In a message dated 1/17/2012 6:47:41 A.M. Eastern Standard Time,
msteitle@gmail.com writes:
Lynn,
Thanks so much for a very detailed reply. It sounds like the
factory EC-2 setting for advance will be pretty close for cruise (5200 rpm)
mode for my p-port engine. I usually lean pretty aggressively, so maybe
a couple of degrees would be in order.
Can you tell me if its normal for the MAP to be different for p-port
engines, particularly around idle (1800 rpm)? My MAP readings are
approx. 17.0 - 17.3 at idle. This is about 2" higher that with my
side-port engine. I'm thinking this is because of the much higher
intake/exhaust overlap with the p-port engine.
Thanks,
Mark
Everything affects everything, all of the time.
So where the side port can have less overlap, or even no overlap in the
case of the Renesis, the Pport has a lot of overlap. So, the Pport is easily
affected by exhaust system and muffler design. At any particular RPM a wildly
differing set of factors plays out inside the engine. The most obvious is the
exhaust gasses re-entering the chamber diluting the intake charge, and making it
over rich (because some of the oxygen bearing charge has be displaced and the
fuel delivery has remained unchanged. This whole scenario may change just a few
RPM up or down the range.
So you might get it idling really well today, and in the morning it barely
runs at all until the oil temps come up a bit. What could cause that? The cold
rotors are condensing fuel back into droplets, which makes for less surface area
to mate up with any oxygen, and the engine is now very much over lean.
Everything affects everything.
If you have fiddled with dirt bike engines, this all comes to be very
clear. There is a similar interaction between intake design and exhaust design
in a piston port 2 cycle engine.
Notice the strange mufflers on those bikes. A seemingly over sized muffler
ending with a very small tube that seems far too small to make any power. And
still it works.
The rotary is a 4 stroke Otto cycle engine that tunes like a 2 stroke dirt
bike engine.
Less so for little or no overlap. Much more so for lots of overlap like the
Pport.
So, it will never tune up in idle quite as well as a side port. But the
higher the idle RPM you can stand the better it will be. Another factor that
removes the engine from its car like idle, is the fact that the prop load is
higher than the engine would see in just stirring up trans oil at idle. So
instead of say 3 HP required to idle you may need12 or 15 HP to spin that prop
even 1,000 RPM.
Your first Viking departure will make it all worth the trip.
Lynn E. Hanover