"The recall involves damage to the catalyst resulting from oil
leaks in the RX-8's rotary engine.
Any engine that does not pass a vacuum test must be replaced, said
Robert Davis, head of product development and quality at Mazda North
American Operations.
Engines prone to failing the test are mostly in hot climates and use
synthetic oils.
Mazda claims that the problem is brought on by hot climates or
the usage of synthetic oil. If excess oil is allowed into the
combustion chamber, it eventually reaches the catalytic
converter and causes a malfunction of that emissions-control device."
The prohibition on synthetic oil is not in the owners manual
I received with my 2004 RX8.
I am using Idemitsu rotary engine oil which is
a Japanese synthetic formulated for the rotary. You would think
Idemitsu would know about the problem if synthetics were the only
problem.
IMHO the problem resides in the oil seal O-rings.
Reading between the lines I think the vacuum test referred to
above is done at top dead center with a special fitting for
the spark plug hole. This checks the O-rings around
the oil scrapers. The intake system and exhaust system
must be sealed for this to work. If the spark plugs are left
in only the exhaust system needs sealing and the vacuum applied
to the intake system.
Mazda uses a material in those O rings in the oil scrapers
but I have no way of knowing what that material is.
I can tell you this. They are not as temperature resistant
as they could be as we boiled some in oil. I drove my 1976 13B Cosmo
for years with burned out oil O-rings and the smoke upon start up
obscured the sun.
The best O-rings for this job are Creavey Teflon encapsulated
silicon O-rings good to 500F. Teflon is inert to all known
chemicals and silicone is good to 500 F. We have used them
for a couple of years with no problems. Teflon is not going
to be bothered by synthetic oil.
http://www.creavey.com/
There is a ultimate solution to the problem of injecting just enough
oil for the apex seals and yet not too much to fowl the catalyst.
There is a gentlemen that lives in the Florida panhandle by the name of
Richard Sohn. unicorn@gdsys.net
Richard manufactures a device that blocks the oil supply
from the oil pan to the apex seal metering pump and allows the connection
if a separate tank holding two cycle oil. Two cyclic oil burns cleanly.
You can then use the best oil for each job. Synthetic in the oil pan and
two cycle oil to lube the apex seals. Mazda should implement this idea
as soon as possible.
I also might add the rotary engine has an unequaled power to weight
ratio. Car weight tracks engine weight. This leads to a lighter
car that uses less natural resources. The RX8 is 500 pounds
lighter in weight than its competitors.
The three chamber simultaneous action is the reason the rotary engine is
so light and compact for the power it is able to generate. Furthermore the
forces in each chamber due to the pressure in each chamber are completely
contained in the one piece cast iron rotor. In a four cycle piston engine
this is not the case. The compression force must pass down a connecting rod,
into the crankshaft and up another connecting rod into another chamber that
is expanding and extracting power from the burning mixture. This makes
piston engine force paths and consequent stresses far far more complicated
and problematic than the rotary engine.
The beauty of the rotary on the other hand is the eccentric shaft is
straight through yielding no concentrated stress problems up through four
rotors and maybe more. The loads on the eccentric shaft are always in
one direction. They do not reverse. Reversing loads are what causes
metal to fatigue. Consequently the life of an eccentric shaft is not
limited. The same thing can be said for the rotor. If the wear of the
seals and the sliding surfaces can be reduced to very low levels then
the life of the rotary could be 10,0000 hours or more.
Because of a bunch of EPA regs that had to be met before the
RX8's release in the USA, there were various
modifications to make the RX8 engine's mixture richer.
That fact really pissed me off. If you start up the RX8 from
cool (55 F) and let it warm up by idling or slowly driving
it around town before getting on the freeway it really
sucks down the fuel. You can mitigate this by getting on
the freeway as soon as possible. My Honda Odyssey and my wife's
PT Cruiser are also afflicted by this. The draconian wackos will
sacrifice anything for a .000001 percent reduction in smog
including billions of gallons of additional fuel burned world
wide. Soon it will be illegal to fart.
I notice most of the people criticizing the rotary have not
owned one. I have owned six starting in 1973 with a new RX2.
Paul Lamar ...No rotor no motor.
Edward Lapham wrote:
Paul,
Sounds like you're really into it. I wonder how many engines are involved.
btw ... My father the engineer taught me that motors have rotors but
engines don't (necessarily). I don't think the good, ol' boys in NASCAR
ever had that explained to them.
Edward Lapham
Executive Editor
Automotive News
1155 Gratiot Avenue
Detroit MI 48207
www.automotivenews.com <http://www.automotivenews.com>
313.446.0339
elapham@crain.com <mailto:elapham@crain.com>
I suspect the problem with the RX8 oil O-rings is related to
the change to side exhaust ports. This is bound to heat the
rotor more and put more heat load into the oil seal O-rings
on both sides of the rotors. It was an obvious over sight
on Mazda part to miss this potential problem. It would only cost
a few more dollars to put in the TES O-rings when the engines
were built. Now they must be completely disassembled to replace
the O-rings. It is related to ambient temperature as that
affects the oil cooling. A one degree increase in ambient air
temp is a one percent loss in cooling efficiency roughly speaking.
The rotors are cooled by oil so if the oil is hotter so too are
the rotors.
We have been using these types of TES O-rings because we are
asking 150 to 200 continuous HP out of the engines hour after hour
when used in experimental or home built aircraft. The rotaries
are delivering that level of HP with reliability and long life.
Mazda rotaries have been used in aircraft starting in 1973.
All car engines on the other hand average maybe 40 or 50 HP. The
car piston engine will not stand up to this kind of abuse. That is
one reason aircraft piston engines cost $20,000 and up.
Cooling is always an issue as each type of kit aircraft is different
and each builder makes his own decisions on what design of cooling
system he is going to use. Consequently what frequently happens is
both the oil and water run well over 230 F. Not a problem
for the oil if you are using synthetic as it does not break down
until about 500 F. Regular oil breaks down about 250 F.
However other parts in the engine do not like the heat.
Particularly the main and rotor bearings. Mostly the rotor
bearings as they carry most of the high RPM load.
As to the number of RX8 cars affected it depends on where people
live. The hot south is going to be the main problem of course.
BTW this is not the first time Mazda underestimated the heat
going into the O-rings. Way back in 1973 the same thing happened
to the water jacket sealing O-rings. The common man assumed
it was the apex seals but that was not the case. It was a simple
50 cent O-ring. History repeats itself.
Paul Lamar ...No rotor no motor.
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