- Joined
- Dec 7, 2020
- Posts
- 7,107
- Reaction score
- 18,109
- Location
- Minneapolis, MN
- Ram Year
- 2017 2500 Laramie Crew Cab
- Engine
- 6.4L HEMI
Most engines have an ideal timing curve,and advancing past that curve even with higher octane fuel doesn't add squat for power.Engine Masters did a test of this,and they found the ideal timing curve on 87 octane,was pretty well the same ideal timing curve for 91 octane.The hemi might be geared for 89 octane,but the power loss by using 87 octane in a truck 6.4 probably isn't as much as you think. I bet if you had the truck on a dyno and tested rwhp it wouldn't be as big a loss as you think,and i'm not sure the knock sensors would pull as much timing as you think,unless you were at or below sealevel on a 100+ day,and under those circumstances the knock sensors would be pulling timing on 89 to
Agree, of course, my point is I don't like the hunt and search for octane algorithm using knock sensors approach to using 87 octane. My engine noticeably runs smoother on 89 octane, as a number of others have posted as well. I can't audibly hear the knock, but the member who posted the data traces showed it.
The marginal increase in fuel economy and torque comes along for the ride, but that marginal increase is the reason why they designed the default timing for 89 octane instead of 87 octane. No point in debating if they should have done it.