| [GMCnet] Calling all FiTech Fuel Injection Owners... [message #316581] |
Mon, 24 April 2017 22:03 |
glwgmc
Messages: 1014
Registered: June 2004
Karma:
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Senior Member |
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Hi Bruce,
What I have learned from FiTech and from my own now rather extensive experience is that they appear to be calculating on the fly the actual target A/F ratio based on those simple base tables plus input from a number of the other sensors all vetted by feedback from the o2 sensor from each ignition event or series of events. While the interpolation appears to be linear, the constantly changing multiplier factors assigned to the other sensor inputs and the constantly changing base table A/F ratios as a result of the o2 sensor feedback looks to me to be shifting those linear interpolations to mimic curves. The microprocessors now available are that fast unlike the ones from a decade or so ago.
The self learning appears to be heavily influenced by o2 sensor feedback which gradually alters the base table settings and the multipliers used for readings from the other sensors. Randy V. found that by manually changing the base table settings from the very rich FiTech ships with to leaner and more appropriate for our use 14.1 to 14.5 starting points that the self learning comes in more quickly as there are apparently smaller adjustments called for from the o2 sensor. That matches my experience as well.
At first I just let the system do its own thing on its own time frame and it worked well, but seemed to me to generally be rich at first and gradually began to lean out. At Randy’s suggestion I leaned out the base table settings for idle and mid- range (just two numbers with are easy to find and change using just the included all metal color display) and my unit(s) seem to come more quickly to the learned leaner A/F ratios our engines appear to prefer to the richer stock settings the FiTech ships with. I would leave alone anything to do with WOT as I want my engine to consume as much fuel as it wants to keep it cool in steep pulls. I never actually go to WOT and always keep 4” or so of vacuum even on the steepest of grades to help keep things cool and keep all the pieces where they are supposed to be.
I have written a lot of computer code in my working life, but have never calculated or created algorithms for multi-sensor A/F ratios so really can only speculate about how the FiTech algorithms might be working, but my speculation thus far matches well my direct personal experience. I do think we have to be careful not to advance the base timing too much in hot driving as I think the combination of constantly recalculated A/F ratios, hot driving and long mountain pulls could result in overly lean conditions in some circumstances. In cooler and less demanding driving the constant recalculated A/F ratios do a good job of improving drivability even in the face of too much initial advance. I am not sure the EBL systems would catch these conditions for us so advise setting base timing a degree or two less than you think you can get away with under more normal driving conditions. Hope this helps.
Jerry
Jerry Work
The Dovetail Joint
Fine furniture designed and hand crafted in the 1907 former Masonic Temple building in historic Kerby, OR
glwork@mac.com
http://jerrywork.com
===============
Message: 2
Date: Mon, 24 Apr 2017 14:42:50 -0600
From: Bruce Hislop
To: gmclist@list.gmcnet.org
Subject: Re: [GMCnet] Calling all FiTech Fuel Injection Owners...
Message-ID:
Content-Type: text/plain; charset="utf-8"
Just wondering how the FiTech manages the fuel with such a small fuel table (3x3 or 4x4 I believe). The example in their manual shows a straight-line
extrapolation in between.
These are a couple curves my my low and hi-speed EBL tables from way back in 2009. I don't have any current tables on-line.
http://www.gmcmhphotos.com/photos/member-galleries/p30956-ve-table-graph-from-dynamic-efi-ebl-system.html
http://www.gmcmhphotos.com/photos/member-galleries/p30957-ve-table-graph-from-dynamic-efi-ebl-system.html
My spark table is a curve as well were it seems the FiTech would be straight-line.
Just wondering..
--
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
Hubler 1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that
==================
Jerry Work
The Dovetail Joint
Fine furniture designed and hand crafted in the 1907 former Masonic Temple building in historic Kerby, OR
glwork@mac.com
http://jerrywork.com
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Jerry & Sharon Work
78 Royale
Kerby, OR
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