2020 Trade Shows are cancelled so let DYNOmite bring them to you...

Trade Show Update

10/28/2020

Trade Shows have been cancelled for 2020 and we are disappointed as you are. But in anticipation of this reality, we have been working hard to create a new-to-the-world virtual booth for our devoted Customers. You will hear more about this in the next weeks, but look for:

  1. Live streaming content with industry experts
  2. Demonstrations with service techs of our equipment
  3. Live chat with Sales and Service staff to discuss industry needs and innovations
  4. Watch as some of the most popular SuperFlow and DYNOMite products are being built
  5. the coolest opportunity the industry has ever experienced – YOUR chance to interact with our Innovation team to finalize versions of software and controls

DYNOmite views this year as an opportunity to engage with you in ways we haven't been able to in the past. Please visit our show page to register for additional information as it becomes available.

AFR Correction Formulas


Read about adjusting AFR Module readings for the effects of pressure and fuel type.

Advanced | 07.28.20

How do I pressure correct ECM AFR readings?

AFR Correction Formulas should be used to adjust your ECM AFR Module’s readings for various fuel types and pressure conditions.

Tip: If both Fuel Type Compensation and Pressure Compensation are required, apply Pressure Compensation first, then Fuel Type Compensation.

AFR Module Fuel Type Compensation

The standard AFR Module output is for gasoline (e.g. with a typical measured range of 8.0 to 18.0 AFR) with a fuel HC ratio of 1.85 and an OC ratio of zero. If a fuel of a different composition is used, the AFR measurement range will be different. The analog output formula and AFR measurement range for commonly used fuels are given in the formula and table below:

AFR corrected = [(2.368 x (m – 2p + 4)) / (m + 16p + 12)] x AFR measured

    where: AFR corrected is the AFR for the fuel of HC=m and OC=p composition.
               AFR measured is the AFR output by the AFR Module (i.e. 8.0 to 18.0 AFR).
               Valid for m > (2p – 4).

Fuel
Type
AFR Reading vs.
Output Voltage
Working Range
Methanol (race car “alcohol”)AFR = 0.888 x Vout + 3.553.55 to 7.99
Ethanol (grain alcohol)AFR = 1.236 x Vout + 4.944.94 to 11.12
M85AFR = 1.039 x Vout + 4.164.16 to 9.36
E85AFR = 1.340 x Vout + 5.365.36 to 12.06
Natural Gas (CH4)AFR = 2.366 x Vout + 9.469.46 to 21.29

AFR Module Pressure Compensation

All wide-range exhaust sensors have pressure sensitivity. Errors occur when the sensor is operated at pressure different from the pressure at which it was calibrated. Variations in the pressure can occur from changes in engine backpressure, weather, and altitude. While there is no error due to pressure under stoichiometric (lambda = 1) conditions, deviation increases the further from stoichiometric the engine is operated. Increases in pressure cause the sensor to read further from stoichiometric (i.e. when lean it reads leaner, when rich it reads richer).

For example, an increase in exhaust pressure of 127 mmHg above the calibration pressure (which would result from calibrating 1 mile above sea level and then driving down to sea level) would make a 12.65 AFR engine read 12.50 or a 16.77 AFR engine read 17.00.

Pressure Compensation for AFR:

AFR(corrected) = (AFR(measured) + B x P) / (1 + C x P)

    where: AFR (corrected) = the AFR corrected for exhaust pressure.
              AFR(measured) = the AFR output by the AFM.
              B = 0.009140 for AFR < 14.57 (rich).
              B = 0.012100 for AFR >= 14.57 (lean).
              C = 0.000627 for AFR < 14.57 (rich).
              C = 0.000830 for AFR >= 14.57 (lean).
              P = the exhaust pressure in mmHg above the pressure at which the sensor was calibrated (using the CAL POT on the AFM while the sensor is held in air).
               Valid for -152 mmHg < P < 532 mmHg.

Pressure Compensation for Lambda:

Lambda (corrected) = (Lambda (measured) + B x P) / (1 + B x P)

     where: Lambda (corrected) = the Lambda corrected for exhaust pressure.
               Lambda (measured) = the Lambda output by the AFM.
               B = 0.000627 for AFR < 1.0 (rich).
               B = 0.000830 for AFR >= 1.0 (lean).
               P = the exhaust pressure in mmHg above the pressure at which the sensor was calibrated (using the CAL POT on the AFM while the sensor is held in air).
               Valid for -152 mmHg < P < 532 mmHg.

Pressure Compensation Equation for %O2:

%O2 (corrected) = (%O2 (measured) / (1 + B x P)

    where: %O2 (corrected) = the %O2 corrected for exhaust pressure.
               %O2 (measured) = the %O2 output by the AFM.
               B = 0.000830
               P = the exhaust pressure in mmHg above the pressure at which the sensor was calibrated (using the CAL POT on the AFM while the sensor is held in air).
               Valid for -152 mmHg < P < 532 mmHg.

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