Stuart wrote that pistons have
been shipped from PE to me via FEDEX. I checked the tracking number
supplied. They are enroute across the Pacific and should arrive May
19.
He also requested that I send my
cylinders to PE for repair. When I responded that I had already shipped
cylinders to ECI for repair, he asked for a copy of the ECI invoice to pay
from. I responded with the quotation from ECI. The cylinders are
currently winging their way to ECI in Texas.
We are heading in the right
direction.
As to the question about oil
analysis and pistons: I have not done oil analysis. I am not sure it is
a readily available option here in Australia, and years of oil analysis on my
TR-182 failed to provide much useful information since virtually all problems
that occurred over a 2000 hour TBO run were at the top end (exhaust valves,
exhaust manifolds, turbos). Oil analysis gave no indication of these
problems which surfaced at annual inspections.
I did pull and disassemble the oil
filters on my Lancair IO-550. First oil filter was pulled at 25
hours after the mineral oil run. Most of what appeared on the paper and
appeared to be shiny metal was in fact shiny carbon bits, and the small
amounts of metal (probably aluminum) found using jeweller’s glasses was within
guidelines for first run engines. (Lycoming has an excellent technical
paper on what to look for and how to interpret oil filter debris.) There
was no magnetic material present. The second oil filter was pulled at 67
hours and had virtually no metal visible to the eye aided with four power
jeweller’s glasses and a 500 watt light. I put the filter elements in
plastic baggies and marked them so I can compare with others in the
future.
While the pistons had suffered
various degrees of scuffing and the cylinder Cerma-Nil plating was visually
scored (not deep enough to feel), the piston rings all looked pristine and
seemed to take it all in stride. The new piston rings used in the
Cerma-Nil cylinders are moly coated and apparently quite tough and wear
resistant. They appeared barely broken in and had a nice polished
appearance on wear surfaces. However, the compression ring groove width clearance
was found to be 0.009 on all pistons. . The groove clearance spec
is 0.0015 to 0.004. Therein lay the source of the ring flutter
problem.
The pistons were remarkably
consistent. Ring end gap clearances were right on the money with the
second ring end gap about 25% greater than the compression ring gap, as per
current recommended practices. It was the piston to cylinder bore
clearance that was insufficient for the forged pistons.
Fred
Moreno