Spotlight on DENSO’s unique A/F Technology

As the most significant range extension of lambda sensors to date is launched, DENSO takes a closer look at its unique A/F technology, designed to offer distinct advantages to the aftermarket.

High profile applications

As one of the most respected and prolific OE suppliers to vehicle manufacturers worldwide, DENSO’s new Lambda Sensors range extension offers the independent aftermarket several advantages. The latest expansion consists of 30 new products, most of them based on advanced A/F Technology. This technology is exclusively produced by DENSO, and therefore offers unique properties that cannot be reproduced by other manufacturers. Replacement prices of such sophisticated sensors are also relatively high, meaning the new range extension offers customers a cost-effective solution. Not only that, but with the average vehicle age of each sensor being relatively low, this enables many years of potential sales ahead.

Customised design solutions

Unlike regular switching lambda sensors, the A/F sensor accurately detects the exact concentration of oxygen in the exhaust gasses. Within milliseconds, the engine control unit receives a linear sensor signal so that the proper adjustments can be taken. Alongside accuracy and detection speed, a fast light-off time (which is the time it takes to operate reliably after a cold start, to bring the engine management in closed loop control) and sensor durability are the four most important design requirements. A/F sensor technology is the best option available to combine these requirements.

Air/Fuel technology is exclusively produced by DENSO, and offers unique properties that cannot be reproduced by other manufacturers

Based on A/F technology, DENSO has developed a wide variety of design solutions to optimise the sensor for each application. No other lambda sensor manufacturer offers more tailor-made design solutions to OEM customers. This is clearly visible from the outside: whereas competitors produce a limited number of different sensor core designs that a vehicle manufacturer can choose from, DENSO provides a wide range of sensor designs. For each OEM project, DENSO listens to specific customer demands and actively develops each design in order to meet specific application requirements.

This type of design optimisation is not solely limited to the geometry of the sensor core. In addition, many different components are customised internally to meet specific customer requests.

Durability and versatility

Due to the harsh environment in which the sensor has to operate, the risk of premature failure is always present. In particular, element contamination (e.g. carbon soot deposit) and thermal shock of condensed water vapour are common failure causes.

In the event of contamination – which is likely to develop gradually over time - the sensor response time will slow down. This forces the ECU to over-compensate by injecting more fuel, consequently increasing fuel consumption.

In contrast, thermal shock will cause an immediate failure. The phenomenon is comparable to taking a fragile plate out of a heated oven, and placing an ice-cube on it. The sudden local cool down will create shrinkage. The internal stress is too large for the material to handle, therefore it will crack. Thermal chock will usually happen during cold starts, when many tiny water droplets will collide on the heating element.

In general, the protective covers over the element are designed to avoid the thermal shock. Their basic function is to separate water droplets from exhaust gas, and at the same time keep the element exposed to that gas with minimum restrictions.

To avoid sensor contamination, the ceramic material has been treated with multiple layers of - among others - aluminium oxide. These coatings allow oxygen ions to pass through, but avoid attachment of any substances.

Different design variations are engineered for specific exhaust configurations. Below are a few examples of exhaust properties that are influencing the sensor design:

Distance from the combustion chamber
The diameter and presence of bends in the pipe
The orientation of installation (upwards, downwards, horizontally)
Operating temperatures
Gas flow rates

DENSO’s Aftermarket range: Uncompromising quality

In contrast with some competitors in the market, DENSO always ensures that its aftermarket products meet the exact same technical specifications as the original DENSO product. Consequently, DENSO does not mix different sensor designs and specifications in favour of a smaller consolidated range. This is clearly visible when comparing the sensor core designs; it is obvious that the same heat shields are attached and that the ‘nose’ of the original sensor corresponds in terms of an identical ventilation hole pattern. The same applies for the internal components – different specifications are never mixed. This way, each DENSO sensor product is guaranteed to be similar in terms of quality, performance, reliability and fitment.

A/F technology: Did you know?

A/F means ‘Air-Fuel’. It refers to the mixture composition control that is required for powerful, smooth and clean engine performance
A/F sensors are also referred to as wideband or linear sensors
A/F sensors are not compatible to other linear sensors (usually 5-wire) or other 4-wire sensors
The evolution of A/F Sensors has already reached its 5^th generation
The latest A/F sensors can detect even a single misfire. Even more impressively, based on the sensor output, the ECU can recognise which cylinder was involved, even though all cylinders share a common exhaust manifold
The light-off time is the most important contribution to meet tightened emission standards
A/F sensors can offer a light-off time of less than 10 seconds
A/F sensors are also used on diesel engines