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The mkiv Supra Owners Club

Wideband/Narrow band?


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The terms refer to the range of the sensor used for Air/Fuel ratio monitoring of the exhaust gases

 

Narrow band will typically be used for NA engines as the AF Ratio will be in a narrow band, e.g. between 14 and 16. The O2 sensor on all NA (and most turbo) cars will be a narrow band - The ECU uses the inputs from this sensor to adjust the duty and duration of the injectors (i.e. the amount of fuel they spit out on each cycle).

 

On the Supra TT for example, another method is used to adjust the fuelling while under boost - on the jap specs the Manifold Pressure sensor, on the UK spec the Mass Air Flow sensor. Instead of using the O2 input to adjust the fuel, it uses these sensors.

 

Now, as the owners of turbo cars we want one simple all-in-one gauge to measure the AF ratio in both conditions - off boost and on-boost. Thats where the wideband comes in. The sensor will have a range from around 9 to 18 which can then be reported on a gauge.

 

Ideally the car should be stoich (14.7) while on throttle and under no boost, and will quickly get richer as boost pressure and rpm increase. 11.7 in generally considered the most lean you can go under high boost and rpm.

 

Hope I got that right!

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Does it change from older style to vvti?

 

Good question. Very much doubt it though, I think the VVTI still uses a MAP sensor. Wideband sensors are expensive items so wouldn't be included unless absolutely necessary. Maybe someone with EPC can check the part numbers...

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