In a message dated 6/9/2007 7:54:52 P.M. Eastern Daylight Time,
msteitle@gmail.com writes:
Lynn,
Can you address the oil pressure limits too please. My 20B runs in
the 90's (warm). Will this hurt anything. In order to check/modify
the relief valve, I would have to remove the oil pan which means removing the
engine from the airframe. If I'm ok running in this range, I will leave
it as is. I would like to hear your take on this.
Thanks,
Mark S.
For years, all engines came with the same (adjustable) pressure relief
valve in the rear iron set at 71.1 pounds. That was the published number, how
many could hit that number exactly
is unknown. The front iron relief would have been about 110 pounds to
protect the oil cooler from a fast cold start up.
In 93 the twin turbo rear relief went up to 110 PSI, with the front relief
up to 140 pounds.
For racing with stock or near stock clearances, 115 PSI.
With .001" extra bearing clearance all around, 100 PSI is plenty.
Racing Beats 900 HP three rotor turbo airplane engine uses 160 PSI, but
they are leaning on it a little bit.
Your 90 PSI is more than enough. If you can hold 75 or 80 PSI hot that is
fine. After a long run at temperature, a slow reduction in oil pressure is a
result of oil foaming.
Foaming makes the oil pump inefficient and insulates the oil from the
coolers and the rotor heat. If that happens you can add a flat tray between the
pan and the engine to help gas off the oil.
Lynn E. Hanover