With the topside engine “stack” together I flipped the engine over and started with fitting of a cast
aluminum large capacity oil pan. The pan is designed to hold more oil, seal better, and add some additional
structural rigidity, over the stock stamped steel oil pan, to the engine “stack.” The FD has a horrendous
problem of oil slosh and blowing the oil out through the oil filler neck during hard cornering at the track
and sometimes even on the street. Bandaid solutions typically include catch cans plumbed from the filler neck
to catch all the oil blown out of the pan and drilled and tapped fittings in the front cover to vent pressure
from the other side of the oil pan and not blow oil out. The real solution is to go all-out and install a dry
sump oil system. Mazda makes a dry sump for the 13B rotary.
It’s BIG money though and ridiculous for a “street” car even though I’d love one for Princess. Totally bad-ass.
How many rotaries can boast of having a dry sump oiling system? So what can one do to address the problem
without dumping a ton of money into a dry sump system? Since the problem is based on controlling oil movement
in the oil pan why not work on the oil pan itself? There is a deep sump aftermarket cast aluminum oil pan
produced by GZ and sold through
Pineapple racing. Expensive? Yes. Perfect? No.
But definitely a step in the right direction.
The problem being that although the aluminum GZ pan is deeper and larger in capacity, as delivered,
there was absolutely no baffling in the pan whatsoever. There was, what was referred to as, a windage tray
but this is really a misconception because rotaries don’t suffer from crankshaft parasitic drag from oil
frothing and “windage.” The windage tray as provided does nothing to manage oil movement in the pan. The pan is great
from an oil volume perspective but actually potentially worse, due to the larger volume, in management of the
oil slosh problem. With this in mind I figured it was time to fabricate some baffling for the oil pan.
Studying other road racing oil pans the key to effective oil management is to have a system of baffles with
one way trap doors to keep oil where it belongs – right next to the oil pickup – and away from avenues where
the oil can escape from the pan – in the rotaries case, up the oil filler neck. With this in mind I fabricated
aluminum baffles to fit the pan and used one way trap doors from an E30 BMW M3 baffled oil pan. The little M3
rubber trap doors were easy to integrate in the baffles I had fabricated (they did not require any welding or
mechanical hinges) and will only allow oil to flow towards the oil pickup (during both left and right hard
cornering but also under hard acceleration - good for those drag racing addicts out there) and NOT away from
it during hard cornering. Simple and effective.
Another benefit of the GZ oil pan is the sealing mechanism. The stock oil pan is notorious for leaking
especially near the front cover and around the bolt holes where the engine mounts are fitted. The stock oil
pan uses a simple paper gasket. Sealing it is possible using gasket sealant and any number of sealing goop
compounds. As many will attest however, it is hit or miss whether the pan will actually seal. The GZ pan
on the other hand uses a rubber O-ring to seal the pan to the engine block (see image above). The pan has a machined groove to
accept the O-ring. I added just a little bit of the factory Mazda “grey” sealant just to be sure. To date…no
leaks. The only other modifications were to extend the oil pickup tube to take full advantage of the deeper
oil pan and to machine a hole in the side of the pan to fit the OE oil level sensor. The GZ oil pan had a flat
area for fitting the level sensor but was not machined to accept the sensor. A BIG drill and a few minutes
grinding and careful drilling and tapping of the bolt holes for the sensor and the level sensor was fitted.
And finally the oil pan was fitted to the block with a stud kit from Moroso. The thicker oil pan flange
precludes use of the stock oil pan bolts anyway so it wasn’t like I had a choice.
On another note I must make mention of the “exposure” concern. Similar to the fears of running large
braided SS fuel lines under the car some individuals have warned about the potential of shattering the cast
aluminum pan if it is hit by a large object traveling under the car…like a brick or chunk of concrete. A
stock steel pan will most likely just dent – the aluminum pan will shatter. Scary images are available on
the web of a large object totally destroying an aluminum pan on an FD and emptying the oil pan’s contents
immediately. Umm…no oil in an engine is a bad thing. I’m sorry, but the chances of me hitting an object
large enough to smash my oil pan are so remote I hardly consider it credible. The pan is largely protected
by the engine cradle and sits no more than a half inch lower than the stock pan so it would have to be a
perfect strike to do any damage. I’ll take my chances.
To round out the oil system I replaced the stock oil filler neck with an aluminum filler neck from
RESPeed that purportedly minimizes that oil “blow-out” issue described
above. The new tubular aluminum neck has internal baffles and maintains the PCV nipples using brass barbed
fittings. Hopefully this new filler neck will never have to be put to the test because the oil pan modifications
will eliminate any oil slosh issues altogether. I also replaced the original oil pressure sensor with a new
unity. I was getting the common zero oil pressure at idle with erratic gauge behavior symptomatic of a bad
sensor. The stock sensors are notorious for premature failure. We’ll see how long the new sensor lasts.
But wait..there’s more. The GZ pan has nice thick flanges. Great. Ok now try using the stock motor
mount bolts. A bit on the short side aren’t they? So I hunted down and found some longer high strength bolts
and of the correct thread. I am big fan of parts that won’t corrode and buy SS hardware whenever I can,
provided the strength rating is sufficient. Alas in this case none were to be found so I settled on some
zinc coated high strength bolts.
For more specifcs on the reconstruction of Princess go to the following pages:
OUR "LOCAL7" COMMUNITY | THE WORLD OF THE RX-7
This page last updated March 19, 2009