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BLUF: I wanted to here opinions about knock count and causes: I'm running COBB's 91 Octane Stage 1 tune (car is filled with 93 Octane) and will see Knock count on Cylinder number 3 sometimes increment to 12-15 counts when puttering around especially on take-off(results in Ignition correction of -4 to -7 degrees). On an 2nd or 3rd gear pull I will not see any consistent knock counts on any cylinder (maybe 1 or 2 randomly on one of the cylinders) and normally positive ignition corrections. MY OAR is consistently at -1. All indications of False knock? Should I be worried?

In Depth: I have a 17 Focus RS, currently running a Scorpion CBE, Mountune recirculation valve, depo racing intake, full Radium Catch Cans, and Powerflex RMM bushing insert. I've had the Head Gasket TSB done and the subsequent timing chain oil leak fixed. I recently decided warranty be damned, I'm going to use my Accessport sitting in my drawer and enjoy the car a bit more. I want to be conservative to start, so I flash the COBB 91 Octane Stage 1 Tune, even though I only ever fill up with 93 octane. Load up my monitors to see knock count for each cylinder and overall OAR.

On any 2nd or 3rd ear pull I consistently see no or 1-2 knock counts on a single cylinder. OAR is hard -1 and ignition corrections on cylinder 3 are consistently positive. All good happy signs.

Puttering around town I'll routinely see knock counts on cylinder 3 of 12-15 counts, especially on take-off in 1st gear. The car will pull cylinder 3 timing and Ignition Correction will show sometimes up -7 degrees. The other cylinders I won't see any knock or ignition corrections, only cylinder 3.

I pulled the plugs and everything looks good. I swapped the plug and coil from cylinder 2 into cylinder 3. No changes.

All indications I can draw are this is a case of false knock. The extremely high knock counts under minimal load, the 91 octane tune knocking on a single cylinder with 93 octane gas. I know our engines have two knock sensors, what I don't know is if the computer correlates piston position to knock to try and identify which cylinder the knock is coming from, or if it's simpler and related to approximate position of the sound in the block.

I don't like how the depo intake mounts, eliminating the rubber grommets and mounting directly to the motor. I also think the split between the two aluminum intake pipes is too close and the aluminum pipes could be rubbing/shifting against each other underneath the silicone connector. I plan to remove the intake and go to a Mountune intake as soon as I can find time to see if this helps. I checked my catch cans and they are tight without any rubbing I could notice.

I feel like I may be on a wild goose chase, but I'm also worried there may be something more serious going on. I don't have logs at this moment. I'm looking for everyone's thoughts on what is going on and additional troubleshooting if it persists after the intake swap. I know on other ecoboost platforms false knock is something that occurs.

Thanks in advance
 

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What version of Cobb OTS maps are you running? Cobb discovered an issue with the HPFP cycles, even in the OEM tune map and changed their tunes a while back. What motor oil are you using? LSPI is a big problem as well. The fueling and/or LSPI can affect just one cylinder, especially #3. I can't say for SURE, but it may have something to do with the cooling flow path and/or the intake manifold design that allows #3 to run hotter.
I've wanted to run individual cylinder O2 and/or EGT sensors to see WTF is actually happening, but I'm not equipped to do it all myself.
 

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I've noticed that same exact "issue" ever since I got my Accessport from Mountune a couple years ago. Same cylinder and everything. It's inconsistent, but when it happens, it's always from a dead start in first gear. It'll dip to -8, but then go up. If I let off real quick, it resets to zero, and then will go up like it normally does when I accelerate. Never happens in any other gear or cylinder. Only bolt-ons in the engine bay at the time was the intake system, intercooler, breather plate, catch cans and RMM. Always thought it was odd it only ever happens in cylinder 3. I know the knock sensors are VERY sensitive in these cars, and these are "noisy" engines. Eric over at Mountune says he sees the same thing. Even when free revving under no load, it'll dip he says. I'm not too concerned about it. I'm 99% positive it's just noise and not actual knock.
 

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I’d recommend a custom tune vs the OTS COBB tune. Don’t watch knock counts when daily driving. You get alot of false knock from the drive train, stiff motor mounts, and even loose parts like the intake. The knock sensors can tell which cylinder the knock is coming from based on the time of arrival and the sensor positions.
The 1-2 knocks per cylinder during a WOT pull is ok according Stratified. Overall sounds normal.
 

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I’d recommend a custom tune vs the OTS COBB tune. Don’t watch knock counts when daily driving. You get alot of false knock from the drive train, stiff motor mounts, and even loose parts like the intake. The knock sensors can tell which cylinder the knock is coming from based on the time of arrival and the sensor positions.
The 1-2 knocks per cylinder during a WOT pull is ok according Stratified. Overall sounds normal.
Agreed on the custom tune. As you can see in some of these threads, every car is different. However, don't think a custom tune is going to make that negative spike in cylinder 3 go away. But from what I've seen and heard, that quick little negative spike is okay. Now I'd be concerned if it was dipping into negatives constantly under acceleration. But that would affect the OAR which would be a clear indication of something wrong.

@monkey302 , not sure where you are based, but also keep in mind the 91 OTS maps are typically meant for "real" 91. If you are in NV, AZ or CA (like myself), you have to settle for the crappy ACN stuff. So if I want to run my best tune, I have to add in about a gallon of E85 to the tank. If I fill up with straight 91, I have to run my slightly detuned slot 4, otherwise I get all sorts of negative corrections (in all cylinders) under acceleration that raise my OAR.
 

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Discussion Starter #6
@monkey302 , not sure where you are based, but also keep in mind the 91 OTS maps are typically meant for "real" 91. If you are in NV, AZ or CA (like myself), you have to settle for the crappy ACN stuff. So if I want to run my best tune, I have to add in about a gallon of E85 to the tank. If I fill up with straight 91, I have to run my slightly detuned slot 4, otherwise I get all sorts of negative corrections (in all cylinders) under acceleration that raise my OAR.
@Si2RS I'm running 93 Octane here in Virginia, the stations I use are all Top Tier fuels. I'm running the 91 Tune to be ultra conservative.

What version of Cobb OTS maps are you running? Cobb discovered an issue with the HPFP cycles, even in the OEM tune map and changed their tunes a while back. What motor oil are you using? LSPI is a big problem as well. The fueling and/or LSPI can affect just one cylinder, especially #3. I can't say for SURE, but it may have something to do with the cooling flow path and/or the intake manifold design that allows #3 to run hotter.
I've wanted to run individual cylinder O2 and/or EGT sensors to see WTF is actually happening, but I'm not equipped to do it all myself.
@FORZDA 2 I'm nto sure of the number, but know it's the latest OTS, I updated the firmware and tunes off their website before installing the tune. I'm running the Motorcraft 5W-50 Unicorn blood.

To everyone, I'm going to run a stratified tune (was pleased when I had my stage 3 FoST) once I get an intercooler. I figured waking up the car through the Cobb OTS would at least make the times I get to drive a bit more fun.
 

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If you have any datalogs, throw them up in datazap and we can see if everything looks good.

modern motors are designed to run on the threshold of knocking/lean to be the most efficient, so under a little to no load situation the risk is low. What matters most is your WOT pulls, which you say are clean
 

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From my understanding of the system as a whole you will always get some knock at some point and this is at the least worrying point. It's not an issue unless you get a CEL as rate of knock is monitored and a threshold set by Ford as to whats an acceptable amount. having said that why cylinder 3? I suspect it's because "nothing is perfect" and cylinder 3 may well be the sensitive one with regards to sensor location and mechanical considerations of the system. It's also the cylinder the balance shaft is driven from from memory and the backlash in the drive gears at the point you mention may come into play.
Don't get me wrong it's all good info and adds to the knowledge base but you still need to be able to weed out the info that matters from the stuff that doesn't and thats what the system does for you with it's knock count and CEL warning algorithms.
Ciao
 

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Discussion Starter #9
From my understanding of the system as a whole you will always get some knock at some point and this is at the least worrying point. It's not an issue unless you get a CEL as rate of knock is monitored and a threshold set by Ford as to whats an acceptable amount. having said that why cylinder 3? I suspect it's because "nothing is perfect" and cylinder 3 may well be the sensitive one with regards to sensor location and mechanical considerations of the system. It's also the cylinder the balance shaft is driven from from memory and the backlash in the drive gears at the point you mention may come into play.
Don't get me wrong it's all good info and adds to the knowledge base but you still need to be able to weed out the info that matters from the stuff that doesn't and thats what the system does for you with it's knock count and CEL warning algorithms.
Ciao
Thanks, yes, I understand what you're getting at. The sheer volume/number of counts had me concerned. I've read all I can find and understand running the system at peak efficiency means running it on the bloody edge of knocking. If it were a full throttle run and you saw -7 ignition correction and 12+ for knock count everyone would be freaking out. Just trying to better understand. The balance shaft being by number 3 make sense too.
 

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From my understanding of the system as a whole you will always get some knock at some point and this is at the least worrying point. It's not an issue unless you get a CEL as rate of knock is monitored and a threshold set by Ford as to whats an acceptable amount. having said that why cylinder 3? I suspect it's because "nothing is perfect" and cylinder 3 may well be the sensitive one with regards to sensor location and mechanical considerations of the system. It's also the cylinder the balance shaft is driven from from memory and the backlash in the drive gears at the point you mention may come into play.
Don't get me wrong it's all good info and adds to the knowledge base but you still need to be able to weed out the info that matters from the stuff that doesn't and thats what the system does for you with it's knock count and CEL warning algorithms.
Ciao
I used to drive myself crazy with that question. Why only cylinder 3? I inspected every part I could (easily) check inside the engine bay and underneath. Changed spark plugs and confirmed proper gapping. I eventually came to terms with it, and my engine still hasn't grenaded itself, so THAT'S GOOD! Haha! Makes sense from what you said about the balance shaft though. Or maybe it goes back to every RS is different, and it may just be variances in the manufacturing tolerance range. I stopped losing sleep about it a long time ago.
 

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From what I understand about knock, the events that occur when you're simply driving around not hammering the car aren't anything to worry about. It's when you stick your foot down, if you're getting consistent and high numbers of negative corrections especially in high boost low RPM situations but high boost in general. That's what you want to be worried about and have your tuner check out.
 
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