MoTeC Global Forum

Hi everyone
I have been adding the flex fuel sensor into my car and running GPR package.
Have some problem with sensor reading.
First when I running pump gas which is E10. The sensor is reading around 7%. I think is good reading.
And when I put ethanol in the tank the sensor is reading way above 100%. Like 128%.
Then I take the sensor out, in the air it read 0% of ethanol. Good
But why it read way above 100%(the fuel I mixed around 85%, not even 100%).
Don’t know what I did wrong.
Bad sensor?
Water in ethanol?
Wrong setup in tune?
Please help me!
Thanks a lot!

Useful information would be what sensor you are using for the Ethanol content, and how you have it wired.
What is your Fuel Compostion Sensor Resource and Fuel Composition Sensor Digital Resource selection?
What is your Fuel Composition Sensor Calibration selection (or Fuel Composition Sensor Translation)?

Hi David
Thank you so much for your reply!
The Sensor I'm using is Continental 13577429.
I wired to 12V power and chassis GND.
The Fuel Composition Sensor Resource is UDIG 3 Hybrid A.
And Fuel Composition Sensor Digital Decode Resource is Universal Digital Input 3.
Fuel Composition Sensor Calibration is Manual.
Fuel Composition Sensor Translation is 0.050v 0.0% to 0.144v 100%(Setup according to MoTeC M1 Flex Fuel User Guide)

Thanks again, David!

The Fuel Composition Sensor Digital Decode type needs to be "Pulse Width" for that sensor, although that should only effect fuel temperature, not the composition, but give it a try.

Perhaps you have a faulty sensor, or the frequency of that sensor doesn't vary from 50 - 150 hz depending upon the ethanol content. BTW, that sensor has a diagnostic to indicated contaminated fuel, perhaps that's what's happening. Here is a note from one vendor's website:

The normal range of operating frequency is between 50-150Hz. The microprocessor inside the sensor is capable of a certain amount of self-diagnosis. An output frequency between 180Hz and 190Hz indicates that the fuel is contaminated.

Perhaps you could use Online->Capture inputs to see what the frequency of the sensor is at the various Ethanol content.

Thanks again,David
I’ll give a shot and let you know!

Hi David
I did change the Fuel Composition Sensor Digital Decode Type to "Pulse Width". No different.
And the frequency is around 190Hz. I think the fuel was contaminated.
But when I go to the local chemistry store bought 99.7% ethanol to test the sensor.
Turn out the sensor is reading 87.6%. Hum!!!
Then I test this 99.7% ethanol with a hydrometer showing the ethanol is 100%
So both sensor and fuel are bad???

What have you specified for the Alternate Fuel Properties Calibration. A common mistake is select the E85, but since you have the sensor, you should be selecting "Ethanol.1.0" as the alternate fuel. The sensor will read 85% if E85 is supplied. That would explain how nearly E100 reads as nearly E85.

The alternate fuel is selected under Initial Setup->Engine Details.

My Alternate Fuel Properties Calibration is "Ethanol.1.0".
So there must something else?

Those sensors are only listed as having a 5% accuracy. Why don't you just change the manual calibration to match your reference Ethanol?

Hi David
I bought a new sensor and find out that my sensor was bad.
But this new sensor still has a higher reading of around 6%.
And then I measure the sensor output frequency it was pretty close to actual ethanol content.
Compare the Fuel Composition number and frequency number is where that 6% come from.

Thank you for all the help, David!