Why the O2 circuit was created and how

lolachampcar

EFIDude started off several years back to develop fully programmable replacement fuel controls for a myriad of different applications. The center point of the effort was the melding of fuel/ignition control with a data acquisition system to provide the user a powerful and friendly tuning environment. A large part of the requirement was the need for a wide band O2 sensor system that provided quality control data along with the normal Lambda or Air/Fuel ratio output.

There are a bunch of lambda meters out there that will tell you what mixture is at any given point but none will tell you if the data is accurate. Exhaust gas transients will pull the control loops off target and the only way to know this has happened is to record loop feedback values. Having that type of quality control data in addition to the mixture values is necessary when relying upon the data to make mapping adjustments. There were no such systems available and thus the engineers at EFIDude created their own based on the very popular Bosch LSU-4.2 wide band lambda snesor used in most of the European cars from Porsche to Audi to VW.

The result was a simple and robust Bosch LSU-4.2 lambda driver circuit that is fast enough to handle transients in exhaust gases while providing quality control data. This data consists of the desired and actual Nernst AC (used to ensure the heater control loop is on target) and the Nernst DC values. The circuit is quick enough to provide well in excess of ten samples a second for data recording.

The circuit itself consists of a core microprocessor, one quad operational amplifier, and instrument grade differential amplifier, a FET for turning on the heater and a handful of passive components. The microprocessor is a small eight pin device which uses a single wire interface to the outside world. The control microprocessor can also be reprogrammed in circuit if necessary. Together, the system can be implemented in anything from a stand alone wide band O2 gage all the way to inclusion in an existing fuel control or data acquisition system. It is scalable in that eight or twelve can be combined on a simple printed circuit board to support cylinder by cylinder mixture evaluation.

EFIDude offers this design for licensed inclusion in our customer’s products. The circuit can be evaluated using the stand alone fuel control as all quality control values are logged as part of the data acquisition set with over 100 hours of capacity. Schematics and estimated bill of material costs are available upon request. Please contact EFIDude for more information.

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