I'm thinking about purchasing a Diablosport Predator tuner for my 2010 Jeep Grand Cherokee 5.7L HEMI but there is one thing that concerns me. The jeep is recommended to run on 89 octane but Diablosport only has a 87 octane tune. Wont i actually lose power by running 87 octane? My dealer recommend 89 because it will provide more power and better fuel mileage because the HEMI retards the timing on 87. If i don't want to spend the money on premium i'd like to stick to mid grade but get the most power out of it and not use 87. Is there a 89 octane tune available?
Mileage at part throttle will not see much difference regardless of which tune you use. Most of DS lower octane tunes(91,89,87) are just the 93octane tune with a bit less timing.
The great thing about DS tool over pos handhelds is that you can easily customize the tune to your liking. And your not locked in to any specific tune.
Datalog ST Knock retard
with the 87tune +89 fuel. If its 0 and LT knock retad is also 0, then just add 2 degrees of WOT timing. Check for ST and LT knock again. If LT = 0 and ST is less than 2.0, you're good to go.
A little higher timing with the 87tune will capture some benefits of using a higher octane fuel.