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Persistent knock retard on e85 flex tune

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I’m dealing with some persistent spark knock timing pull on flex tune e-85. Curious if anyone else has had this issue. 93 octane tune it’s quiet as can be no KR. With e-85 I get 8 degrees pulled at 4K and it runs like crap from 4-6K due to the timing being pulled. On 93 it runs like a scalded dog. I’m still in the tuning phase remotely with my tuner and he’s been super helpful we are trying to eliminate things. There is no knock sensor desensitization at all and that’s the way he tunes which makes sense as he wants to keep the motor safe. It is a weird scenario I have tried two tanks of e85 from different stations the file reads the concentration as 80 -85 percent ethanol. I have not tested it manually as a tester is in the mail. We have pulled timing to see if that helps and so far no change. It only knocks on ethanol and not just a little but a lot 8-10 degrees starting at 4K up until around 6K. No weird noises from supercharger , exhaust doesn’t appear to be hitting anywhere. I have tried the following , different tank of fuel, moved exhaust tips, loosened and tightened all exhaust clamps and bolts, verified clearance, bled intercooler pump. I’m showing 80 percent duty cycle on injectors and fuel pressure commanded matches what is delivered. Doesn’t appear to be a fueling issue at the moment but I’m not expert. Mods are as follows

2018 m6 hellcat
2.82 upper
Ported FAS snout w new stock bearings
Afe CAI
100 mm bbk TB
Cat delete pipes
Muffler delete
FIC 1000 injector
Catch can
Blower spacers and heat shield
Dual in tank pumps
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Well it very well could be a bad flex tune. Flex tunes take a lot of work.
my guess you are going lean and getting knock that way. I just retuned another car on this site that was having knock issues when on e85. He was lean. If you decide you want me to retune the car let me know. If it isn’t knocking on 93 it isn’t false knock you are seeing on e85. If the fuel was 65 percent alcohol the flex should be adjusting fuel and timing for it.
Reach out or let me know if you help help
 

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Your tuner will figure it out but I would start with the tune itself and that sensor or install high quality one if you don't or a gauge of some sort cause something's telling the pcm to pull timing obviously.
we just need to figure out what it is.
 

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Discussion Starter · #6 ·
Well it very well could be a bad flex tune. Flex tunes take a lot of work.
my guess you are going lean and getting knock that way. I just retuned another car on this site that was having knock issues when on e85. He was lean. If you decide you want me to retune the car let me know. If it isn’t knocking on 93 it isn’t false knock you are seeing on e85. If the fuel was 65 percent alcohol the flex should be adjusting fuel and timing for it.
Reach out or let me know if you help help
We are still on the tune phase currently. I appreciate the offer. Mainly looking for things over the weekend to try on my end. Very well could be an issue on my end as I'm just a regular guy and not a shop.


Honestly could be the FAS junk I’d stay far away from them

Believe me I know. I had a bad experience. Was told it would have upgraded bearings, they were stock. Was told it was in stock would ship next day (only reason I chose them was I was in a time crunch, car was down and I needed ASAP). It didnt ship for a week and I had to hassle for a few weeks for my core refund. The blower blanket I ordered was cut all weird and no way to adhere to bottom of blower it looked like a square cut off insulation from ace hardware to me that I got charge 100 bucks for. However, maybe they are all like that I am not sure. I had a poor purchase experience. He was super responsive until he got my money then it would take multiple emails to get a reply.
 

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We are still on the tune phase currently. I appreciate the offer. Mainly looking for things over the weekend to try on my end. Very well could be an issue on my end as I'm just a regular guy and not a shop.





Believe me I know. I had a bad experience. Was told it would have upgraded bearings, they were stock. Was told it was in stock would ship next day (only reason I chose them was I was in a time crunch, car was down and I needed ASAP). It didnt ship for a week and I had to hassle for a few weeks for my core refund. The blower blanket I ordered was cut all weird and no way to adhere to bottom of blower it looked like a square cut off insulation from ace hardware to me that I got charge 100 bucks for. However, maybe they are all like that I am not sure. I had a poor purchase experience. He was super responsive until he got my money then it would take multiple emails to get a reply.
Yep FAS is a known scammer
 

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Imo flex tune is pointless if you have pump e85/flex fuel near you. No reason to run 93 if you have pump e85 near you. Get a tune for “pump” e85 and an aggressive tune for canned e85+. Flex tune is a pipe dream, more issues than it’s worth (I had a flex tune). The flex cal is based off the 6 cylinder, completely different engine. I read through all the patents for how the system works - the 6.4/6.2 does not have the hardware for it to function, period. It’s based on the evap purge solenoid being triggerd and purging fumes from tank to engine after a fill up, and then reading fuel trims/ o2 readings. It reads at key on, ignition, and then for a specific interval after filling up. Hellcats do not have the same evap system or controls as the v6, which is a critical part for inferring alcohol content. That’s why it’s hard to get right based on fuel trims and o2 readings alone. I’m not even sure if there’s a pid in hp tuners for the purge solenoid, but be interested to see someone data log that while on flex tune after fill up to see if it’s actually triggered and actuated, I have my doubts. Also interesting dodge is blowing up engines left and right in their “last call” flex fuel Hellcat. 65%+ there’s really no additional power to be had by fuel alone, just safety in how far you can push it with 85+
 

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I’m dealing with some persistent spark knock timing pull on flex tune e-85. Curious if anyone else has had this issue. 93 octane tune it’s quiet as can be no KR. With e-85 I get 8 degrees pulled at 4K and it runs like crap from 4-6K due to the timing being pulled. On 93 it runs like a scalded dog. I’m still in the tuning phase remotely with my tuner and he’s been super helpful we are trying to eliminate things. There is no knock sensor desensitization at all and that’s the way he tunes which makes sense as he wants to keep the motor safe. It is a weird scenario I have tried two tanks of e85 from different stations the file reads the concentration as 80 -85 percent ethanol. I have not tested it manually as a tester is in the mail. We have pulled timing to see if that helps and so far no change. It only knocks on ethanol and not just a little but a lot 8-10 degrees starting at 4K up until around 6K. No weird noises from supercharger , exhaust doesn’t appear to be hitting anywhere. I have tried the following , different tank of fuel, moved exhaust tips, loosened and tightened all exhaust clamps and bolts, verified clearance, bled intercooler pump. I’m showing 80 percent duty cycle on injectors and fuel pressure commanded matches what is delivered. Doesn’t appear to be a fueling issue at the moment but I’m not expert. Mods are as follows

2018 m6 hellcat
2.82 upper
Ported FAS snout w new stock bearings
Afe CAI
100 mm bbk TB
Cat delete pipes
Muffler delete
FIC 1000 injector
Catch can
Blower spacers and heat shield
Dual in tank pumps
Why would you run anything but the best 93 in these cars?
 

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2020 Challenger Hellraisin Scat Pack.
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Have to question the percentage of ethanol. E85 can run between 51% and 83%. 80% to 85% especially "now" is questionable.


51% is a winter blend. Higher percentage of gasoline helps with cold starts. 83% is a summer blend. Cold starts are not a summer problem.

Suspect the determination of the percentage of ethanol and properly fuel the engine is not working 100%. That would be the tune then, I guess.
 

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We are still on the tune phase currently. I appreciate the offer. Mainly looking for things over the weekend to try on my end. Very well could be an issue on my end as I'm just a regular guy and not a shop.





Believe me I know. I had a bad experience. Was told it would have upgraded bearings, they were stock. Was told it was in stock would ship next day (only reason I chose them was I was in a time crunch, car was down and I needed ASAP). It didnt ship for a week and I had to hassle for a few weeks for my core refund. The blower blanket I ordered was cut all weird and no way to adhere to bottom of blower it looked like a square cut off insulation from ace hardware to me that I got charge 100 bucks for. However, maybe they are all like that I am not sure. I had a poor purchase experience. He was super responsive until he got my money then it would take multiple emails to get a reply.
WOW, I can’t believe this company is still in business being it sounds like their practices have never changed from years ago.
Not knocking your tuner but I can state from my own experience a so-called Pro tuner ruined my first engine with their flex tune attempt and I still gave them a no blame shot on my rebuilt engine, quickly fired them when I saw they turned off misfire detection which it what ruined my first engine. @Jonx96 fixed their F-ups quickly, I put down almost 1100 wheel on pump E83 consistently with no issues. I HIGHLY recommend for your engines sake (and your wallet) you change tuners while you still can. Pulling 8 degrees of timing on ethanol over 70% something is HIGHLY WRONG in your tune!!
Like was suggested here if E is easy to get for you and you plan on running it consistently and most of the time get a dedicated E80 tune and 93 tune if your boost level is not too high for such. If your making over 16 lbs of boost, have peaks of 17 lbs don’t even think of running 93 or a flex tune in my opinion and experience at least.
Best of luck to you
 

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Imo flex tune is pointless if you have pump e85/flex fuel near you. No reason to run 93 if you have pump e85 near you. Get a tune for “pump” e85 and an aggressive tune for canned e85+. Flex tune is a pipe dream, more issues than it’s worth (I had a flex tune). The flex cal is based off the 6 cylinder, completely different engine. I read through all the patents for how the system works - the 6.4/6.2 does not have the hardware for it to function, period. It’s based on the evap system pumping fumes from tank to engine after a fill up, and then reading fuel trims/ o2 readings. It reads at key on, ignition, and then for a specific interval after filling up. Hellcats do not have the same evap system or controls as the v6, which is a critical part for inferring alcohol content. That’s why it’s hard to get right based on fuel trims and o2 readings alone. Also interesting dodge is blowing up engines left and right in their “last call” flex fuel Hellcat. 65%+ there’s really no additional power to be had by fuel alone, just safety in how far you can push it with 85+
WORD!
 

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It’s lean

Neither of the guys I am working with help me do a flex tune. And mines n/a!

Is unholy right and it goes off a burp at fill up? Why does the kit come with a in-line real time sensor?????
 

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It’s lean

Neither of the guys I am working with help me do a flex tune. And mines n/a!

Is unholy right and it goes off a burp at fill up? Why does the kit come with a in-line real time sensor?????
It does 100%. That kit does nothing that you’re talking about - doesn’t adjust spark, just injected pulse width. we’re talking about patched os with flex fuel tables in hp tuners
 

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The best way to do flex fuel imo? Would be to see if the code exists in the GPEC2A from the old Daytona that used a physical methanol sensor, patch os/ enable that, and recalibrate voltage for a Gm flex fuel sensor. One shop tried something like this using the EGR (hellcats don’t have egr). They enabled it in hptuners, and used the pin on the PCM to feed the signal from the flex fuel sensor to the pcm. You need to use a special gauge so you can adjust the voltage range to feed to the pcm. Problem is, there’s no startup/idle tables for the EGR. Just 2 or so spark tables. You can also change BCM and display the ethanol content from sensor by hijacking one of the temp sensors
 
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