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HOWTO: Dual Maps via Custom OS

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To achieve dual maps in the flex fuel custom operating system you can wire a switch into the second o2 sensor input (pin A37). This will require a custom operating system with "dual maps" enabled and "user configured voltage selection".

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Here is the “Blend Ramp” for spark. By setting 0.6 volts to be 1.0 ratio it means once the voltage hits 1.1 volts it will use 100% of the other spark table. Once the voltage drops below 1.1 volts (eg switch off) it will go back to using the normal maps. The O2 Sensor input can read a maximum of 1.60 volts, anything above 1.6 will clip. 5v is the limit of the hardware, above this you may damage the input, eg do not wire 12 v into this input.

auF100010

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Any maps you wish to disable or not use, simply set the following blend curve voltages. This will mean the the PCM only uses the original maps under all circumstances.

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  Finally you could also use a variable rotary dial to allow variable boost/power. This could be infinitely variable, or with various stages of boost.

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How do you tune when you got your fuel tank mixed? Will the O2 sensor look after the tune? Eg. I have 4/10 of the tank filled with U98 then decided to top it up with E85 or vice versa. Will dual map give me clear advantage with tuning? And how? I am thinking about using custom OS hence this is my question ?

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32 minutes ago, Loki said:

How do you tune when you got your fuel tank mixed? Will the O2 sensor look after the tune? Eg. I have 4/10 of the tank filled with U98 then decided to top it up with E85 or vice versa. Will dual map give me clear advantage with tuning? And how? I am thinking about using custom OS hence this is my question ?

See the custom OS thread. It interpolates between the two based on the flex fuel sensor output. Eg E42.5 will be ~2.5volts hence 50% of 98 map + 50% of e85 map

The advantage is you can fill up with 98 if you daily the car and aren't near an E85 pump, you also don't need to empty the tank completely when switching fuels.

To do the full flex fuel tune you require a flex fuel sensor. Danny at Springy Performance sells a complete kit with fuel fittings and O2 sensor loom.

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I’m a bit lost, wire a switch into pin a37?. I thought we would wire the out put signal from the flex fuel sensor into a37.

Edited by will15

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Hi Guys,

Just on using the second o2 sensor for this and other inputs.  Is the second o2 sensor used for anything useful other the detection of the cat failure?  I used to think it did exhaust temp but that is just calculated by the ecu and also how would it do temp, ? ? hahahah, being an o2 sensor.

Cheers,

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Correct it is used to check the efficiency of the catalytic converter. Commonly this check is already disabled as the user has modified the exhaust and catalytic converter meaning it no longer passes the efficiency tests.

FYI Exhaust temperature is calculated by a lookup table of load vs rpm and then multiplied by engine coolant temperature

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exhaust flange temperature =  (auF16613 base stead-state flange temperature  * 200°F ) + auF1605 Exhaust temperature modifier for ECT * (ECT -  200°F)

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5v

You should be able to find a 5v ref in the plug itself, I think it is used for the O2 heater. Make sure you don't use 12v as it may damage the analog input which clips at 1.66v in the BA/BF and 3.8v in the FG mk2

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5v should be fine and it just pegs the value at 1.66 or 3.8v from the testing we have done. If you have a resistor handy it can't hurt to use it though. Higher voltages may damage the input over time, I haven't been able to determine what the A/D limits are as it uses a separate chip on the PCM board and not the internal A/D converters that are used for the other 5v sensors.

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