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Post by ChiMike on Jul 12, 2020 22:19:27 GMT
We’ve all done it. At least I have, used 100LL AVGAS for my P2008 with a 914 turbo. And most of us are familiar with the need to use Decalin as a fuel additive to off set the adverse affects of running AVGAS when no-lead fuels are unavailable—such as cross country trips.
I’ve had waste gate issues before, and they returned. And now my turbo is all apart being fixed. The main issue was an inability to use the throttle gauge to complete open or close the waste gate from the engine exhaust port. It turns out that waste gate mechanism that connects to the throttle cable, consists of a butterfly (where the cable connects) connected to a small shaft that passes through the main turbo housing. This shaft, in turn, is connected to the damper cover that goes over the waste port. It is the opening or closing of the damper cover (and forgive me if I’m not using das korrect Austrian language terms) to the waste port that controls the turbo power.
If the shaft that goes through the turbo housing becomes too dirty, it will bind. Too much binding and there is no Turbo control.
What causes it to bind? Dirty exhaust with lead and probably (over time) the organic blue color dye that heats up and carbonizes. It doesn’t take much. What is the answer? 91* octane no lead fuel, preferably alcohol free if you can find it, instead of AVGAS.
Why is this more important for the 914 than a 912 series? Because the 912 doesn’t have a little shaft that has to go through a flange that is exposed to hot exhaust gases and therefore subject to carbon buildups
Also, I found out from Mark that I have committed another sin: not running my engine in full detention mode for the full five minutes until the turbo boost warning light illuminates. My normal was stay in throttle detent until 3000 feet or so then take it out. So call it 2.5 to 3 minutes. Particularly if using AVGAS, that extra couple of minutes gives need heat to break down the exhaust carbonization and minimize the potential for The binding issue that has me in the. airplane hospital. And lastly, always give the engine enough cool down time: this will also aid in preventing carbon build up.
I’ll update when the repair is completed as to how well things are going.
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Post by ChiMike on Jul 12, 2020 22:24:11 GMT
 Here are a few pics and a video of the movement. |
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Post by ChiMike on Jul 12, 2020 22:34:41 GMT
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Post by ChiMike on Jul 12, 2020 22:35:45 GMT
The ‘open my pic is with a LOT of force, and after two hours of soaking.
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Post by grantopperman on Jul 13, 2020 1:33:03 GMT
When I took my LSA repairman course, the guy who taught it also recommended turning the fuel selector to off and running the engine for a minute or so until it dies at shutdown. That doesn’t help your turbo issue but it does keep the other systems and lines clean of avgas between flights.
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Post by Ed Midgley on Jul 13, 2020 11:49:23 GMT
I’ve always had problems with sticking even when using mogas only. About every 25 hours (usually at oil change) I disconnect the cable and free up and lube the shaft.
I have a friend with a P2008 and his shaft is always free.
It’s possible the tolerance on some is closer than others.
I tried not using lube and just freeing it up but it tightened up sooner.
At this point it’s a maintenance item.
If someone comes up with a fix let us know.
Ed
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Post by ChiMike on Jul 15, 2020 4:51:00 GMT
My P2008t is back in the air. The butterfly to waste gate assembly was completely gunked up and fouled inside the turbo housing. After taking the main components apart and lubricating-attempting to clean-the shaft and inside of the turbo housing with lubricants and degreasers, the play and action were still too tight. The service manager separated the connecting butterfly from the shaft, allowing the assembly to be pulled into waste gate area, and both the shaft and retaining areas to be completely cleaned and properly lubricated. Everything was reassembled and the butterfly was reattached to the waste gate cover shaft. Total, complete and easy-free movement (which I validated) before the turbocharger was reassembled and reinstalled with the muffler assembly.
Currently getting “ Boosting to 40.2 on push up settles back at 39.2 continuous.” I may have him adjust it to get a bit more—what do the rest of you get?
If you need turbocharger work I highly recommend the shop I’m using here in the OKC area—Red Cloud Aviation. Ask for Scott. They are a certified Rotax shop. (405) 808-9079.
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Post by Cluemeister on Jul 15, 2020 10:54:30 GMT
My boost is almost identical to the numbers you cite above.
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Post by allen601 on May 8, 2022 21:28:31 GMT
Good morning all
I have a 914 Turbo issue and suspect the lever that the cable and the spring underneath the engine has come adrift (broken away) from the gate (butterfly) inside the exhaust chamber. The lever can be swung back and forth with no resistance at all, so freely that with a light flick of the finger the lever swings around as if there is absolutely nothing attached to the shaft inside the chamber. Can I ask, has anyone heard of the gate coming adrift from the shaft ?
Allen
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Post by cole505 on May 9, 2022 5:27:16 GMT
Hi Allen601,
That sounds like you need to really get in there and do some serious investigation. Did you check to see that the little pin and cotter pin are still there where the cable connects the Turbo control arm?. I take mine apart on the annuals and make sure the servo cable control is moving with the throttle and that the butter fly valve on the Turbo moves freely. Some owners have had them stick or get stuck and even dead stick the airplane because of this. NOHIPPYCHICKS just posted a good repair shop number just hope your close enough for them to help you. And he posted they’re number you may want to give them a call. Also Leading Edge airfoils is another good source for information ask for Brett he’s awesome! He has helped me with numerous issues super nice guy to talk to…….
Let me know what you find out? Look forward to your posts….
Ray & Lucy ✈️✅👍🏻🇺🇸😊
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Post by cole505 on May 9, 2022 23:00:59 GMT
When I took my LSA repairman course, the guy who taught it also recommended turning the fuel selector to off and running the engine for a minute or so until it dies at shutdown. That doesn’t help your turbo issue but it does keep the other systems and lines clean of avgas between flights. Thats a great solution! There are several good things that happen when you do this! Stand shut down practice for me …… Ray & Lucy ✈️👍🏻✅🇺🇸😊 |
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Post by hds601 on May 22, 2022 1:02:50 GMT
Hi Allen601, That sounds like you need to really get in there and do some serious investigation. Did you check to see that the little pin and cotter pin are still there where the cable connects the Turbo control arm?. I take mine apart on the annuals and make sure the servo cable control is moving with the throttle and that the butter fly valve on the Turbo moves freely. Some owners have had them stick or get stuck and even dead stick the airplane because of this. NOHIPPYCHICKS just posted a good repair shop number just hope your close enough for them to help you. And he posted they’re number you may want to give them a call. Also Leading Edge airfoils is another good source for information ask for Brett he’s awesome! He has helped me with numerous issues super nice guy to talk to……. Let me know what you find out? Look forward to your posts…. Ray & Lucy ✈️✅👍🏻🇺🇸😊 Thank you Ray. Actually I live in Australia. I have decided to re-calibrate the TCU before I remove the exhaust to see if the lever under the turbo has somehow come adrift from the butterfly (Gate valve) inside the turbo. I have found online an exploded view of the exhaust system that includes the butterfly (looks more like a valve of some sort) but the drawing is quite small and difficult to see if there is a spline-shaft connecting the outside lever to the inside butterfly/valve. Regards Allen |
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Post by ChiMike on May 23, 2022 15:35:54 GMT
100% unleaded fuel is the answer but it isn’t feasible. The 914 was not designed to deal with US AVGAS. There is a very narrow channel that the butterfly linkage transits between the housing external to the turbo and the wastegate itself. Once this channel builds with fuel and exhaust residue, exacerbated by using 100LL AVGAS, the waste gate mechanism does not open and close freely, placing additional (non-design) stress on the cable assembly. Candidly it’s a mess. What I do when I have my annual is have my AP remove the turbocharger so he can open up the wastegate assembly. I then use a light solvent, like what is used to clean rifle bolts. It dissolves the residue and cleans out the channel. A couple of squirts—let it sit—then gently work the gate back and forth with my fingers. Give it an hour, repeat, and it will move freely. Now follow up with a light touch of gun oil as a lubricant, put it all back together, and it will work fine.
The system that opens and closes the wastegate only has so much mechanical force. Proactively keeping the channel as clean as possible to minimize blockage/strain on the system is the only way I’ve discovered to not have these wastegate related issues. We can’t avoid using 100LL AVGAS, particularly on cross country flights, so I always use Decelan additive as well.
I hope that helps.
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Post by Flocker on May 23, 2022 22:05:00 GMT
We can’t avoid using 100LL AVGAS, particularly on cross country flights, so I always use Decelan additive as well. You can with a 912iS.  |
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Post by ChiMike on May 26, 2022 14:08:05 GMT
Very true. But if you want Bama Red cylinder head covers you gotta go turbo!!
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