Thread: 93 to 91 octane, how much to retard timing?

I tuned my 12.5:1 motor on 93 with 10% ethanol, now with the convention coming up i am assuming i will not be able to easily find 93 all the way down. So does anyone know how much timing i should take off the upper end of my map? Is 5* enough? Not worried about performance while cruising but i do not want to damage the motor. I will also stay out of the upper RPMs. Anyone with experience?

What about running meth injection for the trip?

Don't quote me, but I'd assume the differences between 93 and 91 are so small that I wouldn't change your driving habits very much. If it's highway, then that won't matter at all while cruising. Just maybe take it easy racing the engine before you can get 93 in the tank. But to answer your question, a decrease of 5* should be MORE than enough imo. I wouldn't even touch the tune though.

Also, I think you'll find 93 octane at the gas station you stop at more than 75% of the time. BP stations seem to have 93 more than other places. Search those out.

-G

Isn't it somewhere around factor of (octane point difference) * 1.5 for a rough safe estimate?

In the end i want to run Meth injection, but i do not have the funds for it now. When i start running meth i will tune on 91 with and without meth so i am covered.

Just to be safe i will drop the timing by a few degrees, 3* should be good based on your theory, but i would better be safe than start to detonate, it is hard to keep off the throttle in this car.

After doing some reading i have not found anything that means anything, other than test each setup with different types of fuel.

Nissan timing is conservative anyway. If you pull 5 , all your high boost timing will be in single digit. Most other car run double digit.

I am not running boost and my peak timing is no where near that low to go negative. This would be done via software, not turning the dizzy.

2 deg from what I have seen!!

x2.

Don't quote me on it, but @SE-Rican told me that 93 should be available in the area. I asked too.