What all causes knock????

[-DSM2NR-]

Somebody please list all the reasons for knock to occur.

I've tried to get rid of mine for months now and I just can't figure out what's causing it. I replaced the knock sensor, fixed my boost leaks, changed my fuel filter, tried lowering timing and boost, lowered fuel, tried adding race gas but nothing helped. I still get knock and I have no clue what's causing it. I get knock readings of 3-8 (with a raw of 22 counts) on 6000rpm+. DSMlink shows a 10.7:1 A/F ratio and base timing is at 5degrees. LTFT's are at -2% Somebody please help me out.

 

[hopwoodp]

How much boost pressure are you running? What do your egt's look like? what is your inj dead time?

 

[-DSM2NR-]

fuel trims are adjusted accordingly. I'm on 12-15psi of boost. EGR's are at 1128 degrees

 

[diablos991]

Here is a good thread about knock in the DIY section.

 

[gatesrs]

knock is caused by detonation
(detonation) self ignition due to pressure increase.
detonation occors when the unburned portion of the air-fuel mixture explodes "violently"after spark ignition has occurred
another cause of detonation occures at low or moderate speeds is the use of fuel with to low of an octane rating in a high compression engine also inoperative EGR valve... this can be comfirmed while running the engine at high idle (1800-2000rpm) while knock occurs manually open the valve (if possable) if the noise disappears the valve is at fault

 

[FORMONTOYA]

Since you're using DSMLink and have done the listed items, I'll ask the stupid question....what's the knock threshold set at? And at what RPM is it showing up?

(ECU menu....Knock)

Has the car ever seen a can of Seafoam?

 

[hopwoodp]

Since you're using DSMLink and have done the listed items, I'll ask the stupid question....what's the knock threshold set at? And at what RPM is it showing up?

(ECU menu....Knock)

Has the car ever seen a can of Seafoam?

Your right. I remember when I put a can of seafoam in my motor and what a difference it made!!! I think that may make a difference.



Dms2nr, How long has this been going on for? Have you added something or adjusted something mechanically that could have caused this? It may just be something to do with some build up. I say run some seafoam and see what happens.

 

[fourreGsixty3]

What are your intake temps at? Are they at ambient temp. compared with the outside air? They should be a few *s cooler then outside when driving. Also how old is your FMIC? Maybe enough oil has built up in it that its not working as efficently, and there for not bringing the intake charge down cool enough. Also where is your EGT probe tapped? The temps will vary from where its tapped. Methg/water injection being ingected into the UICP about 3"s from the TB would help on two levels, firstly, the water in the solution would soak up some of the heat in the intake manifold thus creating a much cooler temp, and secondly the meth will up the octane points of pump gas, and the higher the octane count the better of a knock supresant it is. I would first recommend finding ut that cause before using the meth injection idea because that would just be hiding the problem.

Dustin

 

[perley03]

Not one of you guys even mentioned "phantom knock." Faulty lifters, bad suspension, bad motor mounts, etc...hell even a faulty brand new OEM knock sensor...seen that happen once. How tight did you torque the new knock sensor?? It isn't all about the tune, he could have a perfect running motor and a bad lifter tapping or a bad component in the suspension causing the car to vibrate excessivly and triggering that also. Try to eliminate the fuel knock first, and if you can't get it to go away, then most likely its "phantom knock." Not bashing anyone here, just trying to put my .02 in.

 

[fourreGsixty3]

I fit were suspension I bet he would feel it, also since he is a 2g, the lifters are much better then our crappy 1Gs, Im not counting them out, but if he has seafoamed the engine lately I would count that out, but yes phantom knock is a possibility.

Dustin

 

[-DSM2NR-]

The DSMlink forums are pretty much too slow. It takes around 24+ hours to get a response........that's why I posted in this forum

-Knock CEL is set to 5 degrees
-I already tried Seafoam AND something stronger then it but neither one helped
-The EGR valve has been removed (might this be causing the knock? If so how do I fix the problem?)
-Knock has been there ever since I put DSMlink on (which was the last mod). I couldn't really tell whether or not I had knock before that because I didn't have any engine management before DSMlink
-The average temps I'm getting are: IntakeTemps 95degrees, CoolantTemps 203 degrees
-I don't think there's a lot of oil in the intercooler because both the EGR valve and intake pipe hoses were removed
-EGT probe is tapped 1.7" from the 1st runner
-The lifters only tick for a couple seconds on cold startups. When the engine is warm they don't tick
-Motor mounts are in good shape (no cracking or anything like that)
-All the 3rd gear pulls I did were on rather even roads (no bumps, holes or anything like that)
-The knock sensor hasn't been tightened too tight nor too lose.
-I have no idea whether or not it's phantom knock but the car DOES knock sometimes EVEN on free revs. Somebody told me that if it knocks on free rev that it's phantom knock and that the knock sensor is probably messed up. But like I said before changing the knock sensor didn't solve the problem EVEN THOUGH the old knock sensor was clearly faulty (plastic melted everywhere etc.)

I hope that info helps

 

[GVR4592]

We need to see some datalogs.

 

[perley03]

What did you torque the knock sensor at??? Its supposed to be torqued to 17 lb/ft, anything over that will cause phantom knock. Post some logs from dsmlink, i'd like to see when you are getting knock. Each log do something different, like run less boost, add a little fuel, etc... to compare to. If its getting knock at certain rpm's even with changing some fuel trims or boost levels, its more than likely its phantom knock.

 

[-DSM2NR-]

The car shouldn't be knocking at all at my boost levels. I'm running 15 pounds MAX. So what if I don't get knock at....let's say 6psi?

Do you people have the DSMlink software because I don't feel like posting a log if nobody is going to read it (which happened one time before).
And what program can I use to transform DSMlink data into text and numbers? I've seen it done before but I don't know what to use. I want everybody to be able to read it

 

[perley03]

Yes, i do have dsmlink software. I have used it to help with a few logs from my friends car.

The car shouldn't be knocking at all at my boost levels. I'm running 15 pounds MAX. So what if I don't get knock at....let's say 6psi?

The more boost you run, the higher the cylinder pressure gets, the hotter the combustion will get. Running higher octane requires a hotter burn to completly burn the fuel. Whats happening with knock is its burning earlier in the combustion stage. A few variables will create knock, as in too much timing (hence why the computer pulls timing when it detects knock), too lean of an A/F ratio, too much cylinder pressure, not high enough octane, too hot of a burn. You could have some carbon built up on the pistons, causing it to knock. Hence why someone above said to run Seafoam through your motor, it will get rid of the carbon deposits.
I see that you live in CA, what octane are you running? That could be a variable here too. There are lots things that can create knock, and I'm here trying to help you out. I want to see some of these logs, in DSMLink form, because i can see whats exactly going on at a specific RPM with all the sensors DSMLink uses. I want to see how much airflow you are running, how much timing your running before the ECU pulls it when it see's knock, i want to see your IDC's, etc.....All im here is for is to help you out.
Hell, if i were in your shoes, I'd go to your local track on a damm near empty tank, put in 3-4 gallons of race gas (something higher than 96 octane, i don't know whats availible to you out in CA) run the same boost that you are seeing knock at, and run a few passes down the track and log. If you are seeing knock with that race gas, with the same boost, timing, fuel trims, etc...then you are definatly getting phantom knock. Then at least i know its not coming from inside my motor, and i'd start looking in different places as to what is causing it.

 

[GVR4592]

The car shouldn't be knocking at all at my boost levels. I'm running 15 pounds MAX. So what if I don't get knock at....let's say 6psi?

Do you people have the DSMlink software because I don't feel like posting a log if nobody is going to read it (which happened one time before).
And what program can I use to transform DSMlink data into text and numbers? I've seen it done before but I don't know what to use. I want everybody to be able to read it

To export to text: Select "export" from the file menu and save it as a .csv file.

 

[-DSM2NR-]

thanks guys. I'll get those logs up once I get home. By the way, I'm currently using 92 octane. And I'm actually from Nebraska not California. Weird somebody must've messed around with my settings.....

Anyways.

 

[hopwoodp]

Honestly - the only time I have ever had a problem with knock like you are saying was when I had a bad batch of 91 from the pump. On the next fill up it went away.

 

[GVR4592]

Honestly - the only time I have ever had a problem with knock like you are saying was when I had a bad batch of 91 from the pump. On the next fill up it went away.

I've experienced the same thing, I was stumped for a week trying to figure it out.

 

[-DSM2NR-]

About the race gas. When I added a 70/30 race/pump mix 100/92 octane it actually did lower the knock a bit. But as soon as I added a little more boost and +1 timing the knock increased again.

Here's the logs

"Octane" is on a 70/30 race and pump mix

"Octane2" is the same mix but I added about 2 more psi of boost and +1 timing

"newlog" is the newest log so far. I adjusted the airflow so that LTFT's are nearly equal. It's the worst log so far with the greatest amount of knock. This was on pump gas.

All runs were 3rd gear pulls (til about 80+ mph)
Let me know what you think

 

[perley03]

I looked at your logs. Weird. Every log, i see that you are getting knock right around 5000rpms +- 300 rpms, but your O2 are high. I would say pull a few more degrees of timing back. I really dont think you need to add fuel, i actually would think it would make it worse. Pull some timing back, and definatly get a can of seafoam and clean it out. After you run that seafoam out of the engine, change your plugs with NGK BR7ES and change your oil. Then try it out, see if that knock goes away.
I also see your intake temps are kinda high for the outside temps near you live. Are you running your heatshields? I would try to lower the intake temps a bit, but i don't think its hurting you here. Your logs look good, except that knock, which i think is just carbon built up. Your timing and airflow look good, looks about right. I would pull your boost back 1-2 psi, pull 2-3 degrees of timing, and go from there. Try that seafoam trick, if you don't know how to use it, just search "Seafoam" there is a huge thread about it, with excellent results. I would recommend doing it at night, because it makes a ton of smoke when you get on it. Make sure no one is behind you when you run that stuff, because they won't see a damm thing. Let us know the results.
Shawn

EDIT: Fill up with 92 octane or whatever the highest you can get out there on pump, and tune with that since that's what you'll be running on the street.

 

[-DSM2NR-]

like I said before, I already tried both Seafoam and something stronger but neither one helped. The piston tops are pretty clean so I dont' think it's carbon buildup.

In the logs I didn't add fuel, I mad the car leaner. And I don't really want to run a lower timing since it's not a good idea to run below 2 degrees of timing (on the logs the timing sliders are at -1 timing)

 

[GVR4592]

I agree with everything perley03 said. Pull timing, lower the boost, fix the coolant and intake temps, and try it again.

What spark plugs are you using and what is the gap?

 

[-DSM2NR-]

I agree with everything perley03 said. Pull timing, lower the boost, fix the coolant and intake temps, and try it again.

What spark plugs are you using and what is the gap?

So.........should I run like 10psi then? I'm trying to fix my knock so I could run more boost not less.
How do I go about fixing my coolant and intake temps??? Spark plugs are NGK BPR7ES with a 28 gap

 

[perley03]

Coolant temps, well you start by draining and flushing your coolant system, fill back up with a 50/50 mix and add a product called "Water Wetter", belive it or not, this stuff works wonders. It gets rid of the air pockets trapped inside your coolant, allowing for more heat transfer to the radiator. To learn more about it click here ----> http://www.redlineoil.com/products_coolant.asp
Intake temps, well you can heat wrap your intake pipe to help hold out the heat, create a cold air setup, run water/methanol injection (Hint: lets you run more boost, gets rid of knock.. ). I would try a few of these things and go from there.