VANE AFR-807WB - Wide Band Air:Fuel Ratio

The AFR-807WB uses a true wide-band sensor which takes full advantage of the Bosch LSU dual cell oxygen sensor.  

The AFR807WB makes easy work of optimising the performance of an engine. An ideal diagnostic aid to fast tuning. Displays the Air / Fuel ratio and/or Lambda for petrol, alcohol, L.P.G. and diesel fuel. The easy-to-read display unit mounts on the windscreen or dashboard for road or Dyno testing.

OPTION

The AFR807WB can be optionally ordered with a zero to 5 volt analog AFR output which can be used to interface with various aftermarket engine management systems that require a wide band AFR input.

HOW DOES IT WORK ?

The AFR-807WB uses an oxygen sensor to determine the remaining oxygen level in the exhaust stream after combustion (excess air factor). The sensor is mounted in a sampling tube which is inserted into the vehicle's tailpipe. The sensor, being away from the exhaust manifold, is heated to ensure operating temperature is reached quickly and heating is maintained for the duration of the test. The signal voltage produced across the sensor is sent to the display head and is used to calculate and display the correct Air to Fuel ratio for the fuel type selected.

ABOUT THE LAMBDA SENSOR LSU

The wide-band lambda sensor LSU is a planar ZrO₂ dual cell limiting current sensor with integrated heater.  it is used to measure the oxygen content and the lambda value of engine exhaust gases.  Its output signal in the range of lambda=0.7 to air makes the LSU capable of being used as a universal sensor for lambda=1 measurement as well as for other lambda ranges.  The connector module carries a trimming resistor, which defines the characteristics of the sensor and is necessary for the sensor function.  The wide band sensor LSU operates only in conjunction with the special control unit.

HOW QUICKLY DOES IT READ ?

Since the sampling method is electronic, the display reading response is practically instant. The response time is governed by the distance the sensor is positioned away from the exhaust valves and the rate of exhaust gas flow, so under driving conditions when the exhaust flow is quicker, the display reading response will be also be quicker.

WHAT ABOUT CATALYTIC CONVERTERS ?

Catalytic converters thermally reduce harmful emissions present in the exhaust stream, namely Carbon Monoxide, Hydrocarbons and Oxides of Nitrogen (Nox). The oxygen content through the converter is used by the AFR-807WB to calculate the Air / Fuel Ratio. Older style AFR meters relied on the Co or Hc content to determine the Air / Fuel Ratio, and if those AFR meters are used on modern vehicles after the catalytic converter, they will display incorrect Air / Fuel Ratio readings. The AFR-807WB is accurate on vehicles with or without converters and before or after converters, as some of the of the gases change through the converter, but the Air / Fuel Ratio does not !

HOW LONG WILL THE SENSOR LAST ?

The amount of usage will govern the life of the sensor.  Leaded fuels will dramatically shorten the life expectancy of the sensor. On unleaded fuels the sensor should last for approximately 500 hours of testing but could be as short as 50 hours of testing on leaded fuels. The replacement oxygen sensor is easy to install by the operator and there is no expensive service calls required.

WHAT ADVANTAGE DOES THE AFR-807WB HAVE OVER A 4 GAS ANALYSER ?

In a word - SPEED.   Most gas analysers have a slow response time (6 -10 seconds). When testing for intermittent problems during load the operator wants to know what the problem is quickly and before any secondary damage occurs (example - detonation caused from the mixture being too lean under load). This condition is very apparent with new engines being tested for the first time. If a Gas Analyser is used the resulting damage may occur before the operator is advised due to the response time lag. Another use for this meter is to quickly analyse the mixture content at idle, cruise, wide open throttle, and deceleration modes, for whatever fuel type is selected. This can be achieved very quickly during a road test or Dynamometer test application.

A word about "Lambda"

Lambda is an industry standard value, which relates to the operating efficiency of the engine. A Lambda value of 1.00 indicates a running state with the ideal Air / Fuel ratio (no excess fuel or excess oxygen in the mixture). A lower Lambda value indicates a richer running condition (more power), and conversely a higher Lambda value indicates a leaner running condition (better economy). This chart shows the correlation of Lambda to Air / Fuel ratio, and is a useful tool when fine tuning.

Lambda to air : fuel ratio chart
Fuel	Diesel	Petrol	L.P.G.	Alcohol	Lambda
Power	10.90	11.00	11.60	4.80	0.75
Power	11.60	11.80	12.40	5.10	0.80
Power	12.30	12.50	13.20	5.40	0.85
Power	13.70	13.20	14.00	5.80	0.90
Power	13.80	14.00	14.70	6.10	.95
Emissions	14.50	14.70	15.50	6.40	1.00
Economy	15.20	15.40	16.30	6.70	1.05
Economy	16.00	16.20	17.10	7.00	1.10
Economy	16.70	16.90	17.80	7.40	1.15
Economy	17.40	17.60	18.60	7.70	1.20
Economy	18.10	18.40	19.40	8.00	1.25
Special Note re Petrol Engines: Fuel requirements vary according to the immediate operating conditions of the engine, ie a richer mixture will be required when the engine is under load than is required at cruise or idle. The specific fuel requirements must be found by experimentation. Turbo charged petrol engines require a richer mixture to help reduce exhaust temperatures.   Leaning the mixture out too far may cause thermal damage to the Turbocharger.

SENSOR INSTALLATION INSTRUCTIONS

The Lambda Sensor should be installed at a point which permits the measurement of a representative exhaust-gas mixture, and which does not exceed the maximum permissible temperature.  The sensor is screwed into a mating thread and tightened with 50 ... 60Nm.

• Install at a point where the gas is as hot as possible.
• Observe the maximum permissible temperatures.
• As far as possible, install the sensor vertically, whereby the electrical connections should point upwards.
• The sensor is not to be fitted near to the exhaust outlet so that it is not influenced by outside air.  The exhaust-gas passage opposite the sensor must be free of leaks in order to avoid the effects of leak-air.
•  Protect the sensor against condensation water.
• The sensor body must be ventilated from the outside in order to avoid overheating.
• The sensor is not to be painted, nor is wax to be applied or any other forms of treatment.  Only the recommended grease is to be used for lubricating the threads.
• The sensor receives the reference air through the connection cable.  This means that the connector must be clean and dry. Contact spray and anti-corrosion agents etc must not be used.
• The connection cable must not be soldered.  It must only be crimped, clamped or secured by screws.