flyrotary@lancaironline.net Mailing List Archive

Bryan,

As a reference the original Powersport 13B P-port is rated at 210 HP normally aspirated. The fuel flows are very similar to any other engine producing that level of power. Steve tells me that they were seeing FF very comparable to an angle valve IO-360 producing identical power. This engine was dynoed with butterfly valves in the housing. These p-ports were 1-5/8' diameter optimized for 6000 RPM. The engine would rev higher but you were already at peak power anyway. Larger ports will make more power at higher RPM. Tuning will become more critical with the larger ports. A personal anecdote here. I built a high reving motorcycle engine in 1978 with all the "best" parts at the time. The engine was unreal at high revs, but if you transitioned to anything below 4000 RPM by shutting the throttle off and quickly opening it again the engine would "catch" or hit an RPM plateau and would rev no higher. In fact the engine would die if not returned to idle! This horrible malfunction was TUNED OUT later, and the solution was surprisingly simple, however difficult to find. The key here is that many people underestimate the job of installing and tuning p-ports. There are two aspects, first the initial install being sure there are no leaks . Then second, and most overlooked is that the system must tolerate the heat cycles of a high power engine without DEVELOPING NEW LEAKS for a long time. Powersport used an insert with o-rings sealing the port. O-rings or other elastomers work much better than epoxy on long-term sealing because there are different expansion rates between the port and the epoxy. On a car you can usually get away with epoxy for a while. An aircraft is a different animal. The aircraft engine needs to tolerate 80-100% power for long periods and then long cold-soaks on the ground. The rotary is mechanically tough enough but you need to design your subsystems like a race car that will see a 500 mile long straight-away! When Paul Lamar ran one of the newsletter guys P-port Renesis at MazdaTrix, They got great numbers, but only after changing to an intake that MazdaTrix had spent lots of time tuning. P-ports will run great, and even idle well if not too oversized, but don't expect the tuning to be real easy. Remember you are designing a new intake, exhaust, and the equivilent of a new cam timing all at once. The rotary is very much like a two-cycle in that respect. The results can be very worth while if you understand the difficulty involved.

Bill Jepson

-----Original Message-----
From: George Lendich <lendich@aanet.com.au>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Sent: Mon, Jun 21, 2010 2:36 pm
Subject: [FlyRotary] Re: 13B rotary engines

Bryan,

Not all P-ports are equal.

More power = more fuel.

Talk to Bill Jepson ( on here) about availability of new P-ports.

George ( down under).

All this talk of additional power coupled with an easier intake design has me thinking I should probably go this direction with my Renesis. It’s still on the stand after rebuild.

I haven’t constructed the manifold yet anyway.

I assume fuel flow will be higher than normal?

Is slide throttle best option?

Need to search archives I guess.

Good info Lynn, Thanks

Bryan

From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Lynn Hanover
Sent: Monday, June 21, 2010 12:15 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: 13B rotary engines

In a message dated 6/21/2010 11:03:01 A.M. Eastern Standard Time, rv-4mike@cox.net writes:

Thanks for the feedback Lynn. Unusual to see a "poor port design" actually aid performance.

Mike Wills

It is not obvious until you start graphing the open and close events, but the side port which uses the side of the rotor as a shutter to open and close the port, offers Mazda great latitude in port timing. In the periphery ported engine (both ports) it is impossible to arrive at zero overlap, and have an engine that will produce any power at all. The apex seal does not close off either port at all, it just valves gasses in one direction or another.

In addition, the overlap of the periphery ported engine is far more effective flow wise than overlap in the side ported engine. One apex seal is above the intake port when the opposing apex seal is below the exhaust port. Flow between the two is unobstructed.

So, at low RPM you get fresh mixture leaving through the exhaust port, and combinations of burned and unburned fuel and exhaust gasses flowing partway back into the intake runners.

This reduces the low RPM output to the point that the engine seems quit docile, and is easy to drive around in the car, slowly, or possibly taxi in an aircraft. This would make off idle tuning data useless as there will be fuel burning right on top of the EGT probes, and unburned fuel reaching the F/A sensor.

The engine will act along the lines of a piston engine with a long duration cam. When the engine reaches its happy RPM where all of the mixture is burning inside the engine, it will step up on the "CAM" and you will see what a good idea this was. Use slow throttle inputs until you find the "WOW" RPM, and be ready with all available rudder.

When we first ran a factory periphery port engine, we found that there were places on the track that would not allow full throttle. This with 11" wide slicks. Thank Heaven for rev limiters. The driver reported the rear end getting real loose cresting hills and bumps.

Why yes it was..........

Lynn E. Hanover