> One could argue that, as our inside runners are a bit shorter (1 3/4") than
     > the outer ones, our curves are in fact a superposition of two resonance
     > curves (or possibly 4).    Fine!  So what?  Could we raise max power by a
     > couple of hp by narrowing the curve and raising its peak a bit?  Yes, but
     > that would be also narrow the range of RPM at which we get max power or very
     > nearly so.  I don't think the trade-off is worth it.
     > Gordon built 2 new intake manifolds over the holidays and we are going to
     > test them this week.  I'll come back with some new data shortly.
     >
     > Oh, one more interesting thing.  Some people, me included, pretended that
     > you could improve the rotary's BSFC by going to aggressively lean mixtures
     > (some spoke of 21:1 air/fuel ratio...) Well, tests show clearly that BSFC
     > decreases as you lean the mixture until you hit an optimum, then it
     > increases again as you lean further. This optimum is not too bad as we are
     > down to 0.455 lb/hp.hr at 75% cruise power and believe we still have a few
     > percent to gain.  Of course, fuel consumption decreases as you continue
     > leaning but, past this optimum, power drops faster. I want to do a few more
     > tests before I release the optimum A/F ratio.  Let's say that it is
     > definitely on the lean side of peak, but much less lean than I personally
     > anticipated.  I'll elaborate an other time on the two combustion phenomena
     > (well.. at least two...) that seem to be at work.
     >
     > Best regards,  Francois

     Excellent!! Excellent!! EXCELLENT!! You were right I was fooled by the plot.
     Next question. What are the ID's of the runners?
     We will then have the last piece of the puzzle.

     First good data we have ever seen on a simple tuned side port engine.
     We owe a huge debt of gratitude to you Francois for sharing this
     crucial data with us.

     Thank you very much.

Well, Paul and group, this decides it for me. I am definitely going to
run a 2.8 : 1 PSRU. I also received the notice that Mistral that they
will sell parts, Thanks Francois! I will probably use Mistrals PSRU
with my RV-10 since a constant speed will help a lot with the 10's
wide speed range. No knock on Tracy, but the Mistral PSRU is
already configured for a constant speed. Paul I, like you have
guessed that higher engine RPM in the rotary is the way to go.
Mistral's data shows even if the manifold isn't "perfect" higher
engine RPM produces excellent power.
Bill Jepson

 
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