In a message dated 10/3/2010 6:29:07 P.M. Eastern Daylight Time,
lendich@aanet.com.au writes:
Lynn,
I'm with you on that
memory thing, sadly my memory has never been that good to start
with.
I digress
- again. I spoke to Gordon at Mistral and they felt that the
pick-up was causing a vortex, pulling in air, that would account for
foaming.
Certainly a possibility. That flat plate that the screen attaches
to, has two jobs. Hold up the screen and increases the distance from the
tube opening to the surface of the oil in the pan. This is called by some:
the vortex plate. Some are quite big in racing and seldom have a bug screen
attached. The Mazda engines have always had dismally small vortex plates and
shamefully little bug screen area. The suction tubes are too small and no effort
is made to smooth the edges of the tube opening. I brazed on a giant thick flat
washer to the end of that tube and used a die grinder to produce a big radius
into the tube end. Like a small trumpet bell. The oil velocity at the edge of
the big washer is much lower than at the edge of the bare tube, so the washer
alone cures the vortex problem.
I replaced the vortex screen with one from a Pontiac. Real
big. Never a problem. That vortex problem goes South real quick if some
foam gets into the oil. So the bigger plate, or since racers use a baffle to
keep the oil in the pan, the baffle serves as the vortex plate. I ran the oil
level about 1/4" above that baffle.
I can't quite remember but didn't they use a 2
tube arrangement, you mention feeding the rear
rotor?
They made up a real nice cover and pickup. I had a picture a couple
of computers back. If it is on a memory stick I will post it. It was a long way
to go, but it did the trick.
Question
what is the FD twin turbo?
The first model was the FA the second model was the FC and the last
US model 93-95 was the twin turbo FD.
Body styles I think.
I didn't know about
the flat screen in the baffle plate, I just thought it was a bigger screen, I
don't know why I thought that.
Why was Mistral
having these problems, they weren't running the engines hard or expecting too
high HP from them.
I don't know if they started out with a full baffle or not. With
the oil level just a hair below the baffle, oil from the rotors (falls out of
the center iron drain-back hole) lands on the baffle and gets a few seconds to
dump off some foam bubbles. Even with racing oil and the baffle, there will be
some foaming. So you might see the peak oil pressure drop off about 6 to 8
pounds. Not a problem. Just normal. The stock pump is just a bit small in
displacement. Stock pressure until the FD came along was 71.9 pounds. So, 55 to
71.9 pounds is fine from an early engine. I like 85 from the stock pump, but you
have to screw with it too much to get it.
I can detail that if you want.
The FD relief valve is set at 115 pounds.
When the driver sprang for a real race engine $14,000.00 it had a
Peterson 3 stage dry sump pump mounted on it, so we used those for a while. The
square ones split open the pressure section, so I bought a Moroso dry sump pump.
Works great. Tall skinny reserve tank takes out the foam. Pump is externally
adjustable. Set at 100 pounds. Idle at 2,200 RPM it has 80 pounds. At 3,000 RPM
100 pounds.
Speaking of baffles, in the racer, the entire oil supply will fit
in the front cover under hard braking. The baffle eliminates this. So think
about that when doing stalls and such. Less so with the full width mounting
plate. The only 2 gages in the drivers line of sight are the tach and oil
pressure.
Cars don't cruise at 6,000 RPM. Cars don't use multi grade aviation
50 weight oil. So, in a car (or airplane with the right oil) there is no
problem. Once the oil is foamed and starts to overheat (air in the oil is an
insulator) so the coolers quit working, and the oil quits cooling the
things oil is supposed to cool. A little air gets that vortex thing started.
Very bad mojo. Never leave the pattern bad mojo.
We should remember that very available non synthetic racing oils
have extra anti-scuff zink compounds,
and anti foaming additives. A straight weight racing oil (No
polymer strings) burns clean enough for rotary use. If you get all of your top
oil as a premix, you can use a 40 wt. synthetic racing oil in the sump, and get
the anti scuff, the anti foam and astounding film strength. Or you could install
one of Richard Sohn's gizmos and run a synthetic racing oil in the sump, and an
ash free 2 cycle top oil through the OMP. No premixing at all.
Tracy sells them for Sohn.
I would premix just a bit anyway. The later OMP lines favored the
apex seals and not the side seals.
Why is it no one else
is having these problems OR should they be anticipating problems.
Well we all have to on guard for the Spanish
inquisition, and Obama, but mostly, it's because
everyone reads this forum, and that other one, and
knows that at least 1/3 of the total cooling required is going to be oil
cooling. Start off with too much cooling and add additional cooling from
there.
Lots of this data is in Racing Beats catalogue. Available for free
down load from their web site.
You can download the Mazda Competition manual from the "Nopistons"
web site for free. Lots of good stuff there about computer maps. Dyno passes.
Water injection and so-on.
George (down
under)
There you go.
Lynn E. Hanover