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Right - that will happen. Unless you are running
boost you manifold pressure will be no higher (and generally 1/2" or so lower)
than the ambient pressure. At 8000 MSL that's generally around 21-22
inches Hg for me. I generally cruise with WOT and adjust my mixture to
give me the speed/fuel flow I want.
See my notes and comments to your fuel map - I think you
may be running a bit rich in that region - at least compared to my fuel
MAP
Ed
Sent: Tuesday, May 17, 2011 8:42 PM
Subject: [FlyRotary] Re: Engine Tuning
Thinking on it a bit, I realized
that what would probably happen at WOT when flying as opposed to a ground run,
is that my mp is going to decrease from 29.1 to a somewhat lower value,
since the RPMs will increase up to ~6800 or so, up from the 5200 at static WOT.
So, I would be running at a lower MAP address than the 106 that I see at WOT
static. So, should I not richen the MAP values BELOW 106, and a few adresses
above it since I should see a little gain in mp due to the ram effect of my air
scoop?
Brian Trubee
-----Original
Message----- From: bktrub@aol.com To: Rotary motors in aircraft
<flyrotary@lancaironline.net> Sent: Tue, May 17, 2011 4:49
pm Subject: [FlyRotary] Re: Engine Tuning
Ed,
Attached is my map table as of today after I tuned it tied down on
the ground. I have a 93 13BREW that is normally aspirated, it has 9.1/1
compression, swinging a catto 74 dia x 88 pitch prop through a 2.85/1 PSRU. This
EC2 is set up to accomodate turbo engines, so I have addresses that go up
to 38 inHg. They are not used.
I generally idle at MAP address 11 mp of 14.9 inHg. at around
1600rpm. This is a 60 degree day at barometer setting of 30.3. Advancing the
throttle, the EC2 switches over to the high RPM table at MAP address 17 (mp
17.2), going straight to address 80. My staging point is 84 (mp 19.1) from there
up to full throttle, MAP address 106 mp 29.1, the transition is smooth. At full
throttle on the ground I'm getting 5200 RPM. When I go much past that RPM on
takeoff, that's when the missing starts. I'm still guessing that I need to
richen up the mixture in the addresses above 106.
Any input from anyone on this would be appreciated.
Brian Trubee
-----Original
Message----- From: Ed Anderson < eanderson@carolina.rr.com> To:
Rotary motors in aircraft < flyrotary@lancaironline.net> Sent:
Fri, May 13, 2011 3:18 pm Subject: [FlyRotary] Re: Engine Tuning
Brian, what values do you have in your fuel map
around 90-105? I have values of 172 for WOT and at times (cool OAT)
I have to enrichen the mixture beyond that with the manual mixture
control
Ed
Sent: Friday, May 13, 2011 5:35 PM
Subject: [FlyRotary] Engine Tuning
Since the weather has been cooperating lately, I've had the opportunity
to put a few more hours on the airplane. On the ground, I can go from an idle up
to full throttle and the engine will be smooth. But when I take off, it seems
that as soon as I'm up a few hundred feet off the runway, I get hellacious
backfiring at full throttle. I can mitigate it a bit by throttling back to about
5100 rpm, and turning the mixture knob to near full rich. It's getting to be a
bit nerve wracking to take off thinking I've got it smoothed out and then get a
series of hand grenades going off under my butt. I'm thinking that I'm still
running too lean up at map address 106 or so. So, I go into the edit page and
richen up the mixture around those addresses. I think I'm creeping up on smooth
full throttle running.
The good news is that my coolant runs at 175 degrees and oil at less- so
the cooling is more than effective, I just need to close up my air inlet a bit
or restrict the outflow.
Brian Trubee
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