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Input variables where Inj_out is dependant of...
As my car will be running on Vapourised LPG injection my Inj_output timing will be dependant of Fuelpressure and Fueltemperature. I already have a sensor mounted that's able to collect these values Bosch 0 281 002 576.
Connect the signal to free ADC inputs - mcp3208. Check the shop text for free inputs. Apparently
- EC18pin12 available ADC because secondary_trigger: HALL
- EC18pin6 available ADC because onboard MAP
- injection pulsewidth calculation
- do some research for the formulas. Make tables and examples (octave,matlab, spreadsheet?). You can try to make final functions using +,*,table_lookup operations. Division only with power of 2 (/2, /4, /8... /256, /512 ...)
- I guess the fuel pulsewidth needs a *1/sqrt(fuel_pressure) multiplier (we'll likely use a table for sqrt() for speed.
- I have no idea how the fuel temperature will be used. Most likely another table_lookup for viscosity ? ( --- I don't think viscosity of a gas varies much with temperature. Density does , by universal gas laws ; multiply calculated fuel amount by T/Tref - both in degrees K - to correct for that.)
When the plan is ready, we'll add to the firmware and make it possible to enable it in config.
LPG needs some extra analog inputs to work
I want to run fully sequential injection and ignition with and Hall sensor as secondary trigger.
- secondary trigger is HALL => EC18pin12 available analog input
- onboard MAP sensor => EC18pin6 available analog input channel
- no 1-wire => EC18pin16 might be available analog input channel (added recently)
It's not needed to alter the hardware of my genboard to use it with Vapourised Sequential LPG Injection.
Fully sequential is configured in config (the EC36pin13 is only used for cam-HALL, not normally reused for other tasks anyway).
software:
From what I understand you need 4 look-up tables:
- Vout temperature sensor Fuel_temp => NTC look-up table
- Vout pressure sensor Fuel_pressure => calculated with a code shown below
- Fuel_temp : Density => look-up table with multiplier
- Fuel_pressure : Density => look-up table with multiplier
What is Vsens_out for ?
- I can configure these tables in excel if you want. The values will be between: 0.25V and 4.85V.
- sounds like a good start. I recommend 1/density (not density), try to make a linear formula to have table values in 0..255 range.
Vout from the Fuel_pressure sensor is calculated with:
Vout=(c1*Pabs+C0)*Us
- Vout = signal output voltage in V
- Vs = supply voltage in V
- Pabs = absolute pressure in kPa
- C0 = -5/350
- C1 = 0.8/350 kPa ^-1
- I'll get you an excel sheet asap. Have you got an email-adres I can send them to?
- What does the original code looks like to calculate Injector pulsewidth?
- Can you explain the devisions a bit more? As i'm not a software engineer I don't understand these terms. I think I've figured them out and will be able to put them in a table. But can I use more bits? As I've understood the signal for the NTC sensor will be used like this:
TempSensor=>analog signal (Sensor Vout)=>AD-Converter=>digital signal=>Look-up table=>digital temperature
So the look-up table will contain Temperature and a digital value (devision 2^n in this case a 8-bit value)
Whoooo check this site:
http://www.airliquide.com/en/business/products/gases/gasdata/index.asp?GasID=53
With this graph of pressure and temperature of Propane:
Same graph for butane-n:
