Lynn,
Can you describe your dry sump set-up in more detail. What model of
Peterson
pump do you use and how it is driven?
Could you also give us your thoughts on the best way to install a dry
sump
on a rotary for aviation use, if practical.
Thanks
Graydon Woods
Alberta, Canada
There are three common oiling systems used in racing.
A) The stock system where a wet sump is used to collect used oil spilled
from
bearings, cooling and pressure relief spill. The suction end of a
positive
displacement pump is submerged in the sump as close to the bottom as is
possible.
The pump is turned by some mechanical means. A chain. A skew gear. A
shaft
from the distributor. Also some engines have gerotor pumps built around
the
crank or cam shaft. Same ideas just different drive systems.
B) The external pump system is the same as the stock system except that
the
pump may be an aftermarket pump with a single pressure section, mounted
in a
convenient location on the engine so it can be driven by the crankshaft
by a
toothed belt and sprockets. The external pump is used where the stock
pump is too
small to supply the volume of oil required for the application, or has
some
other problems, like the Mazda pump.
C) The dry sump system is the same as the external pump system, with
this
addition. Oil to be pressurized and fed to the engine is stored in a
remote tank
rather than from the sump or pan.
The pump used in this system has a pressure section with an internal
pressure
control valve, and at least one additional section (two or more pumps
built
on one shaft). The additional pump sections are used to remove oil from
the
sump, pan or in the case of the rotary just a flat plate to seal the
bottom of
the engine.
In racing this system provides two primary advantages.
First, is that ground clearance at the oil pan is a problem so with
racing
engines. Since the engine is the largest mass in the car, good handling
requires that it be as close as possible to the ground. In a piston
engine only
enough pan depth is used to clear the crankshaft. In the rotary, just a
flat 1/4"
aluminum plate is used.
Second, is that the pump is outside the engine, the oil pressure may be
adjusted to anything you want. A higher than stock oil pressure is
helpful in oil
cooling the rotors and sweeping bearings of heated oil.
A large amount of excess volume capacity is available in the event of an
emergency. Both in pump capacity to maintain oil pressure in the face of
a leak or
damaged bearing, and in oil capacity in the remote tank and line to the
pump.
This is where a few extra seconds of power could make a very big
difference
in an outcome. Oil pump speed may be adjusted by changing pulley size.
The
pump can be serviced or changed without disturbing the engine in any
way. A
large supply of pump styles and sizes and configurations is available.
Except for
the rectangular Peterson, they are not experimental but are one of the
most
tested
devices you could ever buy. Thousands of dirt modifieds, super stocks,
NASCAR, TransAm Off the road cars and trucks, and the list goes on, run
these pumps
for thousands of miles of the most brutal road tests that can be devised
every
week.
The pumps are available with a number of mounting options, but most
often
they are ordered with one of many flat plate tabs extending from one of
the
elements that has two holes machined in it. One round hole and a second
slotted
hole to allow for belt tensioning. The pump may be moved slightly even
with the
oil lines connected, to accommodate some movement.
The rotary (my opinion) has three locations to mount an external pump.
Where a flat plate covers the pan area, a second thicker plate might be
added
to mount the pump below or to one side in the area where the pan had
been.
The 12A front cover provides additional stud locations that may be
useful for
pump mounting.
The original alternator location is a ready made location. On my GT-2
car the
Weaver Brothers single stage external pump is mounted there and works
very
well.
Along the drivers (spark plug) side of the engine. My GT-3 car has the
three
stage Peterson pump mounted there. There are two large diameter tapped
holes
in the front cast iron, and another tapped boss in the front cover close
by. I
drilled an aluminum block to fit the three holes and drilled the block
length
wise to take the bolts for the pump mounting tab. Works great. Never
comes
loose.
The dry sump system can be thought of as two separate systems sharing a
single shaft. The pressure system is the same as the basic external
pump system.
So pressurized oil may be routed through filter (s) and cooler(s) and
back into
the engine.
The scavenge system is the part of the dry sump system that removes
spent oil
and returns it to the storage tank. While the oil is again outside the
engine
in this system it may be plumed through filter(s) and cooler(s)
before entering the storage tank.
The storage tank may be nearly any shape, but cylindrical and tall is
better
than square and short. There will be a large amount of air, combustion
blow
by and foamed oil pulled out of the engine by the scavenge sections of
the
pump. Generally, the scavenge section has twice, or close to twice the
swept
volume of the pressure side of the pump. A balance hose connects the
engine
crankcase to the storage tank. This line need not be of large diameter
because it is
usually flowing air from the top of the storage tank into the crankcase.
You will have to seal up the dipstick tube as well. There will be
nothing to
measure, and air and dirt may be pulled in around the seal.
The storage tank may be installed in any convenient location. The
greater the
distance from the pump, the larger the hose diameter must be. There is
only
ambient air pressure to force oil from the tank to the pump.
For example, the NASCAR people have the tank in the rear of the car
beside
the fuel cell.
As you can see there are other thoughts to add up here. A tank mounted
lower
than the pump, and you have a suction lift situation. Pumps like a
supply of
oil that is at a positive pressure already at the suction port.
A pump that is supplied from an oil level lower than the pump cannot
perform
as well as a pump that is fed oil from a level higher than the pump. So
a tank
mounted closer to the pump rather than some distance away is better. A
tank
mounted so that an oil level higher than the pump inlet rather than
lower. A
tank that is round rather than any other shape. (Expended fire
extinguishers
work well.) Tall in shape so that the oil level can be higher than the
inlet.
And so on.
You may construct a system that violates every rule and it will still
outperform the stock pump.
It is also possible to use the stock pump for pressure and a second
external
pump for scavenge.
Just imagine a dash 12 90 degree fitting welded to the flat sump plate
(6061-0) or a bung welded to the plate in line with the stock oil pickup
tube
location.
This could provide additional space for that extra cooler volume you
need.
This could also make the stock pump more effective because you eliminate
the
sharp edged suction tube and the restrictive bug screen of the stock
system.
There is a down side.
We (me, my wife, driver Terry Whitlock and my friends) have raced the
rotary
engine since 1980. We have never damaged an engine to an extent that it
could
not be reused. We have made every mistake it is possible to make in the
building, installation and support of these things and the design has
saved us from
ourselves in all but a few cases.
We raced the early engines from the 70s with the small oil pump. We
gleefully
turned them up over 9,000 RPM week after week, with no penalty at all.
My
bridgeport's were on the small side, and we made under 220 HP. We would
shine up
the bearings on an over wind now and then. We had no rev limiters back
then,
and we did get calls from The "Guinness Book of World Records" wanting
to know
how high we turned it that time!
One memorable day the driver came out from under the bridge at Road
Atlanta
and at top speed started down the face of the hill. We had to brake
hard and
shift to 4th for that turn so during an attempt to shift to 5th, the
driver
selected 1st gear. The damn Hewland went right into gear and the real
wheels
locked up.
Thus teaching the driver a lesson he still remembers. (He doesn't like
dog
ring transmissions).
The Smiths flyball tach only has numbers up to 10,000 RPM. On the tach
face,
Zero is at a stop peg in the
6 o'clock position. the 10,000 mark is at the 2 o'clock position. The
tattletale pointer was hard against the back side of the zero stop peg
at 6 o'clock.
The Guinness people called right away. What was that?
Maybe 16,000 RPM??? Maybe 18,000 RPM??? Yes, a new record for sure, Save
us
the pieces and don't reset the Smiths, we need a picture.
Well, there were no pieces. The car went another lap, and the driver
reported
that the power was down a bit. (No shit Sherlock Holms). We had no spare
engine. We also had no compression and the engine would not restart
after cooling
off. It had stuck the corner seals in their holes when the crank flexed
into
an "S" shape and dragged the rotor corners. We sanded the rotors and
cast iron
a bit and installed used corner seals, reset the tattle tale and raced
the
car. No problem.
I doubt that you could turn even a bare Continental crank shaft 16,000
RPM
without damage let alone the assembled engine. But, I run on as usual.
The dry sump system adds complexity and weight. It can become very
expensive.
Maybe $1,500 for a pump. Not many people will have any experience
working on
the system outside of racing circles.
For engine RPM below 8,000 there is no added value. There are
modifications
that can be made to improve the stock pump and components. The large
sized
pressure sections for both gerotor and gear types, have high pressure
pulse
peaks, and as a result, are very noisy. The Mazda pump has two shaded
sections to
cut down on noise. You can install a new Mazda pump by removing the
front
cover. Use a new chain and pump. Drill new attachment screws for safety
wire. Pack
the new pump with clean bearing grease, so it will prime instantly. The
stock
pump is fine up to about 7,000 or a bit more. The only problem at or
above
this is the pickup and bug screen cause oil foaming. And you can fix
that too.
Lynn E. Hanover
Hey Lynn,
keep on talking! This is way more interesting than any thriller! :)
How do YOU fix the pickup and bugscreen?
Thomas J:)
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