Connecting your eFlexPro harness to your aftermarket wideband w/0-5V output will allow you to datalog AFR/Lambda values and fine-tune your Ethanol fueling with our eFlexTuner software. This guide is intended for those with an aftermarket wideband already installed in your exhaust.
⚠️NOTE: These instructions apply to the AEM Wideband X-Series Wideband UEGO AFR Gauge kit Part # 30-0300 (Store link)
Other aftermarket wideband kits will likely have similar wiring processes. Refer to the wideband sensor manufacturer instructions on how to wire the 0-5V analog sensor wire output.
You must connect two analog wires from the AEM harness for correct readings:
- Connect the AEM WHITE wire (Analog +) to the eFlexPro white/grey analog input. You may use the wire already pinned in your eFlexPro harness, which will be white or grey.
- Connect the AEM BROWN wire (Analog -) to the same ground as your eFlexFuel ground point. If this ground is unavailable, use a good ground point as close as possible to the eFlex ground.
- Failure to connect the AEM Brown wire (analog ground / Analog -) will result in incorrect AFR readings.
eFlexTuner Software Settings
Many popular aftermarket wideband sensor parameters have been pre-saved into the eFlexTuner software as presets. There are two ways to access and set these presets:
- Click on “Tools” then “Settings” and select the “Sensors” tab
OR
- Right click on the “Analog in 1” gauge, then click on “Settings” and select the “Sensors” tab
⚠️IMPORTANT: After confirming the correct sensor, compare your physical sensor readings with the eFlexTuner gauge readings. If the physical gauge and eFlexTuner gauge do not match, perform the following:
- Confirm you have selected the exact correct gauge sensor in eFlexTuner. Different models may display differently, this is critical.
- Check to see if your physical gauge has a physical toggle switch. Some wideband gauges, such as the AEM Wideband Classic have a toggle switch that will alter their analog output. Refer to your wideband sensor manual for confirmation.
- Confirm the ground on the eFlexFuel harness and wideband sensor are as close to one another as possible - ideally, you will use the same ground point.
We recommend getting familiar with Lambda measurements if you aren’t already. Lambda is fuel agnostic when determining how lean/rich your air/fuel mixture is so is the ideal measurement for varying ethanol blends.
AFR Vs. Lambda Overview
AFR (Air-Fuel Ratio) and lambda are two different ways of measuring the air-fuel mixture in an engine. Here's a simple explanation of the key differences:
Air-Fuel Ratio (AFR)
AFR represents the mass ratio of air to fuel in the engine's combustion mixture. For gasoline, the stoichiometric (ideal) AFR is typically 14.7:1, meaning 14.7 parts air to 1 part fuel by mass. In oversimplified terms, AFR is calculated by multiplying the lambda output from your O2 sensor (O2, CO, CO2 and HC) by a fuel's stoichiometric AFR. AFR gauges are typically set by default to stoichiometric 14.7 for gasoline, thus the "actual AFRs" displayed are only accurate for gasoline. Since the stoichiometric AFR differs for all fuel types, this formula will change depending on fuel type.
Lambda
Lambda is another way to display air-fuel ratio but is simpler than AFR. Lambda is calculated directly from the output from your O2 sensor (O2, CO, CO2 and HC), without an additional formula based on fuel type. This means that lambda is a consistent measure of O2 sensor output and reliably reports the air fuel ratio regardless of ethanol %. A lambda value of 1.0 always indicates the stoichiometric mixture, regardless of the fuel type.
Key Differences
- Measurement scale:
- AFR uses absolute values that will differ by fuel type (e.g., 14.7:1 for gasoline)
- Lambda uses a relative scale where 1.0 is always stoichiometric
- Fuel compatibility:
- AFR values vary for different fuels
- Lambda values are consistent across fuel types
- Richness/leanness interpretation:
- For AFR, lower values indicate a richer mixture
- For lambda, values below 1.0 indicate a richer mixture, above 1.0 indicate a leaner mixture
- Calculations:
- Lambda is calculated from O2 sensor outputs (combinations of O2, CO, CO2, HC)
- AFR is calculated by multiplying O2 sensor outputs (combinations of O2, CO, CO2, HC) by a specific fuel's stoichiometric AFR.
- In other words, you can convert lambda to actual AFR by multiplying the lambda value by the fuel's stoich AFR. This is basically what your wideband gauge is doing!
Advantages of Lambda
- Consistency: Lambda provides a consistent scale across different fuel types, making it easier to compare and adjust mixtures.
- Simplicity: It's easier to calculate percentage changes from stoichiometric using lambda.
- Fuel flexibility: Lambda is particularly useful when working with varying ethanol blends.
While both AFR and lambda provide valuable information, many tuners prefer lambda for its simplicity and consistency when working with varying ethanol blends. Remember, normal gasoline is 0-10% Ethanol (AKA E0-E10) while E85 is 51-85% Ethanol, and you can run any mix of the two (E0-E85) with the eFlexPro kit installed.
See this Motortrend article for further reading on AFR Vs. Lambda: motortrend.com/how-to/1711-explained-the-difference-between-lambda-and-afr