[Diy_efi] long term fuel trim

[Tim Marsteiner]

This is on an Excelsior Henderson Super X.

There is no manifold pressure sensor so I assume it is
an alpha-N only system.

I just got the bike and started learning about this
stuff. So I apologize if these are stupid questions. I
did a search on long term fuel trim and didn't come up
with much.

By open loop I mean any time the ecu is not looking at
the O2 sensor. I would assume during closed loop the
ecu keeps track of how it modifies the injector pulse
width over time as compared to some default
value(factory). Then in open loop it uses this value
to tweek the pulse width??. Is this what long term
fuel trim is? This would make sense and it would allow
the ecu to account for say a freeing flowing exhaust
and/or big air kit without a new download.

I haven't purchased the Tuneboy/TuneEdit software yet
because it is $450. I want to understand this stuff a
little more before I spend that much. The tuneboy has
a "O2 related fuel trim" value which can be monitored.


Thanks,
Tim

--- Adam Wade <espresso_doppio at yahoo.com> wrote:
> --- Tim Marsteiner <tmarstei at yahoo.com> wrote:
> 
> > In a SAGEM (Alpha-N, I think) system
> 
> Whose SAGEM system?  I know of at least 3 motorcycle
> manufacturers using their ECUs, and two use speed
> density when alpha is small, and alpha-n when alpha
> is
> large; one uses straight alpha-n (Triumph used to
> use
> straight alpha-n, but I believe they changed to the
> dua system).  They all use different mapping
> strategies from each other.
> 
> > is the long term fuel trim used in the open loop
> > enrichment calculation?
> 
> I gather you are talking about use on an Aprilia or
> Triumph motorcycle?  And when you say "open-loop
> enrichment calculation", are you talking about
> trimming the whole map, or the accel shot?  AFAIK,
> the
> accel shot is not trimmed with either manufacturer's
> firmware.
> 
> The long-term fuel trim, which is set automatically
> by
> the ECU on Triumphs with an O2 sensor, is applied in
> all modes.  It's not adjustable by the end user
> unless
> you have some cool software; only the idle trim is
> adjustable with normally-available tools.
> 
> > Is it used for anything else?
> 
> AFAIK, it is not.
> 
> =====
> | Adam Wade                       1990 Kwak Zephyr
> 550 (Daphne) |
> | "It was like an emergency ward after a great
> catastrophe; it  |
> |   didn't matter what race or class the victims
> belonged to.   |
> |  They were all given the same miracle drug, which
> was coffee. |
> |   The catastrophe in this case, of course, was
> that the sun   |
> |     had come up again."                    -Kurt
> Vonnegut     |
> 
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