Rotary Engine wrote:
Don't buy after market apex seals! Stick with stock Mazda
iron apex seals or Iannetti ceramic apex seals.
We are seeing things on the rotor housing chrome wear surface
we should not be seeing on an engine that has only a few
hours on it.
http://www.rotaryeng.net/history.txt
I am not going to name names yet.
Paul Lamar ...No rotor no motor.
Paul,
This link has several pages of information on the NRS products:
(
http://members.shaw.ca/nrsrotorsports/use.html)
Aubrey
"The quality of this material can only be described in one way. No expense has
been spared, only the best, the toughest, high temperature ceramic was chosen
(gray material). This product is made with the highest quality material that
can withstand temperatures of up to 1400 ēC under continuous use and its
fracture toughness is fantastic. The material is tested for thermal shock
capability by heating it to 1100 ēC then dropping it into a pail of 20ēC water,
without breakage. It has been said that no one has been able to thermal shock
this material into breaking, i.e. it should be ideal for nitrous."
The apex seals run only about 500 F or 260 C. Teflon 800 F would almost work.
1400 C or 2552 F is totally irrelevant. Bricks won't melt at 2500 F either.
They are not telling us what kind of material they are making these from.
Is it Silicon Nitride?
Thermal shock is not the failure mode. The failure mode under detonation
is mechanical shock. There are standard methods for testing material
for impact loads or mechanical shock. They are not telling us what that is.
"The seals will be machined with 0.0055" overall clearance. Growth of the seal
(13B) has been calculated at 420 ēC and is under 0.004. Remember it takes a
lot more than 420 ēC ambient temperature to get the ceramic that hot."
Thermal expansion of bricks and cement blocks is also not a problem.
The seal should have a slight thermal expansion to keep with the rotor housing.
"A second ceramic material (black material) is also offered. These seals are made
from very high quality ceramic material specifically engineered for automotive
applications. This material is used to make intake/exhaust valves, bearings etc."
Is this the Silicon Nitride?
"This is an excellent material that is very tough and resistant to chipping."
How tough? Tell us your testing methods.
"Thermal shock testing for this material is somewhat lower at 600 ēC without breakage.
Growth is somewhat less than the premium material at a given temperature."
Again irrelevant. What is also very very important is surface smoothness and porosity to
retain lubricant.
There are standard test for surface finish and they are not telling us
what that is. They need to compare their product with Iannetti and stock
Mazda seals in meaningful ways such as surface finish, hardness and impact
resistance.
Also stock seals are crowned. No mention of that is made.
http://www.rotaryeng.net/Apex-seal-history3.jpg
http://www.rotaryeng.net/Apex-seal-history4.jpg
A simple test is build up a new engine with both types of seals and
measure the compression pressure achieved. Putting it another way
is compare the HP generated.
I would still not buy these seals until one hundread RX7 cars running them
accumulated 300,000 miles each. This is common for stock RX7 engines.
Quality control is also very important. Unless each seal is tested
for impact resistance there is no way to insure quality control.
Iannetti seals have been around since 1990 and similar seals to Iannetti
seals (Silicon Nitride) were used in the Lemans winning engine.
If you use other than stock seals you are literally taking your life in
your hands. Let the car guys test them for ten years.
Paul Lamar ...No rotor no motor.
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