2022, 10:18 AM
elev666 elev666 is offline
 
Join Date: Feb 2013
Location: Kincardine Ont,Can
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I had kind of the same issue and I chased it for four months before we went looking inside the 0- 320 , very concerning this was occasionally jamming under the valve cover and causing a miss once every couple hours 🤔
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  #18  
Old 01-03-2022, 11:07 AM
mahlon_r mahlon_r is offline
 
Join Date: Jan 2005
Posts: 1,070
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Quote:
Originally Posted by Camillo View Post
I haven't tried to manually lean while making the issue. I will try during the next flight at a safe altitude.

What do you mean for "raw" fuel pressure? Without aux fuel pump? I will try this method.

I only have EGT on cylinder #3...

Thanks.
Raw fuel pressure is the pressure at the fuel servo inlet. either boost pump on or off. If it is significantly higher and out of limits with the boost pump on that may be your issue. Normally less than 25-35psi in either case but should be no more than 45psi.
Good Luck,
Mahlon
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  #19  
Old 01-03-2022, 11:38 AM
Freemasm Freemasm is offline
 
Join Date: Nov 2017
Location: Orlando
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Disclaimer: I haven't read all of the posts here.

Looking at the posted pix. Even with the radiant barriers and fire sleeve, you're not doing yourself any favors with the related proximities. There's not enough velocity in the lines to provide much active cooling. If it's not a vapor pressure problem now, don't rule it out in the future.
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  #20  
Old 01-04-2022, 02:30 AM
Camillo Camillo is offline
 
Join Date: Sep 2006
Location: Roma, Italy
Posts: 531
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Garry, my engine is brand new... The problem rises only during hot weather (as far as I experienced till now).
__________________
RV4 IO-320, Catto 3-blade, Christen, I-BILT
Flight time: 20 hour
Status: flight
www.rv4.it

ROME, Italy
---
RV9A O-320 D1A, Hartzell C/S prop, slider, I-PRCA
Flight time: 350 hours
Status: SOLD
http://nuke.rv9.it
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