Wide Band O2 Question

olddog · #1 (**permalink**) 03-12-2010, 07:31 PM

I watched a video where the engine was off and cold. A wide band was in the exhaust with a gauge mounted in the car. The AFR was pegged at 19%, as the exhaust was full of air. Makes sense so far.

They started the engine and within 3 seconds it was reading. It was jumping around and they claimed fuel dopping out, at different cylinders, in the manifold, was the cause. This smoothed out as the engine warmed up.

Ok I know narrow band O2 sensors have to warm up, before they read. Can a wide band actually read instantly when cold?

I also read that the wide bands are slow to respond and that is why the factory uses narrow band sensor. This video claimed that it was fast enough to respond to different cylinders at a high idle. At 1200 rpm or 20 rev/second times 4 cylinder firing every rev, that is 80 bangs in a second. Just how fast can they respond?

RICK LAKE · #2 (**permalink**) 03-13-2010, 05:36 AM

Olddog If you have a heated o2 sensor the readings are almost perfect after 15 seconds of startup. Doesn't matter if it's a wide or norrow band sensor. If non heated, will take up to 5 minutes depending on location of the sensor and how cold it is out. Old sensor needed about 600f temp to start working correctly. The only problem is the sensor couldn't burn off the carbon verywell and the sensor become slow to respond. Wide band sensor are more for power adder motors because you need alot more fuel with a supercharger, turbo or NOS. The narrow ones are more for emmissions and fuel control. Trying to keep the motor running lean as possible and keeping the tail pipe clean also.
As far as respond to motor running, the one ones are so fast we have to use a snapshot to read the numbers from a scanner. They are as fast or slow as the speed of the computor they are hooked too. Rick L.

CobraV8 · #3 (**permalink**) 03-13-2010, 09:53 AM

Narrow band sensors will give a simple voltage signal output that shows if the AFR is rich or lean. They can't tell you what the exact air/fuel ratio is.

Wide band sensors basicly consist of a narrow band sensor that reads the AFR in a so called pump cell, where the inversed Nernst-effect is used to keep the AFR regulated stoichiomtric. The current that is required to keep AFR at 14.7:1 in this pump cell is proportional to the actual oxygen content in the exhaust gas. With this method the exact AFR can be measured.

Wide band sensors require a controller to operate. All wide band sensors are heated.

Simon