Chasing down knock counts
Thread Starter
Racer
Joined: May 2003
Posts: 304
Likes: 1
From: beaverton oregon
Chasing down knock counts
Okay, we gonna figure out whether its false knock or not... 
...with my trusty TunerCat and Datamaster by my side.
2 Possibilities with Causes:
-False knock
*Bad Knock Sensors
*Noisy valve train (bad lifter?)
-Real knock
*Too much spark advance (why would this be? it was fine before the mods...)
*Slight increase in compression due to thinner head gasket
*Bad gas (Very unlikely, I use Chevron 92 Octane)
2 Areas to isolate:
-WOT
-Normal Closed Loop
Experiment 1: Turn off knock retard and see where and how the knock is occuring
Did this last night. Gonna analyze the data today...
Would appreciate any thoughts... Hope I'm not being too boring...
...with my trusty TunerCat and Datamaster by my side.
2 Possibilities with Causes:
-False knock
*Bad Knock Sensors
*Noisy valve train (bad lifter?)
-Real knock
*Too much spark advance (why would this be? it was fine before the mods...)
*Slight increase in compression due to thinner head gasket
*Bad gas (Very unlikely, I use Chevron 92 Octane)
2 Areas to isolate:
-WOT
-Normal Closed Loop
Experiment 1: Turn off knock retard and see where and how the knock is occuring
Did this last night. Gonna analyze the data today...
Would appreciate any thoughts... Hope I'm not being too boring...
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
I don't know much about the LTx engines. Is it possible to adjust base timing on those? I'm thinking not. Either way, you may want to try revving it in neutral and looking for knock counts. Especially with your good (too good?) gas, it should not detonate in neutral, indicating any such counts are false.
RACE ON!!!
RACE ON!!!
Safety Car
Joined: Feb 2002
Posts: 4,212
Likes: 10
From: Sun City West Az
Originally Posted by CFI-EFI
I don't know much about the LTx engines. Is it possible to adjust base timing on those? I'm thinking not. Either way, you may want to try revving it in neutral and looking for knock counts. Especially with your good (too good?) gas, it should not detonate in neutral, indicating any such counts are false.
RACE ON!!!
RACE ON!!!
Safety Car
Joined: Feb 2002
Posts: 4,212
Likes: 10
From: Sun City West Az
Originally Posted by CFI-EFI
I don't know much about the LTx engines. Is it possible to adjust base timing on those? I'm thinking not. Either way, you may want to try revving it in neutral and looking for knock counts. Especially with your good (too good?) gas, it should not detonate in neutral, indicating any such counts are false.
RACE ON!!!
RACE ON!!!
Melting Slicks
Joined: Apr 2000
Posts: 2,793
Likes: 46
From: Elizabeth City, NC
I suggest a LT4 knock module. No matter what the outcome of your situation you will more than likely need one. The LT1 module is very sensitive. LT4 module takes into account the noisier valve train.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
2027 Corvette vs The World: Every Model vs Closest Competitor
Joe Kucinski
10 Most Common Corvette Problems of the Last 20 Years!
Joe Kucinski
5 MOST and 5 LEAST Popular Corvette Model Years in History!
Joe Kucinski
2027 Corvette Buyer's Guide: Everything You Need to Know!
Joe Kucinski
10 Things C8 Corvette Owners Hate (But Won't Tell You)
Joe Kucinski
10 Best Corvettes Coming to Barrett-Jackson Palm Beach 2026!
Brett Foote
Every Corvette Grand Sport Explained! (C2, C4, C6, C7, & C8)
Joe Kucinski
Grand Sport & Grand Sport X Launch Alongside All-New 535hp LS6 V8!
Michael S. Palmer
5 Reasons Bad Drivers Crash & 5 Ways to Avoid a Costly Mistake!
Joe Kucinski
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Originally Posted by ittlfly
No adjustments possible on base timing on the LT-1. All ECM controlled. When problems develop that can be a royal PIA.
RACE ON!!!
Thread Starter
Racer
Joined: May 2003
Posts: 304
Likes: 1
From: beaverton oregon
okay, first chunk of data analysed from experiment ...
over 1/2 hour drive, knock occurs:
-Closed Loop
1400-2500 RPM
85-100 MAP
-WOT
no knock except during initial throttle tip-in
2 experiments tonight:
-Take 3 degrees of advance out for 1400-1600 RPM/80-100 MAP
-Do the CFI-EFI experiment when I get home...
Results tomorrow...
over 1/2 hour drive, knock occurs:
-Closed Loop
1400-2500 RPM
85-100 MAP
-WOT
no knock except during initial throttle tip-in
2 experiments tonight:
-Take 3 degrees of advance out for 1400-1600 RPM/80-100 MAP
-Do the CFI-EFI experiment when I get home...
Results tomorrow...
Le Mans Master
Joined: Feb 2002
Posts: 7,858
Likes: 2
Your sig says timing set by GM performance. Does this mean your spark advance tables have been editted to be more aggressive? The stock GM numbers in the spark advance tables are already pretty aggressive. At most only another two degrees on the upper end, wouldn't really change the tables if it were me. If anything you should restore them to stock. Let me know if you need a stock PCM bin image in Tunercat for '95 Vette, equipped with auto trans (and 2.59:1 rear). I have one saved from my car I think. You could use it as a reference or baseline, using the 'compare' function in Tunercat.
Last edited by Lone Ranger; Nov 18, 2004 at 10:01 PM.
Safety Car
Joined: Apr 2004
Posts: 4,532
Likes: 7
From: Lahaina Hi
With any mods I would use the LT-4 knock sensor.
The knock sensor is cheap only about $29.00.
If you are running roller rockers the counts will be around 30,th and you will pick up a high knock count at around 1300 rpm why I don't know ,but it will appear as if the counts started around 1500 check it .
I changed my eEGR table to 120 it was at 126.See if that helps,
I have been chasing knock counts for a while and have given up.
The engine has a safe guard in it and will retard weather you try to change it or not.
I run NOS so that is why I was chasing the knock until I gave up.
The knock sensor is cheap only about $29.00.
If you are running roller rockers the counts will be around 30,th and you will pick up a high knock count at around 1300 rpm why I don't know ,but it will appear as if the counts started around 1500 check it .
I changed my eEGR table to 120 it was at 126.See if that helps,
I have been chasing knock counts for a while and have given up.
The engine has a safe guard in it and will retard weather you try to change it or not.
I run NOS so that is why I was chasing the knock until I gave up.
Melting Slicks
Joined: Jan 2002
Posts: 2,238
Likes: 4
From: Milan
Originally Posted by TankerVette
okay, first chunk of data analysed from experiment ...
over 1/2 hour drive, knock occurs:
-Closed Loop
1400-2500 RPM
85-100 MAP
-WOT
no knock except during initial throttle tip-in
2 experiments tonight:
-Take 3 degrees of advance out for 1400-1600 RPM/80-100 MAP
-Do the CFI-EFI experiment when I get home...
Results tomorrow...
over 1/2 hour drive, knock occurs:
-Closed Loop
1400-2500 RPM
85-100 MAP
-WOT
no knock except during initial throttle tip-in
2 experiments tonight:
-Take 3 degrees of advance out for 1400-1600 RPM/80-100 MAP
-Do the CFI-EFI experiment when I get home...
Results tomorrow...
Another way to check is to set the graph on datamaster on TPS , map and retard due to knock.
If at every substantial change of load (and TPS) you notice knock retard, this is real knock retard.
All of us are hoping that our knock are false!
many times (instead) the knock is real.
How many deg the ECM pull out?
-Beppe-