Knock table

[87gmc]

Can someone give me the rundown on how thet tables work on the tuning tool. Like what makes it less sensitive, how the db units work, filters, etc. Just curious on this

Chris

[GMPX]

Can someone give me the rundown on how thet tables work on the tuning tool. Like what makes it less sensitive, how the db units work, filters, etc. Just curious on this

Chris

The filters basically attempt to shut out all other noise that might be picked up by the knock sensor and 'might' false trigger as knock.
Much like a low pass filter in a car sound system where you only want to pass the bass onto the sub woofer, same deal here, we only want to pass sounds picked up by the knock sensor in the 4 - 5kHz range, this is where GM would have done plenty of development getting those frequencies correct.

The gains are like a volume control to the knock signals.
I really don't know why some calibrations have this table zero'd, others have it populated.
If you think you are false triggering the knock sensor you could lower the gain values. A few tuners use them on blown cars where the S/C pulleys etc 'may' cause false knock due to the fact GM did not delevop the knock tables with a blower on the engine.

Hope that helps somewhat.

Cheers,
Ross

[87gmc]

Ok what you have said makes sense so far. Let me ask a few more questions.

I'm looking at the knock sensor sensitivity #1 db, does it mean the higher the number the more knock it takes before it actually detects it? In the car audio world the higher the db the louder it is or am i missing something?

Also what table would you actually use to desen the knock sensors?

On efilive can you moniter the knock sensors separate to see which one is actually sensing knock?

I know I know I should know :D

[joecar]

Similar question to 87gmc:

are there any PIDs for "raw knock on sensor 1" and "raw knock on sensor 2" that anyone knows about...?

(by "raw knock" I mean either knock counts or knock intensity).

[dbaxter_ss]

I was reading this thread and didn't really see an explanation.

main filter
5.0, 5.5, 6.0, 6.4, 6.8, 7.3, 7.8, 8.4, 9.1, 9.8, 10.8, 12.1, 13.7, 15.7 and 18.3
Which direction makes it less sensitive?
currently mine are all at 5.5

Secondary Pass filter
1.65, 2.50, 4.70 and 7.90
Which makes it less sensitive?
currently mine are all at 4.7

I have a blown gto and do get KR which most of it I am sure is false.
SO which direction, up on the main? Since there is only 5 left I am assuming up to filter more out?

[Ira]

main filter
5.0, 5.5, 6.0, 6.4, 6.8, 7.3, 7.8, 8.4, 9.1, 9.8, 10.8, 12.1, 13.7, 15.7 and 18.3
Which direction makes it less sensitive?
currently mine are all at 5.5

Secondary Pass filter
1.65, 2.50, 4.70 and 7.90
Which makes it less sensitive?
currently mine are all at 4.7


I believe those numbers are the center frequency of the filter, probably not something you want to mess with. If you want to make it less sensitive you'd more likely want to modify the sensitivity tables. I have no idea whether 0 or 26 is more resistant to knock and staring at the tables trying to figure it out didn't help me.

Ira

[dbaxter_ss]

main filter
5.0, 5.5, 6.0, 6.4, 6.8, 7.3, 7.8, 8.4, 9.1, 9.8, 10.8, 12.1, 13.7, 15.7 and 18.3
Which direction makes it less sensitive?
currently mine are all at 5.5

Secondary Pass filter
1.65, 2.50, 4.70 and 7.90
Which makes it less sensitive?
currently mine are all at 4.7


I believe those numbers are the center frequency of the filter, probably not something you want to mess with. If you want to make it less sensitive you'd more likely want to modify the sensitivity tables. I have no idea whether 0 or 26 is more resistant to knock and staring at the tables trying to figure it out didn't help me.

Ira

And they are located where?

[Ira]

Engine Calibration->Spark->Knock->Knock Sensor ## Sensitivity

[dbaxter_ss]

Engine Calibration->Spark->Knock->Knock Sensor ## Sensitivity


I don't have that, checked my SS, GTO and a buddies Z06?

Engine Calibration->Spark->Knock->
Knock Sensor #1 - Main Filter
and
Knock Sensor#1 - Secondary Filter

Have
Parameters
Knock Fast Attach gain
Knock Fast Attach rate
KR limit when not in PE
KR limit when in PE
KR default value with knock dtc
kr recovery rate
engine run octan modifier
Knock Sensor #1 - Main Filter ( frequencies describe in my above post )
Knock Sensor #1 - Secondary Filter ( frequencies describe in my above post )

There is nothing that I see that says kr sensitivity?

thats why I wondering that was the filter fq?

[Ira]

Well, at this point Paul will have to answer as I don't know why I can see it unless it's in a Z28 and not in yours.

Ira

[dbaxter_ss]

Thats strange since the SS, GTO and Vette should have the same parameters? What year is your Z28?

[Ira]

2000. I do have the commercial version and this table might be missing from the personal one. Don't see why if you have the rest you wouldn't have that but again, it's a Paul question.

Ira

[GMPX]

Everyone please understand there is NO difference between any versions as far as table access goes, everyone see's the same thing.

'dbaxter_ss', what is the PCM Operating System number you have that table missing from?.

Cheers,
Ross

[87gmc]

Ok i understand how to desensitive it but which way do you go on the numbers up or down? higher number make less sensitive or more?

[Ira]

Save the table and set it to all zeroes. If you suddenly have tons of knock retard, bigger numbers are what you want, if not then try setting them all to 26.8 and try again.

Ira

[Blacky]

Save the table and set it to all zeroes. If you suddenly have tons of knock retard, bigger numbers are what you want, if not then try setting them all to 26.8 and try again.

Ira

Welcome to the world or "reverse engineering" :)
Paul

[GMPX]

Engine Calibration->Spark->Knock->Knock Sensor ## Sensitivity


I don't have that, checked my SS, GTO and a buddies Z06?

Engine Calibration->Spark->Knock->
Knock Sensor #1 - Main Filter
and
Knock Sensor#1 - Secondary Filter

Have
Parameters
Knock Fast Attach gain
Knock Fast Attach rate
KR limit when not in PE
KR limit when in PE
KR default value with knock dtc
kr recovery rate
engine run octan modifier
Knock Sensor #1 - Main Filter ( frequencies describe in my above post )
Knock Sensor #1 - Secondary Filter ( frequencies describe in my above post )

There is nothing that I see that says kr sensitivity?

thats why I wondering that was the filter fq?

Sorry for the delayed response.....I read it and forgot to post a response.
In 2003 the knock filter gain table dissapeared!!.
If you look in factory files from about 2001+ that table was usually at zero anyway, it's the 1999-2000 tunes that had it populated.
My theory is GM perhaps changed the way they did the knock sensor calibrations and the gain table was no longer needed.

You may notice some O.S's have different tables than others, for the most part they will match, but between years some went missing and others were added.

Cheers,
Ross