What horsepower difference would they be in built motor tuning for 91 octance instead of 93 octane.8# lower pulley 2.75 upper I have all the mods installed everything the higher 93 octanes are getting harder to find.

Thanks

 

Probably not much.
You would have to pull some timing out for 91 octane and I was picking up about 4 to 5 HP per degree of timing in my truck.
So even if you pulled 4 degrees out it would only be about 20hp.

Phil

 

Thanks Phil, it seems a lot of gas stations just don't sell 93 octane. I have 3 tunes on my xcal-2 93 95 & 98 octane if i was to get to far away from home and couldn't find 93? well i know i could stay of boost and be alright. But i think i will just get tune for 91 octane on one of my tunes just in case i have excess to 100 octane unleaded and mix my own fuel i can live with a little less timing. Tom

 

A moderator on another L forum tested an individual cylinder knock control system on his HD. It had been running a safe tune at 19 psi and 91 octane for two years before the test.

For the test, he went through two tanks of 89 octane over a month's period while running the 91 octane tune.

At full load, his tune sets the timing to 13°, but that drop in octane of two points required an additional 16° of knock retard on some cylinders.

At the end of the test, he mixed 91 and 89 50/50 and it required 8° knock retard on some cylinders.

There is a short clip of it if you google knock controller demo.