Knock Question

[mnetwork]

I always had a question about knock... When does knock become harmful? I know that a few counts isn't harmful and at most is just hurting performance, but when does it start to get on the verge of dangerous?

[Black_Bullet]

This is sort of a question that will get back opinions.

Depends on how hard you want to push your car. The knock itself isnt directly hurting performance,
for instance, a car tuned with zero knock will probably make less power if that car was tuned more aggressively with knock.

I recall reading in a thread were Evileagle was saying he tuned his car for 20counts of knock back in the day so he could get a lot more extra timing/boost out of it and that he felt that was a good tune and wasnt harming the engine enough.

Me personally, I dont know,I just try to keep my knock count number under 10 counts at all times and that has been working for me on my old stock 6bolt. With my current tune Im likely to see 3-7 counts tops thru a full 4th gear pull, and I dont consider that amount of knock to be significant, these are tough motors.
IMO, not letting the knock go too much higher than that, may be wiser to avoid getting too much pulled timing.

But depending your power level could also have a bearing on what kind of knock can harm the engine.
Obviously 500 awhp on a stock block, you may not get away with surviving a hand ful of knock as you would with say 300awhp on a stock engine, due to cylinder pressures already being so much higher on the 500awhp motor.

Also, different motors have different limits, are we talking about a built motor, stock motor, cryotreated motor, i mean theres different scenarios.
A forged motor could be likely to register fake knock due to piston slap and etc.
So under a certain knock count you have to try to differentiate whats real and not.

Some guys have such horrible phantom knock problems that they desensitive their knock sensors or ignore a certain amount of knock... In the end I think its all up to you what your comfortable with since its your motor, and your the one paying for the rebuild fees if something goes wrong.

[mnetwork]

I have a decent tune right now, but I still see some knock randomly. A 4th gear pull will show it more for me than a 3rd will. I have my CEL set to come on at 3 or more counts. When I first started tuning I was over zealous with getting rid of knock. When I would do a pull and see 7 counts I would just let off because it scared me. I'm just trying to figure out what is the margin where I don't have to worry. I make right around what my old dyno sheet says hp wise and I run 23psi, so the motor isn't pushed to the max.

[Black_Bullet]

Id say set your cel light to come on at more like 10 counts.
3 counts means your probably setting that thing off all the time.

I personally perfer to do 4th gear logs since it IS more likely to show up knock, and I actually use 4th gear. I dont care much for 5th because I have no reason to hit the speeds that 5th would take me to, but on a late night or real early mourning on the highway I log 4th and I take it to redline which is about 125mph
(about the highest speed I will take this car to anyways).... This way if I have a clean tune in 4th I will be sure that I wont be seeing any knock in the lower gears. Were as logging 3rd gear pulls, will only ensure you your not knocking in 1st or 2nd but you could be knocking in 4th.

[hahnsuper16g]

Like the previous posters said its all in what you feel comfortable with. I have been driving my car for almost 2 years now at 22psi with a very agressive tune and i see knock counts as high as 35-40 and as low as 7 depending on the weather etc. I have a fully built motor so I don't have a lot of worries but again it depends on what you are fine with. Running colder plugs, race gas and an aftermarket ignition system helps in knock and misfire reduction.

[mnetwork]

Sounds good. Also, I have another question... If I'm advancing timing at a certain rpm range in DSMLink by lets say 2 degrees and I get 5 counts of knock, it is going to pull timing a few degrees. If I advanced it lets say 6 degrees at the same range, would I get higher timing at that range? Or would it pull even more timing? Basically I am asking the relation between requested timing advance in DSMLink and knock if that makes any sense.

[snowborder714]

If you see knock, to get rid of it you either want to pull timing or add more fuel. If you're seeing knock and increase timing in that RPM range, you will most likely see even more knock, yet your peak timing will remain similar. If you ever look at a log and just view timing and knock, you'll notice that your timing will follow an upward trend, yet will decrease by the counts of knock you see.

[daren_p]

Mark your using DSMLink, correct? So are you actually refering to knock counts or knock retard (which DSMLink users usually refer to)? As these are too very different things. It sounds like you had/have your CEL set to flash at 3 deg knock retard (not 3 counts). When black bullet posted above raising it to 10 counts, I would assume he was refering to counts as you defently don't want your CEL to flash at 10 deg knock retard. I believe .35 knock retard is equal to one knock count. Most try to keep knock under 2 deg, though I'm sure like mentioned, this varies. I personally have my CEL to flash at 2 deg & its pretty rare for it to come on. I run water/meth injection so if it does come on its usually because the meth hasn't been sprayed for awhile & takes abit for it to fill the lines/spray properly. Pre meth injection I use to have the CEL set at 3 deg as well.

[mikelv]

I would avoid knock like the plague!

Unless you like builing engines.

[GVR4592]

Originally Posted by mikelv

I would avoid knock like the plague!

Unless you like builing engines.

I agree, you guys should be tuning for 0 knock. If the knock sensor is picking up real detonation, you have a problem somewhere, weather it's mechanical or a tuning issue. 1g's and 2g's use a different system for knock control, most pda dataloggers use a different system than dsmlink does for displaying knock values, and every car is different.

That's enough variables to destroy an engine or two when people say things like "Tune for 5 counts of knock" or "Tune for 20 counts of knock". 5 counts on a pda based logger isn't the same as 5 degrees in Dsmlink, but a lot of people think it is.

Every car is different, and unless you know for sure that you're seeing phantom knock on the datalogger, you should always tune for 0.

[PIMking]

okay then what is a degree of knock from dsmlink compared to a count of knock?

[1992awdlaser]

Originally Posted by daren_p

I believe .35 knock retard is equal to one knock count.

Correct.

Originally Posted by PIMking

okay then what is a degree of knock from dsmlink compared to a count of knock?

1 Count of Knock = .35 Degrees of Knock Retard

So roughly 3 Counts = 1 Degree of knock retard

[PIMking]

Originally Posted by 1992awdlaser

Correct.





1 Count of Knock = .35 Degrees of Knock Retard

So roughly 3 Counts = 1 Degree of knock retard

Wow that kinda scares me.

You shouldnt be a wiseman you should be a DSMgod.

so 15* is roughly 45 counts of knock? That was the 3rd gear pull that I posted before.

[1992awdlaser]

Originally Posted by PIMking

You shouldnt be a wiseman you should be a DSMgod.

I don't know about that. Thanks for the compliment though.

so 15* is roughly 45 counts of knock? That was the 3rd gear pull that I posted before.

Yes, almost.

[Black_Bullet]

To further elaborate on my previous posts, I just make sure I can do a full drag pass without ever going beyond 10 COUNTS of knock, not 10 degs. So 10 counts of knock is roughly 3 degs of timing retard. And btw I normally log in 4th gear which is even more likely to show knock than the lower gears. I log with MMCD logging software on laptop.
This amount of knock counts isnt even enough to stop me from getting peak timing that I dialed in with my chip.
Having control over your knock decay rates, and the octane value reset feature also helps bring full timing back up quicker.

But 10 counts is my limit, Im not aiming for a 10 counts pull, its usually 3-7 counts and its not like I run my car thru all the gears on the street like at the track, and as long as common sense would tell you that you have good afr's and etc on a healthy engine/ setup then I dont think the amount of knock counts that I allow is enough to hurt the engine imo.

The mitsu knock sensor is over sensitive and tuning for zero counts of knock, I can garantee you will be leaving power on the table and the tune will feel soft.
Now for a newbie I can understand to tell them to tune for zero counts, but this isnt the newbie section so everyone should already understand to proceed at their own risks and by their own judgement and as I said in my previous post, its all about what you feel comfortable with. But the 4g63 wont blow or pop its lid with 3 degs of knock retard, and normally when the ecu is doing its job of retarding timing that makes it even more unreasonable for it to blow from such low knock

[mikelv]

Originally Posted by GVR4592

I agree, you guys should be tuning for 0 knock. If the knock sensor is picking up real detonation, you have a problem somewhere, weather it's mechanical or a tuning issue. 1g's and 2g's use a different system for knock control, most pda dataloggers use a different system than dsmlink does for displaying knock values, and every car is different.

That's enough variables to destroy an engine or two when people say things like "Tune for 5 counts of knock" or "Tune for 20 counts of knock". 5 counts on a pda based logger isn't the same as 5 degrees in Dsmlink, but a lot of people think it is.

Every car is different, and unless you know for sure that you're seeing phantom knock on the datalogger, you should always tune for 0.

I agree as well.

Every car might be different, but 15 degrees of knock is insane. You're playing with fire with that much knock on any motor, stock or built.

The main reason why I prefer DSMLink over AEM is for the simple fact that you can retain many factory settings including the knock sensor. On a 2G the knock sensor is very sensitive, and picks up just about any vibration. Heck when I turn the boost up over 30psi, I always get a reading of .4 deg to .7 deg of knock just because it’s making so much power. I like that sensitivity, it keeps me in check. When you start making big power, you need to be very carful of what you’re doing. Also, I like the feature of changing the stock boost gauge to read knock….works well for me.

Engine Knock:

Think of engine detonation as going against the grain when you’re shaving your face. What happens? You cut yourself and get bad razor bumps the next day when the hair grows back. Bottom line, don’t do it, you know what’s going to happen.

If you guys are tuning for knock, you are going against every principle of the internal combustion engine. What is happening is better understood as “pre-detonation”: The act of the mixture combusting before it was intended to. I mean we can get quite complicated when talking about this subject, but I’ll do my best to keep it simple.

When an engine knocks, you’re causing the engine’s pistons to travel in the opposite direction that it was intended to during the cycle. Meaning when the 2nd and 3rd pistons/combustion chamber are on the compression stroke (for example), and the fire starts too soon for what reason, you force the piston back down too early. Well this has a domino effect on the whole rotating assembly because last time I checked; all four journals are sitting the pistons on the same crank shaft. You make 2 and 3 shoot down too early, and violently vibrate out of direction (my example of going against the grain) then 1 and 4 are going to be negatively effected as well.

There are many factors that attribute to the cause of an internal combustion engine pre detonating, including gasoline, thermal efficiency, environmental conditions, exceeding prescribed volumetric efficiency (i.e.: excess boost/airflow), ignition system malfunction, excessive timing advance, and among others, and probably the most dangerous of all, a loose nut between the steering wheel and the driver’s seat/ head rest.

Gasoline has a certain burning temperature and the lower the octane (generally w/o additives such as Meth or NO2) the lower the burning point. The higher the octane (race fuels/ premium fuel) the higher the burn point, meaning the higher the burn point, the more air you can force induct, and essentially, the more energy you can produce to the crankshaft and essentially the transmission and drive wheels.

I could go on about the rest, (which I’ll probably end up doing anyway) but the bottom line is there is no benefit to pre detonating your engine. To force your pistons up and down before they were intended is not going to give you record breaking power; just breaking power.
Well maybe for some right? But it’s really not worth it for most of us. Tune for safety and efficiency, because IMO efficient power is effective power. There is the top 1% of the guys out there who tune for this stuff, but it’s not in the cards for everyone.

I suppose if you want to call it matter of opinion, then once again I suppose you have a passion for re-building engines.

[mikelv]

Originally Posted by Black_Bullet

The mitsu knock sensor is over sensitive and tuning for zero counts of knock, I can garantee you will be leaving power on the table and the tune will feel soft.

I wouldn’t say you’re going to leave power on the table; it's just going to be tuned efficiently. Efficiency factors are contributed to more than just knock counts as well. Were talking about how much air you can push, and if you can max your Volumetric Efficiency with a given turbo, basically saying you’re able to flow it to its max efficiency, without pre detonating, then you’re doing ok.
If you have to knock your engine to max out power, then you might want re-think your turbo choice for the type of engine you have. That kinda sounds like you’re boosting an engine, and getting things real hot beyond what those rods might be able to handle.
Not to argue you, because I totally understand with you’re saying. Actually, help me out here brother, what do you think? I like to make conversation, it's good to learn something new everyday and experience new things.

[mnetwork]

Originally Posted by 1992awdlaser

Correct.





1 Count of Knock = .35 Degrees of Knock Retard

So roughly 3 Counts = 1 Degree of knock retard

A very important thing that I didn't know... So having the knock retard CEL set to 5 degrees like DSMLink comes default isn't smart?