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Turbo problems???

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Theschultzfamily(at)comca
Guest

Posted: Tue Jun 16, 2009 4:44 pm Post subject: Turbo problems???

Time for some group input. I was bad and did not fly for about 6 weeks. I

went out to the airport with good intentions to rectify that problem only to

find that above 60% power the engine would surge. I traced the problem to a

stuck waste gate. I have since freed it up with a little mouse milk on the

arm and the TCU servo and response to throttle seem to be good. The problem

I am now having is at about 60% power the engine starts to surge and trying

to go to full power just kills the engine. I "assume" it was turbo related

and pulled the air filter to check the turbo. The blades seem to turn fine.

A restart of the engine and all was good for about 2 days and then on run up

the problem returned. I can't seem to shake the feeling that I still have an

airflow problem but not sure how best to trouble shoot this one. Any

suggestions? I will be going back out tomorrow night to do a full power run

up with the plane tied down. I have monitored and logged the engine data but

it really just shows what you would expect with a surging engine. Change in

RMP change in Airbox pressure.... The engine has 180 hours on it and runs

great when it runs. Has anyone shot the inside of the turbo with a oil to

break up any carbon build up? I am trying to get a camera scope to have a

peek inside from the exhaust side.



Regards,



Rich Schultz

N262AE

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garrys(at)tampabay.rr.com
Guest

Posted: Tue Jun 16, 2009 5:20 pm Post subject: Turbo problems???

Try disconnecting the turbo airbox rubber hoses from the back of the carbs. 

This will in effect give you a normally aspirated engine.  Try a full power 

run up and see what happens.  If the surge disappears, then indeed you have 

a turbo problem.  If the surge remains, you've eliminated the turbo as the 

source of the problem and should look to the carbs for a fix.



Garry Stout



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bshafer(at)extremenetwork
Guest

Posted: Tue Jun 16, 2009 5:53 pm Post subject: Turbo problems???

Is it ok to run the 914 like that? I found oil in the airbox and intercooler of my 914. I'm afraid it's coming from the turbo so running without the turbo connected might be a way to check.

Brad



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budyerly(at)msn.com
Guest

Posted: Wed Jun 17, 2009 7:47 am Post subject: Turbo problems???

<?xml:namespace prefix="v" /><?xml:namespace prefix="o" /><![endif]-->  Rich,

 I'm sure you've made sure your gas and filters are clean and fresh.   Look at the fuel pressure to check the regulator is correct.

 I just took a 914 down to Lockwood.  The engine would only come to 34  inches of MP but ran perfectly smooth.    Trouble shot the  sensors, electrics and computer, all was fine.  Dean had me check for the  rubber seals from the airbox to the carbs as that screws up the  works.  No air leaks or cracks.  On final inspection, it seems the  carb diaphram and piston were hanging up on one carb.  I always believed  that would result in a rough running engine.  Go figure.  Kerry  rebuilt both and all was well.  In the last 5 years I'm sure you put in the  gasket kit in your carbs.  Please check them.  The dual manometers  work well in troubleshooting the carbs, but this malfunction hardly showed  up.  Three weeks of on and off shop time out of my life and 200 miles of  trucking this thing.

  

 As for the Turbo.  If the waste gate sticks closed you would see it  in low MP.  If stuck open you will see an overboost (not good).   If the waste gate does not work smoothly, that can cause a surge in the   engine as you go to full turbo.  Picture the servo pulling the  cable to adjust the targeted boost pressure commanded by the computer and  throttle position. In the process the computer command goes to the preset servo  movement and on a hot day, overshoots a little and it begins releasing pressure,  then the arm sticks, the servo tries to loosen the cable more and then vibration  loosens the arm causing a drop in pressure, the servo corrects again and results  in a surge.  Then the servo really starts hunting.  Hitting the reset  switch works to stabilize it if it is a minor sticking problem above the 100%  throttle position normally.  Surging at 60% indicates the tubo arm may  be sticking as it starts out commanding 100% (cable extended) then slowly  reduces the servo position to about 40% (1/4 throttle or so) then up to 88% at  full turbo with the engine off. look to see that the cable moves smoothly and  the waste gate is not hanging up.   

  

 Otherwise, I am out of ideas.

  

 Bud

 Custom Flight Creations  

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air.guerner(at)orange.fr
Guest

Posted: Thu Jun 18, 2009 5:19 am Post subject: Turbo problems???

Hi Bud,

  

 Sorry to correct you Bud, it is just the opposite.  As the name implies, the wastegate is a gate to the waste. When the gate is  open, most of the exhaust gases flow directly to the muffler and  are wasted. When the gate is closed, all exhaust gases flow to  the turbine. 

 I agree this does not help solving any turbo  problem, but using the right wording would avoid adding some  confusion.

 Best regards

  

 Remi Guerner

   

 

<<<<<<<As for the  Turbo.  If the waste gate sticks closed you would see it in 

low  MP.  If stuck open you will see an overboost (not good).   >>>>>>> 



    [quote][b]

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budyerly(at)msn.com
Guest

Posted: Thu Jun 18, 2009 9:15 am Post subject: Turbo problems???

<?xml:namespace prefix="v" /><?xml:namespace prefix="o" /><![endif]-->  Thanks Remi

 You're right, typing too fast and thinking how the arm moves vice the  gate.

  

 Bud

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