not sure why I didn't think when Wessie had a moment on Thursday - some of the facts helping prove I'm not making things up - On a car forum today many owner's with the same car as her indoors, are just noticing theirs playing up with a misfire at low speed... I just gave this info for them,
The AFR (air fuel ratio - the weight of air to petrol) changes as you add more Ethanol, because
Petrol at lambda 1 (where its burning all the fuel in ideal conditions) needs an AFR of 14.7: 1
Ethanol joke fuel has an AFR of just 9.1: 1
Thus on vehicles that don't know what's going on, the more Ethanol you mix in your real Petrol the weaker the mixture, till it stumbles.
Later engine management systems attempt to take all this into account - ideally using Wideband CAT sensors that are AFR sensing - rather than earlier guess it if lucky lambda sensors.
When you have 10% Ethanol your engine needs to adapt to an AFR of 14.1: 1 (note now allowing up to 15% under the latest changes)
The effect of the the wrong AFR tends to be noticed under light loads / steady throttle conditions, because acceleration brings enrichment that combats the problem. And as WOT (wide open throttle) has never been a part of the emission Regs one should note many engines push things to 12.1: 1 as its not usually held there often, and it calms things down - reducing temps and resisting knock.
Unlike the cars, who've had it for at least 25 years. BMW Motorrad have not used wideband sensing nor MAP sensors. Instead allowing Ricardo with the LC bikes to keep Tantalum CAT sensors, allegedly as Ricardo think bikes and MAP sensors won't cope. A distinct view not shared by Honda and Ducati who use them successfully. BMW Motorrad mostly got away with it until Sept 2025 brought us Euro5+ And 2026 Model year bikes like the R1300GS now suffer an unpleasant surging on a steady throttle - the mostly unknown engine management update in March 2026 hasn't helped.
Benefits of tantalum-based sensors over earlier designs:
- Hysteresis-Free Sensing: Earlier switching sensors suffer from hysteresis (lag in readings), causing a delay in feedback to the engine computer. Tantalum arrays provide accurate, real-time data.
- Ultra-Fast Response Times: Tantalum thin-films exhibit extremely favorable hydride formation kinetics, which can achieve sub-second response times—vastly outpacing traditional, ceramic-based oxygen sensors.
- Massive Sensing Range: Standard zirconia sensors are effectively "narrow-band" (only switching efficiently between rich and lean mixtures around λ = 1), tantalum-alloy sensors provide a stable, linear read-out across a larger range of gas concentrations.
- Exceptional Stability & Toughness: Traditional lambda sensors are highly susceptible to "poisoning" from trace airborne compounds, silicone, and exhaust byproducts, leading to premature failure. Tantalum layers are mechanically robust and highly stable, maintaining structural integrity in harsh, high-temperature environments.
What we all need, Wideband O₂ Sensors and MAP Engine Management:
Wideband O₂ sensors and Manifold Absolute Pressure (MAP) sensing form the core of active, closed-loop engine management. They allow an Engine Control Unit (ECU) to dynamically calculate air density and adjust fueling in real-time. In contrast, tantalum "catalytic sensor technology" is an advanced materials concept primarily used for detecting trace hydrogen in materials science, fiber-optics, or as capacitors in ECU circuit boards—not for measuring automotive exhaust
- How it Works: The MAP sensor measures manifold vacuum/pressure to calculate engine load, while the wideband O₂ sensor measures unburned oxygen in the exhaust to output a precise, linear Air-Fuel Ratio (AFR).
- Purpose: The ECU uses this data to map exactly how much fuel and ignition timing the engine needs at any given load point. Widebands allow for closed-loop tuning for optimal performance and efficiency, handling AFRs from 6:1 to beyond 20:1.
