E85/Premium Gas

[Scott Geyer]

Is it an option to be able to run 85 and then switch to premium gas or is it one or the other only?

 

[Scott #321]

You would need to change the tune for it to be right. Tuned for e85 and using premium would be very rich. Tuned for premium and running e85 very lean and things would probably melt or come apart. I have not heard of a flex fuel controller available for the engines we use but it could exist.

 

[Scott Geyer]

Ok. I should have been alittle clearer. That’s what I was asking if there is a controller you can install. My buddy has a 900hp WRX and he can run both

 

[Classy]

You just need a flex fuel controller that taps into the canbus and then have the tune updated for it, it will automagically adjust injector and timing. Worked amazing on my old Miata

 

[Scott Geyer]

Thanks for the info

 

[Rauq]

You just need a flex fuel controller that taps into the canbus and then have the tune updated for it, it will automagically adjust injector and timing. Worked amazing on my old Miata

I don't believe the LSJ (P12) or LNF (E69) PCM can do this. The E37 and E67 (2.4 and later 2.2, not respectively) can be pinned for a flex fuel sensor, but I've not seen it confirmed that they can do flex fuel switching in Cobalt applications. Most aftermarket ECUs can do it, though.

 

[Classy]

I did it on a factory ECU, and yes it was Mazda, but it is super common. It ties into one of your canbus lines (Evap, EGR or something else that you likely aren’t using) and the rest wires in very easily. The tuner just needs to activate that canbus line for flex fuel. I also did the same thing for ECU controlled boost control, so I could change maps and run a different boost level instead of running an external controller

 

[Gtstorey]

There isn't anything to activate to make it "flex fuel" on some GM ECM's or at least with HPT. There isn't any way that I've ever come across for making the E69/LNF "flex fuel". The best you can do is have different tunes for different ethanol content.

 

[Rauq]

It may be super common, but it's not doable on a P12 (LSJ, SS/SC) or E69 (LNF, SS/TC). There's no "activating flex fuel" in HP Tuners for those operating systems. You can get the analog input of a flex fuel sensor into the ECM as many have done with WBO2 data in through the AC Pressure Sensor pin, but the ECM can't do anything with the data other than log it.

Same with boost control, even though the LSJ and LNF both have a PWM boost control solenoid, the computer and the tuning software don't have the ability to make it do non-factory control strategies.

I know it's super common on LS stuff in applications, even V8's that run the same physical ECM as the 2.4's and late 2.2 Ecotecs (E37/E67), but again, I don't know that the 4 cylinder OS will do anything with the ethanol content data. And if the OS isn't set up to change injection and timing data based on ethanol content, there's nothing for a tuner to activate- it just won't work.

 

[Classy]

I looked into this, and you are 100% correct, so dumb being that LS ECU’s from the 90’s support it…

 

[Gtstorey]

I looked into this, and you are 100% correct, so dumb being that LS ECU’s from the 90’s support it…

Not sure I would call it dumb. It just depends on what the ECM was shared with and whether there was a Business or Regulatory case for having E85 available. Then it's just luck to have it available on a vehicle that didn't come with it. The availability on LS cars is probably due to the shared ECM with trucks. And even then, it can be hit or miss on what can be done. The OEMs don't have the "tuners" in mind while putting this stuff together.

 

[Scott Geyer]

Thanks guys. Appreciate your feedback.

 

[Classy]

Thanks guys. Appreciate your feedback.

Sorry for the back and forth