By disconnecting the lambda sensor, fuel consumption will be (choose)

see title and poll.

front or rear?

Good point! Front.

I wonder if there are lambda sensors on the market which sense lambda=1.1 instead of lambda=1.0, as fuel consumption with lambda 1.1 will be lower (but there will be some slight power loss, as well).

Edit: I've found this measuring device which uses a wideband probe. What about removing the original (narrowband?) lambda probe, installing the wide band probe, and manually setting the desired Air-Fuel-Ratio, for example if one needs additional power, set it to "richer", if one wants to economise fuel, set it to "leaner". As the measuring instrument cannot be directly linked to the ECU, one would need a converter circuit. This could be done by feeding both the analog output of the measuring device (which ranges from 0 V to 5 V) and the user input (some voltage which could be provided by a potentiometer) to an electronic circuit (still to build). The electronic circuit compares the two voltages, and generates a statistical relationship of 200 mV (or 0 V, digital false) and 800 mV (or 1 V, digital true) - so if the user wants a richer mixture, turn the knob and the circuit will "trick" the ECU by generating 0V / 1V pulses with a statistical relationship in favour of 0 V or "too lean", if the user wants a leaner mixture the statistical relationship will be in favour of 1 V or "too rich". The statistical relationsship depends on both the analog output of the measuring device and the analog voltage provided by the user setting... and will be in favour or either 1 or 0 until the ECU changes the mixture accordingly. It the desired mixture is reached, the generated relatioship of 1 and 0 will then drop to fifty-fifty...

this might get more power out of the enging (best power) or save fuel (best economy). As the temperture indicator of my bravo always is in the really low range, I don't think I risk engine failure by overheating when leaning. What do you think?

Greetings,
Zardo

you can do that with a resistor to drop the voltage slightly

ok, didn't think of that
but actually, I want to burn less fuel... so a simple resistor wouldn't help...
but, hmm - one could drill an additional hole, plug in a second (narrowband) lambda probe, and connect the two probes in serial mode... so the two voltages will add up to 2 V max. - and then add the resistor (or a voltage divider) to get the maximum voltage into the allowed range...
this way, one could also "replace" an old lambda probe which won't provide normal voltage amplitudes anymore by simply adding a second old lambda probe in series... together, they will have enough power to reach 0,8 Volts again...

disconnecting lambda will equal engine toast

so what happens? if it saves fuel i'm gonna straight dc it now. if it don't i'm gonna get a new one as mine's 10 years running.

it wont overfuel enough to damage the engine, but your cat will get damaged if there is unburnt fuel in the exhaust gas.