Post by wayne on Aug 25, 2021 19:49:22 GMT -5
I came across this in my notes. Provided to me by former member Mike Kalinowski (the Mazda mechanic I quote when I sometimes say "I was told by..."). The price of those O rings sound cheap now but when it was written (decades ago) $22 was a lot for an O ring. I'm sure Mike would be pleased to have this reproduced on the board:
SMOKING ROTARIES
Despite all the care in the world and regular use, my RE still smokes after start up. Mike Kalinowski, one time Mazda rotary rebuilder says that smoking after sitting for a few days or weeks is caused by oil that flows through the rotor and eccentric shaft after leaking past the oil control rings on the side faces of the rotor if it sits in one position for some time.
The oil seeps (gravity) past the seals because the “O” rings around perish or become hard with age and temperature. Further comments from a Mazda chat site note that when you shut off most piston engines, horizontally opposed designs being the main exception, oil drains away from the combustion chambers. This is not the case with the rotary, which leaves small pools of oil in certain locations that can leak from these areas into the combustion chambers when you turn the engine off. On a new engine, this doesn’t happen, but as engine parts wear, certain seals become less effective so smoking on startup is actually quite normal. On engines that have this minor and normal internal leak, the result is a puff of smoke when the engine first starts after being off more than a few minutes.
The colour of the oil smoke is bluish-white, but many don’t notice the blue cast and simply call it white. Also a cold engine runs rich, so this startup smoke will be darker from fuel richness unlike pure oil smoke from a fully warmed up oil burner. Within a minute or two this clears up. It is nothing to worry about. When these seals, actually special high temperature tolerant “O” rings allow oil to pass and cause startup smoke they also cause extra oil to reach the apex, corner and side seals when the engine is running. This also has the benefit of maximizing compression sealing for best power. Just be sure never to let the oil level get below the add line. A low oil level can result in an elevated oil temperature which in turn can reduce the life of the oil seal “O” rings in the engine. The only way to replace the rings is a complete overhaul.
Mike continues that a lot of people do not replace these “O” rings during a Mazda rebuild because they are about $22 each for what looks like a 50 cent “O” ring. They are actually made from a special compound (top secret ??) but in a Mazda there are two per face times two rotors, that makes eight “O” rings @ $22 each so that tells you why people choose not to replace them….$178 for 8 “O” rings does make you squirm when you buy them….it also makes the parts man at the Mazda counter go very quiet !
On the up side, Mike says that he has only ever replaced the steel oil control rings about twice that he can remember …..they are ground with quite a large face angle and can accept a lot of wear and still work well. Remembering that they will seal whenever the engine is running as the gas pressures cause them to press against the side faces. It’s only when the engine is stationary that the “O” rings are required to stop the oil seeping past as described above. When a rotary is rebuilt a large amount of vaseline is used during assembly and this accounts for clouds of white smoke on initial startup (actually, this is normally cause for celebration because it’s running again).
So now you have a better understanding of the sealing of a rotary engine. When “Joe” backyard rotary “expert” re-installs his Mazda engine after NOT replacing those expensive oil control “O” rings he finds that the engine puffs smoke after being left overnight and scratches his head wondering why. Then he condemns the rotary engine a “piece of crud” because he doesn’t know what went wrong. Mike has heard this tale dozens of times over the years. And he adds that if you overheat a rotary (drastically) and the springs lose their tension, you can normally push start the car and it will run perfectly all the way across the country but the minute that you try to restart it, it won’t fire.When the engine is running the internal gas pressures generated push all of the seals tight against the sides but during cranking the springs are required to create enough compression to start.
And, from a very rare Mazda Factory book provide by Mike:
White smoke after engine is warmed up:
Not visible in case of a normal engine, but in case of an engine with high oil consumption (300-500klm per litre), white blue smoke is emitted.
White smoke immediately after starting (ambient temperature over 10 degrees C):
In case of a normal engine, a white blue smoke appears on starting and after some 10 seconds disappears. In case of an engine with high oil consumption, thick white smoke appears immediately after starting and white blue smoke continues after the engine is warmed up.
White smoke immediately after starting (ambient temperature below 10 degrees C):
In case of a normal engine, immediately after starting, because of an inadequately functioning thermal reactor, unburned mixture components and vapour are emitted. They are condensed when emitted to the open air and become white smoke temporarily. This disappears when the temperature of the exhaust gas rises.
Therefore, to claim high oil consumption, it is necessary to have thick white smoke emitted immediately after starting and have white-blue smoke always emitted even after the engine is warmed up.
SMOKING ROTARIES
Despite all the care in the world and regular use, my RE still smokes after start up. Mike Kalinowski, one time Mazda rotary rebuilder says that smoking after sitting for a few days or weeks is caused by oil that flows through the rotor and eccentric shaft after leaking past the oil control rings on the side faces of the rotor if it sits in one position for some time.
The oil seeps (gravity) past the seals because the “O” rings around perish or become hard with age and temperature. Further comments from a Mazda chat site note that when you shut off most piston engines, horizontally opposed designs being the main exception, oil drains away from the combustion chambers. This is not the case with the rotary, which leaves small pools of oil in certain locations that can leak from these areas into the combustion chambers when you turn the engine off. On a new engine, this doesn’t happen, but as engine parts wear, certain seals become less effective so smoking on startup is actually quite normal. On engines that have this minor and normal internal leak, the result is a puff of smoke when the engine first starts after being off more than a few minutes.
The colour of the oil smoke is bluish-white, but many don’t notice the blue cast and simply call it white. Also a cold engine runs rich, so this startup smoke will be darker from fuel richness unlike pure oil smoke from a fully warmed up oil burner. Within a minute or two this clears up. It is nothing to worry about. When these seals, actually special high temperature tolerant “O” rings allow oil to pass and cause startup smoke they also cause extra oil to reach the apex, corner and side seals when the engine is running. This also has the benefit of maximizing compression sealing for best power. Just be sure never to let the oil level get below the add line. A low oil level can result in an elevated oil temperature which in turn can reduce the life of the oil seal “O” rings in the engine. The only way to replace the rings is a complete overhaul.
Mike continues that a lot of people do not replace these “O” rings during a Mazda rebuild because they are about $22 each for what looks like a 50 cent “O” ring. They are actually made from a special compound (top secret ??) but in a Mazda there are two per face times two rotors, that makes eight “O” rings @ $22 each so that tells you why people choose not to replace them….$178 for 8 “O” rings does make you squirm when you buy them….it also makes the parts man at the Mazda counter go very quiet !
On the up side, Mike says that he has only ever replaced the steel oil control rings about twice that he can remember …..they are ground with quite a large face angle and can accept a lot of wear and still work well. Remembering that they will seal whenever the engine is running as the gas pressures cause them to press against the side faces. It’s only when the engine is stationary that the “O” rings are required to stop the oil seeping past as described above. When a rotary is rebuilt a large amount of vaseline is used during assembly and this accounts for clouds of white smoke on initial startup (actually, this is normally cause for celebration because it’s running again).
So now you have a better understanding of the sealing of a rotary engine. When “Joe” backyard rotary “expert” re-installs his Mazda engine after NOT replacing those expensive oil control “O” rings he finds that the engine puffs smoke after being left overnight and scratches his head wondering why. Then he condemns the rotary engine a “piece of crud” because he doesn’t know what went wrong. Mike has heard this tale dozens of times over the years. And he adds that if you overheat a rotary (drastically) and the springs lose their tension, you can normally push start the car and it will run perfectly all the way across the country but the minute that you try to restart it, it won’t fire.When the engine is running the internal gas pressures generated push all of the seals tight against the sides but during cranking the springs are required to create enough compression to start.
And, from a very rare Mazda Factory book provide by Mike:
White smoke after engine is warmed up:
Not visible in case of a normal engine, but in case of an engine with high oil consumption (300-500klm per litre), white blue smoke is emitted.
White smoke immediately after starting (ambient temperature over 10 degrees C):
In case of a normal engine, a white blue smoke appears on starting and after some 10 seconds disappears. In case of an engine with high oil consumption, thick white smoke appears immediately after starting and white blue smoke continues after the engine is warmed up.
White smoke immediately after starting (ambient temperature below 10 degrees C):
In case of a normal engine, immediately after starting, because of an inadequately functioning thermal reactor, unburned mixture components and vapour are emitted. They are condensed when emitted to the open air and become white smoke temporarily. This disappears when the temperature of the exhaust gas rises.
Therefore, to claim high oil consumption, it is necessary to have thick white smoke emitted immediately after starting and have white-blue smoke always emitted even after the engine is warmed up.
