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Persistent knock retard on e85 flex tune

10713 Views 293 Replies 24 Participants Last post by TheGasMan, 4 mo ago

khomes7

Discussion Starter · 7 mo ago

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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281 - 294 of 294 Posts

Jonx96

· #281 · 4 mo ago

Speedy said:
Well, mine's a 2016 and the tunes were pretty hot from the factory for the first couple of model years. I have logs from my car bone stock on 93 octane getting consistent 4° of STKR at WOT. I was shocked to see that but like everyone else at the time thought "well must be fine or they wouldn't have tuned it like this". Some would say must be false knock but I'd put in 109 octane race fuel and it would go away. Definitely wasn't false. That could have weakened something for sure.

The rod bolts were also upgraded in 2018 (I think it was 2018 maybe 2017). So engineering obviously saw something there. Between that and the tune changes we don't hear of engines failing now, at least I haven't.

They were upgraded in 18. Just like the crank bolt was upgraded in 18.

Reactions: 2

Jonx96

· #282 · 4 mo ago

Unfortunately your tuner charges for remote tunes when really they are just email tunes. See this a lot. That same file works on cars abc it should also work on xyz

But yes adding a pulley creates more noise. If you are at 10 degrees of timing and see knock. Add octane and still see knock. It is going to be false knock.

Reactions: 2

TheGasMan

· #283 · 4 mo ago

Vet Rider said:
You also grenaded your stock motor, so no I dont think I will be taking tuning advice from you.

I can understand calling people on their B.S., but what makes his advice bad? How would you troubleshoot this issue?

Unholy707

· #284 · 4 mo ago

Speedy said:
Well, mine's a 2016 and the tunes were pretty hot from the factory for the first couple of model years. I have logs from my car bone stock on 93 octane getting consistent 4° of STKR at WOT. I was shocked to see that but like everyone else at the time thought "well must be fine or they wouldn't have tuned it like this". Some would say must be false knock but I'd put in 109 octane race fuel and it would go away. Definitely wasn't false. That could have weakened something for sure.

The rod bolts were also upgraded in 2018 (I think it was 2018 maybe 2017). So engineering obviously saw something there. Between that and the tune changes we don't hear of engines failing now, at least I haven't.

I 2nd that. My 2015 m6 BONE STOCK put down 683 on the dyno. BONE STOCK.

Reactions: 2

Speedy

· #285 · 4 mo ago

Unholy707 said:
I 2nd that. My 2015 m6 BONE STOCK put down 683 on the dyno. BONE STOCK.

My A8 was 669RWHP bone stock if memory serves so right in line with your M6.

Reactions: 1

khomes7

Discussion Starter · #286 · 4 mo ago (Edited)

Vet Rider said:
No. You need to correct the false knock. Those knock sensors are not for show. You need those working correctly to pick up the real knock that you might not see in crap DA, but you get a negative DA day at the track and might bend a rod when you otherwise didnt know you were on the edge.

You might have too hot of plugs. You might have a header dinging off the body or something near enough the motor. There are lots of possibilities and NONE of which should be solved by lowering the knock sensor sensitivity.

They are not desensitized to the point where they are non functional. I still see a half degree or 0.5-1.3V on occasion in other rpm ranges depending on fuel and load. They are still working just the 3800-4200 spot are desensitized just to the point where they will still see knock if the voltage increases any higher than what the false noise range is. I eliminated almost every variable, leakdown test , visual borescope inspection, swapped back cats to quiet exhaust, moved exhaust location, used boostane with 93 on a very conservative timing curve, tested e85 to like e80 and all conditions pretty much produced the same voltage at the same rpm every time.

TheGasMan said:
OP
It looks like you have your hands full at the moment, but I’m curious if you ever got around to converting your TRX to E85 flex?

Trx has the ported blower installed, 108 mm TB, and 2.85 litens w 1000cc injectors, 1 inch blower spacers and CAI. I have the base flex tune loaded now and am logging 93 at the moment. I haven't made it to the e85 part yet but I will keep you posted. I do not wanna name my tuner but I will say next time I will go with Jon on here ( in this thread) because the days and days later responses from at least one of the top names make me think that most all of the big shops will be the same. I suspect they have such large volumes that it's mostly a canned email tune and they make minor adjustments if any to them. If you for some reason have anything odd like I did with my challenger you will get frustrated very quickly and learn that well known doesnt always mean better or more helpful. The only reason I am using the same tuner on my TRX is because I had already paid for it. Otherwise I would have already switched to Jon. Also, my flex tune is not perfect on my challenger, it does some weird things on e85 every drive that create a temporary hesitation and part throttle bog that is there or maybe 30 seconds then gone. The tuner is aware but no fix at the moment. On 93 it doesn't do it and he did not elaborate as to why it does it I suspect it is related to the fuel curves transitioning to different tables based on ethanol percentage calculations mid drive.

Another example of things that might happen with big shop tuners that will frustrate you, say they want xyz channel list and you ADD knock sensor voltage to their channel list and send them a log (just or your own curiosity say you want to see knock voltage). My tuner would reject the log and I would have to wait several more days because I would have to relog with those channels removed (same data, just extra datapoint) while waiting for a reply again. Things like that are just things that I think show there isn't the interpersonal attention or help that you will expect with your car that I believe you will get with Jon based on my conversations with 16gomango (this guy has been more helpful than any of you guys can imagine, truly a knowledgeable, good guy).

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Reactions: 4

khomes7

Discussion Starter · #287 · 4 mo ago

Speedy said:
What a bunch of us told ya all a long

Yes sir

Reactions: 1

Speedy

· #288 · 4 mo ago

khomes7 said:
Another example of things that might happen with big shop tuners that will frustrate you, say they want xyz channel list and you ADD knock sensor voltage to their channel list and send them a log (just or your own curiosity say you want to see knock voltage). My tuner would reject the log and I would have to wait several more days because I would have to relog with those channels removed (same data, just extra datapoint) while waiting for a reply again. Things like that are just things that I think show there isn't the interpersonal attention or help that you will expect with your car that I believe you will get with Jon based on my conversations with 16gomango (this guy has been more helpful than any of you guys can imagine, truly a knowledgeable, good guy).

That's BS imo.

Reactions: 1

Jonx96

· #289 · 4 mo ago

I believe he was named earlier in this thread maybe not. But I wish you'd name him for sure. Total crap you cant submit a log with knock volts. Not even sure how it is safe to remote tune a car without logging knock volts.

Reactions: 2

TheGasMan

· #290 · 4 mo ago

khomes7 said:
They are not desensitized to the point where they are non functional. I still see a half degree or 0.5-1.3V on occasion in other rpm ranges depending on fuel and load. They are still working just the 3800-4200 spot are desensitized just to the point where they will still see knock if the voltage increases any higher than what the false noise range is. I eliminated almost every variable, leakdown test , visual borescope inspection, swapped back cats to quiet exhaust, moved exhaust location, used boostane with 93 on a very conservative timing curve, tested e85 to like e80 and all conditions pretty much produced the same voltage at the same rpm every time.

Trx has the ported blower installed, 108 mm TB, and 2.85 litens w 1000cc injectors, 1 inch blower spacers and CAI. I have the base flex tune loaded now and am logging 93 at the moment. I haven't made it to the e85 part yet but I will keep you posted. I do not wanna name my tuner but I will say next time I will go with Jon on here ( in this thread) because the days and days later responses from at least one of the top names make me think that most all of the big shops will be the same. I suspect they have such large volumes that it's mostly a canned email tune and they make minor adjustments if any to them. If you for some reason have anything odd like I did with my challenger you will get frustrated very quickly and learn that well known doesnt always mean better or more helpful. The only reason I am using the same tuner on my TRX is because I had already paid for it. Otherwise I would have already switched to Jon. Also, my flex tune is not perfect on my challenger, it does some weird things on e85 every drive that create a temporary hesitation and part throttle bog that is there or maybe 30 seconds then gone. The tuner is aware but no fix at the moment. On 93 it doesn't do it and he did not elaborate as to why it does it I suspect it is related to the fuel curves transitioning to different tables based on ethanol percentage calculations mid drive.

Another example of things that might happen with big shop tuners that will frustrate you, say they want xyz channel list and you ADD knock sensor voltage to their channel list and send them a log (just or your own curiosity say you want to see knock voltage). My tuner would reject the log and I would have to wait several more days because I would have to relog with those channels removed (same data, just extra datapoint) while waiting for a reply again. Things like that are just things that I think show there isn't the interpersonal attention or help that you will expect with your car that I believe you will get with Jon based on my conversations with 16gomango (this guy has been more helpful than any of you guys can imagine, truly a knowledgeable, good guy).

Awesome build BTW!
I don’t want to name names, but is Dusterhoff any good at flex tuning?

Reactions: 2

16GoManGoHC

· #291 · 4 mo ago

khomes7 said:
6gomango (this guy has been more helpful than any of you guys can imagine, truly a knowledgeable, good guy).

Thanks for the kudos, Glad to hear it’s still working good for you!! 👍🏻👍🏻

Reactions: 2

16GoManGoHC

· #292 · 4 mo ago

Here’s something I noticed in a recent engine tear down because #7 piston had severe leak down (25%). Notice how the intake valve brow has been severely eroded away. Then look at piston 2 intake brow area, see the erosion on the intake brow? Was starting on piston 8 as well. Compare this to a piston from other cylinders that were not detonating and the same area is smooth and new looking. This is from detonation eating the material away. Why 2 and 7 and sometimes 8 most always?? Weird it does it on the intake brow, I would think that to be the coolest part of the piston, cooled directly by the intake charge. It’s the Corner cylinders that either run hotter, run leaner, something but this is what true knock does and leads to catastrophic engine failure if not caught before blow by gets the rings so hot they expand, butt, and stick at TDC on turn around and rip the bottom of the piston off, drag it out the bottom of the bore and on next upstroke out of the bore and no where to go except snap the rod off while it makes its own bore pushing the the piston or pin out the side of the block. I’ve seen tunes where the corner cylinders are set to run richer probably for this reason.

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Spoolin

· #293 · 4 mo ago

Damn.....That's definitely some detonation going on there. Very odd that it seems most susceptible on cylinders 2, 7, and 8.

Reactions: 1

TheGasMan

· #294 · 4 mo ago

Any updates regarding your TRX tuning?

281 - 294 of 294 Posts