Retard timing at higher RPMs...
Drifting
Joined: May 2002
Posts: 1,479
Likes: 42
From: Dallas / Ft. Worth The Republic of TEXAS
You are getting false knock it is a big problem with LS2 and LS3 powered vehicles. Have your tuner adjust the following if he hasn't yet:
Engine -> Spark -> Advance -> Spark Correction -> Gas (zero table out)
Engine -> Spark -> Advance -> IAT Spark -> Base (zero table out up to 122 degrees all the way down)
Engine -> Spark -> Retard -> Knock Retard Decay -> Decay Rate (multiply stock table by 2)
Engine -> Spark -> Retard -> Knock Retard Attack -> Base Retard (multiply stock table by .5)
Then have him command the timing he wants at WOT in the main spark tables at of 24-26 degrees. The MAF tables must be dialed in completely then command PE to a flat 12.8:1 AFR by entering 1.15 in all cells here:
Engine -> Fuel -> Power Enrich -> Power Enrichment
In the same screen set "delay rpm" to 0 and Enrichment rate to 1.00
I recommend running pure MAF it works really well, but I'm sure your tuner has his own methods. It is critical that you have the timing dialed in with these settings without knock because if not you will ping. Definitely put some TR6 plugs in just the way they come gapped before you tune it helps.
Engine -> Spark -> Advance -> Spark Correction -> Gas (zero table out)
Engine -> Spark -> Advance -> IAT Spark -> Base (zero table out up to 122 degrees all the way down)
Engine -> Spark -> Retard -> Knock Retard Decay -> Decay Rate (multiply stock table by 2)
Engine -> Spark -> Retard -> Knock Retard Attack -> Base Retard (multiply stock table by .5)
Then have him command the timing he wants at WOT in the main spark tables at of 24-26 degrees. The MAF tables must be dialed in completely then command PE to a flat 12.8:1 AFR by entering 1.15 in all cells here:
Engine -> Fuel -> Power Enrich -> Power Enrichment
In the same screen set "delay rpm" to 0 and Enrichment rate to 1.00
I recommend running pure MAF it works really well, but I'm sure your tuner has his own methods. It is critical that you have the timing dialed in with these settings without knock because if not you will ping. Definitely put some TR6 plugs in just the way they come gapped before you tune it helps.
Last edited by OBSSSD; Feb 13, 2011 at 07:56 PM.
Safety Car
Joined: Jun 1999
Posts: 3,570
Likes: 3
From: Austin, Singapore, Kuala Lumpur, Houston, Dallas, Hong Kong, Elgin, etc.. Texas
You are getting false knock it is a big problem with LS2 and LS3 powered vehicles. Have your tuner adjust the following if he hasn't yet:
I recommend running pure MAF it works really well, but I'm sure your tuner has his own methods. It is critical that you have the timing dialed in with these settings without knock because if not you will ping. Definitely put some TR6 plugs in just the way they come gapped before you tune it helps.
I recommend running pure MAF it works really well, but I'm sure your tuner has his own methods. It is critical that you have the timing dialed in with these settings without knock because if not you will ping. Definitely put some TR6 plugs in just the way they come gapped before you tune it helps.
Some tuners preach using Speed Density which removes the MAF and other preach MAF which removes the VE functions. I personally have both running on my car but its a pain in the butt to get each calibrated because you have to disable one then calibrate the other using a wide band.
If you run MAF only, it should be accurately calibrated to your engine. But be forwarned, if your MAF fails, the car will not run or run like crap.
Depending on what type of WBO2 sensor is used, they can give a huge variance read out. See this test article: WIDE BAND SHOOT OUT
Because I can't totally trust what the WB says, I first tune to 13.0 on the wide band, then subtract 2% at WOT. If the power increases, then I know I'm going in the right direction. If power decreases, I add 2% more until power drops.
Last edited by Mez; Feb 10, 2011 at 02:24 PM.
Drifting
Joined: May 2002
Posts: 1,479
Likes: 42
From: Dallas / Ft. Worth The Republic of TEXAS
Some tuners preach using Speed Density which removes the MAF and other preach MAF which removes the VE functions. I personally have both running on my car but its a pain in the butt to get each calibrated because you have to disable one then calibrate the other using a wide band.
If you run MAF only, it should be accurately calibrated to your engine. But be forwarded, if your MAF fails, the car will not run or run like crap.
Depending on what type of WBO2 sensor is used, they can give a huge variance read out. See this test article: WIDE BAND SHOOT OUT
Because I can't totally trust what the WB says, I first tune to 13.0 on the wide band, then subtract 2% at WOT. If the power increases, then I know I'm going in the right direction. If power decreases, I add 2% more until power drops.
If you run MAF only, it should be accurately calibrated to your engine. But be forwarded, if your MAF fails, the car will not run or run like crap.
Depending on what type of WBO2 sensor is used, they can give a huge variance read out. See this test article: WIDE BAND SHOOT OUT
Because I can't totally trust what the WB says, I first tune to 13.0 on the wide band, then subtract 2% at WOT. If the power increases, then I know I'm going in the right direction. If power decreases, I add 2% more until power drops.
Safety Car
Joined: Jun 1999
Posts: 3,570
Likes: 3
From: Austin, Singapore, Kuala Lumpur, Houston, Dallas, Hong Kong, Elgin, etc.. Texas
Depending on the skill level of his tuner he could do speed density, but IMO mafless works very well. If the MAF fails it will likely throw a code immediately so he would know, and like you said it will run like crap. If his tuner makes the other adjustments I documented, even without running pure MAF, it should eliminate all false knock like clockwork. When I tune I like commanding the timing I want and keeping it super consistent for obvious purposes. As far as tuning WOT that should always be done on the dyno IMO after a street tune has resolved the right base fueling adjustments.
Safety Car
Joined: Apr 2010
Posts: 4,231
Likes: 451
From: Maryland
I have a question, the stock iridium plug in the LS3 is AC #41-110 why not try the Z06/ZR1 plug i.e. AC 41-104 in an LS3? I would think it would be a colder plug.
Is the AC 41-104 on par with the NGK TR6 as far as temp range?
TR55, What does the second 5 stand for?
Is the AC 41-104 on par with the NGK TR6 as far as temp range?
TR55, What does the second 5 stand for?
Safety Car
Joined: Jun 1999
Posts: 3,570
Likes: 3
From: Austin, Singapore, Kuala Lumpur, Houston, Dallas, Hong Kong, Elgin, etc.. Texas
The TR5 spec has the gap at .040" while the TR55 gap is ~.055". The correct plug for the Corvette is TR5 (or TR6) not the TR55.
I confirmed this directly with NGK and their website listed the TR55 plug in error. You can use the TR55 but gap them at ~.055". You should not bend the ground electrode over to ~.040" as it will cause excessive erosion and increase in gap.
I confirmed this directly with NGK and their website listed the TR55 plug in error. You can use the TR55 but gap them at ~.055". You should not bend the ground electrode over to ~.040" as it will cause excessive erosion and increase in gap.
Drifting
Joined: May 2002
Posts: 1,479
Likes: 42
From: Dallas / Ft. Worth The Republic of TEXAS
I have yet to see anyone document a more effective way of dealing with the issue, but given how the system works this isn't a surprise. This is the exact technique that several high volume expert tuners use, but you'll find many are reluctant to share their "secrets". Cheers
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Safety Car
Joined: Jun 1999
Posts: 3,570
Likes: 3
From: Austin, Singapore, Kuala Lumpur, Houston, Dallas, Hong Kong, Elgin, etc.. Texas
Actually what I recommended works great on bone stock and bolt-on cars as well as heads/cam cars. He is getting false knock like everyone else always does and the changes I documented will make a big difference for him. I've tuned over 500 LSx vehicles and on all LS2 & LS3 cars I use these changes to optomize spark delivery while eliminating any chance of what the OP is dealing with. Your experience may be different, but based upon personally dealing with 200 different cars with this exact problem I can tell you it solves the issue. As far as the plugs call NGK they will tell you that if you are running 50hp over stock or in warmer climates they recommend the TR6 every time.
I have yet to see anyone document a more effective way of dealing with the issue, but given how the system works this isn't a surprise. This is the exact technique that several high volume expert tuners use, but you'll find many are reluctant to share their "secrets". Cheers
I have yet to see anyone document a more effective way of dealing with the issue, but given how the system works this isn't a surprise. This is the exact technique that several high volume expert tuners use, but you'll find many are reluctant to share their "secrets". Cheers
I was only speaking to running SD or MAF only for a mild or unmodified car. The other tune changes you listed are fairly well known and I did them on my car. False or Burst knock is a pain sometimes.
As for the NGK plugs, I don't have any opinion so I'll leave that for others to comment on.
Safety Car
Joined: Apr 2010
Posts: 4,231
Likes: 451
From: Maryland
Just did a little checking on sparkplugs.com and for a 2006 LS7 they show the TR6 plug listed; so the "iridium" AC 41-104 may be the same heat range.
Last edited by C7/Z06 Man; Feb 10, 2011 at 02:43 PM.
Thread Starter
Racer
Joined: Sep 2005
Posts: 439
Likes: 1
Actually your quite right. My tuner mentioned this false knocks which he faced when tuning my engine. I have A6 tansmission and the 3" Z06 muffler pipes are pretty tight fitment around the diff. My tuner is thinking that the pipes are hitting the diff and causing this false knock. after the dyno session I had to put extra bracket in-between the 2 muffler pipes and welded them to make more gap between the pipes and the diff. Now there is almost 1 inch gap which I hope solved the problem.
You are getting false knock it is a big problem with LS2 and LS3 powered vehicles. Have your tuner adjust the following if he hasn't yet:
Engine -> Spark -> Advance -> Spark Correction -> Gas (zero table out)
Engine -> Spark -> Advance -> IAT Spark -> Base (zero table out up to 122 degrees all the way down)
Engine -> Spark -> Retard -> Knock Retard Decay -> Decay Rate (multiply stock table by .5)
Engine -> Spark -> Retard -> Knock Retard Attack -> Base Retard (multiply stock table by .5)
Then have him command the timing he wants at WOT in the main spark tables at of 24-26 degrees. The MAF tables must be dialed in completely then command PE to a flat 12.8:1 AFR by entering 1.15 in all cells here:
Engine -> Fuel -> Power Enrich -> Power Enrichment
In the same screen set "delay rpm" to 0 and Enrichment rate to 1.00
I recommend running pure MAF it works really well, but I'm sure your tuner has his own methods. It is critical that you have the timing dialed in with these settings without knock because if not you will ping. Definitely put some TR6 plugs in just the way they come gapped before you tune it helps.
Engine -> Spark -> Advance -> Spark Correction -> Gas (zero table out)
Engine -> Spark -> Advance -> IAT Spark -> Base (zero table out up to 122 degrees all the way down)
Engine -> Spark -> Retard -> Knock Retard Decay -> Decay Rate (multiply stock table by .5)
Engine -> Spark -> Retard -> Knock Retard Attack -> Base Retard (multiply stock table by .5)
Then have him command the timing he wants at WOT in the main spark tables at of 24-26 degrees. The MAF tables must be dialed in completely then command PE to a flat 12.8:1 AFR by entering 1.15 in all cells here:
Engine -> Fuel -> Power Enrich -> Power Enrichment
In the same screen set "delay rpm" to 0 and Enrichment rate to 1.00
I recommend running pure MAF it works really well, but I'm sure your tuner has his own methods. It is critical that you have the timing dialed in with these settings without knock because if not you will ping. Definitely put some TR6 plugs in just the way they come gapped before you tune it helps.
So what your saying is that this false knock even appears in pure stock LS2 and LS3 engines?
I assume 12.8 air fuel ratio and 24-26 degree of timing @ WOT is how you tune LS2/3 engines?
Safety Car
Joined: Jun 1999
Posts: 3,570
Likes: 3
From: Austin, Singapore, Kuala Lumpur, Houston, Dallas, Hong Kong, Elgin, etc.. Texas
Actually your quite right. My tuner mentioned this false knocks which he faced when tuning my engine. I have A6 transmission and the 3" Z06 muffler pipes are pretty tight fitment around the diff. My tuner is thinking that the pipes are hitting the diff and causing this false knock. after the dyno session I had to put extra bracket in-between the 2 muffler pipes and welded them to make more gap between the pipes and the diff. Now there is almost 1 inch gap which I hope solved the problem.
Thanks for the info Sir. I'll definitely pass it to my tuner.
So what your saying is that this false knock even appears in pure stock LS2 and LS3 engines?
I assume 12.8 air fuel ratio and 24-26 degree of timing @ WOT is how you tune LS2/3 engines?
Thanks for the info Sir. I'll definitely pass it to my tuner.
So what your saying is that this false knock even appears in pure stock LS2 and LS3 engines?
I assume 12.8 air fuel ratio and 24-26 degree of timing @ WOT is how you tune LS2/3 engines?
The knock retard could be caused by either or both real knock or false (i.e. burst knock). Real knock is usually solved by reducing timing or changing the A/F ratio. The normal procedure is to first get the A/F established before tackling timing.
Burst knock can be eliminated by a number of ways which your tuner should know how. The changes recommended by OBSSSD@work will help to reduce the amount and rate of recovery when either type of Knock retard kicks in. However, don't be surprised if you still have occasional random small amount of KR. I get some just by hitting a bump in the road. Large amounts (say >2°-3°) at higher RPM at WOT should be checked out.
However, you may actually have more power using less advance over 5500 rpm at WOT, so try different settings. In other words, don't just assume more timing will make more power even without KR.
Good luck.
Last edited by Mez; Feb 11, 2011 at 11:54 AM.
Thread Starter
Racer
Joined: Sep 2005
Posts: 439
Likes: 1
Thanks Mez. I appreciate your contribution to this thread. You were a great help! 
I plan to get my tune checked every once in a while, I dont have tuning skills so I'll leave that to my tuner, I just need to double check weither I'm still experiencing KR. What do you recommend to use to datalog my PCM?
I plan to get my tune checked every once in a while, I dont have tuning skills so I'll leave that to my tuner, I just need to double check weither I'm still experiencing KR. What do you recommend to use to datalog my PCM?
Safety Car
Joined: Jun 1999
Posts: 3,570
Likes: 3
From: Austin, Singapore, Kuala Lumpur, Houston, Dallas, Hong Kong, Elgin, etc.. Texas
Thanks Mez. I appreciate your contribution to this thread. You were a great help!
I plan to get my tune checked every once in a while, I dont have tuning skills so I'll leave that to my tuner, I just need to double check weither I'm still experiencing KR. What do you recommend to use to datalog my PCM?
I plan to get my tune checked every once in a while, I dont have tuning skills so I'll leave that to my tuner, I just need to double check weither I'm still experiencing KR. What do you recommend to use to datalog my PCM?
Drifting
Joined: May 2002
Posts: 1,479
Likes: 42
From: Dallas / Ft. Worth The Republic of TEXAS
Engine -> Airflow-> Dynamic
Set High RPM Disable to 300
Set Low RPM Enable to 200
Drifting
Joined: May 2002
Posts: 1,479
Likes: 42
From: Dallas / Ft. Worth The Republic of TEXAS
Do you have HP Tuners? If so you can download a stock file from their site for almost anything you want and review it. It isn't so easy just to post up the information - since the tables are cross sections of hundreds of numbers each. What a car may pull for timing varies significantly by rpm and engine load as an example. Plus multiple tables can alter those values according to other conditions present. If you want to post your e-mail I can send you a stock file for whatever year you want, but you will still need HPT to view it.
Safety Car
Joined: Apr 2010
Posts: 4,231
Likes: 451
From: Maryland
What I would like to know is what is the max. WOT timing and AFR under the best conditions i.e. no pull back for anything. I have read that the afr is a little rich for the ls3 from the factory but what is it.
Drifting
Joined: May 2002
Posts: 1,479
Likes: 42
From: Dallas / Ft. Worth The Republic of TEXAS
I would say the LS3 would be around 17-19 degrees and mid to high 11's for A/F above 4500. It will vary because other tables can advance or retard timing based upon IAT, coolant temps, COT, and other factors.
Thread Starter
Racer
Joined: Sep 2005
Posts: 439
Likes: 1
Do you think revving the engine to 6800 RPM is not safe on the stock valve springs?