Positive knock

[Dosia]

Pretty common on 91 in az it pretty shitty...mine will go away on e85 or a blend there of.

Yea that log is on e85. Hoping it would clean it up.

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[Dolsvt00]

Thx. Shaun is tuning it so Im sure he will dial it in. Im just trying to understand this data a bit more so I can have a clue on whats going on.

That log from what i can see does not look overly aggressive with regards to timing to me, it actually looks like its adding a pretty fair amount of timing.

Even on e85 i personally see some positive knock during certain conditions, its not often and its random but it does happen. It could be false knock (which it probably is) or just the fact that the knock sensor is sensitive,It never really does it during a constant WOT pull. I'd honestly do a couple back to back logs and use load as your reference line and graph knock sensor under it to make it easier to read. If the load line is flatlined up and the knock sensor line is heading down, its not retarding, its adding.

 

[Jeff_oddo]

I added in some 104 octane race fuel which raised my octane to 96 octane. Did a datalog and the positive knock is gone. So I narrowed mine down to crappy 93 in my area

 

[Dosia]

Shaun said this is certainly false knock since Im on e85. I will have to get my car on a lift again and look over the exhaust from front to back. I did 3 back to back logs and this one was the worst.

 

[v8440]

Guys, can you help me interpret this? It's cruising on the interstate at about 70 mph, does this knock reading mean more timing can be added? The whole log is about a minute, and is basically full of zero knock with occasional excursions into the negative region just like what the picture shows.

 

[Ramen]

Negative knock is good.

 

[v8440]

So, it's a safe bet my tuner could put some more timing in there?

 

[v8440]

Hmm, I just looked at the log of a wot run on 93 octane, same tune as above. Bunch of positive knock. (that's the log shown below) The log of wot on this tune with e85 in the tank showed essentially no positive knock, and a good bit of negative. I guess that means the tuner needs to pull timing under heavy load on gasoline?

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