EfiO2Meter Transfer Functions

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PWM Analog Output Data Transfer Functions

Sequential Analog data sampling rate = 1200 Hz, 0.83 ms ;

Since the analog channel data sampling get's processed in a serial, one after the other, sequence, the effective sampling rate depends on the repetition rate within the sequential sequence. The importand data channels, like the UA channel is getting sampled every 4th time, which relates to a 300 Hz, 3.33 ms rate.
It should also be mentioned that each channel is being digital filterered with different, channel data specific weights, causing the effective data rate to further be slowed down at the benefits of having more stable data available.
But even a data rate of 100 Hz, 10 ms is quite sufficient to the response time of the LSU 4.9 sensor and the CJ125 sensor control and signal processing.

Data Measurement Ranges

The efiO2Meter Data can be provided to the Analog Voltage Output in 5 different O2 value ranges with the reason for it being the data resolution and accuracy restrictions for general Analog Voltage Data Output (noise, linearity, etc ...),
It is desirable to have the range of interest spread over the available output voltage range.

The following Data Ranges are for the PWM Analog Output voltage signal on pin J2.5 and have been grouped into different use groups.

  • Lambda : idx 0, lambda 0.65 – 1.50, for spark ignited engines (gas, etc)
  • Lambda : idx 1, lambda 1.00 – 10.00, for self ignited engines (diesel)
  • AFR : idx 2, air fuel ratio 10.00 – 20.00, for spark ignited engines (gas, etc)
  • O2 % : idx 3, O2 percent 0.00 – 21.00, for self ignited engines (diesel)
  • Custom : idx 4, full range or part of 0.650 - 30.0 can translate to n0 - n1

Note : only the Custom option (idx 4) allows for individual range limit setting. Ranges with idx 0 to idx 3 have a fixed range as outlined above.

The PWM O2-Simulation voltage on pin J2.7 has a programmable range of Lambda 0.750 to 1.200

Voltage Output Ranges

The Voltage Range is programmable within it's limits.

  • Analog Out : min = 0 V, max = 5.0 V
  • O2 Simulation : min = 0 V, max = 1.65 V

PWM Analog Output Voltage Transfer Functions

Command LSUP [cj] [sel] [min] [max] provides the [min] / [max] PWM Out [sel = 0] Voltage for the [cj] sensor.

Command LSUD [cj] [sel] [dat0] [dat1] provides the [dat0] / [dat1] PWM Out [sel = 0] Lambda, O2%, etc for the [cj] sensor.
The LSUD command can only be applied to the Custom Range idx 4 selection.

default values :

min = 0 V, max = 5.0 V

  • Lambda : idx-0 : dat0 = 0.650, dat1 = 1.500
  • Lambda : idx-1 : dat0 = 1.000, dat1 = 10.000
  • AFR : idx-2 : dat0 = 0.650, dat1 = 1.500
  • O2 % : idx-3 : dat0 = 1.000, dat1 = 30.000
  • Custom : idx-4 : dat0 = 0.650, dat1 = 1.500

as individual formulas :

  x0  = Lambda - lam_dat0
  x1  = x0 * (vlt_max  - vlt_min)
  x2  = x1 / (lam_dat1 - lam_dat0)
 Volt = x2 +  vlt_min 
  x0    = Volt - vlt_min
  x1    = x0 * (lam_dat1 - lam_dat0)
  x2    = x1 / (vlt_max  - vlt_min)
 Lambda = x2 +  lam_dat0 

as one formula

 Volt = ((Lambda - lam_dat0) * (vlt_max  - vlt_min))
                             / (lam_dat1 - lam_dat0) + vlt_min 
 Lambda = ((Volt - vlt_min) * (lam_dat1 - lam_dat0))
                            / (vlt_max  - vlt_min ) + lam_dat0 

and the value limit check

 if	 (Volt < vlt_min) Volt = vlt_min
 else if (Volt > vlt_max) Volt = vlt_max 

The hardware provides a voltage output range of 0 V - 5.0 V

EfiO2Meter out.png


PWM O2 Simulation Voltage Transfer Functions

The same commands and formulas apply as for the PWM Analog Output, except the config values for [sel=1] are used.

default values :

min = 0 V, max = 0.950 V

Lambda : dat0 = 1.050, dat1 = 0.950

The hardware provides a voltage output range of 0 V - 1.6 V

EfiO2Meter sim.png


Analog Input Data Transfer Functions

The efiO2Meter has 2 analog inputs, whereas one of them is the Throttle Position Sensor voltage input and the other one EXTernal with a generic 0 V to 5.0 V input voltage. This EXT input can be used to measure the Manifold Absolute Pressure, Manifold Air FLow or whatever analog signal is desired for capture.

TPS Input Data Transfer Functions

Command ICAL [idx] [in0] [in1] [out0] [out1] provides the Voltage Input [in0] / [in1] point pair, which relates to the Percent Output [out0] / [out1] point pair. [idx = 0] selects the TPS Input.

The Tps Data Calibration or Transfer function is very similar to the ones for the PWM Voltage Output Functions. It's basically a 2 point calibration with limits.

as one formula

 TPS = ((Volt - vlt_in0) * (pct_out1 - pct_out0))
                         / (vlt_in1  - vlt_in0 ) + pct_out0 
 Volt = ((TPS - pct_out0) * (vlt_in1  - vlt_in0))
                          / (pct_out1 - pct_out0) + vlt_in0 

and the value limit check

 if	 (TPS <   0) TPS =   0
 else if (TPS > 100) TPS = 100 


EfiO2Meter tps.png


EXT Input Data Transfer Functions

The same commands and formulas apply as for the TPS Input, except the config values for [idx=1]

The EXT Input Data Transfer Function is a 2 point calibration without the value limit check

The [out0] / [out1] output pair can be any numerical value within +/- 32000 to fit a 16 bit signed data entity.

Having [out0] > [out1] will provide a falling output slope.

as one formula

 EXT = ((Volt - vlt_in0) * (dat_out1 - dat_out0))
                         / (vlt_in1  - vlt_in0 ) + dat_out0 
 Volt = ((EXT - dat_out0) * (vlt_in1  - vlt_in0))
                          / (dat_out1 - dat_out0) + vlt_in0 


EfiO2Meter ext.png



Note : All published design documentation is Copyright efiLabs.com and its use is without exception FOR NON COMMERCIAL PURPOSE ONLY. For commercial licenses contact efilabs.com ... try us, we're reasonable :)

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