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EMU Black fuel type selection drop down question.

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Does anyone know exactaly how the drop down menu for fuel type in the EMU black works? Does this option compensate and then change the displayed lambda reading? I will run strictly on e85 from the local pump, which obviously changes in ethanol content. I currently have the drop down set to gasoline + 70% ethanol (my content sensor says 73.5% so this is closest) If I begin to tune my number 1 VE table with the lambda values im seeing, how accurate will they be? Will my whole tune be wrong when i fill up again and my eth% changes by 5%?

I assume the proper way would be to tune on 93 octane first, then drain the tank, and fill with the highest ethanol content e85 I can find and tune the #2 tables, then let the tables blend together. But I just dont see myself ever needing to put 93 octane in it. Do I really need to have both tables just to account for ethanol content changes from the local pump?

Im slowly realizing the answers to these questions while typing this and I'm not amused lol. Any help or knowledge is greatly appreciated.

Hi Boone,

Is the drop down you are referring to 'Fuelling type' under Fuelling - General?.

As a broader answer to your question. Variations in fuel composition is a common issue people face when running a car solely on pump e85.

Depending on your location in the world ethanol blends can vary as low as 50% even though it is sold as e85. This means that without correction based on fuel composition your VE table, ignition timing and boost aim among other things may not be suitable if you are expecting 85% ethanol but are actually only getting 50% from the pump.

The best way to manage this would be to have a fuel composition sensor and make use of the flex fuel system available so that when the fuel composition varies the ECU can account for this, even if you only ever run the car on pump e85.

Hi scott, thanks for the reply. I do have a flex fuel sensor installed, but I am building my first fuel table of my life, and there is currently 73% ethanol in the tank. What i am trying to avoid it having to 1, drain the tank 2, put in premium, 3, tune, 4 put ethanol back in, 5 tune again, 6, blend tables. thats a lot of work. The ecu master people just told me (a couple hours ago) about a setting called Ethanol Fuel Scale Factor, which they said to put aroun 160 to 165 percent. He said this would add fuel volume automatically as ethanol percentage increases and that I did not need 2 maps. This setting however is not in the help file, so i guess I'll just have to try it! Is this a common feature in ECU's and is it called the sam thing?

ECU's that support a fully integrated Flex Fuel functionality will have blend tables (or something similarly named) for multiple parameters in the tuning. These are usually the VE (or Fuel) table, Ignition Timing, Lambda Aim and Boost Aim. Other parameters that may be tunable for changes in the Ethanol content are Charge Cooling, Cranking and Post Start fuel compensation and Injection Timing.

Different ECU's will have different names for these functions, there is not a standard that is used.

Hi Boone,

It depends on the fuel model of the ECU as to how they handle fuel composition based corrections and compensations.

I'm not sure what the Ethanol Fuel Scale Factor does but I suspect it could be a way of normalising the percentage scale in the blend tables? ECU master would need to elaborate further.

typically you would tune for normal pump fuel then switch to e85 with the highest ethanol percentage possible.

In your case since you are already running on a reasonably high percentage ethanol fuel you could enable all of the flex fuel tables and tune all the #2 tables (since these are the tables that are intended for e85). Ideally you want your #2 tables to be based on the highest possible ethanol content that is available to you so as the ethanol percentage reduces the blending can be done by the ECU based on the measured fuel composition.

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