Knock, Knock who's there? (VE Table Question)
09-21-2004, 02:34 AM
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Knock, Knock who's there? (VE Table Question) Knock retard that's who!! Hey guys I'm trying to figure things out. I have a decent understanding of the VE table, and how it's really an air mass table that gives the PCM a base of how much air it should expect. Although I've read that PCM relies more on the MAF for mid and high RPM. I've come across a problem though. It seems the more I deviate from the stock VE... the more KR I get.
Okay so I made some spreadsheet that has NoGo's and Gameover's calculations in it. I did some logging... did some calculations... and found on my stock VE is very close at the lower RPMs (I read that the MAF is inaccurate at low RPMs so WTF). The mid to higher RPMs on the other hand were quite a bit off by my calculations (4-7%). So instead of drastically reducing them. I took those percentages added to them to get to no more than 4% less than stock values. I mostly dealt with higher load areas around 90 kPa and up.
Okay, all done ready to go. Went out did some logging came back... WTF. Knock retard! Keep in mind on the stock VE I got around 1* KR at different points. I was getting ~2* KR at around 49-50 kPa at random times. Also sometimes during WOT I got as much as 4* KR. Not always at high RPMs, but sometime just high load around ~97 kPA accelerating in 5th gear/ low RPM.
Came home, got an idea. Bumped up the troubled areas 1-2%. Saved it. But instead I decided to try a VE table from a 02 SS. I’m thinking it should work perfectly since it's the same engine less LS6 intake and truck cam. I was surprised how different the two tables were. The 02 has much higher percentages. I was thinking I might run rich no biggie... maybe it will help the fuel trims. Wrong! I got even more knock retard... and more frequent.
So I read that the PCM sometimes looks at the Sec. VE too. I noticed it has the exact same values as the Primary. So I updates those values to that of the stock 02 SS VE table. Guess what? Even more KR! I don't quite understand why I'm getting all this knock. Especially on stock 02 tables. I would expect much from my own modified table... not a stock one... geez I don't think I want to try the Z06 one I have now... even higher.
Could any of you experts suggest how I'm getting knock retard (California gas?)? I'm thinking maybe it could be the MAF reading lower than it should. But I'm not sure. I just know it’s rather frustrating since any little deviation from stock results in more KR.
I was getting a slight amount of KR in the same areas with the stock VE, but it seems modifying it exacerbates the problem. Oh and LT FTs are still positive btw (need a WB soon). If anyone's interested I'll post my HP Tuner logs or modified VE tables. Thanks.
Okay so I made some spreadsheet that has NoGo's and Gameover's calculations in it. I did some logging... did some calculations... and found on my stock VE is very close at the lower RPMs (I read that the MAF is inaccurate at low RPMs so WTF). The mid to higher RPMs on the other hand were quite a bit off by my calculations (4-7%). So instead of drastically reducing them. I took those percentages added to them to get to no more than 4% less than stock values. I mostly dealt with higher load areas around 90 kPa and up.
Okay, all done ready to go. Went out did some logging came back... WTF. Knock retard! Keep in mind on the stock VE I got around 1* KR at different points. I was getting ~2* KR at around 49-50 kPa at random times. Also sometimes during WOT I got as much as 4* KR. Not always at high RPMs, but sometime just high load around ~97 kPA accelerating in 5th gear/ low RPM.
Came home, got an idea. Bumped up the troubled areas 1-2%. Saved it. But instead I decided to try a VE table from a 02 SS. I’m thinking it should work perfectly since it's the same engine less LS6 intake and truck cam. I was surprised how different the two tables were. The 02 has much higher percentages. I was thinking I might run rich no biggie... maybe it will help the fuel trims. Wrong! I got even more knock retard... and more frequent.
So I read that the PCM sometimes looks at the Sec. VE too. I noticed it has the exact same values as the Primary. So I updates those values to that of the stock 02 SS VE table. Guess what? Even more KR! I don't quite understand why I'm getting all this knock. Especially on stock 02 tables. I would expect much from my own modified table... not a stock one... geez I don't think I want to try the Z06 one I have now... even higher.
Could any of you experts suggest how I'm getting knock retard (California gas?)? I'm thinking maybe it could be the MAF reading lower than it should. But I'm not sure. I just know it’s rather frustrating since any little deviation from stock results in more KR.
I was getting a slight amount of KR in the same areas with the stock VE, but it seems modifying it exacerbates the problem. Oh and LT FTs are still positive btw (need a WB soon). If anyone's interested I'll post my HP Tuner logs or modified VE tables. Thanks. 
09-21-2004, 03:44 PM
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I have fattened up my midband VE table specifically to
suppress transient KR (tip-in knock). Because the SD
tune is relied upon during "unsteady MAP" even in the
regions where the MAF is supposed to be working, any
lean error in the SD tune will be exposed on throttle
transients. Conversely if you make the VE a bit fatter
than true, it will act as a temporary "pump shot" and
fight the natural leanout from air surge against slow
sensors and control.
Basically every time I saw a KR blip on opening throttle
I added a point on the VE table about the "event origin"
and then hand-smoothed nearby. This worked for me,
I have it down to 1 degree max (so now I am slowly
upping timing to find the real steady state ping limit
rather than being held back by transient induced KR).
suppress transient KR (tip-in knock). Because the SD
tune is relied upon during "unsteady MAP" even in the
regions where the MAF is supposed to be working, any
lean error in the SD tune will be exposed on throttle
transients. Conversely if you make the VE a bit fatter
than true, it will act as a temporary "pump shot" and
fight the natural leanout from air surge against slow
sensors and control.
Basically every time I saw a KR blip on opening throttle
I added a point on the VE table about the "event origin"
and then hand-smoothed nearby. This worked for me,
I have it down to 1 degree max (so now I am slowly
upping timing to find the real steady state ping limit
rather than being held back by transient induced KR).
09-21-2004, 05:09 PM
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would love to see your tables and logs.. Feel free to email them to me.. arleetaylor@westcoastpontiacs.com
09-22-2004, 02:14 AM
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Thanks for the replies guys, much appreciated 
ataylor, you have mail!
Jimmyblue - This was my thinking. I thought a fatter table like that of an 02 SS would cause considerably less KR. Not more. Strange. I thought I would have gotten more with my leaner modified stock table. Hopefully I'll figure it out soon. Even considering that I haven't made much progress yet, I still really like this tuning stuff... Learning this is actually kinda fun.
ataylor, you have mail!
Jimmyblue - This was my thinking. I thought a fatter table like that of an 02 SS would cause considerably less KR. Not more. Strange. I thought I would have gotten more with my leaner modified stock table. Hopefully I'll figure it out soon. Even considering that I haven't made much progress yet, I still really like this tuning stuff... Learning this is actually kinda fun.
09-22-2004, 07:19 PM
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Okay guys I have an update. I put the bone stock tune back in except for the lower fan on temp, and CAGS removel. Still getting some crazy KR. Now approaching 6 degrees in some areas ex. 1400 RPM and 93 kPa and 35% TPS 5.3* KR. 
accelerating on the freeway...
ataylor has been a big help in trying to help me narrow this down. He's a great guy. Perhaps just false knock... I have the latest OS for my year. The car feels okay. It felt stronger with the 02 SS VE table though.
I'm thinking maybe I could have gotten some crapy gas. So I'm going out now to buy about 4 gallons of 100 octane and see what happens to mr.knock retard
It better fix it for flipping $5.35 a gallon or whatever it is now 
I'll keep you guys updated. Attached are screen shots from my latest log with STOCK tune. Average Knock, and Max Knock. enjoy!
accelerating on the freeway...ataylor has been a big help in trying to help me narrow this down. He's a great guy. Perhaps just false knock... I have the latest OS for my year. The car feels okay. It felt stronger with the 02 SS VE table though.
I'm thinking maybe I could have gotten some crapy gas. So I'm going out now to buy about 4 gallons of 100 octane and see what happens to mr.knock retard
It better fix it for flipping $5.35 a gallon or whatever it is now I'll keep you guys updated. Attached are screen shots from my latest log with STOCK tune. Average Knock, and Max Knock. enjoy!
09-24-2004, 04:13 PM
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Okay so here’s the update on my somewhat scientific data. I went and filled up with 6 gallons of 100 octane. This brought my octane level to roughly 94-95, more than enough to suppress any real knock from gas. So then I started logging and I was on my way.
I’ll be a SOB I actually got some KR blips here and there around 50 kPa. I’m almost positive that’s false knock. I did a few WOT runs, and at some points I was getting almost the full 4* for WOT. Not just little spikes… but a long line that progressed through the RPMs. So I’m thinking what the hell is this? Stock tune and by now it has to be getting the 94 octane.
I pull off the freeway and load up a stock Z06 VE table. I do some more logging. It reveals significantly less KR overall, but I was still getting some KR in the higher RPMs. I thought this was a fluke, so I reloading the stock VE again. KR comes back hard again. Hmm… I guess it likes the Z06 table.
So then yesterday I took the stock Z06 table and smoothed it out on the 3D graph, all nice and smooth. I did some more logging and guess what? Very little KR… just those little spikes and hits around 50 kPa. So far nothing at the higher RPMs and WOT. Awesome. It doesn’t make sense to me why it likes the Z06 table over the stock, or even the stock 02 SS table, but it does. The smoothing really made a difference too. The car also seems to pull a bit harder now then with the stock tune. I hit that rev limiter awful quick… I usually try to shift at 6. But yeah it seems that table made a difference.
I’ll be a SOB I actually got some KR blips here and there around 50 kPa. I’m almost positive that’s false knock. I did a few WOT runs, and at some points I was getting almost the full 4* for WOT. Not just little spikes… but a long line that progressed through the RPMs. So I’m thinking what the hell is this? Stock tune and by now it has to be getting the 94 octane.
I pull off the freeway and load up a stock Z06 VE table. I do some more logging. It reveals significantly less KR overall, but I was still getting some KR in the higher RPMs. I thought this was a fluke, so I reloading the stock VE again. KR comes back hard again. Hmm… I guess it likes the Z06 table.
So then yesterday I took the stock Z06 table and smoothed it out on the 3D graph, all nice and smooth. I did some more logging and guess what? Very little KR… just those little spikes and hits around 50 kPa. So far nothing at the higher RPMs and WOT. Awesome. It doesn’t make sense to me why it likes the Z06 table over the stock, or even the stock 02 SS table, but it does. The smoothing really made a difference too. The car also seems to pull a bit harder now then with the stock tune. I hit that rev limiter awful quick… I usually try to shift at 6. But yeah it seems that table made a difference.