[Tom Vaught]

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.