O2 sensor or knock sensor?

[h22a accord]

For arguements sake which sensor is used primarily to find out if you are running a higher or lower octane of fuel?

I would have thought it was the knock sensor because if you use a lower grade fuel in a car not designed for it, the engine will 'ping' and the knock sensor will hear this and send a signal back to the ecu to retard timing.


I nnow a guy that insists it is the O2 sensor that can tell what octane of fuel you are running in the car.

I always thought the O2 sensor determined the a/f ratio.

[JasonGilholme]

I would be leaning towards the 02 sensor. It would be able to see how well the fuel is being burnt in the chamber. Therefore changing the A/F ration accordinly.

I believe the knock sensor is there to prevent pinging and detonation, hopefully before it happens.

[Slow96GSR]

Remember different octane levels burn at different rates and temps. So really both will work in conjunction with each other and that will help the motor. The sensors really won't tell you what octane you are running, just if it's the right one for your motor.

[poid]

O2 sensor feedback is used mainly in closed loop to target an AFR of 14.7 with smallish adjustments, it cant distinguish what kind of fuel you are using (nor does it care).

The knock sensor also cant distinguish what octane fuel you are running, it just pulls timing if it hears knock. So if your car doesnt knock running unleaded for example, it wont knock on 98 and the knock sensor wont know the difference between the two fuels.

[h22a accord]

ok thanks guys,

[Limbo]

if possible get a wideband o2 sensor that will give you better fuel readngs.

You put it in place of your normal o2 sensor and you can tune the car whilst driving

[EfiOz]

As long as you have a programmable ECU.:rolleyes:

[JasonGilholme]

Sorry to hijack but if you change your OEM narrow-band O2 sensor to a wide band item wthout changing the ECU does it work?? Would it make the car run better because it can get a more accurate reading??

Thanks

[EfiOz]

No, the wildly different output would only confuse it. The standard lambda signal is a 0-1V range whereas most wideband controllers output a 0-5V output.

[JasonGilholme]

is that all?!?! wow...you learn somethin new every day.

So wide band O2 sensor = new programable ECU.

sweet. thanks

[barefootbonzai]

Wide band O2 sensor is only handy while tuning or just monitoring your car. I don't think it is used by the ecu for any sort real-time adjustments.

[EfiOz]

Real ECU's can and do use them for real time corrections.

[poid]

No, the wildly different output would only confuse it. The standard lambda signal is a 0-1V range whereas most wideband controllers output a 0-5V output.

many wideband units will output a narrowband 0-1v signal which can be fed to the stock ECU. So you can replace the stock O2 sensor with a wideband to view/record accurate AFR's while still allowing the ECU to use the 0-1v range for its closed loop operation.