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The Pork Wagon (‘14 Cop Charger)
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Discussion Starter #1
While perusing some recent data logs for any KR that might need addressing, and after finding way more than I thought I would/should find, I did some critical thinking on why this KR continues to show up when, for all intents and purposes, it should not be there.

And gentlemen, I have come to an epiphany on this subject: very little of this KR I continue to see pop up in my logs during WOT operation is due to actual knock occurring inside the engine.

I do not currently have a leading suspect for what is actually causing the sounds being picked up by the knock sensors and misidentified as knock, but it is something other than colliding flame fronts inside the combustion chambers during the compression and power stroke of the respective cylinders...of that, I am sure!

As an example of what I now believe to be a case of mistaken identify on my PCM's part, I present the following datalog screen shot with the ST KR, engine RPM, and throttle blade position sensor enabled:

994325


Just about all of the recent datalogs I've got that contain KR spikes have similar looking KR behavior. It is precisely this visual signature in the log files which I believe gives it away as NOT being true knock at the heart of the matter. But before I lay out my hypothesis on why this just has to be false knock, I'm curious about what others are using to decide on the validity of the KR they find in their datalogs.

I have a feeling most people are like me, or like I used to be - blindly trusting the PCM to know what's real and what's false, and so anytime there is KR, it must be due to real knock.
 

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Well I get all kinds of STKR and a certain amount of LTKR on my data logs. I've determined that a good bit of it must be caused by something other than true KR, perhaps the sensors are overly sensitive I don't know. I came to that conclusion because I can't get rid of it or even get it down to very minimal levels. Even with the stock tune in the car and by adding MS109 race fuel I'm still getting short term and long term knock under acceleration. I'm pretty sure that Chrysler's engineers didn't design our cars when running stock to need over 104 octane fuel So I'm coming down on the side that some (maybe many) of us may be getting a certain amount of false knock.
 
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I found my E3 spark plugs were causing false knock. I replaced them with NGKs and the knock disappeared. I've heard stage 8 locking bolts on headers can also give false knock readings.
 
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there's likely some harmonics from the engine that trigger the sensors into false KR

I'm aware the mechanical noises from the M6 do this as the engineers noted the knock sensors pick this up
 

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The Pork Wagon (‘14 Cop Charger)
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Discussion Starter #5
But all of that is identifying false knock by process of elimination, which to be clear, I have also always used to try to weed it out. What I think I am onto now is a way to identify the false knock directly using the log files (instead of indirectly through previously noted means).

Gimme a minute to figure out the best way to lay this out. I don’t want to vomit a bunch of words that will be difficult to digest, but my theory will require some details to make my case...

Hmmmm....

You know, this would be easier for me to pitch if y’all were here in person. If y’all will make a quick trip down here to Dallas, I’ll cook some sort of dead animal n the grill and then explain my new approach verbally, with lots of hand-gestures! 🤓

Can y’all make it here by 6 pm this evening??

Just kidding...8pm is fine 🤣
 

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The Pork Wagon (‘14 Cop Charger)
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Discussion Starter #6
there's likely some harmonics from the engine that trigger the sensors into false KR

I'm aware the mechanical noises from the M6 do this as the engineers noted the knock sensors pick this up
right, but how to ID when that is the case (not necessarily what it is causing it) is the thing I’m trying to prove
 

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I could actually probably be there, seeing as I'm in Midlothian.

Be extremely careful when disregarding knock as "false". I've seen this scenario a few times now and it generally doesn't end well.
 

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The Pork Wagon (‘14 Cop Charger)
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Discussion Starter #8
I could actually probably be there, seeing as I'm in Midlothian.

Be extremely careful when disregarding knock as "false". I've seen this scenario a few times now and it generally doesn't end well.
No, I’m afraid you are not allowed here, sorry.

The mere presence of your 6.4L’s extra torque above and beyond what I have in my 5.7L could be enough to push me over the edge and into the financial rabbit hole that me going out and buying a new 6.4L powered Challenger for myself would turn into.

That’s just too risky for me right now, I cannot take the chance. 😟

Nevertheless, in the interest of saving everyone the hassle of trying to glean meaning from a wordy post detailing my explanation, I have instead committed my thoughts to video and made available on YT.

It’s only a 4 min clip, give it a day in court and reply back here with your thoughts (crazy talk, possibly onto something, couldn’t understand for the drawl, etc).

 

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Here's another angle - perhaps @ChallyTatum might be able to chime in - perhaps during the load on the engine, VVT is doing something during the rpm ramp up and there's harmonics or NVH coming from the timing chain as the cam phaser advances / retards the timing.

the cam timing is changing under various conditions all the time
 

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2 degrees retard is not that bad. Would be helpful to have a wideband to see what your AFR is when you experience knock. I am no expert but comparing commanded AFR and wideband AFR will let you know if the knock is most likely due to fueling. Knock sensor voltage level is also good indicator if the knock is real or not. Have not seen info on phaser/timing chain being noisy enough to trigger false knock.

Desired cam movement at WOT (pedal voltage > 3.509V).
994341


Power Enrichment at WOT AFR = 1/(stoich + PE).
994342


And here is your WOT spark tables (base, VVT lockpin and thermal). Thermal is not used unless COT enrichment kicks in and as the name suggest lockpin is used when cam is in lockpin (usually engine spark runs off base).
994343


Why am I showing all of this? Just eye candy to make Nuke want to switch to HP tuners. :devilish:
 

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There is the possible explanation the knock sensors have degraded.

However, I would not expect them to get more sensitive with time.

Are they secure? Are they bolted too tight?

If the price and effort to replace them not that painful maybe a couple of new sensors would be worth the expense/trouble?

There is another explanation. That is the knock retard is happening because the engine controller is trying to run the timing as advanced as possible and in some cases this means dialing timing back a bit.

Do not have any info on Dodge's engine philosophy but Porsche claims in its low level reference materials it seeks to run its engines just short of detonation to keep the timing as advanced as possible.

In this scenario then knock and timing retard from this will be common but the result of trying to run as close to detonation as possible.

The advantage of running as much timing advance as possible is so great I can't believe Dodge would leave this on the table.
 

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The advantage of running as much timing advance as possible is so great I can't believe Dodge would leave this on the table.
it also balanced around emissions as well. The Hemi combustion chamber while great for making power, presents challenges for emissions.

The VVT system which came along for MY 2009 was able to accomplish a few items:
improve efficiency
increase horsepower & torque (5.7 went from 340hp to 375hp) with VVT and revised cylinder head for more flow
eliminated EGR valve
the major item is NOx as combustion chamber temperatures rise - so does NOx and running very lean mixtures also.

Porsche for example went over to Direct Injection - and there's a number of tricks incorporating DI that enables tuning and emissions that is different from Port Injection such as FCA employs.
 

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The Pork Wagon (‘14 Cop Charger)
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Discussion Starter #13
There is the possible explanation the knock sensors have degraded.

However, I would not expect them to get more sensitive with time.

Are they secure? Are they bolted too tight?

If the price and effort to replace them not that painful maybe a couple of new sensors would be worth the expense/trouble?

There is another explanation. That is the knock retard is happening because the engine controller is trying to run the timing as advanced as possible and in some cases this means dialing timing back a bit.

Do not have any info on Dodge's engine philosophy but Porsche claims in its low level reference materials it seeks to run its engines just short of detonation to keep the timing as advanced as possible.

In this scenario then knock and timing retard from this will be common but the result of trying to run as close to detonation as possible.

The advantage of running as much timing advance as possible is so great I can't believe Dodge would leave this on the table.
I was actually wondering about the knock sensors last night as I sat in the Whataburger drive through watching the live data screen on my laptop. I noticed the knock sensor voltages were rapidly jumping around from 0.32 - 0.47 volts, and that was just sitting there in Park and idling. Two questions popped in my head:

1) how is that voltage induced?
2) what is the voltage at which the PCM declares knock in the CC is the source and should be addressed with KR?

I’m pretty sure the answer to the first one is, “from sound waves the sensor “hears” all around it and converts into an electrical signal.”

I don’t know the answer to the second one yet, but I’m guessing it is adjustable inside the tune if so desired. I don’t desire to right now, but I have heard of desensitizing the knock sensors, and I’m thinking upping that voltage limit is how that’s done.

Anyway, enough Mopar performance theory for now, I have to go perform the Mercedes Benz citric acid coolant flush on a 10 y/o Ford pickup truck that was recently driven until the engine coolant boiled over while simultaneously running it low and oil. I am breaking my own pledge to never work on a Ford again by doing this, but I need some way to get my car’s wheels (w/ worn tires) to the tire shop so the new Firestone Indy 500s I got can be mounted and balanced on them, and this Ford is the current candidate for doing that hauling for me.
 

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The Pork Wagon (‘14 Cop Charger)
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Discussion Starter #14
2 degrees retard is not that bad. Would be helpful to have a wideband to see what your AFR is when you experience knock. I am no expert but comparing commanded AFR and wideband AFR will let you know if the knock is most likely due to fueling. Knock sensor voltage level is also good indicator if the knock is real or not. Have not seen info on phaser/timing chain being noisy enough to trigger false knock.

Desired cam movement at WOT (pedal voltage > 3.509V).
View attachment 994341

Power Enrichment at WOT AFR = 1/(stoich + PE).
View attachment 994342

And here is your WOT spark tables (base, VVT lockpin and thermal). Thermal is not used unless COT enrichment kicks in and as the name suggest lockpin is used when cam is in lockpin (usually engine spark runs off base).
View attachment 994343

Why am I showing all of this? Just I candy to make Nuke want to switch to HP tuners. :devilish:
Well, it might surprise you to know that I am under contract by HP Tuners NOT to publicly use or support their products in any way. Further, it would likely even be more surprising to learn such a contract would include bonus payments built in if I continue using and/or supporting any one of their competitors’ products, wouldn’t it?

Granted, none of that is true, I’m just pointing out how it would be surprising if it were... :ROFLMAO:
 

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Nuke - another thought with nearly 200K on the engine - probably listen to it at idle with a stethoscope.

It could be that there's enough clearance with internals - as you noted the knock sensors have fluctuations at idle.
that the sensors could be picking up noises that aren't audible to your ears. As you're familiar, there's things a 'scope can pick up that we can't hear.

It could be wrist pin clearance, rod bearing clearance, or main bearing clearance or a combination of any of those three.

Pretty much all the head bolts are under the rocker covers, so that's one area you can't tell. But another is the main bearing caps have cross-bolts (you'll see them in block, above the oil pan rail) which is another point to listen to the engine's bottom end for noises.

there reason I mention this is I noticed my 150K 'Benz (all alloy engine with cast-in cast iron cylinders) - I have piston slap on cold startup that lasts for a several seconds and once the pistons warm up with 30 - 45 seconds, it goes away.
 

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The Pork Wagon (‘14 Cop Charger)
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Discussion Starter #17
Thresholds (voltage above considered knock) for all 8 cylinders (stock). I also have thresholds that are used on diablo 93 tune.
View attachment 994363


View attachment 994364
whoa, hold the phone...you stated you have the thresholds for the 93 diablo tune, so am I to understand they are different per canned tune??

higher or lower?

And does that trend hold for the 91 tune as well?
 

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The Pork Wagon (‘14 Cop Charger)
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Discussion Starter #18
whoa, hold the phone...you stated you have the thresholds for the 93 diablo tune, so am I to understand they are different per canned tune??

higher or lower?

And does that trend hold for the 91 tune as well?
I ask because my version of the tune I run is more like a 92 octane tune. So I could use the 91 and up it a scosche or the 93 and dial it back a scosche, depending upon the other differences. I previously thought torque mgmt was the only other significant diff, now maybe I need to reconsider
 

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The Pork Wagon (‘14 Cop Charger)
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Discussion Starter #19
Nuke - another thought with nearly 200K on the engine - probably listen to it at idle with a stethoscope.

It could be that there's enough clearance with internals - as you noted the knock sensors have fluctuations at idle.
that the sensors could be picking up noises that aren't audible to your ears. As you're familiar, there's things a 'scope can pick up that we can't hear.

It could be wrist pin clearance, rod bearing clearance, or main bearing clearance or a combination of any of those three.

Pretty much all the head bolts are under the rocker covers, so that's one area you can't tell. But another is the main bearing caps have cross-bolts (you'll see them in block, above the oil pan rail) which is another point to listen to the engine's bottom end for noises.

there reason I mention this is I noticed my 150K 'Benz (all alloy engine with cast-in cast iron cylinders) - I have piston slap on cold startup that lasts for a several seconds and once the pistons warm up with 30 - 45 seconds, it goes away.
I’ve considered the possibility of errant engine sounds due to age, but am I being overly optimistic/naive to believe the sound frequencies those types of bangs and slaps make would not be in the same realm of the ??khz range that is monitored for evidence of knock?
 

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From what I've seen there's usually a tad (up to 2 deg or so) at WOT. I've heard it can be attributed to mechanical NVH, or engine movement but couldn't exactly tell you the precise cause. Might be a compromise that has to be made in order to keep the range & sensitivity of the sensors where it needs to be for mass-produced engines/cheapest sensors OEMs can buy(?)

You'd think there should be none but then again there's a lot of things you'd think should be one way, but are another, for good reason...
 
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