3-4 degrees KR means it's likely true, repeatable detonation from too much timing or too little fuel.

IMHO start keeping track of it and tune it out. You will not miss the 1* of timing over a few hundred RPM for the sake of safety.

Sent from my SM-N920V using Tapatalk

 

I was seeing KR on my car and ended up getting it retuned. The car actually picked up power by pulling just a little bit of timing in the right places. I sleep better now too

 

Not politically correct to use the word Retard. You must now call it Mentally Challenged...

 

0 is acceptable.

 

This. NO knock is acceptable at all. It only takes ONE detonation to rip a piston apart and ruin the engine. If you are seeing ANY then you need to address it right away and not push the car until you do.

 

The best to have is the 0-1% range. I would not want to push the car if it's constantly throwing a 4-5%. As stated before, adjust some of the timing. The loss of power from that will be negligible

 

^^^^Better to be scared than be facing an engine replacement I guess!

 

Haha. Don't worry I'll explain. I'm in no way saying it's ideal, I'm just saying this engine hasn't "blown" and there are things in that histogram that could explain why it's been "ok" for quite awhile that way.
I'm in the middle of something right now, maybe I'll explain (with a TriTex worthy length post of course) tonight.

 

I think this was what I was really after. That it's hard for those of us without many, many years of experience to know one way or the other.

I have a OEM stock tune 2012 V and I see 8 to 9 degrees knock on the "93" octane pump gas that we have around here. Sometimes, I get random blips up to 5*, sitting idle at a red light.

Knock retard at idle at a stoplight? Really?

 

I have a OEM stock tune 2012 V and I see 8 to 9 degrees knock on the "93" octane pump gas that we have around here. Sometimes, I get random blips up to 5*, sitting idle at a red light.

 

I've been out of the game for quite a few years but back in the day, lol, when we were modding Grand Prix GTP's I seem to remember the consensus that 3-4* of KR was fine AS LONG AS the car is able to recover quickly from it, it was sustained knock that was considered dangerous and even a little sustained knock was very bad.

 

^^^I'm gonna check John but I'm fairly certain it was you or Duck that told me that. That a single detonation event could destroy a piston. I didn't make that up and I wouldn't repeat something from someone I didn't think was way smarter than me in this area. And again - the context I was saying that in was NOT for a stock motor. It was for a modded engine pushing the limits quite a bit...

 

And GMTECH did build an entire car from more or less scratch, including all the electronics and fab work and a hella lot more. So I give him due credit. I never mean to be argumentative. At the same time, I am careful not to spread misinformation. So if I'm off here I'll work just as hard to correct things said previously.

 

heres the email.....start at bottom....







From: Brian D. Rice <waxguys@gmail.com>
Date: Tue, Jan 17, 2017 at 3:00 PM
Subject: Re: [EXTERNAL] Re: Re: Re: Fwd: CTS-V PCM/Traction control/Launch control question
To: Tony Roma <tony.roma@gm.com>




I have just seen too many ring lands break and main bearings beat on LSA's from knock. I actually have a piston myself from my 1st cts-v.




You are certainly smarter on these things than I am. So I won't worry about it.




Thanks for your time




Brian






Sent from my iPhone 6+




On Jan 17, 2017, at 2:05 PM, Tony Roma <tony.roma@gm.com> wrote:






If you are going to run high octane fuel and expect to see a difference then you need to really flush it out. When we do development we run down to about 2 gallons in the car and then add 2 of C16 and run it down to about empty again… then you add 8 or 9 gallons of fuel again.



I wouldn’t be worried about the knock activity you see. Why does that concern you? Is the car not making the kind of power you expect? As I mentioned before, that’s “normal” operation to basically ride the knock limiter all the time.



Tony



From: Brian Rice [mailto:waxguys@gmail.com]
Sent: Tuesday, January 17, 2017 10:17 AM
To: Tony Roma <tony.roma@gm.com>
Subject: [EXTERNAL] Re: Re: Re: Fwd: CTS-V PCM/Traction control/Launch control question





it was 5 gallons of 116 unleaded with about 5 gallons of 93. it was in the mid 50's ambient temp and the IAT2's never got above 100.

I can probably export most of the data to excel if you want to take a look at it. it just scares the hell out of me to take it to my local cadillac dealers. we had a lifter go bad on our escalade and they kept saying it was piston slap. took it to a chevy dealer and their corvette tech said the cam lobe was wiped and metal was all in the engine.







On Tue, Jan 17, 2017 at 10:10 AM, Tony Roma <tony.roma@gm.com> wrote:




I assumed from your earlier email that you had modified the car. I don’t know why you are seeing knock signal on high octane fuel with the stock pulley. How did you purge all of the other fuel out of the system? The system is calibrated to run basically “on the sensors” all of the time to get best performance. So, it doesn’t surprise me that you would see activity basically all of the time. What was the temperature outside when you were doing this?



Tony



From: Brian Rice [mailto:waxguys@gmail.com]
Sent: Tuesday, January 17, 2017 9:44 AM
To: Tony Roma <tony.roma@gm.com>
Subject: [EXTERNAL] Re: Re: Fwd: CTS-V PCM/Traction control/Launch control question









Tony,

the car is 100 percent stock, and it had around10 gallons of fuel in it. it seems when it registers knock, it pulls timing and reduces performance. another well known tuner told me he thought the knock was from TQ Management. Just seems like things are holding it back from 100 percent performance.

thanks again for answering my questions.

Brian





On Tue, Jan 17, 2017 at 9:37 AM, Tony Roma <tony.roma@gm.com> wrote:




Couple of things.



1 – Do you have enough fuel? I know the DI system runs out of fuel quickly if you crank up the power.



2 – You lose the advantage of the DI system when you crank up the power because the pulse width has to go up so far.



3 – Don’t trust the knock system when you crank up the power a bunch. Imagine you are listening with highly tuned up microphone and someone cranks up the volume a bunch. Take them as a guideline at power levels beyond the factory level.



4 – The combustion characteristics on each cyl head are different. So, I’m not that familiar enough with the LT4 heads to know what you should be running.



Tony



From: Brian Rice [mailto:waxguys@gmail.com]
Sent: Friday, January 13, 2017 4:56 PM
To: Tony Roma <tony.roma@gm.com>
Subject: [EXTERNAL] Re: Fwd: CTS-V PCM/Traction control/Launch control question










Tony,

I went back and looked at my HP Tuner logs from the time I went to the track. is it normal to see 5 degrees of knock retard with 116 octane unleaded in the tank? all the way thru the pass it was commanding 22-24 degrees of timing and knocking 2-5 degrees. I never ran 22 degrees on a pump gas tune ever on either of my V2's.

this really concerns me to know that its knocking this much under full power.

thanks

Brian





On Thu, Jan 12, 2017 at 9:57 PM, Tony Roma <tony.roma@gm.com> wrote:




I love the very detailed question. GM doesn’t really enable people directly to go in and modify the engine calibration in any way. There are certainly aftermarket tools that people use but you will notice that we don’t really endorse any of those.



When you push on the accelerator pedal you are actually requesting torque from the engine, not requesting the throttle to move directly. So, the engine controls figure out how best to do that and meet the extremely tight emissions requirements in a modern car. So, I’m sure that’s why your not seeing the throttle open to 100%. At lower engine speeds 100% throttle opening is not required to make full torque (usually not even close to that).



I understand why you want that last little bit. You don’t run the kind of 60 ft times you referenced without stressing the details.



I know Jason Haines over at Lingenfelter quite well and I know he’s worked on other LT4 projects. You might want to reach out to him and see if he has any advice.



Sorry I can’t offer more help,



Tony



From: Brian Rice [mailto:waxguys@gmail.com]
Sent: Monday, January 09, 2017 1:06 PM
To: Tony Roma <tony.roma@gm.com>
Subject: [EXTERNAL] Fwd: CTS-V PCM/Traction control/Launch control question















Tony,

my name is Brian Rice, I recently purchased a 2016 CTS-V. I want to squeeze as much performance out of the stock CTS-V as possible. I notice when I log the runs, it shows the throttle not opening 100 percent at the initial hit. I have tried several ways to better the 60 foot time and still seem to get no better than low 1.7's. My previous 2 V's would pull 1.59/1.60 60 foots consistently.

is there any way to disable this feature when running on drag radials? I feel a bone stock V3 should run at least as good as a stock hellcat on drag radials.

thanks for your time

Brian Rice
410-562-3298





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I wouldn’t be worried about the knock activity you see. Why does that concern you? Is the car not making the kind of power you expect? As I mentioned before, that’s “normal” operation to basically ride the knock limiter all the time.

Thanks for posting that Evil! I yelled out that quote so it doesn't get missed. That's from a GM CHIEF Engineer. Incidentally you were talking to him about a DI engine. You know one way to get rid of KR on a DI engine? Lean it out and advance the timing. Seriously. Having a DI engine running too rich and the timing too far retarded will result in KR in logs. Just another crazy thing I used to tell people that actually worked. (Not in every situation of course before somebody freaks out and jumps on me for that statement.) There's another example of internet "knowledge", what's the WOT afr supposed to be on a DI engine for reasonable power/safety? There are still a whole bunch of tuners that think it's the same as port injected engines. It's not. They're wrong. They're spreading that false information throughout the forums and it gets taken as gospel.

Again, this comes down to internet lore vs. people that know the facts.

BTW, in your screenshot it's the knock retard decay that's the biggest issue as far as making power in a modified car is concerned. That's one of many things where the factory guy's concerns would be very different than the guy at the tracks concerns. Quickening the decay would let the timing come back up if it was just one short knock event that initially triggered it. When you quicken the decay and end up with a "sawtooth" pattern of the kr returning over and over again, that's telling you the timing IS too high.

Obviously the factory guys have different goals in mind when creating a calibration file. But the basic theories of engine operation still hold true in different levels or applications.

 

BTW, in your screenshot it's the knock retard decay that's the biggest issue as far as making power in a modified car is concerned. That's one of many things where the factory guy's concerns would be very different than the guy at the tracks concerns. Quickening the decay would let the timing come back up if it was just one short knock event that initially triggered it. When you quicken the decay and end up with a "sawtooth" pattern of the kr returning over and over again, that's telling you the timing IS too high.

I believe Evil's V3 is unmodified to retain the warranty - and in factory form shows the saw-tooth pattern that none of us here would be happy with; even if we weren't worried about the pulled timing and performance reduction.

"Riding the sensor" to me is more of an excuse than a solution.

ETA: But again, I'm open to discussion as to why we internet keyboard commandos should ignore repeated knock signals under high load on forced-induction vehicles...

 

^^^it's telling that Roma says the car is tuned to simply "ride the sensors all the time". It means the car runs at best possible operation all the time for the conditions presented. UNLESS there is a bad sensor or bad data. Then it's REALLY off...

I guess that's what makes modern systems, whether cars or planes or anything else, much more complicated.

 

There is a difference between "knock" as seen by the ECM through a properly sensitized sensor in the block, with a variety of reasons as to why that signal could be overtly sensitized or de-sensitized - and actual detonation. I'm not here to argue those specifics, but I'll touch on some relevancy below.

So on one hand (option 1), you can argue that "riding the knock-sensor" is okay because you're assuming that there is a tolerance to the sensitivity, and that most of the time it's not "real detonation;" perhaps weird harmonics, or the sensor falsely triggers at higher RPM, etc.

On the other hand (option 2), you can say that - even though the knock sensor and ECM are very accurate and typically very precise (knock is real) - well, we can still "ride the knock-sensor" because the chamber pressure increase and increased bearing loads are small enough as to not typically affect performance over the warranty life of the engine in OEM form.

Option 3 is that both of the above are correct: you have an imprecise sensor with a durable piston/rod/bearing assembly...

However, each of these scenarios has limitations:
1. As cars are modified (most of us here) and different fuels used, chamber pressures go up significantly - thus there is less room for pressure spikes/hot spots before you lose a hypereutectic ring land. After all, most of us are having 20% or more power output over factory with nothing more than a pulley and some bolt on modifications.

2. As these modified cars are tuned, many tuners intentionally de-sensitize the knock-sensor calibration by 20% or more in the ECM; probably for the same reason as option 1: the sensor is probably giving significant amounts of false-positive readings under higher load.

3. Whether the knock is real or not, in every case of "detected" KR, the ECM pulls timing by several degrees and the end user loses performance.

Therefore, with all of the experience of Tony Roma and GMTech arguing about the irrelevance of a few degrees of knock-retard on a data log, I stipulate that this is bad advice for the following reasons:

* The end user may have several modifications that either reduce sensor sensitivity, or create higher cylinder chamber pressures, that drastically alter the accuracy of "seen" knock, the durability of engine components and the livelihood of said engine relative to an "OEM" setup.

* If the knock can be reliably tuned out by using a degree or two of less timing, or more fuel - why would we ever choose to "ride the sensor" with no tangible benefit, other than even less timing through ECM retardation?

* Stating that KR on a datalog isn't always a bad thing is kind of like a PCP saying that smoking isn't bad for your health... eventually, sometimes sooner rather than later, it probably WILL catch up with you - does your time horizon match what the other guy's is, when you're handing out advice under the pretext of being an expert?

I supposed I'd rather see an explanation of why actual detonation is not considered a serious threat / or why the sensors are not accurate at higher RPM, rather than just being told "look - here's a car with a shitty tune that lasted a really long time" when there are plenty of examples here on this board of cars that DIDN'T last a really long time?

 

What do I know. I'm just an uneducated hick.

 

I think there is a big difference between being on KR commonly when the car is all stock vs when it is modified and making 200hp more than stock, too, though. When you're potentially pushing stock part limits and then you start knocking on top of that, stuff can go badly quick. Now whether or not the stock knock sensor calibration is accurate at that point, I have no idea. I can tell you that on my combos (E85 or pump), I can find KR at relatively low timing compared to what other people claim their tuners have done and show no knock, but I leave the knock sensor calibration alone.

 

Random-

You're gonna believe what you've read on the internet over anything I or a guy like Tony Roma says so there's not much point in arguing about it anymore. It doesn't bother me a bit that you don't trust what I'm trying to say, but it is pretty funny that you think Roma is engineering factory engines with an "excuse" instead of a "solution". lol.

Your smoking analogy is kinda funny too. No shit smoking is dangerous to your health. But here's a story for you...

Our neighbor and good friend happened to be one of the pioneers of heart transplant surgeries. He worked alongside Norman Shumway, THE pioneer of cardiac surgery and transplants specifically. Our friend has spent his entire career transplanting hearts and lungs with his own hands. When he wasn't doing surgeries, he was working as a professor at Stanford University School of Medicine. He's a fucking smart guy that's literally seen the insides of people who smoke. Guess what? HE SMOKES CIGARETTES. I asked him about it years ago, I remember him giving me a very well thought out, intelligent and understandable reason for why he continued to smoke cigarettes. It basically came down to knowing the risks and accepting them. He's still alive and well, I just ran into him and his family at a restaurant the other night. I'm pretty sure he's over 80 years old, he was alongside Shumway in '68 doing the first successful heart transplant done in this country so that will give you an idea of how old he is.

You can turn that into me saying smoking is good for you if you want. That's not what I'm saying.

BTW, "KR" is KNOCK RETARD, not knock.

 

Random-

You're gonna believe what you've read on the internet over anything I or a guy like Tony Roma says so there's not much point in arguing about it anymore. It doesn't bother me a bit that you don't trust what I'm trying to say, but it is pretty funny that you think Roma is engineering factory engines with an "excuse" instead of a "solution". lol.

BTW, "KR" is KNOCK RETARD, not knock.

Great.

I'm still waiting for you to explain WHY it's not a big deal? Expand on why "KR" on a datalog - what the ECM reports anyway - is not the same as "knock" - aka predetonation. Does it have to do with sensor sensitivity, ECM processing, and/or the pre-detonation event relative to commanded spark, crank position and load?

So far - unless I've missed it - your expansive discussion has been contrite and absent of actual detail beyond "look at this crazy graph of geographic knock, I'm pretty sure this engine/Camaro is still being daily driven and hasn't blown yet. lol."

You've proposed that KR is not really a big deal.
You've said it happens all the time on all kinds of engines.
You've said that Tony Roma already explained it (he didn't, but obviously "riding the sensor" is an OEM approved strategy for factory setups)
You've said "A "Tooner" would look at it and see imminent disaster. He'd be wrong" - but you didn't say why...
You've also said "ave a qualified "tuner" look at the entire picture of how the engine is running. (good luck finding one. haha. not.)"
You've also condescendingly addressed my questions as stuff that I've read on the internet - but you have not explained your position.

So now here's your chance: explain what the fuck you're talking about, and why your position is the correct one?

In fact, I don't believe you've even answered your own hypothetical question on that Camaro's histogram you posted... I know you're a smart guy - this is where you prove it (seriously) - less narcissism and more detail.

 

Sorry Random, I'm not gonna play your game.

When people start calling me a narcissist, that's when I know I'm trying too hard to make my point. You don't want to learn and you won't ever change your mind on what you think you know. Just please try not to regurgitate your internet knowledge to others, it just perpetuates the problem.

 

My only "game" is asking you to actually justify your opinion - which you're still not doing after 5 or 6 snarky replies.

Paraphrased, you keep saying "look at me, look at me!" and here we are, looking...

It's kind of amusing at how you came in here talking about how Tri hasn't learned more from all your posts, making "examples" in other posts about all the things that should or shouldn't be scary to a REAL tuner... but for all the talk, you've still managed to not actually share any of your knowledge?

Now, you came off condescendingly enough to me and others insinuating that we're fools for having such a limited understanding of knock/detonation/ECM control to where I expect you to explain yourself - but you keep sidestepping the crux of the discussion as to WHY, and now apparently are going to whine and skip out on the rest of the thread? What, are you scared of a little debate?

Geez, I'm not even arguing - I'm stating what my understanding is and waiting for you to expand on why I (we) are mistaken.

 

John - my take was that Random truly wanted to understand and learn. I've been following this thread with the same objective. I've offered to go to lengths to correct any damage I've done.

Like you I value truth, and like random I value learning. Actually I think all three of us have similar values in that regard. John - you often go to lengths to help others learn so I know that's part of your DNA. I honestly DO want to learn a bit more about acceptable knock vs unacceptable. Let's not let a little friction get in the way of our higher principles and aspirations...ok, so things got snippy. Fine - it happens. We're grown men...lets put down the guns and have a glass of our favorite spirits, a fine cigar, and talk about how to make the world better. That's much better than finding my or anyone else's obvious faults and shortcomings. Mine are especially easy prey on a car forum.

I will say this much in my defense of my statement that no knock retard is acceptable:

1) The amount of skill required to know exactly what type of knock is OK, how much is OK, and under what conditions appears well beyond the reach of the average car owner. Based on this thread I would say it's potentially well beyond the reach of even seasoned modded car owners and those aspiring to gain a basic knowledge of such.

2) The ability to recognize knock and say it's bad is pretty much within everyone's reach.

3) The number of people who suffered damage from knock (or detonation?) is many orders of magnitude greater than those harmed from having zero knock detected.

As such, the SAFEST thing to tell anyone...even someone with advanced degrees in science and engineering, medicine, or similar fields, all the way to those who dig ditches for a living, is to avoid any and all knock.

Or better still - all knock is guilty until PROVEN innocent. But at this point I honestly don't know who is truly qualified to pronounce any such knock as innocent. Tony Roma? GM Tech? "The Community"? Your guess is as good as mine.

So again - I will tell the OP you have two choices:

Assume no knock is acceptable, OR...

Roll the dice and see if you can get any three experts to agree that your particular knock is safe. And even then it's dodgy.

 

Just about every modern engine running on totally stock software will show KR. It's a big part of why all these engines from all the different manufacturers are making such big hp stock. They used to have to tune everything for the worst gas in the country, now they tune them for the best. Even then, they normally set them up pretty aggressively so that the ign timing will be as far advanced as possible. That's where the power and excellent response comes from, having ign timing advanced. The knock sensors and knock learn is there to keep it under control, but it's totally normal for it to have some knock.

The biggest misconception, especially on just about every car forum, is that any knock will destroy an engine. It won't. If it did, there would be literally millions of GM engines dead on the side of the roads. Instead, GM's LS engines in the last 10 years or so have been damn near bulletproof. They've been bulletproof even though just about everyone of them is driving around knocking like crazy at times. I can show you dozens of logs from totally stock engines showing 5,10 or even 12 degrees of kr on a normal test drive. Some of the worst are the '07-'13 GM C/K trucks and SUV's. You can actually HEAR them knock. Get in just about any one of them and juice the throttle a few times, you'll no doubt get a pile of burst knock. They all do it.

Sorry to ramble, my point is that I often hear elsewhere about the "dreaded kr" and how ANY amount of it will destroy your engine instantly. I know that's not what anyone is saying here, you guys are too smart for that! Don't get me wrong, I always strive for little to no kr. Sure, it's better to have your modified engine tuned to where there's little or no knock, that's obviously ideal. But 69stang, don't worry about it too much. I have no idea if your car is tuned, but it would run better even with those minor mods if it was.

John - I think posts like this are what caused my response. To be fair - you DID say that stock engines do fine with some KR. At the same time, I also clarified that my context in making such a remark was a modified engine. The guys doing this don't have the benefit of legendary engine designers and tuners. They don't have the deep R&D budgets of major automakers. They don't have access to sophisticated sensors and tools that can detect pressures inside the combustion chamber, and much, much more. They are often in uncharted territory. As such, the ONLY safe advice to give them is to chase no knock.

And when guys like you strive for little to no knock on your own cars, there MUST be a good reason for that. And when GM engineers allow knock to happen all over the place on stock vehicles, there's probably a good reason for that, too. So if we take you as having the expertise you assert - that leaves guys like me in an awkward position: Is knock good or bad? Do I accept it as fine because OE cars do it? Or do I claim it's bad because GMTech avoids it on his own cars?

I hope you can appreciate that guys like the OP probably need a vastly simpler approach - and what's clear to me is that figuring out what knock is OK and what isn't is fairly complex.

 

John - I think posts like this are what caused my response. To be fair - you DID say that stock engines do fine with some KR. At the same time, I also clarified that my context in making such a remark was a modified engine. The guys doing this don't have the benefit of legendary engine designers and tuners. They don't have the deep R&D budgets of major automakers. They don't have access to sophisticated sensors and tools that can detect pressures inside the combustion chamber, and much, much more. They are often in uncharted territory. As such, the ONLY safe advice to give them is to chase no knock.

And when guys like you strive for little to no knock on your own cars, there MUST be a good reason for that. And when GM engineers allow knock to happen all over the place on stock vehicles, there's probably a good reason for that, too. So if we take you as having the expertise you assert - that leaves guys like me in an awkward position: Is knock good or bad? Do I accept it as fine because OE cars do it? Or do I claim it's bad because GMTech avoids it on his own cars?

I hope you can appreciate that guys like the OP probably need a vastly simpler approach - and what's clear to me is that figuring out what knock is OK and what isn't is fairly complex.

I have no dog in this fight, nor in any of the...'politics' or history this site has (which is natural for a forum of its age) but I was really hoping for an answer to Random's (pointed) question in post #44, with a lot of the same internal conflict Tri mentions here.

In the classroom, I was taught pretty similarly to what GMTech has said. Detonation isn't our friend, but it's not a 'golden gun' of danger either. We were even taught that a light amount of detonation could be tolerated for a near infinite amount of run time, in a properly maintained engine, and on motors that might have built up deposits of sorts (like from oil in the combustion chamber) it can even have mild cleaning effects of breaking up those deposits. True, this was largely aimed at production engine engineering, but we had a lot of time focused on 'high performance' as well and there were similar sentiments. The #1 thing my professor was 'scared of' in terms of engine failure was pre-ignition, as it can melt a piston on the first occurrence.

Of course, while my prof was/is an incredibly intelligent individual, the last development project he was on (other than consulting) was the Fiero, so I was hoping to see more recent real-world expertise shed some light on the subject and further my own understanding.

Hell, I'm literally sitting here trying to make sense of my secondhand HPTuners setup so I can gather the stones to learn more about engine calibration firsthand. No judgement or accusations here, just an interest of learning- isn't that the core of why we're here, other than the Friday Ass Thread?

 

I've gotten this much KR on a couple of occasions on light throttle..

 

This

 

^^^Yes, but is it acceptable knock !!!

 

Not sure if it is or isn't lol. Maybe someone can chime in.

 

Well, On the bright side at least we have knock sensors in these cars. Guys with 03-04 Cobras were not lucky enough to be equipped with them.

 

Just reading through this, I had a 03 whippled cobra that was tuned in 94 and I was running on 91+meth instead. Had the pump fail and could just hear the engine pinging, as far as I know she’s still running!

 

came in to this one hoping to learn a lot.


still hoping..