Paul,

 I read about P Porting on the turborx.com site, and they say that

 1.  the engine won't idle much below 2000 rpm
 2.  shorter engine life
 3.  "needs an exhaust system designed to produce excessive noise"

 As I recall, the 13B can produce about 180 HP at 6K [with PP?]
 and perhaps 250 HP with turbo and PP at 6K rpm.  I hope I am
 remembering those correctly.

 Anyway, if I wanted to retain better idle characteristics, and also
 wanted a very QUIET exhaust system [like a car], what HP could
 I achieve with just a "mild" or "street" [side] port and turbo?
 Thanks again.

 Gene Kahn


 A p-port RX8 engine idles just as well as an old perip
 exhaust port 13 B engine.

 Forget all you know about auto engine RPM. A rotary is
 just getting started at 6000 RPM.

 They are wrong on both counts. The p-port engine will produce
 300 HP at 9500 RPM. A turbo street car engine can and has  been
 built with as much as 450 HP.

 How quiet it is for a street car depends only on the muffler.

 It all depends on how much HP you want for your street car.

 Paul Lamar
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 Gene,

 My p-port 20b will idle at less than 1000 rpm, and sounds really
 cool doing
 it too, although I usually idle it around 1600 rpm.  I actually saw
 860 rpm
 on the tach while doing some tuning recently.

 I have been trouble-shooting a symptom of power dropping off above
 6000 rpm.
 On Friday I removed the tangential muffler and replaced it with my old
 3-into-1 design which incorporates a DNA muffler (the same exhaust
 system I
 was running on my old side-port motor).  This was a big improvement in
 performance, but was considerably louder.  Climb rate is noticeably
 improved
 and I picked up a good 10-12 mph on the top end.  It is evident that
 it is
 breathing much better with this low restriction exhaust system.
 With that
 said, I would hate to have this exhaust system in a street car.  You
 would
 need to wear ear plugs to drive it around the block.  It is way too
 loud for
 driving on the street, unless you like getting tickets.

 I believe the p-port motor is more sensitive to exhaust back
 pressure than
 the side port motor is because of the overlap between the exhaust
 and intake
 ports.  It needs a low restriction exhaust to optimize performance.
 Free
 flowing exhausts are louder by nature, but that's what ANR headsets
 are for.


 Mark Steitle
 Lancair ES n/a p-port 20B

 Mark's 3 rotor has peripheral exhaust ports.
 Perhaps that is one reason the P-port RX8 engine
 runs so well as we did not have a low restriction
 muffler on the dyno. We had a regular automotive muffler.
 The p-port intake RX8 engine is the best of both worlds.

 Muffler effectiveness/verses back pressure is pretty
 much a function of size.

 We used this giant empty muffler on our race car and it
 had a db reading of only 102 db about 30 feet away WOT.
 We also had it on the dyno and it had little
 or no effect on power.

 If you look underneath the back of an RX8 the muffler
 is huge.

 Paul Lamar


Mark, Paul, and all...

Thanks for the info.  Love your plane, Mark.  I think my plan will be
to use 3 or 4 rotors, turbocharging, and street porting, and try to
keep the need  for a noisy exhaust system to a minimum.  Do you
have any serious objections to that approach off the top of your head?

Gene Kahn


A turbo 4-rotor would sure be a handful to keep pointed in the right
direction.

Mark Steitle