One
of the more common reasons for failure
of rotary engines is actually very preventable
and in many cases reversible. This entry
will cover just how itās done and why
it works 95% of the time.
Rotor
Seal Design
The
rotary engine is among the simplest
in overall design. No valves, cams,
heads or any of the parts commonly associated
with piston engines. This makes them
extremely reliable with one major exception.
. . the apex seals.
To
seal the three tips of each rotor, a
groove is machined to accept a long
thin cast iron (in stock engines) insert.
This is the apex seal. A spring, located
behind the seal, applies the force needed
to hold the seal in contact with the
rotor housing wall as it passes around
the inside housing wall. As the apex
seals pass the narrow points in the
housing, they are compressed against
the springs and then move back outward
in the wider parts of the housing. A
corner seal at each end of the apex
seal is also spring loaded to prevent
combustion gasses from leaking around
the ends of the rotor tip. Additional
seals on the sides of the rotor complete
the set to form a relatively leak-free
chamber.
Over
time, carbon, ash and oil sludge deposits
will accumulate in the machined groove
in the rotor tip. If allowed to remain,
the apex seals will eventually begin
to bind in the grooves and will not
move outward completely during the combustion
cycle or intake cycle. This allows gasses
to escape into the next chamber, reducing
compression. In the extreme, the apex
seals will stick in the compressed position
to the extent that virtually all compression
is lost. At this point, the engine will
likely refuse to run at all.
Dirty
oil and general lack of maintenance
is the most common cause of compression
loss. The oil injection system on the
rotary is designed to feed oil in to
the chamber to keep both the housing
walls and the apex and corner seals
lubricated and clean. Dirty oil will
simply throw grit, sludge and other
combustion debris back into the chamber.
Result, thousands of perfectly good
12A and 13B engines, or complete cars,
rotting in the junk yard, for no good
reason!!!!
Preventive
Care
The
obvious solution here is consistent
oil changes. Never more than 3000 miles
between changes and good (spelled Castrol
GTX 20W50) oil with a new filter. By
the way, the puny little factory filter
is COMPLETELY inadequate. A remote filter
setup that will allow the use of a 1
qt. filter is much better. At the very
least, use a K&N or WIX filter in
the stock location. These will filter
particles down to 10 microns. A better
oil cooler on those 83-85 12A engines
is also an excellent idea.
The
Fix
So
what if your engine is already suffering
from the dreaded sticking/seized apex
seals, you ask?? Never fear. An old
mechanics trick used to free up sticking
valves and lifters works WONDERS on
your rotary. The procedure works a little
differently for carbureted engines that
the EGI models, but accomplishes the
same results.
1.
Disable
the ignition primary circuit by disconnecting
the igniters or the negative lead on
each ignition coil.
2.
Remove
the air cleaner lid on carbureted engines,
or pull the Leading (lower) plugs on
13B EGI engines.
3.
For
carbureted engines, pour 2 oz. Automatic
Transmission Fluid (ATF) (the cheap
stuff is fine) down each primary bore
(the small ones) of the carb, while
an assistant cranks the engine for 5
seconds or so. On EGI engines, use an
oil squirt can and pump two or three
shots into leach leading spark plug
hole. Have an assistant lightly bump
the starter two or three times, squirt
in more oil, bump the starter, squirt,
bump, squirt, bump. . . you get the
idea. You want to get ATF in all chambers
and thoroughly distributed. Reinstall
the spark plugs on EGI engines.
4.
Allow
the engine to sit in the ATF stew for
AT LEAST 24 hours. Donāt be tempted
to rush the process. This takes time.
The detergents in the fluid, used to
keep the small polished valves in an
auto trans valve body free, will soften
the carbon and sludge deposits.
5.
PLEASE.
. . Make sure the car is outside for
this step. You'll see why. Reconnect
the ignition system, hold the throttle
open ø way on carbureted engine and
start it up. Allow to idle. The neighbors
will now think that Mt. St. Helens has
erupted in you driveway or a massive
brush fire has broken out. It will take
about 5 minutes for the smoke to clear
completely, since some of the ATF has
worked itās way into the exhaust pipe
and must be burned off.
6.
Install
a new set of plugs. The ATF will foul
the old ones and may cause hi-speed
misfire. Take the car out on the e-way
and THRASH IT for a few miles to completely
clear the chambers. 6 to 10 redline
runs will do it.
At
this point, the apex and corner seals
can move freely again. In extreme cases,
you may want to repeat the treatment
after a week or so of driving. If so,
hang on to the old plugs to use again
for the second treatment.
If
you were to perform a before and after
compression test, you could potentially
see an increase of 20 psi or more and
will feel a whole lot of power that
wasnāt there before. I have revived
engines that would not start and know
of a couple ITA drivers running junk
yard engines brought back to life this
way.
ITāS
CHEAP. . . IT WORKS. . . And you can
end up with a nearly new engine for
$2. Youāve gotta love it!!
HAPPY
ROTORING!!
Bobrx7
