FlexFuel Boost Target by Gear

This is the boost target for maximum Ethanol content and the progression between this and the normal boost target map is set by FlexFuel Max Boost Target Blend. It would be sensible to lower the boost target for lower gears due to the likely increased torque available when tuning with high Ethanol contents; enough to overcome the available traction in first and second gear on cars with normal road tyres. When more traction is available it would be normal to increase the available boost where turbo size allows, on cars that would previously have been limited by octane when trying to run such high boost on pump gasoline.

FF Boost Limit Fuel Cut

Used with the main boost limit to provide a different boost limit when using ethanol. Typically this will be lower than the pump fuel boost limit on stock engines to safeguard against engine damage, but higher than pump fuel limit on built engines.

FF Boost Limit Fuel Cut Blend

The boost limit for ethanol is blended in the same way as the boost target

FlexFuel Quantity Multiplier

This dictates the additional fuel based on Ethanol content (0-100%) and coolant temperature. It would not be unusual to need to add additional E85 when cold due to some unburnt fuel going through the engine. Pure Ethanol typically requires 40% more fuel to maintain the same lambda (or apparent AFR) as gasoline, there is no significant change to injector flowrates when using E85.

If you want to run a richer or leaner AFR when using E85 do not try and compensate with this map as the ECU will use fuel corrections to hit the same target AFR you are running in a given map switch mode.

FlexFuel Cranking Multiplier

The fuel quantity at cranking will be affected by the FlexFuel Quantity Multiplier map however it may be required to change the fuelling further at low temperatures when cranking. This map is a 0-2 scalar and will multiply the base fuelling only when cranking.

FlexFuel AFR Addition Max

This map has units of AFR and a positive number will add to the preceding target AFR resulting in a leaner final AFR. Blank by default, the pictured table uses +0.5 at high load to lean out the AFR from (for example) 11:1 at very high load on pump fuel to a cleaner and crisper 11.5:1. However if the base map is already using a good fuel or even a race fuel that would typically be mapped to run more like 12.2:1 then it would be entirely possible to want to lower the target AFR when using high levels of E85.

FlexFuel AFR Addition Blend

This map dictates how much of the AFR change is used for a given Ethanol content. The resulting AFR target is defined as:

FlexFuel Ignition Timing Max Addition

This represents the absolute maximum ignition advance that can be added, typically at 100% E85 but it can be added at lower concentrations using the FlexFuel Ignition Timing Addition Blend map. The values in the table below are not tested but purely representative. They would result in significant torque gains and would not necessarily be suitable on a stock engine.

We have chosen to use an addition map as it would require 4 ignition maps, one for each MapSwitch mode in order to have totally independent maps. An adder map is easier to comprehend for most tuners but should you wish to use total advance maps, it can of course be done using Custom Maps.

FlexFuel Ignition Timing Addition Blend

The values are a multiplier of the FlexFuel Ignition Timing Max Addition values and dictate how much of that advance is added for a given Ethanol content. The resulting ignition advance is calculated as ((Gasoline Ignition Timing + (Blend Multiplier * FlexFuel Ignition Timing Addition)).

The example shown below adds all the max advance by 70% E85 which is going to be close to ideal for many setups. The default map is linear 0-1.00 and will give conservative results at low to medium Ethanol content. 

FlexFuel Sensor Scaling (part of sensor scaling in Phase 6and later)

This map sets the sensor scaling using a 0-5v input defined by FlexFuel Sensor Source that many aftermarket FlexFuel gauges or sensor interfaces use. The map is shown with its default values and many setups will not require anything different but you can fine tune to match the RaceROM Ethanol content to that of a gauge.

FlexFuel Sensor Source (part of sensor scaling in Phase 6 and later)

Choose the ECU 0-5v input to use for the FlexFuel sensor. The option of a fuel level sensor is available only because it’s possible and may suit circuit cars with replacement fuel tanks.

FF Ethanol Content Override

It is not always practical to add a FlexFuel sensor to every car that uses alcohol in the fuel, and many users may wish to pre-mix a specific amount of ethanol, methanol or E85 with their regular gasoline to improve performance. Premised ratios of alcohol can now be catered for in the RaceROM FlexFuel strategy but entering the ethanol content in this map.

A default value of -1 is employed to use the ethanol content from the sensor. In the screenshot shown above, modes 1-3 use the output from the sensor while mode 4 is configured to assume an alcohol content of 40%.