wideband controller ALM – LSU4.9D

ALM (Accurate Lambda Meter) is an air-fuel-ratio (AFR) meter which uses the Bosch LSU4.9 wideband oxygen sensor and Bosch semiconductor chip CJ125 to accurately measure the AFR or lambda for variant combustion engines.

ALM-LSU4.9D is a version of ALM that uses the diesel version of Bosch wideband O2 sensor. LSU4.9D is pretty much same as LSU4.9 sensor internally, but has a different tube structure. The dual layer tube of the LSU4.9D gives more protection to the sensing element by keeping the soot out. Diesel engines generate a lot of soot compared to the gasoline engines, and the soot has multiple adversary effects to the sensor. It is vital for a wideband O2 sensor to be soot-proof in a diesel engine environment, especially if you are looking for sensor durability.

Here is a picture to show the difference of 3 Bosch LSU sensors: LSU4.2, LSU4.9, LSU4.9D.


As you can see, the LSU4.2 sensor has 6 big holes that gives no protection of the sensor from the soot. The LSU4.9 sensor has 12 smaller holes (plus the more sophisticated dual layer structure), which give better protection to the sensor. The LSU4.9D sensor has no holes directly connect the exhaust gas to the sensing element, therefore gives the maximum protection from the soot. Note: latest LSU4.2 sensors have adopted the LSU4.9 sensor outer tube structure. So you may not be able to tell the difference between 4.2 and 4.9 any more.

ALM-LSU4.9D was born for those diesel engine applications, especially for those engines that run for continuous operations and a long life time. If you are running a small diesel engine occasionally, and you don't mind to pull out the LSU4.9 sensor to clean the soot every few months, the LSU4.9 sensor is good enough for your diesel engine. If you want to install the sensor once and for all, and never want to worry about the soot accumulation on the sensor, you better choose the LSU4.9D.

ALM-LSU4.9D has different packages, similar to our gasoline version ALM. It has the below variants: ALM-LED with LSU4.9D; ALM-CAN with LSU4.9D; ALM-Board with LSU4.9D. Note, there is no ALM-gauge version of LSU4.9D. The regular gauges show AFR for gasoline and have the AFR range of 10-20 only. That does not apply to a diesel engine at all. Diesel engines run lean most of time and have a AFR like 100 easily. This is actually our ALM's advantage. ALM can measure the AFR or lambda to the infinity (free air). While many other wideband controllers need to use the free air to do calibration, ALM measures the free air. In other words, you can use ALM to calibrate those wideband controllers.

Again, all our ALMs have the high accuracy and fast response characteristics, which are the root of our design at the very beginning.

LSU4.9D and LSU4.9 share the same sensor core. All LSU4.9's advantages apply to LSU4.9D.

All our ALMs use the more advanced LSU4.9(D) sensor instead of a LSU4.2. LSU4.2 is still used by most other wideband controllers. LSU4.9 is the new generation wideband sensor. It is superior to LSU4.2. One obvious proof is: Bosch uses LSU4.9 across the board for their wideband applications. (See the appendix: LSU4.2 vs LSU4.9)

Click here to see why LSU 4.9 is superior to 4.2

Second, Bosch chip CJ125 is the integrated chip (IC) specifically designed for LSU 4.9/4.2 Sensors. Bosch's own wideband controller, "LambdaTronic", uses CJ125 driver chip. In fact, Bosch uses this chip wherever a LSU sensor is used. The CJ125 and LSU sensor are mated-pair by Bosch. Presumably LSU sensors work the best with CJ125 chips.

Together, LSU 4.9 and CJ125 make our ALM a more accurate lambda meter in the automotive aftermarket.

Click here for some news on customer applications
Click here to see a successful story of an OEM multi-fuel engine application

List of ALM-LED parts
Small ALM controller
built-in LED display (or other packages, contact us for details)
Harness (1.5 meter default, 3 meter optional)
Bosch LSU 4.9D sensor
Sensor plug and bung
Serial communication calbe
USB to serial converter (included)
Blue tooth for a Droid phone app (optional, not included, $50)
CD - documents and ALM GUI software

ALM technical specifications

Power supply
Input voltage range: DC 9V~15 V (12V Typical)
Input current: 50mA typical plus the heater current
Voltage protection : Reverse polarity protected, & overvoltage protected
Load Dump Clamp : Maximum voltage
Compatible: LSU4.9D
Number of Sensors: One
Free air calibration: No need (it measures the free air)
Lambda range: λ = 0.55 ~ ∞ (Gasoline AFR: 8.08 to free air)
Lambda accuracy: ±0.008 @ λ=1.00
±0.01 @ λ=0.80
±0.05 @ λ=1.70
Air/Fuel Ratio: Fuel dependent (see lambda range and accuracy)
Response time
5ms updating rate (everything finished in 5ms)
Control built-in PID control with CJ125
Current Typical 1A; Max 1.5A
Heater return (H-) Separate wire from Ground
Lambda analog output: 0~5V user programmable
Analog accuracy: ±0.005V error with a 10-bit DAC chip
Analog type: Reference ground to ECU
second Lambda analog output: 0~5V for a third party gauge, user programmable
advanced CAN bus communication (optional)
RS232 or USB (via an adaptor) for logging or programming
User-friendly PC software for data acquisitions and analysis
4 digit LED display
including 2 digit floating numbers
AFR, lambda, O2% configurable
CPU: FreeScale 16-bit micro-processor S12P (auto industry rated)
Speed: 32MHz
Memory: 128k Flash, 6k Ram, 4k Data
Load Dump Clamp
Maximum voltage
Special features
On-Board-Diagnosis and error report
Self-learning of part-to-part variations, aging effect
Working with different types of fuels (gasoline, diesel, E85, etc)
Temperature range: -45C ~ +125 C (can be installed in the engine compartment)
Dimensions: 4" x 2.6" x 1"

Appendix:LSU4.9 vs  LSU4.2

Characteristics LSU4.2 LSU4.9 Notes
lambda range lambda = 0.65 ~ ∞ lambda = 0.65 ~ ∞  
Accuracy only good at
lambda = 1 or moderate rich
accurate at
both rich and lean, wider range
LSU4.2 is only accuracy at lambda = 1 and moderate rich, between 0.8~1.0 lambda; LSU4.9 has better accuracy in both rich and lean conditions, suitable for gasoline, diesel, CNG, etc.
Response time Slower Faster Thinner sensing element of LSU 4.9 makes it more responsive to the AFR change, dynamically more accurate, and easier to light off, less heating power needed.
Heating power 10W 7.5W LSU4.2 has the off-centered-heater vs. LSU 4.9 has the centered-heater in the laminate; LSU4.9 has better heating efficiency, less heating power needed.
Free air
needed not needed LSU4.2 is susceptible to reference air contaminations, which is called CSD (characteristic shift down), requires frequent free-air calibrations. LSU4.9 uses reference pump current instead of reference air. No more CSD. No requirement of free-air calibrations
Nernst cell
resistance vs. temperature
80~750C 300~790C LSU4.9 has higher resolution of internal resistance vs. temperature characteristics, which makes the temperature measurement more accurate, and better heater control, therefore higher accuracy of lambda.
Light off time long short LSU4.9 lights off faster. Lambda controls can be active much faster during warm up phase.
Reliability   Improved reliability LSU4.9 is superior to LSU4.2 with regard to the reliability and life.
Check with Bosch Still selling it Recommended Bosch recommends LSU4.9 to all OEMs.
Bosch uses LSU4.9 for its own wideband controller.



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