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Hello Brian:
Don't know what happened to that last post; it was a jumbled mess. I don't subscribe to the feed so I have to cut and paste.
Anyway the first attachment was obviously your MAP and the second attachment includes Ed's MAP in light blue (hope you don't mind Ed) and mine is the one in purple for comparison ... hope these graphs are useful.
Jeff
From: bktrub@aol.com
Subject: Re: [FlyRotary] Your Fuel Map: [FlyRotary] Re: Engine Tuning
Date: Wed, 18 May 2011 00:02:01 -0400
To: flyrotary@lancaironline.net
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
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