Altering Calibration of Ethanol Content Sensor

[ellisd1984]

As above, is there any way to alter the calibration of the ethanol content sensor? I'm wanting to use it on methanol so it gives different output frequencies for fuel percentages

 

 

 

 

 

 

[dx4picco]

In your multi fuel table, that's where you define your fuel tables / fuel properties depending on reported ethanol content

[ellisd1984]

I'm Talking more for the sensor's calibration itself not the blend tables

[koracing]

As far as I'm aware the sensor calibration is fixed for all ethanol content sensors with data provided from the sensor manufacturer to (GM) spec. 

That said, it may be possible to read it in as a frequency input and then create a calibration table from that frequency input if you can measure the frequency versus some known methanol concentrations?

[Electredge]

6 hours ago, ellisd1984 said:

I'm Talking more for the sensor's calibration itself not the blend tables

you can turn off multi fuel and use dual map with a trim knob and just watch the ethanol % on the sensor and manually move the knob where you need it.

[Adamw]

You currently cant change the ethanol sensor calibration and the only source options are DI pins so you cant fudge it with a math block either.  

The only fudge I can think of would require 2 DI's and an aux output.  Input the Ethanol sensor into a DI but set it up as GP freq. Set up a GP PWM with a frequency and DC table referencing the Hz and DC coming from the flex sensor, use these to send a modified Hz and DC out of the aux output.  Loop a wire from the aux into your 2nd DI and set this to ethanol sensor. 

 

[ellisd1984]

If I was to keep everything as is would it still inject the correct amount of methanol in using the modeled fuel equation?

 

For example 50%meth equals around 70% eth on the sensor.  

I can set the second fuel table to be 100% active at a reading of 70% eth content(blend 100%)

 

My question is what properties will I need to put on for the second fuel?  Do I put the 100%methanol numbers?  And if I do will it overfuel because its trying to inject 70% instead of 50% because that's what the sensor is seeing

[Adamw]

You have a blend table for the fuel properties so you can set that up with whatever values you like in it.  For example use 100% of "fuel 2" properties when ethanol sensor is reading 60% or whatever.  

 

6 hours ago, ellisd1984 said:

For example 50%meth equals around 70% eth on the sensor.  

I have seen others quote similar relationships before, and I will say up front Im no chemist and I have never personally tested it myself, so really im just another internet expert with an opinion - but I have researched the ethanol content sensors probably more than most.  From my understanding of how an ethanol content sensor works I have some doubts that these assumed linear relationships are correct.  Im suspicious the people or person that came up with this quote have probably only tested with methanol at room temperature - or at least only tested over a very small range of temperatures.  Both permittivity and conductivity of most fluids vary greatly with temperature, these are the properties that the ethanol sensor uses to approximate ethanol content.  To generate ethanol content from temperature, permittivity, conductivity and dielectric constant, none of which relationships are linear, would have to be hardcoded in either multi-dimension lookup tables or complex equations. I just cant see the result of all those variables for 2 very different solvents when put through a complex set of equations, somehow by magic work out with the same perfectly linear relationship over a range of temperatures...    

[ellisd1984]

OK, what I've done is to adjust the fuel properties of Fuel table 2 too hopefully represent the highest blend I'll use (50/50 petrol methanol mix). I've used the output from the ethanol sensor at this point to run off Fuel table 2 100% and the more petrol that is in the blend the closer I will go to Fuel Table 1 settings.

Presumably for a 50/50 mix the fuel properties for both fuels would just be halved and added together.

I know in theory with all these values set there shouldn't be a real need for the 2nd VE table but I will make any further adjustments in that table as and when they are needed.  I just didn't want to make all the adjustment in the VE table.   I can also log some points and see what fuel temp does to effect the Lambda value.