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e85 content sensors vs 02 sensor

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So far iv seen some manufactors use the 02 senor to calculate for flex fuel instead of using a content fuel sensor im after some info on how this works and how it can be put into use on todays after market ecu

I'm not 100% sure exactly what you're referring to? If you're running in closed loop then this could be utilised to account for E% if that's what you're referring to? You'd need to allow for around 30-40% maximum trim to account for the ethanol content though which I wouldn't necessarily recommend. I guess with the current cost of fuel composition sensors it would be hard to see why you wouldn't just incorporate one?

Because if a manufacturer can save $10 in the cost of a sensor, then they will take that option.

The way that it is done is through a fairly complex startup process on the engine that also involves the knock sensors. The basic premise of the system is that on startup, the ECU will adjust the fueling on one or two of the cylinders to move the lambda values around until it gets the lambda actual value to match the lambda aim, once it has done this, then it uses a predetermined lookup table to match the IPW with the E%, it then validates this value by advancing the ignition timing in one or two cylinders to a point where light knock can be initiated with light engine loads. This allows for a further refinement of the actual E% and also helps to deal with water contamination of the fuel that can give a false (higher) reading through a E% sensor.

Interesting BlackRex. I wasn't aware this was being used by OE's. Thanks for the information.


Great info on strategies it uses to achieve the outcome

Can't wait for the results of your research on this one Simon

More interested in how to set it up using factory programming and after market ecu such as link etc

In the aftermarket right now, the typical approach with flex fuel is to incorporate a fuel composition sensor. Given the low cost of these sensors, they are probably going to remain the natural choice for some time yet. I'm not sure I see the advantage of an aftermarket ECU manufacturer using the OE approach discussed - The complexities for us as tuners in setting up and configuring the system would probably exceed the value of the fuel composition sensor. I can see however for an OE manufacturer why saving the cost of the sensor would be advantageous.

yes i definitely understand that iv just been looking into opensorce tuning on late model subaru that can do this feature with the 02 sensor and wondered if it was possible to use on aftermarket ecu reliably

I will just stick with the zetronix sensors until there is more info on this topic in the future

What opensource tuning allows for Ethanol sensing without using a Fuel Composition Sensor?

Ford does this on their new f150 platform but it can also be enabled on the mustang coyote platform as well using HPTuners.

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