ner: You accidently posted an incorrect picture... the wideband pic you posted was the current pump slope... not the wideband voltage out put slope... here's the output of the techedge.com.au unit, this is the type of pic ner meant to show:



But back to the topic at hand:

The first thing you have to bear in mind is that there are different ways of tunning your fuel system:

1.) Some (most) people here are running rising rate fuel pressure regulators, as Avenger rightly points out with a rrfpr you CAN be running rich at some points and lean at others... and still be putting out black smoke at times... does not mean you are safelly rich, and does not mean you are lean... without a true wideband you cannot be sure!
2.) Others here are running programable fuel systems of one kind or another, with these systems you CAN tune your car to be safelly rich... but again this does not mean you will or will not emmit black smoke... CAMS and other things have a lot to do with this... Boost level and airflow for instance... think about it, the more air moving through the system, the more there is a chance some fuel could go right out the exhaust...

Now one thing that is true is that it's not good to be throwing fuel out the exhaust when you are not on boost or when you are at idle... this is usually a sign of being too rich, but again only at that point in time...

So to sum this up, if you dont have access to a wideband, then play it safe on both the boost levels and on the fuel side... run rich if you can until you can get a wideband... And don't trust that narrow band!

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Megasquirt powered 420A
Custom turbo system

http://www.ms-custom.com