I just finished tearing down my engine. I am doing a rebuild for low
compression on one of the faces (determined by a change in the force
required to pull the prop through on that face and a quiet
'ka-chunk'), and
some leaking of combustion gases into coolant causing occasional loss of
coolant if not checked before every flight.
Results of tear down..
Where are the rubber buttons? There are no rubber buttons in any of the
corner seals.. not even a residue. Do they usually disappear?? I am
pretty sure I recall them being there in the past, or am I mistaken? I
used the strip that comes in Tracy's gasket kit.
I found a side seal that was stuck at one end. quick clean should fix
it.
Coolant issue: Not sure I am happy with the TES 0-rings. Yes, they seem
to have been very resistant to the heat. In general they are in
excellent
condition. Except, they have very little elasticity and have molded to
the shape of the channel. In the hot area, they no longer extend
above the
top of the channel and are more or less flush with the top. It seems
that
in this area they would be exerting minimal sealing pressure there. I am
thinking about going back to the stock. Anyone else have a similar
experience or heard of this problem?
Otherwise the engine is in OK shape. No evidence of overheating.
There are quite of bit of chatter marks on the rotor housings, the rotor
bearings seems pretty well worn but probably re-usable.
--
David Leonard
Turbo Rotary RV-6 N4VY
http://N4VY.RotaryRoster.net
http://RotaryRoster.net
Did you mic the rotor housings? Any shrinkage?
Were the rubber buttons silicon rubber or were they black rubber?
Check the apex seal springs for stiffness and height. The temper
can go away on certain non stock apex seal springs due to
temperature effects of the wrong spring material. This is one of the
causes of chatter. Are the apex seals Mazda stock? If after
market they could be steel and steel does not retain lubricant
like the microscopically porous stock Acicular cast iron.
I think this was discovered 100 years ago in piston engines :)
Apex seals look simple to make but they are far from it.
http://www.keytometals.com/articles/art21.htm
http://www.rotaryeng.net/history.html
Inconel apex seal springs would be best.
Also the amount of 2 cycle oil in the fuel
has a strong effect on the temperature of the apex seal and
springs. Increase the 2 cycle oil in the fuel to 2 ounces
or more per gallon from one ounce per gallon.
Also try increasing the amount of lube oil going to the rotors
for better cooling. You may need a 3rd gen oil pump. The 3rd gen RX7
turbo engine was making 280 HP in final form.
I suspect a p-port would cool the apex seals and the apex seal
springs better. It would also reduce the back pressure on the
exhaust at a given boost level.
For the new people this engine went 229 MPH at the recent Reno air race
in an RV6 and is a more or less stock 1991 Turbo II engine with a highly
modified stock turbo running 45 inches of Hg. The stock Turbo II
usually only made 200 HP at about 35 inches of Hg max.
Paul Lamar
Hey David;
Combustion gases in the coolant and loss of coolant are signs of overheat.
Typically iron warpage, rotor housing shrinkage or failing orings.
These overheats symptoms seem to more common with after market TES-orings.
Particularly as you described the condition on yours.
They tend to take a bit of set, but not molded as you described,
the teflon splits in the hot area with most failures I have seen.
Do you have any pics?
As Paul said, mic the rotor housing width.
Not sure whose apex seals/springs you have -Mazda apex springs
Check irons for warpage.
The rubber corner seal buttons tend to disappear in high power
applications such as yours.
You might look into solid corner seals - although, I haven't heard
enough history on any of them.
Your rotor bearings have now been clearanced :)
Cheers
Cary
--
The Rotary Engine NewsLetter. Powered by Linux.
ACRE NL web site.
http://www.rotaryeng.net
Youtube key word PaulLamar2
Copyright 1998-2011 All world wide rights reserved.