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Flex fuel sensor with limited input options
https://mailserver.romraider.com/forum/viewtopic.php?f=36&t=19794		 Page 1 of 1
Author:  Iceman.kcmo [ Sat Aug 06, 2022 2:49 pm ]
Post subject:  Flex fuel sensor with limited input options
Hi all,
So here is the deal. I have a JDM EJ205 with AVCS. I believe it is out of an 02 or 03 forester. While testing the Ethanol sensor, I found the Rear o2 sensor will only read up to 1.25 volts. It doesn't seem like the ECU that came with this engine had TGV's, so I am missing inputs there.

My options as I see them:
1. Rescale the sensor to output between 0V and 1.25V (or .1-1.1V?) and have no wiggle room for error.
Note: I put together my own Flex-fuel setup using a GM sensor and an Arduino. See https://forums.nasioc.com/forums/showthread.php?t=2810122 for details on that.

2. Find another ECU
If I were to use another ECU, What would I be looking for?

Any other suggestions?
Author:  Iceman.kcmo [ Wed Aug 17, 2022 7:32 am ]
Post subject:  Re: Flex fuel sensor with limited input options
Well, I figured I would update those who are listening. After a few drives and logging the ethanol sensor with 0 ethanol fuel, I observed a lot of fluctuation around the base voltage of 0.49v up to 0.54v. I decided that was too much for just for that limited range for something that was controlling both fuel and timing.

I ended up calling the the Importer that I bought my engine from to pick up an ECU from a WRX with TGV's (and maybe a 5V rear o2 input). Should be here the end of this week. Once it comes it, all will be resolved.
Author:  jon7009 [ Fri Aug 19, 2022 8:08 pm ]
Post subject:  Re: Flex fuel sensor with limited input options
if you're on speed density, you could log it through the MAF reference. Basically anything that has a 0-5v reference to ecu that can be datalogged in volts.

Some ecus, you can use the EGT circuit.
Author:  Iceman.kcmo [ Sun Aug 21, 2022 10:52 am ]
Post subject:  Re: Flex fuel sensor with limited input options
I am trying to use the Map blending in Carberry (without using a pot/knob). I am not sure how to change the input on Carberry to the MAF. The options given are TGV L/R and Rear 02. Also, I haven't converted to SD. Still using the MAF. I'll be honest, I am not really sure what the benefits of switching MAF>SD are, and haven't done much reading on what it takes to switch.
Author:  skrimshaw [ Sat Jun 15, 2024 2:51 am ]
Post subject:  Re: Flex fuel sensor with limited input options
Iceman.kcmo wrote:
Well, I figured I would update those who are listening. After a few drives and logging the ethanol sensor with 0 ethanol fuel, I observed a lot of fluctuation around the base voltage of 0.49v up to 0.54v. I decided that was too much for just for that limited range for something that was controlling both fuel and timing.

I ended up calling the the Importer that I bought my engine from to pick up an ECU from a WRX with TGV's (and maybe a 5V rear o2 input). Should be here the end of this week. Once it comes it, all will be resolved.


That ecu wont be able to run your avcs, no usdm 2.0 with tgv had avcs.

I too am in this situation where i want to run flex with an ej207 on the jdm ecu and carberry but have yet to find a good answer. The biggest problem is how to tell the carberry rom to look at the maf/egt for the flex signal when the only options are tgv/rear o2. I myself am on speed density so i can easily run the flex through the maf, so i guess i just need to figure out how to write the necessary code in order for the rom to see it.
Author:  bar2555 [ Sat Mar 15, 2025 1:18 pm ]
Post subject:  Re: Flex fuel sensor with limited input options
sorry to revive a thread but is there a solution to this? is rear o2 1.25V limit software related or is this a hard limit? I also have an STI without TGV's.. (EDM)
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