The attached picture is from my single rotor PP engine after
about 10   hrs running time. Most of the time was running at WOT and
6000RPM. fuel   flow was around 8gph.   If this an indicator of
mixture distribution at ignition, what does it   mean? if anything.
Has that been observed by anyone else?

   Richard Sohn
   N2071U

   You got me. I have never seen anything like that.
   What kind of oil are you mixing?

   Paul Lamar

I am using 1.25oz/gal ECHO two stroke oil.

Richard Sohn   N2071U

It looks to me like there is silicone partly blocking the coolant
passage to the left of the leading plug. There is a difference in
the marking of the housing to the left of the plug. Almost as if
there is damage to the apex seals as they cross the leading plug.
Also of note is the burn mark before the trailing plug. Could this
be blow by past damage to the apex seals? There is also a curious
line across the housing just before the trailing plug. It also looks
like the apex seals were not following the rotor housing after the minor
axis indicated by the burn discoloration. How is the coolant flow
with the new end housings? I would put a thermocouple in as per
Paul's description to monitor the metal temp on further runs.

Dale Davies

Good call Dale. Richard is building his own end housings so that area
may not be getting as much water as it needs. Could also be your
water pump is not up to it Richard. As I recall the 2 rotor needs
about 30 gallons per minute.

Here is the picture from my book How to Cool Your Wankel.
"installing a "cylinder head temperature" gage. This can be done by
drilling a small hole in the rotor housing in the place shown and
installing a thermal couple."

BTW Mario called me from Germany this morning and took me to task
for the careless use of the word "Wankel" since he now owns the copyrights.

It is like copy and Zerox.

Paul Lamar

Richard,

Could the spark plug be kinda bottoming in the threads and
distorting the rotor housing? It is polished right at the sides of
the plug hole, but burnt farther out.

Dale Davies

--
  Hi Richard;
  The centerline smudge running left from both plugs is a sign of heat.
  Were the smudges there previously?
  It might be blow by, grooved surface, apex clearance?
  Have you checked the rotor housing surface and apex seals with a ruler
  and back lighting for flatness?

  Those orings also appear to be too large.

  Cheers
  Cary

  Richard,

  Attached is a picture of a rotor housing that was severely overheated.
   It has a similar pattern that you're seeing.  I think the residue
is  from burnt coolant.  From the looks of the TES o-ring, it
appears the  teflon got very hot, possibly compromising the seal.
Has the engine  been overheated?  What EGT do you see at WOT?

  Mark S.

Thanks for all the excellent responses.
After doing some more checking on all the parts and indicators, it appears
to me now that high temperature in the plug area is the most likely culprit.
The EGT at my test runs was pretty constant 1600 to 1650F , and coolant
temperature never went above 180F. One thing could have caused a
local overheat is the fact that I run all these tests at a
atmospheric coolant pressure. There was leak I could not find, so I
started with the testing anyway. However, when I disassembled the
engine, there was a damaged stud o-ring, which very likely was the
reason for the leak.  --

Richard Sohn
N2071U

I would still install the thermocouple near the lower spark plug.
You may have local film boiling in that area which is allowing the
metal to go higher than 500 F coking the apex seal oil. You cannot
always rely on the pressure in the cooling system to reduce the local
film boiling.

I would also measure the coolant flow through the block with a flow
meter set up just to be sure you are getting enough water flow. I'll
loan you my flow meter set up  if you send me your shipping address.

Paul Lamar


Richard,

What is the clear or opaque stuff by the seal? It looks like clear silicone.

You state you test at atmospheric pressure and a damaged seal may have caused
the leak leading to over heat. In my experience, leaving the rad cap loose
will slow a leak. It would have had to be quite low in coolant to allow it to
get that hot. The water pump is less efficient at atmospheric which could
reduce the coolant flow. Monitoring flow with Paul's meter would be highly
recommended, especially considering the changes made. In conjunction with a
thermocouple any problems should be shown up before it gets expensive again.
I would try testing flow with and without pressure to see what happens.

Dale Davies