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Old 01-04-2011, 02:53 PM   #1
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Default Thoughts on knock

Since putting in headers @ WOT with stock pulley I'm only seeing knock @ the shifts, is this false knock? Also because I have headers am I in a safe zone now that even running a 3.6" pulley wouldn't chip a piston? I know every car is different. When I ran the 3.6" pulley on a 50 degree day we had with headers I was seeing maybe 1.5* of knock or less @ WOT. I believe this is false knock but I could be wrong? Maybe I just need to be retuned to kill all the knock, but am safe for now?
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Old 01-04-2011, 02:55 PM   #2
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Originally Posted by Deathwish99 View Post
Since putting in headers @ WOT with stock pulley I'm only seeing knock @ the shifts, is this false knock? Also because I have headers am I in a safe zone now that even running a 3.6" pulley wouldn't chip a piston? I know every car is different. When I ran the 3.6" pulley on a 50 degree day we had with headers I was seeing maybe 1.5* of knock or less @ WOT. I believe this is false knock but I could be wrong? Maybe I just need to be retuned to kill all the knock, but am safe for now?
As you noted, every car is different. I'm a firm believer that any knock is too much knock. You also should be tuning on hotter days. 50 degrees is a bit cold to be getting a good tune unless you plan to get another tune for warmer weather. Also keep in mind that blown engine mounts can easily register false knock.

What other supporting mods? I run a 3.4 with the same SD headers, but that'* a Series 2 L67, CAI, hood vents, 180 t-stat, autlite 104'*, high flow 3" cat, and 2.5" exhaust. I run 19 degrees of spark advance at WOT with no KR.

The Series 3 3800 also has more aggressive timing tables. Might want to look into that as well.
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Old 01-04-2011, 03:01 PM   #3
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Knock is never false. There is a reason for it, tuning or mechanical.

The more I've learned and listened about various things....I've learned so much about knock.

Knock can be introduced at shift points to lessen the power of the motor during the shift. This is part of torque management, aka programming that is in place to keep us from destroying our transmissions.

Going lean is typically what chips pistons. Tuning can do wonders for knock, power and potential issues.

One last thing to keep in mind is ..when it'* cold out the air is denser, therefore the cold helps us...but the denser air can cause us more problems. This is why with the same size pulley you can see more boost pressure in cold temps.
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Old 01-04-2011, 03:11 PM   #4
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Knock is never false. There is a reason for it, tuning or mechanical.

The more I've learned and listened about various things....I've learned so much about knock.

Knock can be introduced at shift points to lessen the power of the motor during the shift. This is part of torque management, aka programming that is in place to keep us from destroying our transmissions.

Going lean is typically what chips pistons. Tuning can do wonders for knock, power and potential issues.

One last thing to keep in mind is ..when it'* cold out the air is denser, therefore the cold helps us...but the denser air can cause us more problems. This is why with the same size pulley you can see more boost pressure in cold temps.
Knock can be false if it is bad motor mounts, or just metal to metal surfaces contacting under or hood or somewhere on car. I do know that torque management has been upped on the 04+'*. I didn't think it would be a full 1.5-2* @ WOT at the shift that this would pull. Running the 3.8" ZZP MPS I've got laying around my knock is about the same when running them in 20 degree weather. This is why I was wondering if I could safetly run the 3.6. I did get a tune earlier this year in fall which subsided a ton of my stock knock, so i'm tuned to an extent. I will be getting retuned in spring time for sure, just wanted to know if putting a 3.6 on would net me any gains safetly seeing I have 180tstat, CAI, Autolite 104'*, and Speed Daddy Headers that are catless.
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Old 01-04-2011, 03:15 PM   #5
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I'm seeing 8-9PSI with the 3.8" Pulley on in 20-30* weather. Call me nuts but my aeroforce is reading advanced ignition spark of like 40 generally? Is this normal? I'm running Autolite 104 Iridium XP'*, could this be my potential unfriendly knock source? I've heard that running copper is better, but I wanted long life from the plug.
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Old 01-04-2011, 03:23 PM   #6
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I'm seeing 8-9PSI with the 3.8" Pulley on in 20-30* weather. Call me nuts but my aeroforce is reading advanced ignition spark of like 40 generally? Is this normal? I'm running Autolite 104 Iridium XP'*, could this be my potential unfriendly knock source? I've heard that running copper is better, but I wanted long life from the plug.
Under cruise, 40 degrees of spark advance is normal. Have you ever seen a spark table?
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Old 01-04-2011, 03:28 PM   #7
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Well seeing that I don't have a tuner myself, I don't get to view these things very often:(. I did see my spark table, etc in fall but that was when I was running 3" Downpipe and not headers. I couldn't remember the values of what I was running then, and from the posts here it sounded like 40 was "high".
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Old 01-04-2011, 03:28 PM   #8
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Here you go anyway. Here'* an example of a spark table in hptuners.



Spark is determind based on airmass at a given engine RPM. Airmass is determined by your MAF sensor and to some degree, your MAP sensor. Your spark changes across the table. Under cruising, spark is advanced quite a lot in order to increase fuel economy.

Now, the spark table'* numbers are not final. There are modifiers in the tune where if some conditions are met, the spark changes. For example, if manifold temperature exceeds a certain threshhold, all spark will be retarded by a given amount. The opposite is also true, such as spark advance when the EGR valve is opened.
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Old 01-04-2011, 03:30 PM   #9
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Man, if only I had HPT. Looks like I need to start saving!
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Old 01-04-2011, 03:33 PM   #10
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Man, if only I had HPT. Looks like I need to start saving!
Bob (BXX) swapped in my L67 and let me borrow his hptuners to finish tuning the car. Definitely worth buying if you plan on modding.
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