[Diy_efi] long term fuel trim

[Adam Wade]

--- Tim Marsteiner <tmarstei at yahoo.com> wrote:

> This is on an Excelsior Henderson Super X.

Didn't know they had used the SAGEM.  Thanks for the
data point.

For your reference, the other makes I know of that use
the SAGEMs are Triumph, Cannondale, and Aprilia.

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

If there are no pressure sensors on the intake system,
it would have to be.  I am assuming it doesn't have a
MAF sensor, as those are exceedingly rare on
motorcycles.  Twins and big singles tend to work
better with alpha-n, all other things being equal.

> I just got the bike and started learning about this
> stuff. So I apologize if these are stupid questions.

Not at all.  There is a great deal of
complexity/diversity in how ECUs are used by various
manufacturers.

I can't say for sure that the long-term trim is used
for open-loop on the E-H, but it would make a great
deal of sense to use it that way.  I am tending to
think that they are likely to have borrowed a lot of
the code/strategy from Triumph, who has the longest
history of using the SAGEM ECU (which is now actually
owned by Johnson Controls, but most people still refer
to it as the SAGEM line).

> I did a search on long term fuel trim and didn't
> come up with much.

With how short a time the E-H lasted, I'm surprised
you came up with anything at all.  :D

> 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??.

That is how Triumph does it (and I think Aprilia does
it this was as well on some models, but I am not
certain).  It's the sensible way to gather and use
such data.

> it would allow the ecu to account for say a freeing
> flowing exhaust and/or big air kit without a new
> download.

It would allow it to do BETTER with those changes than
a full open-loop system, but it won't eliminate the
"need" for a change in mapping based on exhaust and
intake changes.  If you don't change anything inside
the engine, then it should do a pretty good job,
within the limits of its range of adjustment.  Keep in
mind too that alpha-n can have the same alpha and
engine rpm under some pretty different conditions, and
thus the "learned" trim won't be as good at improving
fueling accuracy as a fresh map would.

If they are borrowing most or all of the code from
Aprilia and/or Triumph, then there is probably a way
to flash-remap the ECU.  I would contact Wayne
MacDonald, who created TuneBoy for the Triumphs and
Aprilias, to see if his software and cable can be
adapted for the E-H. 
http://members.optushome.com.au/wmcdonal/

> I haven't purchased the Tuneboy/TuneEdit software
> yet because it is $450.

Ouch!  I don't see on his website where it claims to
gain access to the E-H system.  However, for a single
bike, the TuneEdit is $150 per bike, and the TuneBoy
cable and software is $150.  Maybe you are not using
$US?

> The tuneboy has a "O2 related fuel trim" value which
> can be monitored.

Ideally, you should see almost no trim dialed in
there.  If you are seeing bigger trim numbers, then
chances are good you could benefit from a custom flash
tune.  It may not make better power with a flash tune,
but you are likely to find that throttle transitions
are smoother, especially switching between cloed- and
open-loop (like roll-on after being at cruise).  One
very important thing to attend to before playing with
the maps is that the SAGEM-based alpha-n systems (and
indeed, most alpha-n systems) are very sensitive to
TPS calibration.  If you find a similar bike to yours
that has a custom tune, you can load it, but make sure
your TPS is calibrated the same as the bike you got
the tune from, or I can almost guarantee you will have
problems at or near closed throttle.

=====
| 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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