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Brian, If using the 2.85:1 then 4800 rpm is definitely on the
low side, Tracy was referring to his rpm of 4800 when using the 2.71:1.
With my old 13B and a 2.85:1, I get 6000 rpm static with a 75x88 prop, so I
would say you need to be above 5500 rpm. I think you stated you reached
that with the cowl off.
Check and make certain that there are not any intake
hoses to/from the throttle body that can collapse or close/clamp down. I
know of one situation where an air filter apparently cause just enough lower
pressure in an intake to cause the intake hose the builder was using from TB to
manifold to crush and restrict air flow. Once the filter was removed
the problem would clear up - it took longer than you might think to discover
that was the problem.
So if you can get 5500 rpm without cowl and only 4800 with
cowl/filter - something is a miss.
At 4800 rpm 14.7:1 air fuel ratio, you are making
around 115 Hp, assuming you have it rich (12.65:1) then
its around 130 HP. I flew on around 130 Hp for the first year or so it
took me to get my problem identified and fixed. The RV will fly fine (if a
little lacking in performance on take off and climb) on 130 HP, my top speed was
186 MPH - not steriling for an RV but better than most single engine certified
by far.
Go get'er done
Ed
Sent: Sunday, September 12, 2010 12:00 PM
Subject: [FlyRotary] Re: First flight
I'm using the 2.85 to one, I'll try some tuning first before I remove the
air filter. It's easier to turn a know than to remove the air filter. I'm pretty
sure I'm running way too rich.
Brian Trubee
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