When using 2 engines together with a common power output is
 there a     simple way  to assure that both engines are contributing
 equal power?     I can imagine that one or the other could be doing
 more work even     though they both are running at the same rpm
 (obviously). I'm thinking     of using 2 of the smaller available
 rotary engines on the    helicopter,  but my question could apply
 more broadly to any engine  type.

      John McEverett

    "is there a simple way  to assure that both engines are contributing
   equal
   power?"

   Same problem exists in EVERY multi-cylinder engine.

   brian gochnauer

   That suggest a simple way to do it is compare EGT's.

   Paul Lamar

 You would probably be much better off comparing CHT's.  EGT's are
 only an imaginary number.  The EGT probe sees about nothing
 interesting 3/4 of the time because the exhaust valve is closed most
 of the time during the intake, compression, and power stroke.
 During the other 1/4 of the time there is exhaust flow.  The
 measured temperature in the exhaust manifold varies according to the
 configuration of the manifold.  Same thing as the problems with
 pressure variability in the intake manifold depending on several
 variables.

 See http://www.sportaviationonline.org/sportaviation/201010#pg89 for
 a nice article on the subject.

 Mark LaPierre

 What exhaust valves? :) We don't have no stinking
 exhaust valves :) Normally people don't install
 CHT's on rotaries with at least one exception but I advocate
 and  maintain it is still a good idea. They just monitor coolant
 temp which is common on both rotors.

 Now for two engines you could monitor coolant temp but
 there could be significant differences in the two separate
 (if used) cooling systems.

 Paul Lamar


 The EGT's in a rotary will have a fairly constant temp reading as the
 pulse
 from one side of the rotor is almost done exhausting, the apex seal is
 crossing the port. The next chamber starts flowing. If the temp probe is
 installed just down from where the two exhaust pipes from the ports are
 joined, the "cylinder" temps are averaged. Then the two engines could
 be compared.

 Dale Davies

Usually twin engine aircraft engines are set with matching manifold
pressure and RPM's plus a slight tweak on the throttles to match the
revs exactly, ( with constant speed props) , my guess is that if both
were built and run exactly as a pair the manifold pressure plus EGT's
would tell the tale?
  John Burey.

You can also match RPMs by ear, similar to tuning a musical instrument.
Probably more accurate than using EGT or MAP.

Mark S.