From: Blake Qualley <vrm2@earthlink.net>
Date: Fri Nov 1, 2002 11:50:40 US/Mountain
To: <fc3s_org@yahoogroups.com>
Subject: Re: [fc3s_org] Apex Seals
Reply-To: fc3s_org@yahoogroups.com
nak1017 wrote:
Hello,
What is the best type and size of an Apex seal for High reliability
on the street with a ~400hp engine? What reliability modifications
should be made to insure good reliability? Thanks,
Nick
I'll just pass on (as best I can recall) the wisdom of Rob Golden of
Pineapple Racing <http://www.pineappleracing.com>:
2mm vs. 3mm
3mm seals *are* stronger, but the 2mm seals seal better. He advises
the use
of 2mm seals to those running stock engines, those running proven
combinations of mods and tuning maps (professionally developed), and to
those *who have great tuning skills* or use a *professional tuner* to
set up
a unique combination of mods. For those who are doing it themselves
and are
in uncharted water, he highly recommends 3mm seals as they really can
take
multiple hard pings before letting go, so you (usually) have time to
back
off and save the engine. Professional tuners can get away with 2mm
seals
because they (1) have a great amount of experience, (2) don't
cheap-out on
supporting systems (e.g. fuel system), (3) generally don't make stupid
mistakes, and (4) can afford to rebuild if something goes wrong. Peter
Ferrell is famous for his fanatical promotion of 2mm seals in *all
applications*, but that is not an opinion Rob (nor many other
professional
engine builders) shares.
1 piece vs. 2 piece vs. 3 piece
One piece seals definitely seal the poorest, but are the strongest. Two
piece seals accommodate end wear, so they seal better over the life of
the
engine. On the down-side, they readily chip at the top, where the two
pieces
meet. The end-piece of two-piece seals can also wear a groove in the
rotor
housing, but you should not be reusing the rotor housing in a proper
rebuild
anyway, so that is a non-issue unless you are being cheap. Three piece
seals
are far and away the best sealing design as they prevent blowby from
one
chamber to the next when the seal rocks in the groove during
transition from
Compression to Power strokes. The stock seals are 2mm 3-piece. Great
if you
can use them, but they cause a lot of damage when they break. Most
aftermarket seals are 2-piece because they are simply more rugged than
3-piece seals and (I'm speculating) cheaper to manufacture.
Materials
The stock seals are very high quality, and seal better than most
(2-piece)
aftermarket seals. However, Rob prefers to use Hurley seals whenever
possible. Their 2mm and 3mm 2-piece seals are of excellent quality
and, when
they do break, generally cause *no* damage to the rotors or housings.
Basically, the fragments get crushed and disintegrate into a power-like
substance without gouging anything. This alone is reason enough to use
them.
Higher up on the materials scale are ceramic seals. These badboys are
virtually a non-wear item, so you can reuse them over and over. Also,
they
seal much better than even the 3-piece factory seals, providing a
*significant* improvement in torque (10-25 ft lbs)! And finally, they
are
extremely tough and can take more abuse than just about anything out
there.
But they can be broken and the financial implications are potentially
devastating, so you generally tune as if that is not a feature. Ianetti
seals are extremely expensive, but Rob has been talking to someone who
has
developed a new ceramic seal that will both be more effective (better
design) and less expensive (by about half, IIRC). Obviously, time will
tell
as to whether they stand up to the manufacture claims but Rob was
impressed
by the initial reports.
General engine advice
When building a car, BUDGET THE ENGINE LAST. In other words, spend the
money
on a proper fuel system, engine control unit, and set aside money for
proper
tuning and troubleshooting. Once you have everything else in place,
then buy
as much engine as your remaining budget will permit. Just never buy
more
engine than you can properly support. Also, when tuning, first tune it
to
the edge of what can be supported, then BACK IT OFF (add some fuel and
retard the timing a couple degrees). The cylinder pressure on the edge
of
detonation is about double that you will experience just a slight bit
back
from the edge (1 or 2 degrees timing). You won't be able to discern the
power difference but your engine will last *much* longer. And finally,
if
you are doing anything serious, consider performing some internal oil
modifications. I don't just mean shimming the stock regulator, but
actually
porting the passages and oil pump cavity.
Hope that helps. And, again, this is as best as I can recall, so there
may
be one or two things that require clarification or correction.
--
Blake Qualley
http://www.rotaryengineillustrated.com