Flex fuel tunes

[s8v4o]

For anybody wanting to know more here is the link.

http://www.hptuners.com/forum/showthread.php?50917-Flex-fuel&highlight=flex+fuel

From what I can gather the O2 sensor still just reads oxygen, no surprise there. What's actually happening is upon enabling flex fuel in the ECU you unlock a few new tables that were dormant. The ethanol content is inferred data based on how far off the AFR is. If the AFR is 30% off of what the ECU thinks it should be it will calculate how much ethanol it thinks is in the fuel and then adjust the new demands on the new tables that were enabled. Exactly what tables are enabled I'm not sure. My guess would be a new ignition timing table and fuel table at the very least

 

[Sky Render]

For anybody wanting to know more here is the link.

http://www.hptuners.com/forum/showthread.php?50917-Flex-fuel&highlight=flex+fuel

From what I can gather the O2 sensor still just reads oxygen, no surprise there. What's actually happening is upon enabling flex fuel in the ECU you unlock a few new tables that were dormant. The ethanol content is inferred data based on how far off the AFR is. If the AFR is 30% off of what the ECU thinks it should be it will calculate how much ethanol it thinks is in the fuel and then adjust the new demands on the new tables that were enabled. Exactly what tables are enabled I'm not sure. My guess would be a new ignition timing table and fuel table at the very least

Seems to me like that method of determining ethanol content might not be the most reliable.

 

[utm18]

Datalog the base tune yesterday on pump gas. Received the final today with directions of how to fill up and change over. Will be doing this tonight after work.

 

[s8v4o]

Seems to me like that method of determining ethanol content might not be the most reliable.

I thought the same thing initially since GM uses a dedicated sensor that reads ethanol content. Meanwhile Fords do not have a sensor so all the data is inferred and apparently it works.

Datalog the base tune yesterday on pump gas. Received the final today with directions of how to fill up and change over. Will be doing this tonight after work.

Are you doing a flex fuel tune or an E85 tune?

 

[utm18]

Flexfuel

 

[utm18]

This is the direction that came with the tune:

Drive the car to very low on fuel and fill up with E85, then drive with light load between 2000 and 3500RPM for at least 20minutes to allow the Ethanol to reach the engine and the ECU to adjust the content. Do not go WOT until the ECU has learned the new Ethanol content.

This will be your procedure every time you change from gas to E85 and vice versa.



Flex fuel tunes work via Logic based on the front O2 sensors to determine the Ethanol content of fuel after a fill-up of 3 gallons or more.



After an increase of 3 gallons or more is detected the ECU monitors Fuel trims at part throttle between roughly 1500 and 3000RPM.

Based on the Front O2 trim data the ECU will adjust the tune for the new Ethanol blend in the tank.

If you monitor Air Fuel (via factory track pack gauge or aftermarket) you can watch the Stoich change as the ECU learns the Ethanol content.

Once entry conditions for learning are met it will take 10 minutes or less for the ECU to learn the new fuel.

The engine must be up to full operating temp and airflow between a Min and Max (typically 1000 to 3500RPM at part throttle with light load).

After fuel is added to the tank it is important to cruise the engine in this RPM band and stay out of WOT until the ECU has learned the new Ethanol content.



*NOTE* When Keep Alive Memory (KAM) is cleared the vehicle may experience a hard start until the ECU learns the Ethanol content of the fuel.

 

[s8v4o]

Interesting, doesn't really sound like a true flex fuel vehicle. A flex fuel vehicle shouldn't need to be near empty when changing fuels. You should be able to be almost out of gas then fill up with E85 and drive. I wonder if Ford requires the same hoops to jump through as your tune does?

 

[utm18]

I'm not sure, I originally was going to do a straight E85 tune. Didnt like to idea of having to change tunes when I was unable to find E85. I was told this flex will have the same benefits as a deicated E85 tune with out the hassle of switching tunes due to availability.

 

[Sky Render]

Based on that, it doesn't need to be empty to do the relearn; it needs to have a fill-up of 3+ gallons. Then it would trigger the relearn. So you could theoretically have a tank that is 12 gallons of gas and 4 gallons of ethanol, and it would learn that ethanol mix based on the above procedure.

 

[utm18]

Based on that, it doesn't need to be empty to do the relearn; it needs to have a fill-up of 3+ gallons. Then it would trigger the relearn. So you could theoretically have a tank that is 12 gallons of gas and 4 gallons of ethanol, and it would learn that ethanol mix based on the above procedure.[/QUOTE

That is the way I understand it, and after talking to a few others that are running the same tune that is how it has worked for them.

 

[JEWC_Motorsports]

Based on that, it doesn't need to be empty to do the relearn; it needs to have a fill-up of 3+ gallons. Then it would trigger the relearn. So you could theoretically have a tank that is 12 gallons of gas and 4 gallons of ethanol, and it would learn that ethanol mix based on the above procedure.

That is how it works.

 

[Unreal]

Better than nothing, but nearly as cool as how GMs do it. My car just runs a sensor, and it takes seconds to adjust, and is constantly adjusting.

 

[Bullitt 3309]

I can say that I have successfully flipped between E85 and 93 during s recent road trip. Since I was using the nGAUGE, I could live monitor the ethanol content change after I put in 8 gallons of 93. It went from 81% to 30% after the relearn (as shown on the logger as a 1 from 0). The fun thing was watching my MPG go from 12 to 117 from just the fuel swap to 93...