Spliting analog output signal (0-5v) to two inputs.
 

So I just bought a Flex Fuel kit and its going to be utilizing the rear o2 sensor for input to the ECU. My goal is to hide the ECA for the kit and use its analog out to display the e85 percentage on a P3 vent gauge.

This is where I get a little confused. If I have the ECA's output feeding P3 gauge and the rear o2 input will the fact that the ECA will need to split its voltage across two inputs cause the signal to be halved?


Its probably an obvious answer but Im not very experienced with wiring theory.

this probably isn't the answer you want to hear, but you probably should've bought the eca-2. it's better suited to what you're trying to do.

that said, you should be able to just split the wire into two and run it to both the gauge and the ecu. i'm no electrician, but i've done things like this in the past without seeing anything weird. the voltage output should be the same on both wires in the end. someone could definitely correct me if there is something i'm unaware of...

Watch out for electrical noise.

Marco (this is David from FB). After having the ECA gauge in my car, it doesn't hold much value. Its nice to know, yes, but as long as the ECU is getting the signal its not that important.

To prevent a possible issue with the ECU signal (splitting the cable), I would recommend you to buy an Ecutek cable so that you can access the result of your custom map and know that way.

I can meet up with you from time to time if you don't want to buy the cable but want to check your E content.

But lastly, contact Moto Mike and ask them about it. The engine sensor plug should have two different output connectors, one for a gauge and one for the ECU (at least that is how my kit is).

The voltage will be fine to be split between two inputs.

Yeah Im pretty sure eventually Ill need to get the ecutek. I appreciate the help in the mean time David. From the research Ive done it looks like the sensor (at least on the kit Im receiving) doesnt output a analog 0-5v signal but instead a signal that is processed by the ECA.

This is what I found on the Zeitronix site.(Copy/Paste)

ECA Analog Outputs
Ethanol content and temperature analog outputs are available as part of the ECA. The flex fuel sensor does not provide these outputs. We have created the ECA to provide these outputs making use of E-85 easier with after market engine control modules and data logging systems.

http://www.zeitronix.com/Products/ECA/ECA.shtml
http://zeitronix.com/Products/ECA/Et...ugh_Sensor.pdf

So the signal that is sent to the ECU is generated by the ECA not the flex sensor. The sensor itself has 3 pins (output/power/ground).

I think you have the early visconti kit? Cause I remember seeing that kit had a different sensor.


I hope Im wrong and can tap the sensor, It would make life soooo much easier lol.

I cant find anything in their documentation about the voltage of the sensor output. :(

If you wire the inputs in series, you will have voltage issues, as there will be voltage drop across each input load. However, if you just tap the wire, the voltage to each will be the same as they will both be seeing the same voltage from the power source. Now, what WILL be reduced assuming it is fixed in the first place is the current.

Remember: in a parallel circuit, voltage remains the same across the parallel loads, but current is split. In a series circuit, current is the same through each load, but voltage is split (not evenly either, but based on resistance).

Since this is a DC circuit, basic DC circuit theory applies, BUT for so simple a mod, basic DC circuit theory isn't really even required unless you're doing a full-on circuit analysis.

I see your kit will include the ECA gauge.

http://www.moto-east.com/store/media...zt-eca-2_1.jpg

One of the cables coming off the brown connector is the one you will use. That same cable that you would use to connect the ECA gauge, you will instead route it to the P3 vent gauge.

It is a cable that will come from the Flex sensor in the engine bay. Its the same concept as the kit I have, but you will use the P3 gauge instead of the ugly ECA gauge I use. It is an 0-5V output signal that will work with the P3 gauge. You are good to go.

So is the ECA gauge even necessary for my application? My goal was to eliminate it but I wasn't sure if I could based on what I read in the documentation. From what I gathered the ECA isn't just a gauge but a "Content analyzer" then again I could just be over thinking it


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Form what I UNDERSTAND, you can eliminate it and only use the Vent P3. The only thing the ECA gauge does is show the E%, the actual measuring comes from the FF sensor inside the engine bay, which outputs the 0-5V signal shown on the gauge.

Spliting analog output signal (0-5v) to two inputs.
 

Apparently from what I read on the GTR forums the ECA "measures both impedance and temperature to analyze ethanol content" what exactly that does that mean? I have no f-ing clue . But sounds like there is some magical math going on inside the eca

But if I can just get rid of it all together then even better

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It means it measures both the electrical resistance (impedance is the technical term since resistance is technically only referring to the real component of impedance, when in real life there's both a real and imaginary part, b/c even in a normal wire there's going to be inductive and/or capacitive elements to it, not just pure resistivity) and temperature of the sensor wire that is used to determine the E-content of the fuel in order to make its determination.

Took some time tonight to check this out. It seems you are correct, The ECA display unit does play some magic in determining the E%. So yes, there is only one output cable (white/blue wire coming from the ECA display), which is the one that would go to the ECU.

So yes, you would have to splice into it and connect it to the ECU AND the P# gauge analog input. Not a big deal and doable.