False Knock or nah?

[dyn085]

I've heard a lot in the FiST community about parts causing false knock. While I'm sure that some people may have gotten false knock during some of their pulls, I don't think that individual parts have been the cause and would most likely blame it on maintenance, i.e.-loose mounting hardware, clamps touching parts, etc. In the sake of helping people understand what they would be seeing, I grabbed a few shots from datalogs that I've taken to help give a visual comparison. And if anyone has legitimately experienced false knock due specifically to an aftermarket part then please post some charts so we can compare to others that may have the same part.

First things first, you absolutely must be grabbing your datalogs correctly to begin with. I'm not going to cover that here, but speak with your tuner and clarify exactly what data they want you to collect and find the smoothest and most level road within what you consider reasonable distance. The key is to eliminate as many variables as possible for accuracy, and if you have done enough pulls you will start to see variances between road imperfections, incline, etc. I have the perfect stretch of road immediately leaving my subdivision, but it's always populated so my next best option is 45 minutes away-which is what I use. Again, the best road within your own convenience.

Secondly, you must take multiple logs. There have been a few times where I started a log too soon or didn't transition to WOT very well and had variances in my data, and I wouldn't have known if I hadn't taken multiple logs. Just because you see negative corrections or a misalignment between cylinders does not mean that you are experiencing false knock, which I'll show in a bit, and that's why it's imperative to have another log to compare it against.

Here is an example of what is normal. This is two logs from an OTS tune on my FiST with high-quality Shell 93 octane.

You'll notice that the cylinders are all in near perfect alignment, the corrections are consistent and clean, and that the data is very similar between both logs. This tells you a lot, but the main takeaway is that they are clean logs free of noise. I could post more FiST logs but it would be a waste of tune for you to look at because even though the data changes they are all extremely linear.

By contrast, here are some FoST logs with the Cobb RMM and fuel from the exact same station-

Which you can compare to the OEM RMM-

So, there's a lot to learn from comparing just the 6 pictures posted. First, at least from my perspective, is that the FiST is significantly easier to get properly tuned as it's significantly more consistent. Second, if you compare the Cobb RMM logs to each other you'll notice that the corrections are not only different individually, one log has two cylinders paired and the other has one cylinder completely inconsistent with the other three. Finally, in the logs with the OEM RMM installed they all follow a continuous pattern in comparison to the Cobb RMM. Of course more tuning can bring them better in line, but the difference between the pics should give a good idea of differences and the inconsistencies that you would run into with actual false knock.

Hopefully this helps or leads to better discussions.

 

[BryanD]

Good info that I feel will help a lot of people.

 

[Harvick]

Great stuff Dyno

 

[rexdriver85]

Thank you for this information. [emoji106]

 

[dyn085]

I definitely hope it helps some people. I've heard lots of stories and asked to see lots of logs, but I have yet to see anyone post any. Because I never experienced it on the FiST I never had anything to be able to show, and once I had collected enough in the FoST I was unsure of how to present it without numbing everyone's minds. I'm not saying that there's no possibility of parts creating false-knock, but we need to establish trends if so and that can only be done with good data.

I have somewhere around 20-30 logs on the FoST with the Cobb RMM, and they are all crazy and inconsistent. We tried lightening the knock sensors sensitivities and I went through every inch of piping just to verify clearances. I was already aware of other FoST's having false-knock issues with different RMM's, so I finally just threw in the towel and went back to stock. As soon as I did, all of the rest of the data became manageable and consistent again.

But I digress. I realized that many people may not actually be able to tell the difference between false knock and regular negative corrections. If you're getting negative corrections that are consistent and repeatable, you have regular corrections and need to figure out why-whether that's a tune that's too aggressive, worn plugs, poor fuel, etc. If your corrections are inconsistent and un-repeatable, negative or not, you need to go through a quick checklist-

A. Is my car mechanically correct, i.e.-parts torqued on properly, clamps/parts free of interference, OAR at -1, etc?

B. Is my datalog surface smooth? Don't underestimate this.

C. Is my datalogging procedure smooth, effective, and repeatable? A buddy of mine sent me some logs to look at and they were freaking off the charts and all the data was a wreck. After a little bit of looking and comparing his logs I realized that he wasn't giving his car any cooldown in-between his pulls-he would start his pull, hit his max rpm and end the log, then hit the brakes and immediately turn the car around to do it again. His car was starting with 70 degree charge temps and was in excess of 150 on his third log. Between that and a few other changes in his setup and procedure I was able to help him collect much more manageable data to evaluate.

The underlying concept is that you can't make good decisions with bad information and you can't collect good information with bad procedures or environment.

If everything above is checked and correct, go back to the last mechanical/tune setup you had where your logs were consistent and see if they're still solid. If they are then you have a part that is indeed causing the knock, because we ruled-out the mechanical installation in A and a bad tune would still be consistent. Even though I had made the stage 0 to stage 3 jump, I just happened to know the right place to start and was correct.

One final note-if you made the stage 0 to stage 3 jump and now have no consistency between corrections on your logs and have gotten this far, you're going to want to start one piece at a time and you're going to want to take that part back to OEM, log and evaluate, and if you still have the inconsistency reinstall the part. This allows you to rule parts out one piece at a time.

 

[koozy]

why don't the logs show the knock sensors to show their activity? when the tune, limiters, etc. that may be inducing the ignition retard and the knock sensors aren't picking up any knock, putting more of the emphasis on the tune instead.

 

[dyn085]

Most tuners don't want/need you to collect your knock sensor count.

 

[koozy]

seems convenient for tuners to blame ignition retard on false knock, but have no data on the knock sensors.

 

[dyn085]

seems convenient for tuners to blame ignition retard on false knock, but have no data on the knock sensors.

Well, that's basically why I created this thread and something that has been frustrating me for a while. You don't need actual knock sensor data due to the corrections that are being made, but it's very simple to be able to tell if you're getting legitimate false-knock or not. Knowing when you're getting knock is important, especially if you're getting negative corrections from it, but I think that many just haven't known what the difference is and how it would come across in datalogs. Knowing the difference between them can be the deciding factor between selling off a perfectly good part that you bought and being able to tell your tuner that your car is working fine but the tune is not optimal (not that you should ever have to do that, but still).

It might hopefully also stop people from spreading rumors about how they hear that 'x' part causes false-knock. Someone with the part can grab a few logs and post them to say, 'x' part does/does not show signs of false-knock, and here are the logs to prove it.' Then, like I said above, we can establish legitimate trends based on legitimate data about parts that do or don't.

 

[koozy]

that's a reason why I'm wary of e-tunes. I realize some have no option and have to use this service, but claiming false knock seems to be a regular cop out to 'fine' tuning issues with these e-tunes.

 

[Hijinx]

that's a reason why I'm wary of e-tunes. I realize some have no option and have to use this service, but claiming false knock seems to be a regular cop out to 'fine' tuning issues with these e-tunes.

Again, this goes back to your datalogging process, more specifically, the road you're using. If you're inconsistent on a bad road, you might not get a great tune.

 

[dyn085]

I'm actually about 62% of the way through a datalogging write-up as well. Collecting the best possible data should always be on the forefront of someone's mind, whether they're doing it for their tuner offer for their own testing.

I've only worked with Justin at FreekTune and I can say that, at least for my situation, he never once brought up false-knock or used it as an excuse to do less. He was very diligent in trying to work around it, but I didn't want to sacrifice too much knock sensitivity given the FoST's penchant for cylinder 1 and 4 ringland issues. Ultimately, I'm the one that made the decision to remove it.

Make your concerns well-known to your prospective tuners and hold off on making a complete decision until you have found one that gives you the peace of mind that you need before purchasing.

 

[crankin]

Wow, even my good logs don't look that consisent. So possibly the RRM is causing the inconsistencies? I might visit that as my next part to swap out to try and smooth things out.

 

[dyn085]

Wow, even my good logs don't look that consisent. So possibly the RRM is causing the inconsistencies? I might visit that as my next part to swap out to try and smooth things out.

Well, my RMM issue was with the FoST and the RMM in the FiST had zero impact on my logs. Depending on the severity of your inconsistency on your good logs it's always a possibility, but I wouldn't jump to that quite yet.

 

[iso100]

Crap. I have the CP-E mount and have noticed similar negative corrections during logs for Cyl 2 and 3.

At the same time, I don't think I'd want to go back to stock on the mount... but I also wouldn't want to filter out the knock sensor input. I want my engine intact.

I have noticed that while going through the e-tune process with Randy running one of is -1 global spark maps seems to eliminate the negative corrections. Of course this is at the expense of timing and that means less power.

I guess with an engine that uses the KS input so frequently, this is unavoidable. I mean, the KS is an integral part of the engine's tuning strategy and small negative corrections aren't just normal but are part of how the engine knows how much ignition advance it can get away with. The only other option is backing off on the timing so much that torque limits are reached and no further boost or ignition advance is required to reach the goals.

Thoughts?

Here's one of my recent logs:

 

[dyn085]

Crap. I have the CP-E mount and have noticed similar negative corrections during logs for Cyl 2 and 3.

At the same time, I don't think I'd want to go back to stock on the mount... but I also wouldn't want to filter out the knock sensor input. I want my engine intact.

I have noticed that while going through the e-tune process with Randy running one of is -1 global spark maps seems to eliminate the negative corrections. Of course this is at the expense of timing and that means less power.

I guess with an engine that uses the KS input so frequently, this is unavoidable. I mean, the KS is an integral part of the engine's tuning strategy and small negative corrections aren't just normal but are part of how the engine knows how much ignition advance it can get away with. The only other option is backing off on the timing so much that torque limits are reached and no further boost or ignition advance is required to reach the goals.

Thoughts?

A large portion of tuning and analyzing data is being able to see and have data that can show a larger perspective of the overall picture, so it's nearly impossible for me to be able to formulate an opinion based on a single set of data points. With that being said, here is the general direction I would approach the situation-

1. Are all of your recent logs consistent with each other? If yes, continue on to the next step. If no, you'll want to re-evaluate your datalogging procedures and the road you're collecting it on. While my FiST was extremely easy (once I changed the road I was collecting on), my FoST was difficult-and that was despite being on the 'better' road. I ultimately had to make changes to my overall procedure in order to collect good enough data to compare.

2. If your logs are similar and still showing an issue, then the next step is to start trying to isolate the problem. I agree with not wanting to overly de-sensitize the KS's, so I would approach it with a step-by-step approach to eliminate possible issues. I'm in the process of writing-up a thread showing datalog breakdown with it's applicability to parts testing, but maybe I should do one on problem elimination as well because I have a few people that I'm working similar issues with. Isolating the problem is going to move in this general direction, which is a breakdown of A in post 5-

2a- Is the part properly installed? Everyone is going to say yes, so the first thing we're going to do is loosen and re-tighten the applicable mount hardware. Obviously a torque-wrench is preferable, but I understand that not everyone has one. All we're going to do in this step is verify that the part isn't causing a false-knock due to moving around. You need to loosen all of the mounting hardware before re-tightening, not just one bolt at a time. After you've loosened and re-tightened your mount hardware you're going to go collect new datalogs to see how it affected the problem. If the problem is gone you're done, if not, you'll move to the next step.

2b- Now that we know it's not the installation, we're going to replace the part with the OEM unit. Once replaced, more logs need to be taken. Something will change at this step, and if it doesn't then you're free to reinstall your aftermarket part because you're looking in the wrong area. If your problem goes away with the installation of the OEM part then you're done and you've officially found a part that creates false-knock.

It's pretty short in description, but in reality the overall process can take much longer and become mind-numbingly frustrating. This assumes your fuel and tune are good and removes a lot of extra steps. When trying to isolate a problem there are a multitude of factors that can affect the decision-making process, and occasionally you will be looking in one direction only to find out that something external to your focus is causing an effect and you've been chasing your tail for nothing. This could be as simple as a bad tank of gas or an intercooler clamp touching a frame that you overlooked. The main key is to systematically identify possibilities and rule them out one at a time instead of making a bunch of changes and introducing possible error into the data collection/analyzation system.

Edit: I should also point out the possibility of OEM-part failures. There is always a possibility that you have a OEM failure (or most likely simply a less-than accurate reading/measurement) that may not ever be thought about or remembered. Always keep this in the back of your mind that, while minimal, there is always a possibility of a KS having gone bad (simply as an example). Maybe you damaged a wire or kinked a line or something during a maintenance procedure, so if you've gotten to the point where you've done tons of work and absolutely aren't seeing an improvement the possibility is real that there's something related to the system that's failing or been damaged.

 

[airjor13]

Man, my car been pulling lots of timing, in the 3-4* range Knock count across the board 3-5 per cyl.

Got a hold of Matt @ Panda and see if we can figure out whats going on, got a bunch of logs going his way. If you guys want a look for thoughts, let me know!

 

[dyn085]

Man, my car been pulling lots of timing, in the 3-4* range Knock count across the board 3-5 per cyl.

Got a hold of Matt @ Panda and see if we can figure out whats going on, got a bunch of logs going his way. If you guys want a look for thoughts, let me know!

What occurred or was there any specific event that happened before you noticed it?

The first thing I would do is flash an OTS tune and try to replicate the problem. If it still exists, I would pressure-check the system, verify plug gap, and do a general mechanical check to make sure nothing is noticeably loose and that no clamps have magically started touching something.

It could be as simple as a bad tank of fuel, but I would imagine that you have ruled that out by now.

 

[airjor13]

I am leaning towards an physical issue with car. Ran OTS stage 3 over the weekend, KAM reset fresh fuel everything, pulling timing at the same rate across the board.

 

[dyn085]

I am leaning towards an physical issue with car. Ran OTS stage 3 over the weekend, KAM reset fresh fuel everything, pulling timing at the same rate across the board.

If it's doing it on both tunes then you can rule-out the tune, and if it's across the board and uniform then you can rule-out mechanical looseness. The fact that you say it's uniform and repeatable means that you have something wrong with your fundamentals-fuel, air, or spark. Off the top of my head I can't think of anything else.

Verify your plug gap (I stay between .026-.028" though the factory manual calls for .031") and compare your boost/afr/airflow mass measurements along with your fuel rail pressures between your recent logs and the last-known good ones. Obviously you'll want to pay more attention around the rpm range that the knock develops, but looking outside of it can give clues as well.