|
Hi Brian,
I have my fuel MAP values and comments (in blue) buried in
your spread sheet. IF I had to make a stab at this point and quick look, I
would say you are probably running excessively rich at your higher map values
> bin pointer 75 < bin pointer 103. See my notes. I took my
MAP values (turbo block street ported - good intake - no turbo) and converted
them to your reference - that column is in blue is my value for direct
comparison with yours. Some places we different but it probably doesn't
really matter - in other areas where we differ, you are running considerably
richer than my engine.
I have the 2.84:1 gear box swinging a 74x88 prop and
consistently get 6000 rpm static on a normal day and can get up to 6200 on a
colder day. My fuel flow will range from 16.5-18 GPH on take off and has
hit 20 GPH on a cold day. I use a 91 Turbo block street ported sans
turbocharger. I have a fairly decent intake system (about the sixth
version - so I did quite a bit of experimentation to get it right and I think
it’s a pretty descent intake)
Do you have an air/fuel ratio indicator? If so I
suggest you run your engine at some of those bin numbers and record what it is
telling you (lean, Medium Rich, etc). While at higher Manifold pressure
you do want an air/fuel ratio running closer to 12.5:1, I suspect your air/fuel
ratio may be even richer than that. Now all of these comments apply to
bin/manifold pressures in the non-boosted range < bin 103 or so.
Take a look at my notes - it is possible your problem
could be too rich. Too much fuel in your mufflers getting ignited can
certainly produce a loud bang. Perhaps ignition could also cause it, but
right now it appears to me you are simply way too rich between bins
75-103. If you have an air/fuel ratio indicator, I would try reducing the
mixture in those areas.
Hope this helps
Ed
Sent: Tuesday, May 17, 2011 7:49 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
--
Homepage: http://www.flyrotary.com/
Archive and
UnSub:
http://mail.lancaironline.net:81/lists/flyrotary/List.html
|