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TOPIC: TSIO-520M Fuel Flow Concerns

TSIO-520M Fuel Flow Concerns 1 year 3 weeks ago #718

  • Jonathan Shill
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Unrelated to FF concerns, but posting this here since I mentioned that the plane had been sitting for many many years. I'll be keeping my eyes on the iron, but right now I'm very thankful to be living in a desert.
Sample No. 44150165169
XC Aviation MV
Phillips 66
SAE 20W50
Hrs Since New 2314
Oil Hrs 24
Date Sampled 01-Aug-17
Date Tested 10-Aug-17
Oil Added 3.0
Rebuild Hrs 937
Metals (ppm)
Aluminium (Al) 14
Iron (Fe) 62.20
Copper (Cu) 12.42
Nickel (Ni) 14
Chromium (Cr) 19
Silver (Ag) <1
Contaminants (ppm)
Silicon (Si) 16
Sample No. Diagnosis/Recommendations
44150165169 All values appear normal. Resample next oil change to establish wear trend.
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TSIO-520M Fuel Flow Concerns 1 year 3 weeks ago #717

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So I've put about 35 hours on the plane, but we're still working out fuel system gremlins.
Bottomline Up Front: New fuel components produce good pressures but mixture control inop inflight.
Highlights over the last year:
Applying SID-97-3G, the new mechanic had some difficulty setting the correct fuel pressures. Fuel pressure was somewhat erratic. It turns out that the original mechanic never flushed anything before installing the new pumps, FCU and manifold. Obviously, I was concerned that the garbage in the fuel system from an airplane that had been sitting for many years had negatively affected the new fuel equipment. (New mechanic was less concerned than me.) Eventually we got the system to make more than enough pressure on takeoff, but the fuel flow meter was still jittery and the mixture control wasn't very authoritative. While building confidence in the motor on a local flight, I pulled back the mixture but the flow never dropped below 22GPH. Eventually I got to Idle cutoff with the engine still running at 22GPH. I pushed the mixture in about 1.5" and maintained level flight. About 60 seconds later, the motor died. Full Rich returned power to normal and I RTB'd directly. At this point I thought that there had to be a metering valve problem. The mechanic sent the valve back to the original rebuilder. After installing the newly rebuilt metering valve, it started having issues shutting down. He couldn't kill the motor with the mixture control. So he sent back the metering valve again and asked that they send out en entirely different one.
With another new valve installed I had reasonable (not crisp) mixture authority. I still had a +/- 1 GPH jitter, e.g. bouncing between 14 and 16 GPH in cruise. Because my confidence in the fuel metering was low. I spent the year flying at low power settings (<65%). I started to see other issues that were leading me to believe that I had gunk affecting my fuel pump aneroid and fuel manifold valve. In climb at a constant MP, my FF would drop. Eventually I would run Low Boost to maintain at least 20 GPH in the climb. Finally, in August during a touch and go I applied full throttle and got 36"MP but only 22GPH. So accustomed to automatically turning on low boost, that's exactly what I did. This gave me the full 31 GPH. [Hindsight, I should have aborted the TnG.] At this point, I asked my mechanic to change the fuel pump and the fuel manifold again.
Today he test flew the new fuel components and noted good fuel pressure, including no FF needle jitter. Unfortunately, it is now demonstrating similar mixture behavior to before. While at an MP >20, the mixture control seem ineffective. There's plenty of fuel. Our guess is that it's running about 150 degrees rich of peak. Of course we can't get to peak because it doesn't lean. He reported reaching ICO with no variation in FF in cruise. That said, the aircraft has no problem shutting down. Could it be anything other then the fuel metering valve?

Unrelated to fuel, but very good news: I've been pleased to find very little of anything in the oil filter. I had the oil sampled and it came back well inside all norms.
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TSIO-520M Fuel Flow Concerns 2 years 6 months ago #479

  • STEVE ELLS
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Great move;
Please keep me up dated.
Best,
STeve
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TSIO-520M Fuel Flow Concerns 2 years 7 months ago #478

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Steve,
I've found a new mechanic that has significant experience tuning fuel systems. I'm going to have him re-run TCM SID 97-3G completely as well as change the oil and borescope the cylinders. I'll let you know what he finds.
Thanks,
Yama
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TSIO-520M Fuel Flow Concerns 2 years 8 months ago #457

  • STEVE ELLS
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Hi Yama;
I'm very interested in finding out what you found with your engine. Please give me an update.
Thanks
Steve
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TSIO-520M Fuel Flow Concerns 2 years 8 months ago #438

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Steve,
Thank you for the time you've taken to provide detailed feedback and thoughtful questions. They've helped me develop a path forward. With respect to your last questions, after the annual inspection, I asked if we needed new plugs and the mechanic confirmed that the resistance was all within limits. I also asked if the mags would need replacing and he didn't think so. I didn't interpret that as if he opened them up though, unless that's a standard procedure that would have been part of the annual inspection. However, I did notice an almost 200 rpm drop during the mag check on runup, but it was an equal drop for both the left and right mags. I'll check on the wastegate maintenance to verifiy it was performed. I know that at least a visual inspection of the turbo was done but I'm not sure if he felt it spin. We previously had verified that the Tach was reading about 100 RPM slow and my initial post took that into account.
My next action will be to pull the filter and look for metal, as well as borescope the cylinders.
Thanks again,
Yama
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