Hey guys,

I am getting the new Haltech EMS to replace my existing Haltech and I had a few questions regarding the flex fuel function.

Is this the correct process to tune it correctly for flex fuel?

1) Tune car completely on 91 octane
2) Empty gas from vehicle and replace with e85
3) Tune car for e85

After these 3 steps are done will the haltech unit calculate timing and afr based on the amount of ethanol? Or do you need to have a tune with a mix of e85 and 91?

 

you need to tune various increment of ethanol percent, ie 85, 80, 75, 70, etc etc to get the offset table correct.

prepare to spend hours on the dyno doing so.

 

That doesn't sound fun. So basically I have a partial tank of 91 gas and then add e85 until the sensor reads 5% then 10% then 15% then 20% etc... At $200-250/hr that seems pretty ****ing expensive.

 

I have my Osiris tuned for E85 and 91...I have a 91 tune, an E85 tune, and a 50/50 E85/91 tune for emergencies...in any event, if I want a reliable tune on boost, I can only use my 100% 91 and E85 tunes...

 

well you drain your tank and add E85 and go down from there. Yup, very time consuming and possibly very expensive if you are paying hourly.

An experienced haltech tuner could probably dial in the trims pretty quickly though.