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Yes, good point, that's the one thing I neglected to look at and record while tuning yesterday.
Brian Trubee
-----Original Message-----
From: Ed Anderson <eanderson@carolina.rr.com>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Sent: Wed, May 18, 2011 4:56 am
Subject: [FlyRotary] Re: Your Fuel Map: [FlyRotary] Re: Engine Tuning
Ok, different size (smaller) primary injectors can change things a bit.
I run four 42 lb/hour injectors, so that gives me more total flow capacity and so would presumably require less injector open time and therefore smaller MCT values than you give you have 2 28 lb primary injectors. However, since you do have the O2 sensor and monitor, I would certainly look to using that to help you tune. I have not found anything better to aid in tuning.
Ed
Sent: Wednesday, May 18, 2011 12:02 AM
Subject: [FlyRotary] Re: Your Fuel Map: [FlyRotary] Re: Engine Tuning
Ok, that is interesting. I forgot to mention that I am running 28 lb primaries and 40 lb secondaries. Looks like I will be doing some more setting of the tables and experimentation.
I do have an O2 sensor and monitor, so I'll be looking at that also.
Brian Trubee
-----Original Message-----
From: Ed Anderson < eanderson@carolina.rr.com>
To: Rotary motors in aircraft < flyrotary@lancaironline.net>
Sent: Tue, May 17, 2011 8:28 pm
Subject: [FlyRotary] Your Fuel Map: [FlyRotary] Re: Engine Tuning
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
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