Question about flex fuel sensor

[2GNS4ME]

Sorry for my ignorance but with the flex fuel sensor do I have to have 2 programs on my XFI to run my car on the street? One for E85 and one for 93? The reason why I ask is I only have 1 gas station by me with E85 and if I run out I would like to run 93 until I can refuel on E85. I just don't want be stuck anywhere. Any info is greatly appreciated.

 

[HighPSI]

As long as the program is setup for the flex fuel sensor. The flex fuel sensor will compensate for whatever fuel mixture you have.

 

[2GNS4ME]

Thank You Cal. Once I get my motor back and ready to setup I will be giving you a call.

 

[Rafs-T-Type]

As long as the program is setup for the flex fuel sensor. The flex fuel sensor will compensate for whatever fuel mixture you have.

But is it going to turn your boost down to a safe level?

 

[marleyskater420]

As long as the program is setup for the flex fuel sensor. The flex fuel sensor will compensate for whatever fuel mixture you have.

If he has an XFI from you with the thumbwheel that has a E85 program in it, could he save money on the fuel sensor and just switch the thumbwheel over to the E85 setting?

Would that be doing essentially what the flexfuel sensor does-letting the ECM know its on a different fuel?

I don't know much about XFI but I'm wondering if that is how it works(at least with your thumbwheel piece)?

 

[HighPSI]

I can make the programs in a thumbwheel for whatever fuels you are running, but you have to have a pure mixture of that fuel. In other words, you have to drain the tank when swapping fuels. The flex fuel meter allows you to have a variable mixture of fuels and the tune will still work. If your running low on E-85, you can dump some gasoline in without draining the tank and the car will still run fine with a flex fuel sensor.
If the XFI is controlling the boost, the thumbwheel method allows diferent boost settings for diferent fuels. If you are using a flex fuel sensor it won't pull the boost if the octane isn't there.

 

[marleyskater420]

I can make the programs in a thumbwheel for whatever fuels you are running, but you have to have a pure mixture of that fuel. In other words, you have to drain the tank when swapping fuels. The flex fuel meter allows you to have a variable mixture of fuels and the tune will still work. If your running low on E-85, you can dump some gasoline in without draining the tank and the car will still run fine with a flex fuel sensor.
If the XFI is controlling the boost, the thumbwheel method allows diferent boost settings for diferent fuels. If you are using a flex fuel sensor it won't pull the boost if the octane isn't there.

Oh gotcha. So how bad would it be if you had a 10 gallon cell and lets say 2 gallons of 93octane and filled it with 8 gallons E85, and switched it to the E85 thumbwheel setting, but did not race/get into boost ?

If the fuel mixture is not 100% pure of the type of fuel for your program, how detrimental will that be to the driveability of the motor? It seems like the flexfuel sensor will just recognize there isn't a pure mixture, but its not going to do anything for the boost/timing?

If that is the case (and I appreciate your explanations, btw, thank you) then doesn't the fuel sensor seem almost "not-needed" if you can get the mixture to within 75-90% of the selected fuel on the thumbwheel? (so you select the 93 octane setting, and you only have 75% of the tank with 93)

Sorry for all the questions, I'm just quite curious about this. Always wondered how modern cars were able to determine what timing map to use.