Paul ,

 I have been out of the loop for a couple years. Looking forward to
 getting back to my 13B Murphy
 Elite project this winter. I was hinging on the P-port as an intake
 option but never really got
 enough info with regard to my application to make a good decision. I am
 setting the plane up for
 STOL and alot of my flying will be river bars and back country strips.I
 need crisp responsive low
 RPM throttle response . Does the p-port intake have any low end throttle
 penalty's for bush flying
 as opposed to a factory 4 port intake.

 Geir Anderson.

 Not that I noticed. Idle is 2000 engine RPM. Prop RPM is 700.
 Do you have the 2.17 gear box? If so prop RPM is then 920 RPM.

 A p-port will help a lot depending on your current manifold but will
 not be top HP with a 2.17:1 PSRU. It is 250 HP at 7500 but you will
 not get that high with a 2.17:1. You should see about 200 HP at 6000 RPM.


 Is this still your current intake manifold?

 Is that Ross a 2.17:1 ?

 Paul Lamar

 --
 I have a Ross 2.85:1

 I will not be using the intake you have shown ,However if the P-port does
 not suit my type of low
 and slow flying I will rebuild something along the same lines .

 if I remember correctly Daryl Drummond dyno'd the engine with that intake
 at 180HP/7200 RPM
 geir andersen

 That is pretty good HP. Steve Beckman has a lot of experience flying a
 p-port.
 What about throttle response Steve?

 Paul Lamar



 --------------------------------------------------------------------------------

 Paul, throttle response of our peripheral port engines was very good on the
 ground and in the air, and at any point throughout the operating range. No
 discernible lag. No stumble with throttle advanced from idle slightly or
 full throttle when on short final, etc. so made it very nice to fly. Idle
 speed approx. 1000-1200 engine rpm. But we had the throttle shaft and
 plates located inside the rotor housing. Although locating the throttles in
 the rotor housings is probably the optimum for response and idle speed, it
 involves a lot of work. Putting a slide or throttle-body with plates/shafts
 just outboard of port probably next best location.

 Steve Beckham

 As I recall Mazda placed the injectors close to the P-port on the Lemans
 engine for throttle response reasons as it is very important when road racing.

 http://www.rotaryeng.net/Mazda_R26B_US.pdf

 Also it might be a good idea to use a Megasquirt in this application.
 The 555 system and Tracy system has no provision for rapid engine acceleration.

 We did discuss it at one time by putting a special switch on the throttle knob to
 temporarily enrich the mixture.

 "Basically it is short stroke pancake air cylinder mounted on the slide throttle
 knob inside the cockpit with a small air hose connected to the back
 side of the diaphragm in the Tillotson type carb. The increased air pressure
 will inject an extra shot of fuel and open the supply needle valve at the same
 time. When the knob is released the diaphragm spring will slowly restore the diaphragm
 and close the needle valve again.

 Something like a 1 inch bore (2" OD) cylinder with a .5 inch stroke
 or smaller should do the job. A spring inside the cylinder will restore the
 stroke after the knob is released. A one way valve on the intake port to the cylinder
 will fill the cylinder with air."


 Paul Lamar

         Paul,

Attached is a mock up I was working on a couple years back using aluminum P-port inserts instead of the S.S. you are using now.Is there enough room between the housing and the slide throttle you have available to install perhaps just install the primary injector in an effort to improve throttle response.Any thoughts on an injector housing fabbed and welded to the S.S. stub pipe between slide throttle and housing .

Thanks                
Geir Andersen


We have something almost as good as that.

I think you won't be able to measure the response difference
within a couple of inches of the port.

The new RX8 type skinny injectors give more flexibility on mounting.
You can rotate both tubes about 45 degrees to lower the height if you
need the clearance under the cowl. That Murphy will be a great bush plane
with 250 HP.

Paul Lamar