Since you asked, Devil's advocate here.  P-)
After thinking about the no waste gate layout Greg used I've

developed

an

appreciation for it.  This comes from some failure mode analysis

(strictly

armchair stuff).  OTOH Continental Lycoming, et al, have went with

waste

gates most likely to reduce their liability, not increase it.  The

round

engine drivers of old had to watch the MP and know what kind of fuel

they

took on last so they could set the throttle properly for take off.

Flying

by MP was part of the job and from the perspective of this old

piston

(ahem) head, it keeps you in tune with your engine's performance.

You

may

have already considered the following.

Waste gate = added complexity and failure modes:
Does it fail open?  That is if you are on takeoff at Leadville, CO,

on a

hot August afternoon at full gross, will you get out of ground

effect

and

over the obstacles at the end of the runway?
Does it fail closed?  If you are not in the habit of watching your

MP as

you firewall (nose cone wall??) the throttle while departing Copper

Hill

International in the winter, will the engine survive?

Like I said, armchair analysis, I'm going NA 'cause a turbo won't

fit in

a

RV-4.   P-)
Mike McGee
Control Systems Engineer

Mike McGee, RV-4 N996RV, O320-E2G, Hillsboro, OR
13B in gestation mode

Well, this is my take....
Most piston turbo'd engines have the oil pressure controlled wastegates
(usually controlled by a "differential controller" to maintain a
specific boost or sl pressure), spring loaded, AND a very nice safety
feature called a blowoff valve (to limit overboost).  Most tc cars also
have "blow off valves". Most aircraft failures are due to grit in the
oil (sticks in the oil fed actuators, which is why you run the oil to
the stuff after the filter!) or lack of maintenance (mouse milk on
Wastegate every so often!). I'm still waiting for some electronic genius
besides the people at GAMI (who have done this electronic boost control
for piston engine certification as part of their electronic knock
protected fi/ign product!) to come up with an appropriate set up having
the same features that eliminate the oil stuff and use the same
components electronically (again like cars). This group might have some
able person do make such a product? Last I heard that might be in the
making. BTW, Gami's set up measures each pistons internal rising
pressure, and does not sense knock as noise! What a novel thought.
[Marc Wiese]

The AirCraft Rotary Engine NewsLetter.  Powered by Linux.
ACRE NL web site. http://home.earthlink.net/~rotaryeng/            
Copyright 1998-2002 All world wide rights reserved.