RE: [alfa] Re: alfa-digest V9 #1191

["Peter Webb" <webb.p@xxxxxxxxxxx>]

> The above is a completely different question than the one I
> answered.  What Clay
> was asking for was what to do with his new exhaust system using a standard
> computer to run the car and make emissions.  For that, I suggested using a
> heated NB sensor, since that is what the computer uses...  Since
> one is not
> tuning, and the computer can only read a basic O2 sensor, there is no real
> benefit to a WB for this.  And one can even make an argument that
> a WB might
> not even be as good considering where the computer even uses the
> O2 sensor (the
> synthetic switch from a WB is not as accurate as the real switch
> in a NB- our
> research and control system bears that out).
>
> On the other hand, if you are tuning, WB is the only way to go.
> It is all I use
> here at work.  And the units I have range from $2500-$5000
> depending on who
> made them.  Of course, for any use beyond making perfect
> emission, one does not
> need that kind of tools.
>
> If you buy any of the real WB systems, they would speed up the
> time to calibrate
> your SPICA system like you can not imagine.  And you will also
> find out how
> consistent the SPCIA pump really is- as I found out a few years ago...
>
> I would say go for it- I've got one that I bought from
> Austrailia, and it works
> well.
> or email "unsubscribe alfa" to majordomo@domain.elided

If Eric doesn't mind, to expand on this a little bit, and the source of the
debate last week...

NB02 is exactly what it's name implies.   The stoich voltages .485 to .515
is the entire span of the accurate AFR readings on a NB02.  We talked around
this last week but never got into details.

Voltages below that indicate lean and above that indicate rich but not a
true represntation of AFR in degrees.  That's the point I was trying to
make.   The oscilation is telling the stock ECU whether you're rich, lean or
stoich, basically a 3-position switch.   Stock ECU's expect this kind of
behavior, as Eric pointed out.  Now in an off-list discussion, I don't mean
to step on the toes of anyone who does ths professionally.  I don't think I
made the point I was trying to make.   I'm not talking about modern engine
controls here.   That's a far more complex subject with ignition, ion
sensing and the like.

The value of a WB02 is to obtain the true AFR number (lambda in EFI
geek-speak).   The controller will display the true AFR and still output a
0-1v reading for input to the ECU.  What I was getting at in that discussion
was the best of both worlds when you've modified your car and still use a
stock ECU.   The stock ECU, and we're talking in terms of a fuel-only L-Jet
here, can still use the output from the WB02 controller while the tuner can
get a true AFR reading.

The inherant difficulty with WB02 is calibration.   Each controller needs to
be calibrated to a specific sensor.  The most popular sensors are usually
covered, being the L1H1 (Honda) and the LSU4 (Bosch).   Both cheap(ish)
sensors.  There are some low-budget and kit based controllers out there from
Tech Edge and the DIY-WB, that derived from the original EFI332 project, the
predecessor to the MegaSquirt.   Bruce Bowling is about to release a
precision wideband controller in kit form that works with these low-buck
sensors.   He hasn't given a price point yet, but indicated it's under $100
for the controller itself.  This will be part of the upcoming
UltraMegaSquirt project that brings the MegaSquirt into the 21st century as
far as engine controls go.

Now, I wouldn't buy say a new VW or Honda and rip out the factory engine
control.   As Eric pointed out to me, there's far more to it than just
injector opening times and head temperatures.   If you had a more primitive
system like an L-Jet or early Motronic, EEC-IV, GM-ECM, it would be
worthwhile.   The UMS will support sequential injection.   The debate over
sequential rolls on whether it really buys you much.   I'll try and post
info on these projects as they are announced and released by B&G.  The PWC
(precision wideband controller) might be of interest to many here.
Apparently, the LSU4 sensors are available cheap from VW (~$50).  The L1H1
sensors are a bit more expensive, as anything Honda does.   I hear of people
grabbing them out of junkyards for short money though.

-Peter
--
to be removed from alfa, see /bin/digest-subs.cgi
or email "unsubscribe alfa" to majordomo@domain.elided