Tune + Fuel Options

1

14SHOCAR

New member
Everyone -- I am curious how dynamic our vehicles are for fuel selection. I found a gas station that sells 103 (I believe) in Wisconsin at the pump. Without changing the 93 tune on my car, does it make sense to run higher octane fuel in our vehicles? I am not sure if the car is smart enough to adapt to the change in the fuel selection. Thoughts? Bad Idea?
 
Need a tune change to take full advantage.  If you have to change tunes for 87, 89, 91, 93, no way you are going to make the leap to 103 without a tune update.  You could probably run 103 safely on a 93 tune, but at unnecessary cost/waste.
 
IMHO, Likely a bit of overkill, but it might ensure you get the maximum timing advance (7degrees) from the ECU. For maximum advantage Manu is correct!
 
Very interesting... I just figured that the 93 tune was dynamic where it kept a better a/f based on a higher octane fuel. I guess I don't understand how the timing won't be dynamic in the sense that it can advance and retard it based on the kind of fuel that is put in... much like added e85 into the mix....

So why are people mixing e85, if the car can only advance the timing so much? Here comes the larger discussion lol.
 
I have wondered about this, too.  Most of the guys running some E85 mix it with 93 to achieve around 95 octane.  Correct?  I can see a car with a 93 tune adjusting to that and having less tendency to pull timing and more tendency to add timing.  However, I wonder if 102 or higher might actually be counter-productive?  Aren't engines at their best just prior to knock?  Would the 102 be so much overkill that the engine is actually less efficient? 

 
Everything runs off tables & ranges of parameters.  Each tune will carry with it a limited base of information to work with.  That means there is a window within any  given tune that maintains a balance of performance and longevity.  The fuels you use may not be exact every time.  So you need that cushion.  A powertrain's performance is also not linear or flat over a wide range.  You could accommodate a wide octane range in a single tune, but you would likely need more processing power and memory in the PCM to complement.
 
If you aren't knocking, race gas will be a waste. For max power, you want the lowest octane fuel that doesn't knock, that's why I'm playing with the ACES IV.

E85 is a little different because we are talking about effective octane. It is knock resistant as well but when directly injected it cools the charge massively. Cooler charge equals denser equals more power. The effective octane of direct injected e85 is over 160.

I had 3 retunes after the 12.66 that we didn't test at the track before trading. Torrie was getting ready to start cranking the timing as well because the car wasn't knock limited. The car was a beast.The car was fuel challenged in spots and the blend was moving down.....to restore volume. Its a delicate balance.
 
I'm pretty sure Rich's car made more power with a splash of E85 as well.

Consider the role temperature and humidity play with how our cars run.

E85 helps negate that when those iats climb at the track. The old big girl was super consistent at the track regardless how high iat2 got.
 
It seems like too much octane on the 93 tune is a waste. As FOMOCO stated, there is a delicate balance...sweet spot.

No E/85 and I get about a 2.x knock on WOT pull that just doesn't seem as strong (slower ET) as a healthy mix of around 17-20% E that'll pull a +1.x knock reading on a 1/4 mile WOT run. If I lower the corn mix to around 14-15% I get zero knock on the 1/4 mile pull.

Daily driving a 15% mix is perfect I think...step it up to around 18-20 for track day is my theory.


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E85 also has a lower btu value so you want just enough to get that charge cooling with as much straight fuel as possible.

Ajp is running lots of boost without knock so maybe the 10 percent in the 93 is enough....of course id say that strongly depends on fuel quality.

FYI one gallon of e85 gets you to 15% if you are running oxygenated fuel which 95% of us are.

On a 2013+ that also keeps you in the rated 15% happy spot.
 
FYI you guys are effing awesome with all this info. The knowledge here is just awesome!!!! It's hot and humid today in Milwaukee, and I have space in my tank for e85. I'm going to play with it a bit. I'm going to do 1 gallon e85 and top it off with 93. I'll let you know if I see anything different about the running of the car.
 
I'm wondering now should I get a tune? Do I need to mix e85 into my gas to avoid issues?


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Try the vGate iCar WiFi adapter, works quite well with Android/iOS devices.  And no, e85 is not a necessity to make your SHO run well, but if you are in the hunt for a bit of improvement, it's worth a shot.  Try and use the same station/pump each time for consistency.
 
Nah my goal is to do a tune , complete exhaust (installed tomorrow) tstat, plugs, 3bar, and a mdesign cai hopefully. Is that good enough? And what should I expect as far as gains from a livernoise tune. I have purchased most of the items from a board member. I'm hoping for a night and day difference. But I'm unsure how effective it'll be here in this Houston heat and humidity.


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