I recommend you wait and see how Mark Steitle comes out with his setup first. He already says he would probably not go this route again. He is having problems with idle, which Lynn pretty much explains with the overlap of the intake/exhaust. Also even with the MT prop, Mark is having trouble getting rpms up to the range that Lynn says the PP engine works best at. We would like to get 7K rpm on take off and climb, but the balance of operation will be in the 5-6K rpm range. Lynn says the PP doesn’t start to kick in till 7K+.
The rpm problem is a conundrum with the MT prop. If you assume the prop is going into fine pitch, and the gearbox is not binding, and the engine is not going lean, and the timing is correct, it would seem that he should be able to rev to the same 7500 or higher rpm that he was going to originally.
By the way, Mark, I was doing some calculations to see what the prop pitch would have to be to get your speed, and discovered a discrepancy in your reported rpms. You said 5200 engine, 1700 prop. That wont work with the 2.85 ratio??? Can you tell us more? Maybe someone can help you troubleshoot.
Bill B
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Bryan Winberry
Sent: Monday, June 21, 2010 12:23 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: 13B rotary engines
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.
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.