Paul,

 I hope you don't think I'm nuts, but what would you think of essentially
 using your muffler as a manifold for mounting a turbocharger?  The
 turbocharger would be used mostly for normalizing  for altitude and the
 reduced heat and energy out of the muffler would prolong the life of the
 turbocharger.  The muffler must also be fairly stout to survive being
 mounted directly to the exhaust ports it should minimize the weight for
 the
 whole installation.  I think it would also be more compact than using a
 manifold and turbocharger with a muffler downstream.

 Steve Brazil

 It will work. What you wind up with is a slightly less efficient
 aerodynamic systems so you lose a bit of velocity on the turbine.
 The same goes for the intake side. If you want the best BSFC
 on a turbo engine use p-ports.

 Paul Lamar


 Another thought..  A turbocompound engine should be very quiet without
 a muffler.  Turbines in series.  Except when wastegate(s) is(/are)
 open.

 Matt-


 Matt,

 I agree that the turbo-compound would be the best, but I'm looking at
 hardware that is available or at least not prohibitive for me to develop.
 I
 can build the muffler.  The goal is an affordable helicopter engine with
 turbine-like performance and reliability.  I can live with a little less
 efficiency if the turbine lives longer and the package is lighter and more
 compact.

 Steve



Steve,


 I have been thinking along these lines as well.  The only
issue I found is under the cowl clearance.  It other words
the addition of the  six inch 'log' the manifold to it and
then the seven inch width of the turbocharger adds a significant
amount of  width to your engine installation.  Compare that
to the auto engine package which is extremely tight and
only adds about seven inches to  the engine width.


Doug in Japan


Paul,  It seems like putting the muffler in front of the turbocharger has
more disadvantages than advantages (if there are advantages which I am
overlooking). First the normal turbo manifold is a heavy wall part which
reduces sound transmission. The ability to mount a turbo at the exhaust port
on a rotary eliminates heat losses and the accompanying reduction in exhaust
velocity resulting from the surface area radiation of the muffler case.  The
exhaust gases slow due to the area increase of the muffler diameter
compared to the exhaust port diameter. Then the exhaust has to be funneled
back down to fit into the turbo inlet which would be expected to further
reduce system efficiency.

The muffler first strategy also raises the
temperatures inside the muffler higher than the muffler without a turbo in
the system due to back pressure  which propagates heat stress and fatigue
failures of the muffler which is already a concern.  As far as packaging
inside the cowling goes I would suggest the water radiator under the engine
with the wedge style diffuser, and the inter cooler on the cold side of the
engine. The oil cooler would be below the inter cooler at the front of the
cowling.

No matter which order the turbo and muffler are plumbed they would
be on the hot side of the engine.  If it is muffler first the turbo would
then go on the end of the muffler not the side opposite the engine. This
would not increase the width required in the cowling, and allow the turbo
outlet to be plumbed around the accessory end of the engine to the
inter cooler avoiding the radiator  and inter cooler ducting.
       If there is an advantage to putting the muffler first rather than
change for the sake of change I would be interested in what advantages there
are.

George grimes