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Just now, gsxrpilot said:

The 231's never came with an intercooler. And there's a heap of them around.

My Rajay doesn't have an intercooler. Nothing wrong with that.

Adding a pop off valve as an overboost backup... nothing wrong with that.

Adding a pop off valve to a Rajay and using it for boost control *could* lead to high intake temps with the wastegate all the way closed at lower altitudes, and would exceed the 28.5 inch maximum MP of the STC.

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Since the dental camera is going in the cylinder to look at valves...

Look at the piston crown as well...

If there was detonation... a TC’d engine can melt the aluminum pistons within minutes while climbing out...

Often, detonation is not detectable by the pilot...

The loss of a small boundary layer that keeps the pistons cool, allows them to heat enough to melt....

I saw melted pistons from a Cessna once... the detonation occurred on climb out...

Be on the look-out for things...

  • that are caused by over pressure on the intake...
  • a corresponding over pressure on the exhaust...
  • Signs of damaged rings... like scratched cylinder walls...
  • Signs of melted aluminum...

PP conjecture on the worst things that could possibly happen... no actual experience in this situation...

Best regards,

-a-

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3 hours ago, N201MKTurbo said:

When you close the throttle, it blocks the airflow from the compressor side of the turbo. The engine doesn't instantly stop making power, so there is still exhaust to drive the turbine plus the turbine and compressor wheels have inertia. This situation can build up a very high pressure between the compressor and the throttle. This is very hard on the turbo. That's why the popoff valve is put there, to relieve that pressure spike when the throttle is closed. It also serves as a safety valve for over boost, but that's not their primary function.

https://en.wikipedia.org/wiki/Blowoff_valve

 

The pressure relief is to prevent surge of the compressor.  If you put all the energy into the air, and it does not flow anywhere, it will make flow happen in the form of flow reversal known as surge.  Surge can be quite severe and breaks blades and bearings.  I don't know of high pressure itself causing a problem, which is why I asked if there was a failure mode of the turbo I was not familiar with.  High pressure can certainly hurt things downstream, like clamps/seals or the engine itself.  

from the wiki page..."Blowoff valves are used to prevent compressor surge, a phenomenon that readily occurs when lifting off the throttle of an unvented, turbocharged engine."

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12 hours ago, Chris Strube said:

1965 M20E with Rajay turbo

I screwed up, as follows.  It's getting harder to get into and out of our Mooney.   As my hips don't bend as they should, I push all the controls in to give myself more room.  I forgot to pull out the turbocharger control, and departed with an overboost.  What are my options now?

I heard the heuristic that "Insurance covers failures of gray matter, not failures of aluminum." Since this *could* be a full teardown and crank shaft replacement, definitely worth seeing if your insurance covers this particular failure of gray matter (just as they would if you'd landed gear-up).

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20 hours ago, Chris Strube said:

Acceleration was spectacular, and the climb rate was about 2400 fpm.  Manifold pressure gauge was topped at 35 inches for about 10 seconds, until I realised what was happening.  After talking with a Mooney expert, I'm going to check the intake tube o-rings, and the cylinder base gaskets, as well as bore-scope the valves.  It won't run smoothly LOP now, so I'm sure that I now have an intake leak.  Prior to this, it ran smoothly at 100 LOP.

chris,

the average time from power applied to lift off is aprox 20 sec, even being light and turbo engaged I am pretty confident you exceeded the 10 sec mark if you were climbing before you noticed. also if you were reading off a standard gauge that only indicates to 35" i would bet you were well over 35" unless you were taking off from a high altitude airport. 

I highly recommend you pull the engine and follow the SB, there are things that could be damaged that you will not see borescoping and changing gaskets. I would not be surprised if you cracked a cylinder or 4. also talk to your insurance company, hopefully they will cover the cost because i truly believe your going to need to replace the crankshaft.

Brian

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46 minutes ago, orionflt said:

chris,

the average time from power applied to lift off is aprox 20 sec, even being light and turbo engaged I am pretty confident you exceeded the 10 sec mark if you were climbing before you noticed. also if you were reading off a standard gauge that only indicates to 35" i would bet you were well over 35" unless you were taking off from a high altitude airport. 

I highly recommend you pull the engine and follow the SB, there are things that could be damaged that you will not see borescoping and changing gaskets. I would not be surprised if you cracked a cylinder or 4. also talk to your insurance company, hopefully they will cover the cost because i truly believe your going to need to replace the crankshaft.

Brian

 Which SB applies to a Turbonormalized I0360 ?

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In accordance with RAJAY Service Letter No. 6, operators of RAJAY Turbocharged Lycoming engines is directed to Lycoming Service Instruction No. 1023B dated January 15, 1965. It is suggested that the recommendations set forth in the above service instructions be applied to Lycoming engines equipped with RAJAY Turbochargers. See attached.

RAJAY Service Letter 6.PDF

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1 hour ago, tomgo2 said:

In accordance with RAJAY Service Letter No. 6, operators of RAJAY Turbocharged Lycoming engines is directed to Lycoming Service Instruction No. 1023B dated January 15, 1965. It is suggested that the recommendations set forth in the above service instructions be applied to Lycoming engines equipped with RAJAY Turbochargers. See attached.

RAJAY Service Letter 6.PDF 131.8 kB · 1 download

SB 369 and SB 592 supersede SI 1023.  

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  • 1 month later...

I've seen this, as part of the SB.  I can guarantee that it was lawyer driven.  The IO360 is regularly used in racing, far exceeding 10 inches of boost.  They are well known to be reliable.  I should hear from the shop this week on the forensic investigation.

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20 minutes ago, Chris Strube said:

I've seen this, as part of the SB.  I can guarantee that it was lawyer driven.  The IO360 is regularly used in racing, far exceeding 10 inches of boost.  They are well known to be reliable.  I should hear from the shop this week on the forensic investigation.

you do realize these race engines are not stock? they are modified and get torn down and inspected after just a few hours. At Reno these engines get less then 30 minutes under race conditions for the whole week. some of the engines don't last that long.

Brian

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Edited by orionflt
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‘Used in racing’ is great for the outlook...

IO550s are also known to produce 500+ bhp for some applications...

The engine is capable of doing some amazing things... under the right conditions...


As the owner operator... you want to make sure your engine has survived the over rev...

Some similar engines have not survived the over rev, that is why the inspection procedures exist...

 

In racing, they have no problem with tearing the engine down for inspection... it is part of the race plan...

They do this because they don’t want to afford the engine out experience...

 

Speaking of racing and OHs...

Our Mooneys fly around at Indy speeds for 2,000 hrs.... 400k miles... a lot more than the Indy .5k miles... :)

They are amazing machines when operated within the envelope...

 

When operated outside the envelope... Additional risks start to accumulate.

Over rev often creates problems with counterweights inside the engine...

Over pressure often creates problems with cracked and separated cylinder heads...

 

PP thoughts only... stuff I have read about in MS...

Best regards,

-a-

 

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OK, just spoke with the engineer.  Compressions are 78 or better all cylinders.  Borescope shows no signs of detonation in piston tops or valves.  Plugs (fine wire) are good.  Intake runner gaskets are shot as expected.  No cracks found in cylinders.  No leaks in cylinder base gaskets.  After the oil analysis, we'll make the decision on tear-down or not.  BTW, it was overboost, not over revved.  Fingers crossed...

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Just now, Chris Strube said:

OK, just spoke with the engineer.  Compressions are 78 or better all cylinders.  Borescope shows no signs of detonation in piston tops or valves.  Plugs (fine wire) are good.  Intake runner gaskets are shot as expected.  No cracks found in cylinders.  No leaks in cylinder base gaskets.  After the oil analysis, we'll make the decision on tear-down or not.  BTW, it was overboost, not over revved.  Fingers crossed...

is the insurance company covering this??? if they are bite the bullet and tear down the engine.

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  • 2 weeks later...

Engine teardown showed no damage to bottom or top end.  No signs of detonation.  The oil smelled burnt, but the filter was clean, and the oil analysis was normal.  All fine wire plugs were undamaged.  Damage was confined to intake runner gaskets, and cracked air box.  I'm happy to have my baby back, and if we can find someone to mind the cat, we're heading for warmer weather soon.

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