I just found an old letter in my paper files of a letter sent to me
in 1999 from Dr. Francesco Iannetti enumerating the advantages
of his apex seals. Some advantages have not been well
publicized.
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PERFORMANCE BENEFITS
Higher Engine Performance (Torque & HP)
The sealing capability of the IAS is better than that any metallic
(stock or after market) or carbon seals. As such, the combustion in each
chamber is better controlled. The additional sealing quality allows the
engine to be tuned with more timing before TDC and a leaner air/fuel
ratio for better performance without the on-set of detonation.
Both of the IAS (1- or 2-piece design) exhibit better sealing
performance than carbon or metallic steel seals. The IAS 2-piece design
seals better, and thus, provides better performance than the IAS 1-piece
design. The main advantage is more torque in the mid-range (~6000 to
7500 RPM) on normally aspirated engines and greater power potential with
turbo engines as boost goes up.
Engine Retains Original Performance throughout its Life Cycle
Since the IAS wear rate is practically immeasurable, the performance of
the engine remain at least as good as when the engine is first
assembled. In many instances, the engine improves its compression
characteristics with time. After many hours of operation only the apex
seal springs will need to be replaced. The IAS will work effectively for
several spring/engine component exchanges, especially in normally
aspirated engines.
Minimum Wear of Engine Components
The low friction characteristics of the IAS do not wear either the rotor
housings or the rotor apex seal groove. This low friction characteristic
is due to the excellent tribological qualities of the material when
running against steel or chrome, as well as the very high polish of the
IAS. This very difficult to obtain high polish level is also a
requirement to provide the necessary reliability to the ceramic IAS.
Maximum Protection under Adverse Conditions
The structural integrity of our product, especially the 3-mm lAS,
provides excellent protection against adverse events such as detonation
or extremely lean combustion conditions.
Applications
We recommend the use of the lAS, 2-piece design (2-mm or 3-mm) for
Normally Aspirated applications since this design provide a noticeable
torque improvement in the mid range. Any 3-mm seal will always be
stronger than a 2-mm thickness. This implies that under unwanted or
adverse conditions, the 3-mm seal will be stronger and less likely to fail.
We recommend the lAS, 1-piece design, 3-mm for its integrity and well
documented performance. We have tested the 2-mm lAS, 1-piece design with
excellent success, especially in alcohol. As expected, the 2-mm IAS has
a lower strength level than the thicker 3-mm version. With a properly
tuned engine, boost levels of 25 to 30 psi are not uncommon with the
3-mm IAS product in gasoline.
We feel that our product is the best available anywhere. However, even
these high quality products can break under extreme conditions in an
engine with a malfunction or one that is improperly tuned.
4. An electronic detonation warning device
The detonation alert device discussed during our conversation is made by:
J & S Electronics in California
(Tel: 714 - 534 - 6975)
This device seems to be the most popular among my clients who have made
the greatest investment in engines mainly for drag racing applications.
Using a sophisticated engine management system such as MOTEC or EFI
generally minimizes or eliminates the use of this device.
5. Engine builders for the rotary engine
We are fortunate to have become acquainted with some of the best rotary
engine builders in the USA and abroad. If I had to place my life on a
flying vehicle, I would definitely trust the craftsmanship of one these
guys which can make reliable horsepower under the extreme conditions of
a racing environment and survive a 24 hours endurance test. As your are
well aware/ nothing is as simple as it seems.
A novice builder in this field or one which assembles it for the masses,
can never perform the same attention to detail than the builder which
needs to make things last under extreme conditions. I recommend those
individuals racing the SCCA RX-7 stock class for the best compromise
between cost, performance and longevity for an airplane engine builder.
These guys have to generate the most power and reliability from a
totally stock rotary engine. Some of my clients are getting -185 HP from
a 138/ side port with a stock engine block except for lannetti Apex
Seals and tuning modifications (exhaust and intake systems).
6. Our assistance to the Lamar Rotary Engine News Letter for Aircraft
Applications
We will gladly provide you with any assistance which may be usefl:ll to
your program. Our main request is that we are allowed to review any
statements which are implied as being our opinions or explanations
before they are published in any medium.
We are also not capable, at least at this time, to answer bulk type
e-mails. As such, minimizing the diffusion of our web address to the
masses is greatly appreciated.
We would welcome the opportunity to have you become our ambassador in
the aircraft application of the rotary engine. We will answer as many
technical issues as possible (in writing) if given enough time.
2. The SAE Motorsport Report lIThe Rotary Engine In Motorsport - An
Overview"
Last year, we presented a summary of the Past, Present and Future of the
Wankel Rotary Engine in Motorsports at the SAE Motorsports Conference.
It was an in-depth description of its advantages and disadvantages
versus the piston engine.
Also presented were our recommendations for the next areas of
development to improve not only its performance but its thermal
efficiency, particularly for Motorsports applications. Due to time
constraints, this project could only be presented in an oral format. We
are hoping to publish a copy of this lecture in the near future.
3. The Wear Pattern on the housings/rotor of the Rotary Engine when
using metallic or carbon apex seals
3A. The wear pattern on the rotor housing
The groove which forms on the rotor housing when using a 2- or 3-pc.
factory or any other metallic type apex seal is due to the wear of this
part.
As the long section of any metallic apex seal reduces in height due to
wear, its length, of course also changes, becoming shorter. In other
words, the long section of a worn metallic apex seal will be shorter
than a new one.
Since the function of any multipiece apex seal is always to maintain a
tight seal along the entire rotor housing dimension (which can be more
or less than 80 mm for the 138 depending on heat loads or shrinkage
conditions), the small piece must be exposed further into the rotor
housing to compensate for the smaller length of the long section of the
seal. This sharp point loaded with the pressure from the spring becomes
an excellent cutting tool past 500 RPM's resulting in the groove on the
rotor housing.
It should be stated that the groove on the rotor housing of a passenger
vehicle begins to appear after 20 to 40K miles depending on the
oil/lubrication and the RPM engine life cycle. The lower the oil to gas
ratio and the higher the Rf'M life cycle of the engine, the faster and
worst this wear pattern will be.
38. The wear pattern on the apex seal groove of the rotor
Another problem which happens in time on a rotary engine is the change
in dimension of the width of the apex seal groove on the rotor (and the
apex seal itself) when using a product which wears, such as any metallic
apex seal 2-pc or 3-pc. or a 1-pc. carbon seal. This wear pattern is
mostly due to the rocking action experienced by the apex seal as it
changes direction on the minor axis. Amazingly, an apex seal that is as
soft as a carbon seal will wear this groove just as bad or worst than a
harder metallic seal.
The 3-pc. apex seal, in particular, (made to this configuration for
better sealing of this gap to reduce low RPM emissions) has the
detrimental effect that the joint area of the 2 long sections becomes a
knife edge inside of the apex seal groove. The rocking action of these
two sections as they change direction on the minor axis not only cuts
the rotor groove unevenly in this area but also drastically enlarges the
width of this groove.
None of these problems have been experienced with the lannetti Apex Seal
after 6 years of testing in a racing application
3C. The wear pattern on the side housings along the compression side of
the engine
This wear pattern is due to the combined effect of high contact stress
from the corner seal/apex seal on the highest temperature region of the
engine, i.e., where the metals is the weakest and where there is a
dramatic change in direction of the force applied by the apex/corner
seal. This cutting action is similar to the gouging-like wear pattern
observed inside a cylinder of a piston engine along the area where the
compression ring changes direction (i.e., @ TDC).
We have minimized or eliminated this problem with the use of advanced
but expensive coatings on the cast iron housings for racing engines.
Racing Beat has made aluminum side housings with a flame sprayed coating
which should be excellent in your application. You also get the benefit
of lower weight.
1A. The lannetti Apex Seal is available in 2 and 3 mm for the 13 B
engine size. It is also made in a 1-piece and a 2-piece design.
1 B. The product is currently made on a per order basis. It takes 4-8
weeks to deliver a set of 1-piece design, 2- or 3-mm lannetti Apex Seals
from receipt of order. This delivery schedule will be reduced
dramatically in a couple of months.
The lannetti Apex Seal, 2-piece design will continue to be manufactured
on a special order basis.
1 C. We are currently working on a catalog for the various products
manufactured. It should be stated that our office is a design and
development entity focusing on special projects in Aerospace,
Biomedical, Advanced Vehicles, Propulsion Systems which, of course,
include the Rotary Engine rather than a "wholesale parts house." The
lannetti Apex Seal is a product which emerged from one of these projects.
1 D. For your information, we have enclosed a description of our product
as well as data showing the performance advantages obtained with the
lannetti Apex Seal by one of our clients in Australia, #Pac
Performance", the fastest full bodied drag car in that part of the world.
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I need to do a bit more OCR but this is most of it.
This was 1999!!! Since then there have been 18 years additional
experience with these seals
verifying what he says here.
We have certainly abused the hell out of them in the TTC :-)
Paul Lamar
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