[Diy_efi] long term fuel trim

[Adam Wade]

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

> Supposedly this is the same ecu as the Triumph and
> there is EH specific Tuneboy software that does
> allow remapping, but it is expensive at $425.

Is this from Wayne MacDonald, or someone else?  There
was nothing on his website about it (he write the
original Triumph version).

I don't know how you are with hacking and playing
around with things like that, but I know that Triumph
uses a regular OBD II interface, and of course has
custom codes/tags that allow the extra "features" like
reflashing the ECU, but all of it conforms to the OBD
II handshaking routines and data protocol.  If you had
a spare ECU and didn't mind spending some time, you
could probably figure out how to alter the flash
mapping in the same way the Tune Edit and TuneBoy do.

> I am going to try some cheaper options first. The
> first thing to do is gather some wideband O2 data
> so I've ordered all the stuff for the DIY-WB kit so
> I can monitor what the ecu is doing.

Do keep in mind that there is no "perfect" target for
O2 when mapping, unless you are mapping for emissions
with a catcon.  While best power will always be rich
of stoich, how FAR rich of stoich will give best power
tends to vary.  WBO2 information can get you very
close in many situations, and will definitely show you
any significant trouble spots.

> Most guys are saying the Super X is running really
> lean from the factory.

That would not surprise me.  The whole point of going
to EFI on bikes was to meet emissions requirements
while keeping drivability from going in the toilet. 
Most of the systems out there are amazingly primitive
in both mapping strategy and operation, and can
generally be improved upon for drivability and power.

> I get a lot of pop on decel and it runs very hot
> compared to my yamaha roadstar. There are reports of
> burned exhaust valves...

Yikes.  Does it have hydraulic lifters?  Staying on
top of valve adjustments (if it does not) will do a
long way toward preventing burned ex valves.

Richening things, or retarding the timing, will both
cool down the burn a bit, but richening will tend to
slow the burn as well, which is something to keep in
mind.  Everything ends up being a compromise somewhere
along the line, and it's a matter of finding the best
compromise for your purposes.

> My first plan is to replace the narrow band O2
> sensor with a wideband. I have bread boarded a
> comparator circuit which will create a narrow
> band "toggle" waveform from the DIY-WB voltage
> output.

That was going to be my suggestion, but you beat me to
it.  ;)

One thing to keep in mind is that O2 sensors
(especially WBO2 sensors) are like spark plugs in that
the longer you use them, the less life they have
remaining.  I would recommend you do what top-level
professional race teams tend to do, which is to
install the WBO2 for data-gathering, and then remove
it and store it away until you need more baseline
data.  Leaving it in the exhaust stream when you're
not using its capabilities is a waste of the sensor's
lifespan.

> I can set the "toggle" voltage of the comparator to
> any value. I believe this will effectively allow me
> to fool the ecu by controlling the long term fuel
> trim.

That's an interesting idea.  Have you been able to
find any data on how long it takes to "learn" a trim?

The only drawback I see is that you'd pretty much need
to keep the WBO2 in there all the time, or eventually
the ECU would "unlearn" the trim after you reinstalled
the original O2 sensor.

> Somebody must have already done this
> with a car. Anything to look out for?

Well, aside for the fact that the only reason stoich
is used in cruise is to run the cat, and is not ideal
for economy OR power, I don't see anything significant
to be concerned about, except that your cat will
eventually stop functioning properly (if it is on the
bike at all any more).  Cars have tended to get away
from the "add-on box" mentality, and have gone with
flash loads, new chips, or replacement ECUs, by and
large.

> I know the real fix is to get the tuneboy and do
> some dyno tuning and tune to each point in the fuel
> map.

Dyno tuning with an exhaust analyzer is definitely the
best approach.  You can find out what the actual O2
targets should be for best power at various throttle
openings and engine rpms, and then you will have a
baseline that WILL be truly useful to you.

> BTW there is no maf sensor on the super X.

I was pretty sure there wasn't.  ;)  Bike engines and
their throttle and plenum layouts don't lend
themselves to the use of a MAF, plus there is a size,
space issue with them, as well as the cost.  I think
BMW uses them in a few models, but almost everyone
else is either straight alpha-n (which is being phased
out due to emissions and drivability concerns), and
speed-density at small alpha (for good drivability and
emissions with small throttle openings) and alpha-n at
large alpha.

=====
| 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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