Wideband lambda meters
Overview
Many performance engine builders and tuners have discovered the benefits of using the wideband oxygen sensor technology to monitor air/fuel ratios. Being able to evaluate the actual air/fuel ratio at any given instant in time allows the fuel mixture to be fine-tuned and adjusted online, something which previously could only be done on a dynamometer using expensive equipment.
The lambda meter is used to measure the Air Fuel Ratio (AFR) or Lambda on internal combustion engines. It can be installed on naturally-aspirated, turbocharged and Diesel engines. It is used to measure oxygen contents and the lambda value of exhaust gases in the range 0.80 to 1.10. The lambda ratio refers to the proportion of air and fuel present during combustion. The chemically optimal point at which this happens is the stoichiometric ratio (lambda=1.0). It is the ratio that modern fuel injection systems try to reach. A mixture with lambda less than 1 is called rich, while a mixture higher than 1 is called lean. Optimum horsepower is achieved at around 0.90 on aspirated engines, and 0.85 on supercharged engines. The Ontronic wideband lambda meter has been especially designed for automotive racing, where lambda values are typically in the rich side (lambda < 1).
The lambda value is displayed using a colorized led bar, so that reading and interpretation is straightforward. The first led on the left side corresponds to a lean mixture (from 1.10), while the last led on the right side corresponds to a rich mixture (up to 0.80). Development efforts have focused on accuracy and ergonomy. The led display has proved to be more convenient than digital display, especially if the meter is mounted in the engine compartment or under the dash.
The research and development efforts have focused on accuracy and ergonomy. The led display has proved to be more convenient than digital display, especially if the meter is mounted in the engine compartment or under the dash. Digital displays and data acquisition are addressed using the integrated Ontronic Electronic Fuel Injection (EFI) systems.
Technical aspects
The lambda meter is compatible with the Bosch LSU 4.2 wideband, 5 wire oxygen sensors.
This wide-band sensor uses a dual sensing element that combines the potentiometric cell (Nernst effect) in the planar design with an additional oxygen pumping cell and diffusion gap on the same strip of ceramic. The result is a sensor element that can precisely measure air fuel ratios from very rich to extremely lean (straight air). Like a zirconium thimble or planar-type sensor, the wide-band sensor produces a low-voltage signal when the air/fuel ratio goes lean, and a high-voltage signal when the mixture is rich. But instead of switching abruptly, it produces a gradual change in the voltage that increases or decreases in proportion to the relative richness or leanness of the air/fuel ratio.
Lambda to AFR conversion table
| Lambda | AFR Gasoline | AFR LPG | AFR Diesel | AFR Mehanol |
|---|---|---|---|---|
| 1.10 | 16.17 | 17.05 | 15.95 | 7.04 |
| 1.08 | 15.87 | 16.74 | 15.66 | 6.91 |
| 1.06 | 15.58 | 16.43 | 15.37 | 6.78 |
| 1.04 | 15.29 | 16.12 | 15.08 | 6.66 |
| 1.02 | 14.99 | 15.81 | 14.79 | 6.53 |
| 1.00 | 14.70 | 15.50 | 14.50 | 6.40 |
| 0.98 | 14.40 | 15.19 | 14.21 | 6.27 |
| 0.96 | 14.11 | 14.88 | 13.92 | 6.14 |
| 0.94 | 13.82 | 14.57 | 13.63 | 6.02 |
| 0.92 | 13.52 | 14.26 | 13.34 | 5.89 |
| 0.90 | 13.23 | 13.95 | 13.05 | 5.76 |
| 0.88 | 12.93 | 13.64 | 12.76 | 5.63 |
| 0.86 | 12.64 | 13.33 | 12.47 | 5.51 |
| 0.84 | 12.35 | 13.02 | 12.18 | 5.38 |
| 0.82 | 12.05 | 12.71 | 11.89 | 5.25 |
| 0.80 | 11.76 | 12.40 | 11.60 | 5.12 |
Sensor heatup
The meter includes a heater controller, so that the temperature of the sensor is kept at nominal operating temperature for accurate measurement, and to reduce thermal stress during the heat up phase. The transducer includes a special filter to increase measurement stability. The sensor takes about 20 seconds to reach operating temperature.
Installation and setup
The Ontronic lambda meters are robust aluminum device. Installation of the device is easy. The kit includes the meter, a Bosch wide-band
oxygen sensor, the cables, exhaust bung and plug, manual and a fixation system.
There are two plugs to connect:
- LSU connector: standard sensor connector (Bosch)
- Power supply: +12V (brown wire) and ground (white wire) to be connected to the engine power supply or to a cigarette-lighter adapter
To achieve maximum precision, the device is pre-calibrated at the factory. Due to the long term stability of the sensor, there is therefore no need to recalibrate it.
Technical data
- Function with a variety of fuels, including leaded or unleaded gasoline, diesel, methanol, and natural gas
- Display range from 0.80 to 1.10 lambda
- Very short response time (<50 ms)
- Can work as a stand-alone unit or can be coupled to the ECU
- Accurate to +/- 1.5%
- Improved display stability and readability
- Small size (4.7” by 2” by 1”) and low weight (200 g)
- Unobtrusive and easy to mount.
For more information, please refer to the user manual (see below).