Premium Fuel Advanced Timing?
 

I've see it mentioned here that continually using higher octane premium fuel will eventually cause the ECU to eventually advance the timing (netting some performance benefit similar to an aftermarket tune for higher octane fuel). Any truth to that?

Yes and no... Typically the tune has a High Octane, and a Low Octane timing table. If you run crappy gas, over time the car will adjust itself down to running on the low octane timing table.

I believe over time the car may learn itself back to the high octane table, but it will never add more timing that the high table calls for, so that's it's "limit" if you will

Fastest way to get back to the high octane timing table if you've been running crappy gas for a while is to disconnect the battery to reset the computer.

^This

Thanks to the info. So, if I’m understanding correctly, the “high table” of an aftermarket tune is higher than the “high table” of the factory tune?

And if you run low octane gas all the time, the factory tune will adjust to its respective low table?

Tuning the car modifies the current tables, and if you are doing a 93 tune you overwrite the low octane table with the high octane table timings. But you can no longer run 87 octane. Which honestly I would never do in a performance car anyways.

:word:

What Dustya said on the tune part.... +1


And, Basically on the second question.


Some tuners have tweaked a low octane tune to run 89/91, and tweaked the high octane to run 93+. All depends on what the tuner finds easiest or if something special is requested.

Silly question, but resetting the battery on these cars will the radio and everything else hold its info or will it need a code and all the presets reset? I didn't know if it had an internal battery or not.

presets and everything are held even your seat presets etc.. will still be stored there must be a settings battery somewhere that holds this information however your heads up display and dash diplay settings will reset and you will need to do the window up and down thing .

Thank you!

So, on a stock tune, does it make sense that running 93 octane will eventually allow the engine to make a few more HP? The 335HP rating is on the 87 octane tables?

No any performance numbers 1/4 mile 0-60 etc.. would all be done on the high octane tables.

Thanks, so the factory 335HP rating is with 91-93 octane fuel? Would it make less HP on 87 octane?

Yes as you will be running less timing on 87 octane = less torque and horsepower. Basically your timing is what point the spark plugs ignite based on where your piston is before top dead center. when you run less timing you get less power because you are not creating as much combustion , which in turn means you are not pushing the piston down as hard. 87 octane doesnt burn as clean as 93 if the timing is too high you will get pre detonation and spark knock which is very bad. so the car goes yuck!!!!! I am pulling timing and putting you in a table that isnt as aggressive .. So now you are not creating as much combustion therefore not creating as much power.

If you want the most out of your car run 93 octane

is it a huge noticeable increase some say yes some say no.. when I ran 87 octane in my car bone stock I could feel the power loss and sometimes could even hear some knock and the car would fall on its face.. coulda been bad gas but after 1 bad experience with 87 octane I never ran it again and the car never had another problem.


As for 91 octane I am unsure if that falls into the low octane or high octane tables there is only 2 tables so its based on the cars Learned experience what your short and long term fuel trims look like based on your Air/Fuel Ratio the o2 sensors are reading. Based on if the car sees knock etc... There is no way to know unless you are logging it to see what your timing is at.

Also the car will pull timing for all kinds of reasons not just fuel. If it senses something not right the idea is pull timing pull timing pull timing.

I disagree with that thought. The hosrepower rating and gas mileage #'s are based on 87 octane, there are no notations anywhere saying that the advertised power/torque and gas mileage figures are based on anything but 87 octane. There isnt even a note that 87 octane is Ok but 91 is preferred. To get the V6 into the highest timing table you have to run 93 octane all the time. For highest power/torque and gas mileage, run 93. The factory timing table's have to be very conservative as these little motors are running 11.5 to 1 compression and is tuned to run on 87. Spark knock city on a warm day with a manual trans on 87 octane, retard, retard, retard timing = a no balls V6