13BREW Engine Rebuild - Modified GZ Alumnium Oil Pan


The Pros and Cons

Comparison of size, depth, and configuration of the GZ aluminum oil pan and the OE pan.

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.


Baffling???


Where's the baffle?

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.


The BMW "non-return flap" trap doors. The pan baffling I fabricated prior to installation.

Oil pan baffle walls and trap doors installed. The bolt indicates the approximate location of the oil pickup and the bump out in one of the baffle walls is to accommodate the oil level sensor.

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.


The prepared oil level sensor hole. Note the slight bevel in the sensor hole.

Oil level sensor installed. It sits lower in the pan to account for the deeper sump.

The oil pan cover (aka "windage" cover) installed. Note 4 extra holes (left rear of the pan) in the cover to allow better flow back into the pan from the engine block. Oil pickup tube spacer plate installed. Moroso oil pan kit studs installed.

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.


The installed GZ aluminum oil pan with Noltec urethane motor mounts (note the steel mount on the pax side). Shame no one will see all the work that went into the insides.

Next page for 2-stroke oil injection system

For more specifcs on the reconstruction of Princess go to the following pages:


Rebuild and porting of the 13B short-block to include port matching the intake side.
Replacement of all the fuel system lines with SS braided hose and AN fittings – tank to engine.
Installation of a dual fuel pump arrangement with fuel tank baffle box cover.
Replacement of all turbo hoses with SS braided hose and AN fittings.
Relocation of the ignition coil packs to the drivers’ side fender wall.
Simplification and rebuild of the engine wiring harness and removal of all un-used control solenoids.
Porting and polishing of the throttle body and removal of the double throttle control assembly.
Turbo “improvements” to fix lower grade hardware and potential trouble areas.
Installation of 3 Bar MAP sensor and tuning for higher boost applications.


And for review:
Rebuild Overview Part 1
Rebuild Overview Part 2
Rebuild Overview Part 3
Rebuild Overview Part 4



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This page last updated March 19, 2009


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