[GTSilverBullit]

I posted the thread on a dyno tune, but now im wondering what Octane to tune for? I use 91 octane from chevron right now, cause thats all we have where i live, its really good gas...

Ive read around that the 91 octane at chevron is equivalent to others' 93 octane, is this true? and if so, would i need to tune for 93 octane?

[cliffyk]

The octane ratings applied to pump gas are very well documented and regulated--irf it could pass the 93 octane standards you can bet they'd call it that...

That said however most handheld and otherwise "end user configurable" tuners are very conservative in their timing settings (most just add 2.0° regardless of what octane you select, change the closed to open loop delays to 0 s, and richen up the stabilised open loop AFRs a bit).

If you have a global WOT setting on your tuner then add 2° and listen for pinging--you probably won't have any so go for 2.5° and listen again...

[GTSilverBullit]

so then i would have to dyno tune for the timing right?

[cliffyk]

Originally Posted by GTSilverBullit so then i would have to dyno tune for the timing right?

You don't ever have to "dyno tune" if you have sufficient experience with tuning, or if you are willing to work at gaining such experience.

There is no magic involved in utilising a dynamometer to tune an engine, all it does is make it convenient for someone tuning cars for a living because they can do it in one place and have some immediate feedback on the effect of their changes. That's it, it's just a measuring tool that really doesn't have a damned thing to do with the tune itself...

Also, because "dyno tunes" are not done under real on the road conditions (airflow and temperature are the two biggest challenges) they really just represent starting place for further tweaking for anyone that's serious about getting their ride fully dialed in.