30 lines
1.9 KiB
Markdown
30 lines
1.9 KiB
Markdown
# Speed Density
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Speed density is the most popular fuel control system employed but rusEFI users are present. This is due to its simplicity of tuning and it's suitability for turbocharged cars.
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It is due to this widespread use that it is the most well developed fuel control method and is the primary recommendation for fuel control at present (27/4/2020).
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## The detail
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Speed Density is probably the most popular algorithm since with knowing MAP calibration, CLT, IAT and TPS and injector flow rate we get a good enough tune without much difficulty.
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fuel_squirt_duration = injector_lag_curve_lookup(V_BATT) + warm_up_curve_lookup(COOLANT_TEMPERATURE) *(cylinder_displacement* VE_table_lookup(RPM, MAP) *MAP / GAS_R* charge_temp(COOLANT_TEMPERATURE, INTAKE_AIR_TEMP, TPS)) / target_afr_table_lookup(RPM, MAP) / injector_flow
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where:
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MAP is the average of multiple 10KHz ADC readings within specified camshaft angle range, value in kPa
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VE is intake volumetric efficiency coefficient
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GAS_R is gas constant
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[Speed Density calculation](http://rusefi.com/docs/html/speed__density_8cpp.html)
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[MAP sensor processing](http://rusefi.com/docs/html/map__averaging_8cpp.html)
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charge_temp (Tcharge) is charge temperature heuristic formula: Tcharge = CLT *(1 - Tcharge_coff) + IAT* Tcharge_coff
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Where Tcharge_coff is interpolated between 0.25 if RPMs are low or throttle is closed to 0.9 if RPMs are high and wide open throttle. See [http://rusefi.com/math/t_charge.html](http://rusefi.com/math/t_charge.html)
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[//]: # "ToDo: aware this needs more detail or cleaning up, hoping it will hold for now, happy for someone to add to the detail"
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## How to tune
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The Speed density strategy in rusEFI shares its basic tuning method with all other speed density systems in other aftermarket ECUs.
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If you are familiar with the tuning of another aftermarket ECU then it is likely the tuning of speed density on rusEFI will be very easy to get into.
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