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Persistent knock retard on e85 flex tune
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
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
1 - 20 of 294 Posts
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.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
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.
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.
I have a tester en route arriving tomorrow. I am getting 10 gallons from another station to test and I will post results.
I am seeing 15 lbs. I highly doubt it's the tuner as there is a stellar reputation and I know he has a done a lot of these. He has been super responsive, it is a process. My reason for this post was to see if there were things I could try over the weekend on my end while awaiting further recs on monday. I favor currently fuel issue or something on my end rather than tuner.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
I am learning the ins and outs of e85. I will for sure be testing moving forward. I was under the false assumption than even minimal percentage or winter blend would be far superior to 93 octane and unlikely to cause knock. I also did not and still do not understand how percentage is calculated with ethanol in flex tunes so I will be testing my fuel moving forward to eliminate that variable.
I will get back with you on that. I know we pulled timing on the e85 side once already and I suspect on monday will do more.Start with getting a physical test of your fuel in the tester. Let us know what it shows.
How much spark is commanded on 93 at 4000 rpm? How much on e85?
Ok so tested e85 today from previous tank it is at least 75 percent. Added 5 gallons of renegade race fuel (100 or 110 octane I forget, it is the purple pump stuff to a near full tank and it still did the same thing. Talked to tuner, he wants to go back to 93 and see if something has changed so I will run this tank out and switch back and relog. I checked my catch can and it looks fine, oil looks fine. I can rev engine and no smoke, no misfires it drives/starts normal w no signs of damage but with this much knock I am worried and thinking of pulling number 7 plugs to have a look. I will post some log screenshots. It wont let me upload the log due to file type I believe.
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At this point would u pull a plug? I am worried some given the degree of timing pull that the motor could be hurt even tho I see no signs of such. It is all just so odd. If when I go back to 93 it is still there something big has changed and i think that points to mechanical for sure.
twin 285's drop in fuel system. So far the commanded fuel pressure has been right on. Injectors at 6500 are showing 80 percent duty cycle on e85 and something like 60 something on 93.1000cc injectors might be getting maxed out as well. What dual pump setup do you have in the trunk? Maybe you're not flowing enough fuel?
R.K.
Your guess is as good as mine lol.And what the heck were you doing with the throttle right before your 93oct pull??
View attachment 607992
I was just happy to see the tips were still there and the ceramic wasn't burnt off.Need light and a magnifying glass
*and to know what to look for lol
@khomes7 I don't see anything in the screen shots you posted that look way out of whack, but I'm not here to tell your tuner what to do either. I'm just some guy on the internet after all.
My first recommendation is to either change the scale on the KR PID to negative, so -15 for min and 0 for max since you're reading it in a negative number. That will give you a line on the graph to see. To set this, right click the chart, and click "Chart Properties", select the PID KR, and set the scale. Alternatively you can change the KR PID to STKR and leave it as is as STKR will show up as a positive number. 6 of 1 half dozen of the other, but I use STKR personally. I would also add Knock Sensor Volts 1 and 2 to the graphs.
The next thing I would do is remove 7° of timing at that point in the tune or set it to something like 2° and test. That will usually show if the knock is real or false. If you remove a bunch of timing and you still see that much KR then it's likely supercharger noise plus you have cat delete and muffler delete so I imagine that car is VERY loud which probably doesn't help things.
Finally, with pulley changes I've not seen a car that didn't need some adjustment to the knock sensor thresholds. The factory sensor settings were tuned for the factory pulley. Changing pulleys changes the frequency of the noise the supercharger makes and the knock sensor pick it up. You don't want to adjust them much, only just enough. It took me a long time to dial mine in but any experienced tuner should have a base line that typically works for them to speed up that process. On my personal car 4,000 RPM was especially fussy in terms of false knock. I tested using race fuel at the time and dialing out timing as described above. I still had 7+ ° of STKR so I knew it was false and adjusted accordingly.
Your plugs look exactly like mine did as well. The true tell for knock is to shine a light down in the plug and use a magnifying glass to look for flakes of glitter. Some deposits are normal so don't get confused by those.
I appreciate the advice and if I was tuning it myself I would follow it. However, I think my tune file is locked and even if it wasn't I don't think I could disrespect my tuner and make changes until he has exhausted all known routes to determine the issue and he just gives up I am limited at the moment to non tune file things to diagnose and just ordered SUR&R Line Adapter: Fuel Line, 2 Pieces, Silver, Includes Clamps, 2 PK - 52HJ15|K445 - Grainger to drain this fuel so it will be a few days before I have more info or logs on 93 octane.. I couldnt stomach just wasting that whole tank of e85 plus 100 octane so I am gonna save it and drain via fuel pump. I learned quickly you can't siphon these cars.
@khomes7 I don't see anything in the screen shots you posted that look way out of whack, but I'm not here to tell your tuner what to do either. I'm just some guy on the internet after all.
My first recommendation is to either change the scale on the KR PID to negative, so -15 for min and 0 for max since you're reading it in a negative number. That will give you a line on the graph to see. To set this, right click the chart, and click "Chart Properties", select the PID KR, and set the scale. Alternatively you can change the KR PID to STKR and leave it as is as STKR will show up as a positive number. 6 of 1 half dozen of the other, but I use STKR personally. I would also add Knock Sensor Volts 1 and 2 to the graphs.
The next thing I would do is remove 7° of timing at that point in the tune or set it to something like 2° and test. That will usually show if the knock is real or false. If you remove a bunch of timing and you still see that much KR then it's likely supercharger noise plus you have cat delete and muffler delete so I imagine that car is VERY loud which probably doesn't help things.
Finally, with pulley changes I've not seen a car that didn't need some adjustment to the knock sensor thresholds. The factory sensor settings were tuned for the factory pulley. Changing pulleys changes the frequency of the noise the supercharger makes and the knock sensor pick it up. You don't want to adjust them much, only just enough. It took me a long time to dial mine in but any experienced tuner should have a base line that typically works for them to speed up that process. On my personal car 4,000 RPM was especially fussy in terms of false knock. I tested using race fuel at the time and dialing out timing as described above. I still had 7+ ° of STKR so I knew it was false and adjusted accordingly.
Your plugs look exactly like mine did as well. The true tell for knock is to shine a light down in the plug and use a magnifying glass to look for flakes of glitter. Some deposits are normal so don't get confused by those.
I did not inspect with magnifying glass and now I wish I had. In my mind I had convinced myself they were burnt off or something so when I saw everything intact I just leaped for joy in my mind and reinstalled them.
I am halfway tempted to install my cats back while I am waiting to see if it fixes things (If it is knocking now on 93 I will start really examining for false knock.)
If there is any other diagnostics that you guys can think of in the meantime that doesn't involve tune changes I am willing to try them.
I am not so luckyIf your 2018 has the schrader valve on the driver side fuel rail, you can use one of these to drain the fuel:
Maybe the early production 18's didn't get the shrader valve I am not sure but mine doesn't have one.105758"]
21° at 6600
18° at 5500
12.5° @ 4500
The OP’s tune didn’t have any timing in it to start with. Before it pulled the 7. Seeing 78.5% ethanol
Something must be way off
[/QUOTE]
Correct , this is second revision where timing was pulled (trying to figure the knock thing out)which did not change the amount of KR or the onset rpm. The first one had more timing I have the log from it too but it looks the same as except more timing I believe.
agree, something is way off which points me back to mechanical.
Couple of mechanical things I noticed upon my inspections, one of the diff brace bolts backed out (the two that mount from bottom )which could be allowing some movement under torque. The rubber gasket is still there and unmoved. (I will be replacing )
Second, my accessory belt is the original incognito length which is longer (1/2 inch?)which could be causing harmonics via accessory drive but no noises and It has been on there since 93 tune but weather is colder. (I have zero noises and nothing revving in neutral.) I may change this today.
21° at 6600
18° at 5500
12.5° @ 4500
The OP’s tune didn’t have any timing in it to start with. Before it pulled the 7. Seeing 78.5% ethanol
Something must be way off
[/QUOTE]
Correct , this is second revision where timing was pulled (trying to figure the knock thing out)which did not change the amount of KR or the onset rpm. The first one had more timing I have the log from it too but it looks the same as except more timing I believe.
agree, something is way off which points me back to mechanical.
Couple of mechanical things I noticed upon my inspections, one of the diff brace bolts backed out (the two that mount from bottom )which could be allowing some movement under torque. The rubber gasket is still there and unmoved. (I will be replacing )
Second, my accessory belt is the original incognito length which is longer (1/2 inch?)which could be causing harmonics via accessory drive but no noises and It has been on there since 93 tune but weather is colder. (I have zero noises and nothing revving in neutral.) I may change this today.
1 - 20 of 294 Posts
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