[Diy_efi] long term fuel trim

Tim Marsteiner tmarstei at yahoo.com
Mon Jun 30 19:39:42 GMT 2003


> 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.


Do you have any good links to OBDII info? 


> 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.


How does one go about dialing in the ignition timing
advance? Just tweek until it knocks a bit then back it
off some for a reasonable margin?? Does this need to
be done on a dyno?


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


I believe it is reset by disconnecting the battery and
I’ve heard numbers like 50 miles or so for it to
“learn”...

 
> 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.


Yes, I know this. However, I’ve actually got this
comparator working with my narrow band sensor. I’ve
got it set with hysteresis to 0.75 V to trip low and
0.8 V to trip back high. I can see the output of the
O2 sensor is in fact indicating the bike is running
richer, very cool!! All of this is stationary testing
just sitting the garage though. This may be enough
“richening”. I'll get the wideband setup working,
collect some more data.

If I want to keep the narrow band sensor in place AND
monitor with the wideband, can I just lay the wideband
sensor up in the exhaust a few inches or does it
definitely need to be installed in a bung up near the
engine?

Thanks,
Tim

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