Well I think what is happening in your test rig is the rapid expansion
of the oil pipe immediately after the pressure restrictor valve is
causing
the foaming problem. the red arrow points to the spot where I think
this is happening. A more gradual reduction in pipe diameter may
not show the same results.
Perhaps it would be better when designing the test rig
to have the rest of the engine on there so one could get a more
realistic
view of the oil exiting the engine. Now having said that it is well
known that the oil circulating around inside the rotors on a running
engine generates a lot of foam. this is addressed by having a plate
between pan and engine with small holes to act as an air oil separator.
I think what I should do is motor the whole engine with my 5 HP electric
motor with the spark plugs removed. I'll see how many RPM's I can get
out of it doing it that way. At the same time I will be able to
measure the motoring HP for academic interest using Vance's water pump
test rig.
Another approach is the have the engine assembled without the rotors
and e-shaft to simulate just the oil passages. Perhaps the oil feeds to
the main bearings could be restricted.
I'll use transparent hose between the engine
and the oil cooler.
I am not sure I will have time to do this any time soon.
But if anybody else is willing to do this we would all appreciate
nailing
down this problem. I do agree that foam in the oil cooler is not good.
There is no question that a larger and or better pump will pump more
oil and generate more pressure.
Paul Lamar
********************************************
Hi Paul,
Our new oil pump body and dual pickup tube are built, tested and work
great. We get 20-21 gal/mn at 6000 shaft RPM and 5-6 bar (70-85 psi),
with no cavitation and no air mixed in the oil, just a little louder
noise than with the stock pump and stock pickup tube (which gives 9.5
gal/mn at the same RPM).
In a few words, we use standard rotors and shaft, but our new pump body
and dual pickup tube replicate the modification brought by Mazda in its
1993-95 oil pump (side channel feeding oil to the rear rotor) WHILE
BEEING DIRECTLY AND WITHOUT MODIFICATION ADAPTABLE ONTO A 1986-92 IRON.
Anyone interested by this mod out there?
Results: double the flow and more pressure than the stock pump, some
more noise... the pump obviously works harder (we measured 2-2.5kW)...
we are going to test its endurance. We are also concerned with the
resistance of the drive chain. Calculations show that we are getting
close to the chain's specs. We'll keep an eye on this and will consider
changing the chain for a heavier-duty one.
We have also learned in the process that, at these high flows, every
sharp corner that the oil flow must go around costs a 10-20% flow
reduction if not properly radiused... every detail counts... some more
than others of course. The stock pickup tube screen alone costs 40% in
flow reduction... at least if it rests on or very close to the sump's
bottom.
We are seriously considering installing an air-oil separator plate in
the sump. What do you think of the idea of cutting a number of holes
with the proper total surface and at the proper locations, and covering
the whole plate with a steel mesh? We would thereby achieve the dual
purpose of separating air from oil and preventing any debris from being
sucked into the pump, without inducing the headloss on the suction side
that the stock oil screen induces.... it might even be easier to
manufacture.
The only little problem I see is the turbo oil return line which would
be below the plate. If the turbo bearing gives up the ghost and debris
find their way into the oil return line, than there would be no
protection for them to be ingested in the oil pump. How likely a
problem is it?
Next step for us is to install the pump in the Arrow and see if it
solves the cooling problem as we think it should. I'll keep you
informed.
Francois Badoux
I would buy a anti foam plate from Racing Beat and see how they do it.
We have had reports of taking the oil directly out of the front end housing
(like you did in your test rig) without going through the front cover reducing
the oil temp 20 degree F.
Paul Lamar
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