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Bosch LSU 4.9 vs Bosch LSU ADV

The Bosch LSU ADV is arguably the successor to the popular Bosch LSU 4.9 and brings many minor upgrades such as; ~15% increase in Lambda accuracy, slightly higher maximum temperature tolerance, more optimized vents for better exhaust flow into and out of the sensor, smaller heater and lower thermal mass.

The biggest upgrade that the ADV sensor brings is that it does not require a calibration resistor for ~0.01 Lambda accuracy because the sensor is made precisely. The 4.9 is made less precisely than the ADV and each sensor is then tested and a bespoke lazer cut resistor is installed into the sensor connector that compensates for the imprecision of the manufacturing process, this allows the LSU 4.9 to achieve 0.01 Lambda accuracy.

A wideband controller measures very small currents into and out of the sensor pump cell to determine Lambda, typically the current is between -2.5 to 2.5 mA. That current is usually passed through a "sense" resistor to covert the pump current into voltage and then digitized using an Analog to Digital Converter. Because the LSU 4.9 has a calibration resistor, a sense resistance of exactly 61.9 ohms must be used, if not then you have to rely on free air calibration and lose the Bosch factory calibration. Since the LSU ADV does not require a calibration resistor you can use a much larger sense resistor and thus greatly increasing Lambda resolution while maintaining ~0.01 Lambda accuracy without any additional calibration.

When using a LSU 4.9 sensor with Spartan 3/Lite, the wideband controller will use a 61.9 ohm 0.1% tolerance sense resistor. When using a LSU ADV with Spartan 3/Lite, the wideband controller will use a 2k ohm 0.1% tolerance sense resistor, this means a 32x increase in pump current resolution which translates into a 20x increase in Lambda resolution. 

Spartan 3/Lite is the only wideband controller on the market that takes advantage of the LSU ADV's lack of calibration resistor to increase Lambda resolution.


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