REFLECTOR: Turbo Oil Blow-by

Scott Derrick scott at tnstaafl.net
Fri Jan 23 09:15:02 CST 2009


Bob,

Thanks for the info.  I will keep it in mind.

My turbo system has 1600 hours on it.  But has sat for 15 years, which 
is why the O-rings are a bit stiff in the controller, I think.

I ran solvent through the turbo oil lines prior to re-installation. 
Maybe I shouldn't have?

I am getting just a bit of oil out the tail pipe and into the induction 
system from the turbine. I was thinking of having it rebuilt but I will 
wait until I get a few hours of flight on it before doing that per your 
experience..

thanks,

Scott


Bob Jackson wrote:
> Another possible source of oil leaks into the upper deck side of a
> turbocharger plumbing can be the turbocharger itself -- especially when
> they're new (and before the 'slug ring' that is created over time has been
> created).  
> 
> When setting up our custom twin turbocharged IO-550N (on the ground) we had
> A LOT of oil coming out both the turbo tail pipe and being sucked into the
> upper deck tubing.  After talking with the Kelly people and a number of
> other turbo experts, we learned that to minimize oil blow-by during initial
> turbo set-up:
> 
> 	*  don't spend a lot of time at idle on the ground,
>  and	*  if it's a manual wastegate -- keep it fully closed on the ground.
> 
> Once we started flying and got the engine broken in (you need to get the
> turbochargers real hot), apparently the 'slug ring' they talk about formed,
> and we now have no oil coming out of the turbo tail pipes or into the
> induction system.  
> 
> Early on, we were getting tablespoons-full of oil in the induction piping.
> Turbocharger oil rings are not very tight fitting.  The slug ring is created
> over time as the turbos get very hot and small amounts of oil get burned,
> with the deposits that remain forming a slug ring around the oil bearings to
> help, especially statically, to seal the bearings.  Also, when you run at
> high power settings, the increased pressures on both sides of the turbo oil
> sealing rings helps minimize oil blow-by past the bearings.
> 
> Bob Jackson
> Custom Twin Turbo IO-550N
> 50 hrs flight time now!
> N2XF
> 
> 
> -----Original Message-----
> From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
> Behalf Of Scott Derrick
> Sent: Thursday, January 22, 2009 10:32 AM
> To: Velocity Aircraft Owners and Builders list
> Subject: Re: REFLECTOR: Special O-Rings
> 
> Senior moment.
> 
> The standard size has a 1/16 width and I need a 3/64, not 3/32 as I 
> previously indicated?
> 
> Sorry for the confusion,
> 
> Scott
> 
> Brian Michalk wrote:
>> McMaster is showing 18 products for that width and I.D.  3/8 O.D.
>>
>> Scott Derrick wrote:
>>> Whilst attempting to tune the turbo/induction system on a TSIO520, I 
>>> found out the wastegate controller was leaking oil into the upper deck 
>>> pressure side of the unit.
>>>
>>> I dissembled it and found the "O" rings needed replacement. not many 
>>> hours on the unit but a lot of years.
>>>
>>> The three large rings were a standard size but the small one is not. Its 
>>> close to a -008 size O-ring(3/16x5/16x1/8) but with a width of 3/32 
>>> instead of 1/8 of an inch.
>>>
>>> I've searched and searched for an O-ring with a (3/16x5/16x3/32) but 
>>> can't find one on line.
>>>
>>> Any suggestions?
>>>
>>> Scott
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