Well, I am pleased to report that my turbo, stock housing with TO4
 wheel and
 60-1 compressor with a fixed open waste gate has lasted over 230 hrs
 without
 a single problem. The solution to good enough? Make it better. I just
 finished my annual during which I upgraded my turbo to a similar TO4 big
 shaft wheel, but now it has a TO4E 50-trim compressor and the wastegate
 flapper and actuator are back in place. Why the change? Either I am a
 glutton for punishment or I am starting to pin down this turbo issue.
 For
 those of you not familiar with my turbo history, here is a quick recap:

 First turbo - the stock second generation with waste gate flapper
 installed, ridden hard and put away wet... it was run at full
 throttle at
 high altitudes, often at peak EGT. It lasted 70 hrs before the turbine
 wheel fell apart and broke off. The thought at the time was that the
 stock
 turbo was just too small for this heavy duty abuse and was
 overspeeding at
 altitude.

 Second turbo - small shaft TO4 wheel with 60-1 compressor and removed
 waste
 gate flapper. It was also run mostly at peak EGT but the power
 produced was
 somewhat lower because of the bypassed exhaust. It lasted about 140 hrs
 until it suffered the same fate as the first turbo while I was in a long
 full power decent (read extra high RPM and EGT's). My thinking at this
 point is that the high EGT's are primarily the problem.

 Third Turbo - The one I just removed after 230 hrs. Same
 configuration as the second but I kept the EGT's under 1600 F,
 mostly as lean as I could while keeping the engine running not
 too rough. It was also run at pretty low pressure ratios. It
 could only make about 38" HG MAP on take off and about 40" HG at full
 bore down low. At 16k altitude it was down to about 22" HG. My
 curiosity now is weather I can perhaps increase the boost and
 continue to have the turbo last, as long as I keep the EGT's
 under 1600 F. I know, glutton for punishment...


 Other issues..

 Lean of Peak operation. During the turbo change I discovered that my
 stock cast iron exhaust manifold had developed a number of serious cracks
 and some advanced erosion. Much of the erosion/oxidation was near the mating
 surface with the turbo and it had started a small leak. My concern is that all
 those hours of LOP operation allows too much oxygen into the exhaust to
 promote to oxidation and accelerates the problem. The question is,
 should I  start running rich of peak to prevent rusting away the exhaust system
 components? ROP operations also allow me to keep even lower EGT's
 (for the  turbo) and smoother engine running (for the wife). Turbos and exhaust
 components that I get from cars usually have the appearance of being run
 rich, rather than the dry orange color of the inside of my
 components. The  only obvious downside is the obvious much increased fuel usage. I think
 that for the next couple hundred hours I have going to have to bite the
 bullet and fly ROP (while at higher power settings). Thoughts?

 S.A.G. is really baffling. Spark plugs only seem to be lasting 20-30 hrs
 before SAG starts kicking in. Noted by a distinct and marked loss of
 power  as I cross through about 1500' AGL after take off. The problem is
 usually  intermittent and mildish at first becoming more consistent and
 remarkable as  the hours accumulate on the spark plugs. The problem is
 always solved by  changing out the spark plugs. I am switching to colder
 platinum plugs in  order to try to get them to last longer. Perhaps
 running ROP will  help them  last long too?

 Time for a new Prop? On a test flight yesterday, the engine was
 running great. No SAG. At 7000' and 33"MAP I was at 6500 RPM,
 about 1/3 throttle and doing 175 KTAS [201 MPH]. It is a 64
 length x 77 pitch 3-blade Cato, but that is more like an
 effective pitch of closer to 71". I seem to remember being able
 to get closer to 185 KTAS [213 MPH] at 6500 RPM in the past on
 the same prop but I did have a little taken off because of the
 low output of the previous turbo. After some more experience I
 may discover that it is time for another new prop. Might soon
 contact Paul Lipps, I liked his article in the last issue of
 Contact! mag. If that is my worst problem, I am going to be
 pretty happy.

 Doing some formation flying with the guys next week that may make its way
 into a movie...

 Keep building!
 -- David Leonard

 Turbo Rotary RV-6 N4VY
 http://N4VY.RotaryRoster.net
 http://RotaryRoster.net

 Hi Dave;
 Regarding SAG - what type and temp range plugs are you running?
 coils?
 How do the SAG'ed plugs look?

 Cheers
 Cary

I was using the stock plugs called for by Mazdatrix BUR something something
7,and 9. The plugs look pretty good except the center electrode gets worn
down somewhat. I just switched to Platinum and may also try the Iridium
and/or go to colder plugs (all 9's).