2018 GT knock with flex fuel

[AZ18yote]

I have been data logging my ff tune as my AFR was higher than expected. After a KAM reset AFR dropped some (high 11s and 12) and proceeded to send in WOT pulls. I now have knock showing up that was not there before. AED is thinking it's the e54 blend here. My first full ff tank and subsequent half tank was at location A. I topped off today at location B but not enough for it to be getting logged yet. I am thinking of letting this tank run its course going easy on her then do another full tank at location B or find a 3rd location (AZ is limited) and do a full tank and log. If knock is still present then switch back to our good old 91 octane.

It seems like most places around the country have real e85. Just curious peoples thoughts on this scenario and experience with e54 ff blends in general.

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[msweet]

Have you got a catch can? When I was logging for my Lund flex tune they suggested installing a catch can to see if that helped. Put the JLT on the car and away it went. YMMV

 

[AZ18yote]

Have you got a catch can? When I was logging for my Lund flex tune they suggested installing a catch can to see if that helped. Put the JLT on the car and away it went. YMMV

Interesting I hadn't heard that as a possibility. Considered doing one if doing a CAI and already had the cover off. Wouldn't be against trying it though my confusion would lie in the fact on the same tune at WOT on 91 no knock. Only reared its ugly head after 1.5 tanks of ff and KAM reset.

 

[AZ18yote]

Interesting I hadn't heard that as a possibility. Considered doing one if doing a CAI and already had the cover off. Wouldn't be against trying it though my confusion would lie in the fact on the same tune at WOT on 91 no knock. Only reared its ugly head after 1.5 tanks of ff and KAM reset.

Also not sure if relevant but has been warm 110 on avg and I believe may have forgotten to turn off ac on the last submitted log.

 

[Joe 5.0]

Well of course your AFR is going to be higher than normal when you're not running pure E85. When my nGuage was reading that I had pure E85, my AFR was around 9.8 - 10.0.

Now, I have a mix of gasoline and E85, and my AFR reads around 12.0. The knock is most likely from that terrible blend you're running. I'm surprised your tuner hasn't recommended an octane booster.

 

[AZ18yote]

Well of course your AFR is going to be higher than normal when you're not running pure E85. When my nGuage was reading that I had pure E85, my AFR was around 9.8 - 10.0.

Now, I have a mix of gasoline and E85, and my AFR reads around 12.0. The knock is most likely from that terrible blend you're running. I'm surprised your tuner hasn't recommended an octane booster.

If the blend is the culprit, which it likely is it sounds like, what are options. Multiple source checks, octane booster on every fill up if cannot find better source for blend?

Interesting enough there is a member locally here running with the same tuner and filled up a couple of days ago at location B ( location I only got half tank to top off but was planning on doing another full after) with AFR in high 10s and low 11s. He will be logging when possible to see if knock is present. I am hoping it shows not and going forward I can just avoid location A like the plague.

Are the boosters enough to compensate when blend is crap?

 

[Joe 5.0]

If the blend is the culprit, which it likely is it sounds like, what are options. Multiple source checks, octane booster on every fill up if cannot find better source for blend?

Interesting enough there is a member locally here running with the same tuner and filled up a couple of days ago at location B ( location I only got half tank to top off but was planning on doing another full after) with AFR in high 10s and low 11s. He will be logging when possible to see if knock is present. I am hoping it shows not and going forward I can just avoid location A like the plague.

Are the boosters enough to compensate when blend is crap?

I personally wouldn't run an octane booster all of the time. Something about putting liquid that's not pump gas or E85 into the tank freaks me out. However, you can use the octane booster with your current tank of gas to see if the gas is the culprit. If you still have knock while using the octane booster, then fuel isn't the issue. If the knock goes away while using the octane booster, then the fuel is trash.

Obviously run this by your tuner before you do anything and make sure your tuner will allow it. Also, make sure you read and abide by the instructions on the back of the octane booster bottle.

 

[Lonmon]

If you haven't already, please buy a tester and test your fuel to know what the actual ethanol content is. That will help you find which locations have decent fuel and let you and your tuner know the realistic e content. I have found most e85 stations around here at least to actually be more like e75. The kit is made by Holley, you can get it online cheap and is super easy to do. I am not sure if octane booster works the same with ethanol fuels as it does with gasoline. Lund told me not to use booster with e fuel. Also, it takes a couple of tanks to get the maximum e content of the fuel. Your left over gasoline will water down the e fuel some even if you ran it almost completely dry before fill up. I usually don't see full afr change until the second fill up.

 

[AZ18yote]

The flex fuel location test seems to have been successful. Another full tank from the location assumed to be good. Log showed at WOT negative knock through 6k. Conditions didnt allow to push higher but considering I was seeing positive knock of 1+ through 6500 before on the presumed bad fuel this seems promising.

I did see a tad of positive knock from about 2200-2400 but quickly switched to negative for the remainder of the pull today.

Will be getting a tester as well as mentioned above.

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