My tuner just finished developing a 100 octane tune for my EcoBoost for me to use during HPDE sessions. I noticed on the datalog after the final revision that it shows an intermittent knock count of 1or 2 every once in awhile under full throttle at high rpm; sometimes does and sometimes doesn't. He declared that final revision good-to-go. I am wondering if those minor intermittent knock counts are okay when running hard for 20-25 minute sessions, or should I go back to the prior revision that has a little less power but zero knocks showing on the datalog?

If it was me, I would choose a knock free tune. It's HPDE, right? Why risk grenading an expensive motor when you are just running for fun?

Is the “prior revision” tune 100 octane as well?

Yeah that's my thought to just go with the prior no-knock revision. Yes the prior revision is also a 100 octane tune; my tuner starts conservative and then bumps the tune up a little bit at a time after each datalog until he determines that's as far as we can go safely. That was version 8 and the knock occurred on version 9 when he said that's as far as we go. He developed a 93 octane street tune for me that has no knocks.

GJarrett said:

Yeah that's my thought to just go with the prior no-knock revision. Yes the prior revision is also a 100 octane tune; my tuner starts conservative and then bumps the tune up a little bit at a time after each datalog until he determines that's as far as we can go safely. That was version 8 and the knock occurred on version 9 when he said that's as far as we go. He developed a 93 octane street tune for me that has no knocks.

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Yep, back it down, you're not racing anyone

GJarrett said:

My tuner just finished developing a 100 octane tune for my EcoBoost for me to use during HPDE sessions. I noticed on the datalog after the final revision that it shows an intermittent knock count of 1or 2 every once in awhile under full throttle at high rpm; sometimes does and sometimes doesn't. He declared that final revision good-to-go. I am wondering if those minor intermittent knock counts are okay when running hard for 20-25 minute sessions, or should I go back to the prior revision that has a little less power but zero knocks showing on the datalog?

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What’s the datalog look like? Have you ruled out false knock? In my experience, tune revisions are generally for ironing out fuel trims, not always adding timing, so going back one version would negate other beneficial changes and not solve the root problem. As always, this is a discussion to have with your tuner, not a forum (no offense to those offering support).

Understood. I've emailed my tuner and am waiting for reply; but it never hurts to hear opinions from the vast experience on this website. I guess my original question was seeking opinion on if a random occurring low knock count of 1 or sometimes 2 is acceptable, or if the only acceptable knock count is zero.

I hadn't considered false knock - I'll pour some extra Boostane in and see if that makes it go away. I think that might tell me if it was false or not(?) If it's false, I'd like to keep this revision since the est hp/tq reading on the Cobb datalog is 25hp/27tq higher on tune v9 than v8, and it's enough that I can feel the difference on my seat-of-my-pants dynometer.

Any knock is going to result in the PCM pulling timing, negating any benefit of the additional base timing in your tune.

If it was false knock you'd probably see it all the time and in all tunes.

Run the previous tune.

If you want more power, get an e85 tune and exclusively run that.

Different car, different tuner here, but when AED was tuning my Boss, even with False knock, this showed up early in the tuning process. I had to fix before a new revision was sent to me. Nevertheless, if you have a reputable tuner, I would just run the prior tune. Current one possible running on the edge.

False knock can show up at any time regardless if it wasn’t happening before, that’s why I asked what the datalog looks like. Ive chased it on several cars at a previous job and it has a definitive profile; kind of looks like a declining staircase. It is worth doing a test on the prior revision to rule it out.

Alex_murrica said:

False knock can show up at any time regardless if it wasn’t happening before, that’s why I asked what the datalog looks like. Ive chased it on several cars at a previous job and it has a definitive profile; kind of looks like a declining staircase. It is worth doing a test on the prior revision to rule it out.

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Just found this comment. What do you think of this?

Isn't E85 cheaper than 100 octane gasoline?

100 Octane is easier to come by at the track than E85 (at least here in TX at MSR Cresson and Eagles Canyon Raceway) so I can see the appeal of doing the 100 octane tune if you drive your car to the track and back home afterwards.

Exactly. I can find premium or 100+ fuel anywhere at almost any track - or premium at a gas station closest to the track, and add Boostane to get my 100 octane. E85 would not only require me to fill up more often during a track day but also be unobtanium in many/most cases when I do run out my tank.