About to throw in the towel nailing down idle

[Michael_D]

Yes, it is a royal PITA. Drives me friggin nuts.....

For your cam, I'd start with about 15 deg. 26 is way too high. Heck, my cam is 235/255 .660/.672 113 lsa, and my idle spark is 18. I just monitored manifold vac, and raised spark till vacuum did not raise further (24 deg). Then I removed 6 deg to give the idle adapt spark room to work. Idles great, starts great.... What CID is your engine?

I also like to change the min air table to grams / second. Start out with the OE table, and add 2 grams to the entire table. Start there and work your way up/down. Be patient. Bill's procedure does work for polishing.

[rio95]

How long are you letting the engine idle in each rpm cell? It takes mine about five minutes per cell to really find stable average values after trims settle.

Do this in CL, AC on. After you flash a new cal, make sure the car is not in its"lean after flash" mode. And yes, it happens even doing min air table adjustment.

OK I tried this again thinking that maybe I wasn't letting it run long enough. I started with a tune with 17 degrees of timing at idle and used airflow numbers I logged from the other day and scaled them down 20%.

I zeroed out fuel trims and let it idle for about 6 minutes. The trims weren't abnormal so I don't think I was having any lean flash issue. I then shut the car off and logged again by commanding 650, 800, 1000, and 1200 RPM and collected data for about 7 minutes in each idle adapt histogram cell. Once again the trims weren't out of whack throughout the logging. What you can see in the log is that timing averaged 16 (timing histogram), which is 1 less than commanded, for every RPM I logged and you can also see that my idle adapt histogram numbers are all very close to zero (why were they not -1deg). This makes it appear that my airflow is good, but what's the chances they would be with no adjustment yet? Seems hard to believe. It still seems like something else is going on. I have a feeling that if I doubled my airflow and reclogged I would end up with idle adapts around zero again. I'm definitely not seeing things react like everyone is explaining.

I can report though that the car seemed to run quite well with this tune so maybe I should just throw in the towel.... I have a very large cam and didn't even have trouble idling at 650rpm. I didn't seem to be getting the dips I was complaining about, but I'll need to drive some more to be sure. Also, if seems like the dipping is worse in hotter weather and it wasn't too hot tonight.

I really would like to see things respond like people describe, but maybe I'm just being too anal about learning.

idle tuning.cfg
17deg with derived airflow scaled down 20percent.hpl
17deg with derived airflow scaled down 20percent.hpt

[edge04]

wow 16 ok. I see that is 3 above stock so will start there. Assume I wil have to start over after lowering the timing?

How do you change to grms/sec in the tune, I know how in the histogram? I am running a COS

It is a stock ls2 with ls3 heads. Thanks

Yes, it is a royal PITA. Drives me friggin nuts.....

For your cam, I'd start with about 15 deg. 26 is way too high. Heck, my cam is 235/255 .660/.672 113 lsa, and my idle spark is 18. I just monitored manifold vac, and raised spark till vacuum did not raise further (24 deg). Then I removed 6 deg to give the idle adapt spark room to work. Idles great, starts great.... What CID is your engine?

I also like to change the min air table to grams / second. Start out with the OE table, and add 2 grams to the entire table. Start there and work your way up/down. Be patient. Bill's procedure does work for polishing.

[Michael_D]

OK I tried this again thinking that maybe I wasn't letting it run long enough. I started with a tune with 17 degrees of timing at idle and used airflow numbers I logged from the other day and scaled them down 20%.

I zeroed out fuel trims and let it idle for about 6 minutes. The trims weren't abnormal so I don't think I was having any lean flash issue. I then shut the car off and logged again by commanding 650, 800, 1000, and 1200 RPM and collected data for about 7 minutes in each idle adapt histogram cell. Once again the trims weren't out of whack throughout the logging. What you can see in the log is that timing averaged 16 (timing histogram), which is 1 less than commanded, for every RPM I logged and you can also see that my idle adapt histogram numbers are all very close to zero (why were they not -1deg). This makes it appear that my airflow is good, but what's the chances they would be with no adjustment yet? Seems hard to believe. It still seems like something else is going on. I have a feeling that if I doubled my airflow and reclogged I would end up with idle adapts around zero again. I'm definitely not seeing things react like everyone is explaining.

I can report though that the car seemed to run quite well with this tune so maybe I should just throw in the towel.... I have a very large cam and didn't even have trouble idling at 650rpm. I didn't seem to be getting the dips I was complaining about, but I'll need to drive some more to be sure. Also, if seems like the dipping is worse in hotter weather and it wasn't too hot tonight.

I really would like to see things respond like people describe, but maybe I'm just being too anal about learning.

idle tuning.cfg
17deg with derived airflow scaled down 20percent.hpl
17deg with derived airflow scaled down 20percent.hpt

What's the cam?

I can tell you have too much enough air, because your idle spark drops under 17, but does not rise above 17. It should oscillate over and under. Just drop the OE values back into this table, then add 2-4 g/sec to the entire table and start over. I don't like seeing zero values above 1200.

wow 16 ok. I see that is 3 above stock so will start there. Assume I wil have to start over after lowering the timing?

How do you change to grms/sec in the tune, I know how in the histogram? I am running a COS

It is a stock ls2 with ls3 heads. Thanks

Yes, start over. No idea what a "COS" is.........

Highlight the entire table by clicking on the corner box where the Colum and row axis meet. Right click > Units > G/sec...... works for just about every table.

[rio95]

What's the cam?

I can tell you have too much enough air, because your idle spark drops under 17, but does not rise above 17. It should oscillate over and under. Just drop the OE values back into this table, then add 2-4 g/sec to the entire table and start over. I don't like seeing zero values above 1200.



Yes, start over. No idea what a "COS" is.........

Highlight the entire table by clicking on the corner box where the Colum and row axis meet. Right click > Units > G/sec...... works for just about every table.

hell widow. 24x/25x with a lot of overlap and lift.

I'll take a look at the timing variation a little more to see what you're referring to, but too much airflow should be resulting in some negative idle adapt numbers though, right? I was wondering how you know what the commanded timing really is. I mean I have 17 deg in my idle and high octane tables, but aren't there a bunch of modifier tables making it hard to know what timing should actually be at? Or do none of the modifier tables affect idle? I don't have my tuning computer with me right now so I can't check.

I wasn't going to leave the values over 1200 at zero for ever. Although I don't really see what those values do either. I drove the car to work today with the tune above (no values above 1200) and it drove great this morning. Nice steady idle with no dipping or hanging worth worrying about. Would you recommend just carrying the 1200 numbers over to the right?

[5_Liter_Eater]

I drove the car to work today with the tune above (no values above 1200) and it drove great this morning. Nice steady idle with no dipping or hanging worth worrying about.

If this is the case then stop beating your head against the wall RE: histo11 results. Call it done.

[edge04]

ok been getting good results at 15 degrees. However I'm a little confused with the throttle follower tables. First, one thing I notice is that while sitting at idle when I goose it there is a slight hesitation. Will the throttle follower table help resolve this or is my base final airflow too low?

If so, the article states "When you look at this table, you'll notice that engine speeds higher than your target idle have negative values while speeds lower than your target idle have positive torque values."

Mine does not, mine has all positive numbers and matches the stock table. There is two tables, Throttle Follower Step Up and Down. These are based on Pedal Position. Are these the right tables?

[rio95]

If this is the case then stop beating your head against the wall RE: histo11 results. Call it done.

Yeah I know, but I'm a curious engineer lol. This won't be the last time I do this so I'd like to understand what's going on.

[rio95]

What's the cam?

I can tell you have too much enough air, because your idle spark drops under 17, but does not rise above 17. It should oscillate over and under. Just drop the OE values back into this table, then add 2-4 g/sec to the entire table and start over. I don't like seeing zero values above 1200.



Yes, start over. No idea what a "COS" is.........

Highlight the entire table by clicking on the corner box where the Colum and row axis meet. Right click > Units > G/sec...... works for just about every table.

I think you're on to something with your observation! You were right that the timing never went above 17deg. This made me wonder what would happen if I added timing with the same airflow. Check out the results! Very interesting. For a given airflow, the timing never goes above the commanded timing. This is data I took while commanding 800 rpm. I would have expected the idle adapt average to change with each timing change, but it didn't. So confused! I also increased the airflow by 10% with 17deg at idle and once again commanded 800 RPM and once again idle adapt average is zero. I still have NEVER gotten idle adapt average to be anything other than pretty much zero. Something else is coming into play and I don't think it's fueling. Notice that the ETC position decreases with increased timing. There seems to be some issue with this procedure unless my car is just different than everyone else's....

p.s. thanks for all the help. I'm determined to figure this out!

[edge04]

my ETC drops as I add timing as well although I'm in single digits. And the other thing I notice is that the longer I keep it in the cell the closer it gets to zero. When I was commanding 800 that cell would go to zero.

I notice you IAT's are high, is it pulling timing due to that?

I think you're on to something with your observation! You were right that the timing never went above 17deg. This made me wonder what would happen if I added timing with the same airflow. Check out the results! Very interesting. For a given airflow, the timing never goes above the commanded timing. This is data I took while commanding 800 rpm. I would have expected the idle adapt average to change with each timing change, but it didn't. So confused! I also increased the airflow by 10% with 17deg at idle and once again commanded 800 RPM and once again idle adapt average is zero. I still have NEVER gotten idle adapt average to be anything other than pretty much zero. Something else is coming into play and I don't think it's fueling. Notice that the ETC position decreases with increased timing. There seems to be some issue with this procedure unless my car is just different than everyone else's....

p.s. thanks for all the help. I'm determined to figure this out!

[rio95]

my ETC drops as I add timing as well although I'm in single digits. And the other thing I notice is that the longer I keep it in the cell the closer it gets to zero. When I was commanding 800 that cell would go to zero.

I notice you IAT's are high, is it pulling timing due to that?

I looked at the IAT adder table and it can't pull timing at idle loads. Same with the ECT adder table, so I'm not sure there is any modifier table that can alter timing at idle, but I'm not positive.

Like I said I get pretty much zero for average idle adapt no matter what I do. The longer I stay in the cell the closer it gets to zero. If I wait long enough it almost always equals exactly zero.

[edge04]

mine does the same. starts at around 1.5-2 an works its way to zero or close to it in less than a min

Like I said I get pretty much zero for average idle adapt no matter what I do. The longer I stay in the cell the closer it gets to zero. If I wait long enough it almost always equals exactly zero.

[Michael_D]

A couple weeks back, I was experimenting with min air for low rpm highway cruising. Just to see if it had an effect...(it does btw). Whilst doing this, my min air was double what it needs to be. My final idle spark was 12 deg, with very slight dips below 12, and swings up to 18. My idle spark table value was 18. The average (histo 11) would dial in to <.1, even though adaptive spark was grossly biased towards the negative.

After I was done futzing around with this, I moved my air back to where it should be. My idle spark is back to 18, and adaptive spark moves it +/- from 18 nicely. I suspect if you were to halve min air, you would see the opposite effect, and idle spark would max out at whatever base is, + adaptive. It would then bounce around a bit, but not much.

So, based on my observations, I would always start out with the OE min air table (assuming you can actually start the engine after a cam swap). I would then set idle to about 1000, and then find where your main idle spark should be. You can get all scientific if you want, but I don't see a need when you can watch your MAP. Keep raising spark until you do not see an increase in vacuum. Then lower it a few degrees. Refer to your adaptive spark table, and lower it a corresponding amount, to give adaptive spark room to work (add/pull spark). At this point, you can start fussing with min air. Raise it a couple g/sec, log, watch your spark. Keep raising and watching. When you find final running idle spark start to lower from too much air, you know the upper boundary. Then work your way back down. When you know your close, use the adaptive spark histo to dial it in. After done, if the throttle still hangs, or dips too low - move to the follower torque table.

As far as the min idle air cells above 1200, I think they need values. If you are out rallying around, fourth gear, 4500 rpm, then pop into N and coast – you don’t want the engine to die. If you don’t have a value in the cell, what’s to keep the throttle blade open? I dunno, maybe it won’t, but why risk it? Some super smart GM engineer thought it was important enough to put some work into the table values, so I’m going to follow his/her lead.

So what do you move them to? Not real sure what the “correct” amount is, but I’ll describe what I did, and I think it’s working……..

After I got my 600, 800, 1000, 1200 idle values dialed in, I dropped the OE table values back into the cells above 1200, so I had the OE values to work with.

I then used Excel to figure out percentage based differences in the entire OE table. I found the % increase between the idle 1200 cell, and highest OE value in this row. I then multiplied my “modified” value by the same amount in this cell and used the HPT interpolate function between this cell and the 1200 cell. I then carried the 1200 value to the far right. At this point my idle row was done. I once again referred to the OE table, idle row. I then compared this row to the remaining rows, using Excel. Found the percent difference between the idle row, and all others. Then I just took my “modified” idle row, and multiplied it by the % difference I found with the remaining OE table row values. Then it’s just a copy/paste into the table. For example (not using actual values): 1800 rpm value / idle row, verse 1800 rpm value 4th gear row = +4%. Clear as mud?

[rio95]

A couple weeks back, I was experimenting with min air for low rpm highway cruising. Just to see if it had an effect...(it does btw). Whilst doing this, my min air was double what it needs to be. My final idle spark was 12 deg, with very slight dips below 12, and swings up to 18. My idle spark table value was 18. The average (histo 11) would dial in to <.1, even though adaptive spark was grossly biased towards the negative.

After I was done futzing around with this, I moved my air back to where it should be. My idle spark is back to 18, and adaptive spark moves it +/- from 18 nicely. I suspect if you were to halve min air, you would see the opposite effect, and idle spark would max out at whatever base is, + adaptive. It would then bounce around a bit, but not much.

So, based on my observations, I would always start out with the OE min air table (assuming you can actually start the engine after a cam swap). I would then set idle to about 1000, and then find where your main idle spark should be. You can get all scientific if you want, but I don't see a need when you can watch your MAP. Keep raising spark until you do not see an increase in vacuum. Then lower it a few degrees. Refer to your adaptive spark table, and lower it a corresponding amount, to give adaptive spark room to work (add/pull spark). At this point, you can start fussing with min air. Raise it a couple g/sec, log, watch your spark. Keep raising and watching. When you find final running idle spark start to lower from too much air, you know the upper boundary. Then work your way back down. When you know your close, use the adaptive spark histo to dial it in. After done, if the throttle still hangs, or dips too low - move to the follower torque table.

As far as the min idle air cells above 1200, I think they need values. If you are out rallying around, fourth gear, 4500 rpm, then pop into N and coast ? you don?t want the engine to die. If you don?t have a value in the cell, what?s to keep the throttle blade open? I dunno, maybe it won?t, but why risk it? Some super smart GM engineer thought it was important enough to put some work into the table values, so I?m going to follow his/her lead.

So what do you move them to? Not real sure what the ?correct? amount is, but I?ll describe what I did, and I think it?s working??..

After I got my 600, 800, 1000, 1200 idle values dialed in, I dropped the OE table values back into the cells above 1200, so I had the OE values to work with.

I then used Excel to figure out percentage based differences in the entire OE table. I found the % increase between the idle 1200 cell, and highest OE value in this row. I then multiplied my ?modified? value by the same amount in this cell and used the HPT interpolate function between this cell and the 1200 cell. I then carried the 1200 value to the far right. At this point my idle row was done. I once again referred to the OE table, idle row. I then compared this row to the remaining rows, using Excel. Found the percent difference between the idle row, and all others. Then I just took my ?modified? idle row, and multiplied it by the % difference I found with the remaining OE table row values. Then it?s just a copy/paste into the table. For example (not using actual values): 1800 rpm value / idle row, verse 1800 rpm value 4th gear row = +4%. Clear as mud?

I don't think the results I posted in post #269 jive with what you're saying I should see. I doubled and then tripled airflow and adaptive idle average was zero every time AND average timing was VERY close to commanded of 16deg every time. I could feel the change in airflow though (hanging idle) so it seemed to be doing something. I'm very confident the airflow was way too high when I doubled and tripled it, so shouldn't that have resulted in an average idle of lower than 16?

[rio95]

A couple weeks back, I was experimenting with min air for low rpm highway cruising. Just to see if it had an effect...(it does btw). Whilst doing this, my min air was double what it needs to be. My final idle spark was 12 deg, with very slight dips below 12, and swings up to 18. My idle spark table value was 18. The average (histo 11) would dial in to <.1, even though adaptive spark was grossly biased towards the negative.

After I was done futzing around with this, I moved my air back to where it should be. My idle spark is back to 18, and adaptive spark moves it +/- from 18 nicely. I suspect if you were to halve min air, you would see the opposite effect, and idle spark would max out at whatever base is, + adaptive. It would then bounce around a bit, but not much.

So, based on my observations, I would always start out with the OE min air table (assuming you can actually start the engine after a cam swap). I would then set idle to about 1000, and then find where your main idle spark should be. You can get all scientific if you want, but I don't see a need when you can watch your MAP. Keep raising spark until you do not see an increase in vacuum. Then lower it a few degrees. Refer to your adaptive spark table, and lower it a corresponding amount, to give adaptive spark room to work (add/pull spark). At this point, you can start fussing with min air. Raise it a couple g/sec, log, watch your spark. Keep raising and watching. When you find final running idle spark start to lower from too much air, you know the upper boundary. Then work your way back down. When you know your close, use the adaptive spark histo to dial it in. After done, if the throttle still hangs, or dips too low - move to the follower torque table.

As far as the min idle air cells above 1200, I think they need values. If you are out rallying around, fourth gear, 4500 rpm, then pop into N and coast ? you don?t want the engine to die. If you don?t have a value in the cell, what?s to keep the throttle blade open? I dunno, maybe it won?t, but why risk it? Some super smart GM engineer thought it was important enough to put some work into the table values, so I?m going to follow his/her lead.

So what do you move them to? Not real sure what the ?correct? amount is, but I?ll describe what I did, and I think it?s working??..

After I got my 600, 800, 1000, 1200 idle values dialed in, I dropped the OE table values back into the cells above 1200, so I had the OE values to work with.

I then used Excel to figure out percentage based differences in the entire OE table. I found the % increase between the idle 1200 cell, and highest OE value in this row. I then multiplied my ?modified? value by the same amount in this cell and used the HPT interpolate function between this cell and the 1200 cell. I then carried the 1200 value to the far right. At this point my idle row was done. I once again referred to the OE table, idle row. I then compared this row to the remaining rows, using Excel. Found the percent difference between the idle row, and all others. Then I just took my ?modified? idle row, and multiplied it by the % difference I found with the remaining OE table row values. Then it?s just a copy/paste into the table. For example (not using actual values): 1800 rpm value / idle row, verse 1800 rpm value 4th gear row = +4%. Clear as mud?

Man I'm getting sick of wasting gas in church parking lots haha.

Still totally stumped here. I zeroed out the airflow table and drove the car and let it idle for about 10 min. It didn't want to idle too well, which isn't surprising. What is surprising though is I was expecting the timing to be higher than commanded and it wasn't. In fact it is a little LOWER. Then I tried the stock airflow numbers and once again I'm close to commanded timing and idle advance is pretty much zero. What the heck??



idle tuning.cfg
stock airflow without adapt.hpl
stock airflow with adapt.hpl

[rio95]

stock airflow with adapt.hpl
no airflow with adapt.hpl

[edge04]

I'm confused. Are you saying it runs good with the stock airflow table? If so why not leave it?

[Michael_D]

There is a particular place I do this too. Out of town. Can't really do it in my driveway without pissing off the neighbors, and I have Borla Touring muffs now.

I dunno..... nothing jumping out at me as abnormal in your logs, but I'm hardly qualified to know what normal should look like..... It does look like your adapt spark swings more with stock air flow, then none. Have you checked for vacuum leaks?

Also log your TPS to see where it lands.

Another thing you might try, is to spread your under speed spark table out to the upper rpm range. I interpolated mine from the 164deg cell, to the far right cell in both p/n and gear.

Or, just call it a day, seeing how it seems to be idling fine.

[edge04]

Do you guys log ETC or TPS? I was logging TPS and that was around 18% during idle however when logging ETC that's 9%.I notice that rio's is 13%, my guess is because of the size of his cam

[5_Liter_Eater]

This process isn't gospel. LOL It's something I put together after messing around with trying to tune the gen 4 idle because there wasn't any guide or process. Maybe the second portion isn't beneficial or maybe there's a better way to histogram it.