O2 Sensors – Engine Performance from a Capsule

O2 Sensors – Engine Performance from a Capsule

Long gone are the days when car engine were simply using 4, 6 or 8 pistons, a carburetor and a few other auxiliary elements in order to make the vehicle move forward. While, from a mechanic’s point of view, such powertrain units were simpler and easier to fix or upgrade, they featured a big downside: efficiency.

More efficient thermal engines needed a way to create a better mixture of fuel and air and make use of better motion delivering mechanisms, all to generate a bigger power output. While various materials have replaced iron in engine construction to ensure a higher degree of kinematic movement, to enhance air and fuel mixture, you would first need to figure out how much of each product gets mixed within the cylinder.

Obviously you can’t just section a running engine in half to check it out; this is how the need of O2 sensors was created.

Where and how does it work?

In case you are wondering, yes, your car is most likely to have at least one oxygen sensor mounted right at the end of the exhaust manifold. It’s just one of the dozen sensors modern cars use in order to increase efficiency and power output; after all, that’s what all is about: getting more and more of it.

If the term O2 sensor or oxygen sensor doesn’t sound familiar to you, it may be because this very same capsule with a wire at the end is also called a lambda sensor.

Does that ring any bells?

The placement of the O2 sensor on the exhaust manifold isn’t random; in fact, that is the best place to create a precise estimate on how much oxygen actually gets used in the air-gas mixture happening inside the cylinders. There are two main cases:

  1. Too much oxygen

When there’s too much oxygen used while mixing air and fuel, we are calling it a lean mixture. What happens is that during the mix, the air to fuel ratio (AFR) exceeds its preset value. To create a better picture, a regular gasoline engine works at an AFR of about 14.7:1. This means that for every part of gasoline, 14.7 parts of air should be used to attain an efficient combustion. If more oxygen gets through, peak pressure inside the cylinder increases and by default, chances of knock increase. When a cylinder knocks, it can basically create a rotational force that opposes the one generated by the crankshaft, generating severe consequences.



  1. To little oxygen

We’ve found out that too much oxygen is definitely not as good as it may have been initially presumed. However, the other extreme isn’t promising. A low oxygen level within the mixture (an AFR below 14.7:1) won’t allow the entire amount of fuel to be burnt, and thus generate an efficient combustion process. This is called a rich mixture. The immediate result is a considerable increase in fuel consumption; those injectors are pumping more fuel than the available oxygen is able to aid burning.

An oxygen sensor constantly monitors the amount of oxygen output traveling through the exhaust manifold, then sends the acquired data to an Electronic Control Unit (basically a computer for the vehicle) which then adjust the amount of fuel being pushed through injectors into the combustion chamber. Since it’s purely electrical, an oxygen sensor varies its electrical input in order to feed data to the ECU: 0.9V for rich and 0.1V for lean mixtures.

What is it made of?

The probe itself features a ceramic cylinder with platinum electrodes plating both on the inside and on the outside. On top, a metal gauze protects the whole system, like a capsule. It is important to know that oxygen sensors only work effectively while heated at about 600 F (or 316 C). That is the reason why modern sensors also feature heating elements added to the ceramic cylinder, speeding up the heating process. Unlike them, older sensors based solely on the exhaust gas heat to warm up.

Oxygen sensor failures

The best indicative for the wellbeing of an oxygen sensor is the way your vehicle performs. A lower overall performance may be caused by a faulty oxygen sensor, but it isn’t always the case. First of all, it is perfectly normal for a vehicle to exhibit lower performance when cold started. It takes a while for the lambda probe to heat up; until then, since it gets no input from the sensor, the Electronic Control Unit of the vehicle will supply a preset amount of fuel, usually a little above the normal Air to Fuel Ratio.

Electronic Control Units also consider input data from engine coolant sensors when “deciding” how much fuel to inject into combustion chambers; this is why a faulty coolant sensor indicating a higher temperature will cause the ECU to push less fuel through injectors.

If your vehicle traveled more than 100,000 miles, then find out that this equals to the average lifespan of a heated lambda probe. Although you may not feel any serious downshifts in performance, it may actually be a good idea to replace your car’s oxygen sensor with a new one, maybe even opt for a premium product.


Premium Oxygen Sensors

Is there an actual reason you should switch to premium sensors or it’s just a new marketing stunt? The truth is, yes, your car can benefit from having a premium oxygen sensor installed. Considering the fact that premium quality sensors are built with higher grade technology and come with various prerequisites such as coated threads with anti-seize compound, fuel efficiency and power output of your vehicle may shift from good to better.

Although premium sensors are mostly after-market products, they are built by the same brands employed by major automakers to develop OEM parts. It is, however, important to check full compatibility with your vehicle before acquiring a new oxygen sensor.



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