Turbo grief!

[Richard]

2 years of sweat, rebuild everything but.... that rear wastegate.

On the third flight I lost boost and went to 27" at 2000 feet. First thought... stuck open wastegate. Landed. Nope it moves freely. Spun the new turbo... yep spins nice. Check oil pressure to the waste gate...... good as it gets... no exhaust leaks.... no induction leaks that I can see....

question: The wastegate is original 3000hrs. It was adjusted, but looked pretty worn. It that the most likely failure point? Have you ever heard of one going bad? Where else can I look? How big of an induction leak would be needed to loose that much pressure? How big of an exhaust leak would be needed to cause zero boost?

I also capped off the return line to the wastegate so that off idle I would have fully closed the wastegate. Started the engine and nope 28" is all I can get out of it. Assuming that the exhaust and induction are in good shape, is the turbo and wastegate the only places to look? If the turbo spins freely and smooth, would that rule out the turbo?

Thanks

Richard

P.S. Performance is AWESOME!!!!!

2400 rpm, 22" clean, at sea level, gave me 150-160mph. Can't remember if that was good, but sure felt fast.

[SkyKing]

Richard,

You could have some debri blocking the inlet orifice of the wastgate actuator... have you tried back-flushing it? Remember now, the oil line comes off the bottom of the accessory case and the oil pump... and this oil is unfiltered.

Is this engine newly overhauled or what?

SkyKing

[Richard]

New engine.

I did clean and backflush. Then when I capped the return line and started the engine I did get full movement out of the wastegate. So it's closing.

[bede1@msn.com]

I just replaced the front turbo on my bird for the same reason. Found that the exhaust turbin was rubbing in the housing. Would spin free with my hand but when we pushed onthe compressor side it moved back enough to rubinthe housing. According to my overhaul manual on the turbo there should be nomore than .003 movement in the turbo. Mine had .009 and only would move with a lot of pressure. My mechanic felt that under high power the exhaust pressure would move the turbine in the chambers causing it to rub and slow down. After the new turbo was installed I have not had any more loss in power. Hope this helps

Bob

[SkyKing]

Bob, I think you were trying to describe "axial" play of the shaft, and there shouldn't be any, except the minimum spec which you addressed.

As far as Richard's problem, if the wastegate closes completely with the return line capped, then the problem might be one of two things: either a faulty pressure relief valve, or the controller is not right or improperly rigged. The engine should go to full boost at about 2/3 throttle if everything is set-up correctly.

Richard... was the controller newly overhauled? I understoof or presumed the engine WAS performing just fine -- and THEN something apparently occurred where you lost boost in flight. Are all the hoses secure?

SkyKing

[Richard]

I capped the return line "pre" controller. Bypassing the controller completely. Yes, it was performing perfect for the first 3 hours. This is a brand spanking new turbo. Right out of the box too. I don't think I have excessive axle play, but something I plan on measuring today. Way I see it. Since I've bypassed the controller, going to full boost off idle, and verified shaft throw on the wastegate. I've either got one of four problems. Wastegate butterfly valve has collapsed, turbo is capuut, induction leak, or exhaust leak. Am I on the right track?

I would lean tward the wastegate valve going bye bye, since it is the oldest component on the engine. Have you ever heard of such a thing?

Richard

[Jerry De Santis]

Richard, I would look more in the area of exhaust or induction leaks. Have you tried hooking a leaf blower to the manifold and with soap and water check all connections. Simple to do and not expensive. Only pulling 27 inches sounds like a pretty big leak and you should be able to find it quickly.
good luck
Jerry

[Richard]

It was the turbo. Manufacturer flaw, thrust bearing wasn't secured on the compressor side. Allowed it to fall out and end play was enough to gawl up the housing. Now I know what the Skymaster performs with a seized turbo.

[SkyKing]

Richard,

Inquiring minds want to know: Which shop did the overhaul on this turbo anyway? Are you saying that the nut on the impeller-compressor came loose? I can't imagine a shop not torquing the nut on to specs!!! That COULD have caused a lot of internal engine damage if had really come apart. Whoah!!

And now the fun part... that rear unit isn't the easiest puppy to get in and out.

SkyKing

[Richard]

The shop is being nice to me so I'm going to leave the name out of it. I'm not sure, something inside the center section was loose. Not that easy to get out... yes. True. Had to remove the lower skin. Got it removed and another installed in one day.

[SkyKing]

Well, I can see why! One-day service turn-around. Now that's what I call real 'AOG' service!!!

SkyKing

[kevin]

Interesting. The same thing happened to me a few years ago (not the same defect in the turbo, just the broader concept of a defective turbo out of the box). This was a brand new turbo from Cessna (ouch) because the turbo before it self destructed in the way Skyking descrbed and sprayed metal through my front engine. That was what caused my only power loss in a 337, and my overhaul. So anyway, when we put the new engine on, remans do not come from Continental with a turbo, so we had to buy a new turbo (no core to give Main Turbo, or whomever). And that new turbo would not deliver pressure, I never did pay attention to why, because we got another one under warranty. I was thinking of mentioning this during this thread, but it seemed like such a bizzarre case that it was not worth discussing. I was wrong about that apparently...

Kevin

[Richard]

Those yellow tags don't mean much I guess.

[SkyKing]

It seems real difficult to hire a good hand these days and it's gotten to the point that if you don't do the job yourself, it never does get done right. Everybody seems to be cutting corners... and quality of workmanship doesn't happen when it's a hurry-up and get-it-out-the-door thing. And some shops, with inexperienced people working on rather complex systems like the turbocharger set-up who don't understand have been known to misdiagnose a problem and repeatedly send a perfectly good part, like a controller, out to a distant repair/overhaul facility, costing the owner big time... when the problem all along was a small carbon particle blocking the inlet orifice to the wastegate. But do you think the shop would rectify the 'problem' they created? NOPE! It's part of their 'troubleshooting.' And that's why it's best to have a retired IA work with you on your plane where YOU take responsibility for getting the job done. Yah, their are exceptions like having to send out a turbocharger or whathaveyou, but the majority of things can be accomplished with a little common sense. That too seems totally lacking in most shops.

SkyKing

[Kim Geyer]

knew of a guy to install the oil lines on the tee fitting wrong.
One nipple has a restrictor in it, the other does not.The turbo will last about 30 min. if hooked up to the restricted side. poor guy bought 3 turbos before he figured it out.