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Ethanol & Flex Fuel Tuning: Ethanol Hold Functions

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Ethanol Hold Functions

01.59

00:00 - As we've just discussed in the last module, a constant flow of fuel through the ethanol content sensor is essential for reliable ethanol readings.
00:08 And if the sensor is fitted to the return line and you're near the limit of the fuel pump flow you may find the ethanol content fluctuates at high RPM and load.
00:18 This is potentially dangerous as the ethanol content reading will be reduced from what the true ethanol content actually is, and this will result in the air fuel ratio moving lean.
00:30 To confirm whether this is an issue on your application you can simply log the ethanol content the ECU is seeing during a full ramp run on the dyno, or alternatively an acceleration test on the road.
00:43 You should see an ethanol content that is stable and not changing by more than about 1% to 2% through the run.
00:50 If you're seeing erratic swings of much more than this as the RPM increases the flow through the sensor may be inadequate.
00:58 The real fix here in my opinion is to fit a larger fuel pump that's capable of supporting the engine's fuel requirements.
01:05 However depending on your ECU platform, you may have the option of incorporating a hold function on the ethanol content.
01:14 This hold function allows the ethanol reading to be sampled at low load and low RPM, where there's adequate flow through the sensor and hence the ethanol value can be relied on.
01:25 You'll normally be able to set either RPM and load points, or possibly an injector duty cycle point, where the ethanol content will be held or latched at the last known value.
01:37 What this allows us to do is ignore the output from the sensor under high load and high RPM conditions where the sensor reading may become unreliable.
01:46 This is a function that can be used very effectively if your fuel system flow is a little marginal.