#1  
Old 04-23-2022, 02:53 PM
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Default E-85 ELECTRONIC SENSOR.

Do we have any electronics type experts who can build a E-85
electronic sensor?

I was pulling up some old files and came across this info from a
friend of mine DAVE2 from the Turbo Forums.

Here is the info he posted.

http://www.theturboforums.com/smf/in...opic=108727.25

Do you want the good news first or the great news first????
jesse* * Your meter from Sears works great!* I bought one this morning (model 82344, $31.99 + tax).* Only .02 Cycles off my $350 Fluke and my meter may be the one thats wrong!
I picked up the second (FCS) sensor this morning, brought it home and it did not work!* I said that this cannot be, this sensor is not that old.* Got out the Ohm meter and determined the color code (cannot read the pin numbers on the connector) from the MegaSquirt site was wrong!!!* The correct connections are: G. M. sensor # 12570260
* * * * * * * * * * * * Black is GROUND (Ohm to chassis to prove).
* * * * * * * * * * * * Pink is 12VDC. (car battery)
* * * * * * * * * * * * White is the output signal. (A pull up resistor is needed here because the output is an open collector transistor inside the sensor so any voltage interface will work)
* * * *
Attach a 33 K Ohm resistor from the White wire to the Pink wire if you are just using the meter.

Attach a 10 K Ohm resistor (1/4 watt) from the White wire to a 5 VDC refference voltage if you are logging data or doing an interface. Remember to use common grounds.
* * * *
Attach your shinney new Sears meter to:* Red lead to White wire, Black lead to the Black wire.* Switch to Hz.* *

You now have an E85 % testor!!!!!!!!* *Remember 50 Hertz equals 0% ethanol, 150 Hurtz = 100 %
I tested a few things today:*
* * * * * * * * * * * * * * * * * * * * 0 fuel = 44.50 Hertz
* * * * * * * * * * * * * * * * * * * * 93 Octane in my gas tank = 65.74
* * * * * * * * * * * * * * * * * * * * Isopropyl alcohol 91% = 137.50
* * * * * * * * * * * * * * * * * * * * Miller Lite = 169.96
* * * * * * * * * * * * * * * * * * * * *

Quote from jesse "Those sensors use a 12v input? I would have thought they would need 5v like a map sensor."* Your question opened my eyes as to why they built a computer inside of this sensor but left out 1 resistor.* So it could be interfaced to anything!!!
5 VDC is a very precision voltage in car computers and very smooth and is used for sensor refferences only. Anything needing lots of power is run off the 12 VDC battery.* Example: The throttle position sensor runs off the precision 5 VDC.* When you put on the cruse control the car is very smooth and the speed steady.* If the cruse was run off the 12 VDC (not smooth and a lot of serges) the car would run with a lot of jerks and speed changes.*


More on the E85 / Ethanol sensor. These tests were run with the out-put pull up resistor of 33 K Ohm, hooked between the out-put wire on the sensor and the 12 VDC power supply, using the Sears meter set on Hz and other back up test equipment ( oscilloscope, Fluke digital meter, precision / adjustable power supplies).* *

Freq stability check:* Turn on power @ 9:30 am* * Freq. = 69.99 Hz
* * * * * * * * * * * * * * *Turn off power @ 10:30 am* Freq. = 69.99 Hz
* * * * * * * * * * * * * * *Test room temperature was steady at 67 Deg. F.

Opinion:* Sensor very stable with time.

Freq. vs input voltage changes:* *5.5 VDC power supply,* Freq. = 69.99 Hz
* * * * * * * * * * * * * * * * * * * * * raised up the power supply voltage in 1 volt steps to
* * * * * * * * * * * * * * * * * * * * * * *16.0 VDC power supply,* Freq. = 69.99 Hz
* * * * * * *Note, sensor stops operating below 5.5 VDC.* 16 VDC was the upper end of testing.

Opinion:* No Freq. change with any operating voltage used.* Excellent power supply isolation.

Current draw at power supply voltages from 5.5 VDC to 16 VDC:
* * * * * * * * * * * * * * * * * * * * * * 25.7 ma to 25.9 ma* *or* .026 amps!
Opinion:* Excellent, no strange waveform or current changes with voltage changes.*

Waveform description during operation with gas / some Ethanol.* Freq. at 69.99 Hz.* Power supply voltage a 13.5 VDC.* Pull up resistor @ 33 K Ohm:

A square wave with a duty cycle of approx. 82% positive and 18% negative. The positive transition starts at about .6 VDC and rises to approx. 11.0 VDC. continues for 82 % of the duty cycle, than transitions negitive waiting 18% till the next positive transition at the ground level.* Note, this waveform will change the % of up / dn with temperature but we are not using this fuel temperature function out-put from the sensor and it would be hard to detect the changes.

Fuel calibration:* * * I need several days to complete this test to collect pure samples of gas, E85 and 100% Ethanol.* I'm sure the sensor will pass with flying colors.

Bonus test for all of us!!!* *Transistor 9 VDC Battery test.

Found a used 9 volt batt, voltage read 9.01 Volts, with no connections, well used.
Hooked Ethanol sensor to battery, voltage read 8.87 VDC, Freq. was 69.99 Hz.* Current draw was 25.6 ma on the 9 volt battery.* 7 volt peak to peak square wave on scope.* Ran sensor 15 minutes on battery.* Battery voltage down to 8.69 VDC, Freq. was 69.99 Hz.* Sensor still working well.* Test over!!!* * * * * * * * * * * * * *


Final opinion:* *This sensor has an excellent design by Siemens!
Rock solid Frequenccy out-put, variable voltage power supply in-put and a open collector out-put for universal connections!!!

Review of findings: This GM / Siemens Fuel Composition Sensor(FCS) (GM12570260) works great!*
* * * * * * * * * * * The sensor will test for 0 % to 100% Ethanol, not just around E85 ratios.
* * * * * * * * * * * The sensor will run off of a car electrical system or a 9 volt battery for a while.
* * * * * * * * * * * The Sears Craftsman Model 82344 meter reads the sensor out-put very well.
* * * * * * * * * * * A resistor is needed depending how you use the sensor. 33 K OHM for meter use.

* * * * * * * * * * * * * *Costs: Meter about $35, R.S. resistor-5 for 99 cents, GM sensor(shop wisely, $25)

enough for now...........* *Dave two


The Sears Craftsman Model 82344 is most likely gone.

The GM / Siemens Fuel Composition Sensor(FCS) (GM12570260)
may be gone from the GM Parts Books.

But a Sharp Electronics guy might come up with a electronic tester
that will perform like a modern vehicle and read the actual fuel vs the
EGO SENSOR output for E-85 content.

Tom V.

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  #2  
Old 04-23-2022, 03:57 PM
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Scott65 Scott65 is offline
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Tom, is it possible that using a modern GM ethanol content sensor and deciphering how the voltage from the output wire gets interpreted would be easier than designing a ground up sensor where one already exists? A lot of the aftermarket ECU's interface with this common sensor. I think it outputs in frequency (hz). The numbers you posted of 50-150 sound familiar and may be exactly what these sensors use.

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  #3  
Old 04-23-2022, 08:36 PM
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The sensor used years ago by Dave two was a factory GM sensor but without the GM computer required.

Tom V.

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  #4  
Old 04-23-2022, 09:49 PM
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Here's a screrenshot of how the modern GM content sensor gets interpreted. Seems that a digital meter(perhaps analog?) that reads hz would get the job done huh?
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  #5  
Old 04-24-2022, 10:00 AM
mgarblik mgarblik is offline
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I am not an electronics expert by any means. But we have 3-4 of the fuel composition sensors/testers you are referring to that you read hertz output with a Fluke meter to determine alcohol content. I can say the tool produces results +- 1% vs the old standard method of mixing fuel with water to extract the alcohol in a measured vile. We used to do back to back testing all the time in class. Kent Moore tool vs manual method. I could possibly get one of the tools donated to me for "scientific purposes", if it would help someone here.

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Old 04-24-2022, 10:55 AM
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My point was that there is a sensor commonly available, that along with the fluke meter will do the job. Personally, mine is installed on the car, where it both reads, and adjusts for content on the fly. Can't see a reason it couldn't be mounted as a temporary test fixture for those in the need

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  #7  
Old 04-24-2022, 10:56 AM
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The ability to create an accurate fuel composition sensors/testers set-up you be a good project for anyone wanting to test pump fuel.

Dave2 used it on trips with his vehicle, (two stage Turbo system), One turbo blowing into a second turbo, when competing on Car Craft type Chassis Dyno Shoot-outs.

Tom V.

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  #8  
Old 04-24-2022, 02:16 PM
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This would be a great application for an Arduino with a simple LCD readout.

Below is what I put together to run and monitor a ground-based prototype AC system for what I eventually installed in my homebuilt airplane. The display shows PWM power to the variable-displacement compressor as well as high-side pressure and evaporator temperature. The pressure sensor being monitored (and used to modulate the compressor) is a standard GM 3-wire AC sensor and the evap temp sensor is a thermistor from a Honda.
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Last edited by hgerhardt; 04-24-2022 at 02:40 PM.
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