REFLECTOR: Update on Engine Upgrade

Chuck Jensen cjensen at dts9000.com
Sat Mar 28 14:16:13 CDT 2009


Scott, the swamp is rising and the alligators are getting hungery, but just keep your eye on the shore and keep plugging away.



-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org]On
Behalf Of Scott Derrick
Sent: Saturday, March 28, 2009 10:16 AM
To: Velocity Aircraft Owners and Builders list
Subject: REFLECTOR: Update on Engine Upgrade


Well, I thought I was basically done with my turbo woes after rebuilding
the wastegate controller and installing new seals in the turbo.   A few
prolonged high power runs blew that out of the water.

1.) The turbo still leaks though the engine is now running really
sweet.  I finally located a table of limits for the series turbo I
have.  I pulled the turbo, disassembled again and discovered the seal
surface on the turbine side was four thousands out and somewhat oblong.
There was some slight pitting also. It appears that even though it only
had 1400 hours on it, the center housing was trash.  With my recent
experience with  T210's  and the  horribly  inaccurate instrumentation,
even if it was run by the book, the turbo was still fried by way too
high an inlet temp.  I called the Garret dealer  that provided the
seals, and through a process of measuring certain faces and inlet outlet
sizes determined which specific housing I needed and got that and a full
rebuild kit. cost $290 including shipping.  I have the new parts and
will hopefully rebuild the unit today.

I really hate that the aviation turbo industry is so closed minded and
locked down.  There help factor is ZERO for DIY homebuilders.  They
wanted $1000 to inspect my turbo, anything wrong was more $$. The center
housing alone was an additional $1000.  They are crooks maintaining an
almost monopoly on the industry. 

2.) During the high power runs a new oil leak started. I initiated the
high power run at a temp just inside the low temp oil range and saw
about 85-90 psi oil pressure, well within redline but I think it
revealed a weak spot.  The leak of course is on the back of the engine
up against the firewall! You can only see the area with a mirror and not
very well at that.  I believe it is the oil pump, which I rebuilt per
the overhaul manual.  I asked an experienced overhauler and he asked if
I double threaded it. I said, no the manual calls for a single thread.
He said he always doubled threaded those pumps because one thread failed
to seal every now and then(no change to the TCM overhaul manual though)
and he thought that was the reason for the leak. SO, I'm pulling the
engine off to rebuild the pump. 

3.) I used silicon 90 degree 2.5" hoses to route the induction are from
the controller to each side of the induction run.  I reworked the
induction system to get this 520 to almost fit a Std Cowl which required
longer induction runs. They work but have such a large outside diameter
they are almost/barely rubbing in places.  I never really liked it but
there are so many other issues I let it be.  Once installed they are a
real PITA to get in and out as they are buried on the back side of the
engine.  Since I am removing the engine to rebuild the oil pump  I
started to think about this fitting issue again.  I found aircraft grade
90 degree induction elbows made from 6061 seamless tubing for $15
apiece!  Of course they are auto racing parts...  They will have to be
cut down and re flanged but will see if I can replace the larger
silicone turbo hoses for these much more compact 2.5 inch aluminum
elbows while i rebuild the oil pump.

4.)  95% done with the cooling plenum.  I can't believe hoow much of a
time sink this has been!  Getting it to fit snug, be reasonably
airtight, be easily removable is no small task.  Maybe since the plug
was made for a 550 and I'm fitting it to a 520 contributed some, I don't
know. 

Spring is finally here, though we did have a cold front move through,
dump a couple inches of snow and drag the temp down into the high 30's
low 40's for a few days. I'm looking forward  to  a long spell of good
building weather.

Scott




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