Submitted by William Knose on
FlexFuel Over Straight E85 (dual maps), why is it better?
There is a lot of debate on whether you really need FlexFuel over running straight E85 (or Cobb dual maps), in our opinion FlexFuel is much safer and more reliable. Here is s little article on E85 / Alcohol and the good/bad with it by Paul Yaw of Injector Dynamics.
ASTM D5798-11 Standard Specification for Ethanol Fuel Blends for Flexible-Fuel Automotive Spark-Ignition Engines
"The original specification set the minimum ethanol content at 75% which was lowered to 68% in June of 2010, and lowered again to 51% in June of 2011. As of February 2012, this is the current specification and E85 purchased from the pump could have an ethanol content as low as 51% and still be within spec."
From this small bit of information (quoted above from the article link) we know that filling up at any time, at any pump the content of ethanol can change and range anywhere between the mythical 85% ethanol, to as low as 51% ethanol. Now what impact does this have on tuning? This can cause any vehicle running a non-FlexFuel setup (E85 custom tune), to potentially run rich and far too much timing, which can lead to engine problems. On an E85 tune that is conservative, if the ethanol percentage becomes E75, the tune will more than likely be fine, but if the fuel changed to E60, this can definitely cause problems. So as long as you are testing the E85 every time you're at the pump, you really are not sure the content of ethanol going into your gas tank. On top of that, you don't know what the percentage of ethanol is in your gas tank / fuel sytem, if you had any other 91 or 93 octane in it that mixes, which also has a variable percentage of ethanol in them.
Now with EcuTeK RaceROM or Cobb running FlexFuel, the timing, fueling and boost can all be calculated based on the reading from the FlexFuel sensor, so you know it is within spec and the car is tuned properly for whatever mix is in your tank.
Here are some example information on how EcuTeK's FlexFuel is setup through RaceROM custom mapping.
Image #1
Image #2
Notes on EcuTeK RaceROM Custom Mapping
- As you can see these are custom maps in EcuTeK RaceROM, more than just the standard features available such as launch control, auto-blip, etc...
- These maps allow you truely create new maps based on X and Y inputs channels and an output channel.
- X and Y Input channels are listed in Image #2, along with the optional output channels.
Notes on FlexFuel RaceROM Custom Mapping (Map A)
- X channel input as Engine Speed (radio button X channel image #2)
- Y channel input as CPC Pressure Sensor (radio button Y channel image #2), a wire used on the OEM harness
- Output Channel is a "Calculation Only" used in Input Channel on other custom maps (such as Map C in Image #1)
Notes on FlexFuel RaceROM Custom Mapping (Map C)
- X channel input as Coolant Temp (as seen in image)
- Y channel input as calculated result from output channel on Map A
- Output Channel is a multiplication factor of the total fuel quantity, so as E85 becomes more pure the fuel quantity increases accordingly.
Additional FlexFuel RaceROM Custom Mapping Tables
- Ignition Timing based on the calculation from the calculation from Map A
- Cranking Enrichment for cold and hot starts, so the vehicle starts even in the coldest climates.
- And of course a lot more can be added, such as dynamic boost control and dynamics cam control
With all these features from EcuTeK you can have a true FlexFuel system in your vehicle that will run consistent without ever having to check the content of E85, ever again. Just fill up, drive and go.
