Cammed C7 idles but has negative timing. 3 bar map sensor seems to be reading high

[JASON11WS6]

none

[lt1z350]

If you only got the DVD from DTM, we made a few more GENV videos since then. Everything is hosted on our streaming site HERE now. Specifically, we made addendums to the torque model and idle control strategies for GENV with more information. This segments are available separately from the main GENV video so you don't need to "re-purchase" anything to get them.

GENV idle is really a balance of torques, so getting it right requires that you have VVE, VT, and MBT all correct for your specific combination.

I had to pay to see teh virtaul torque lesson the same with the idle lesson. I had first did the gen v one but in the end had to pay to see the others.
You refer to the mbt table a lot on these videos but its unclear how to properly set it up. Factory its a mess its really high up at what would be stock idle and pretty low down in the WOT ranges plus its moving around a lot. If this is key to reporting other things like VT correctly whats the best way to set that table up? And its really odd how gm puts all negative values in the flex mbt adder table. For instance on 93 and meth I make peak power around 24 degrees timing and on e60 its around 27 degrees yet even on stock gm flex vehicles they reduce the mbt table rather then add 3 more degrees to it. I feel like so much of this is just do what it takes to make it work vrs do whats right to make it work. So its very hard to look at any stock gm cal and try to understand what it is doing when values being used make no sense to what the car even makes in stock form. I feel more of this needs more depth to it for sure so to understand it better. I really want to tune my car to be correct and not just make it work out if that is even possible with what everyone knows. Also on the vt editor you can click on that nm at the top and change the tables over to ft lbs. I had spent so much time trying to build them to really represent a torque graph yet being more just flat and smooth seems to get the job done from what I see on the video.
My car drove great on SD ad now with the maf back in play I get that same surging on the shifts as in the video so guess I need to refrence the map and follow suit on the airmass now. Then its do it again on ethanaol.......

[lt1z350]

Jason I figured out something pretty big this weekend on the virtual torque. If you have gone in and tried to edit tables with out keeping them linked together you might have too much seperation on them at this point. I was having these odd issues on the shifts throttle acting stupid at times and I had done a lot of tweaking on the vt tables. Wot was fine other then random timing dips on certain shifts but not all so it wasnt right. I looked back over the stock ones and stared to compare numbers across the tables from -10 to 40. I had unlinked them and smoothed and raised them one by one as some were worse off then others. That turned out to be a mistake. So I took what I had already and tightend them up a lot. I picked a spot on the table say .400 at 1800 rpm and I wrote down the the spread on the stock airmass tables. I then having a guide tighten mine up to around that just to see what I got out of it. I was having lazy long shifts at light throttle with surges my guess is this is it takes a long time to spread what I had when dropping the timing down as say from 35 degrees of timing to the bottom the 10 degree table it was a long run of torque I was dropping. Both timing and throttle wasnt happy. So after the changes the throttle was no longer trying to open causing that surge and the timing drop was much quicker to recover.
So easiest to go back to stock most likey and tune them all linked as Greg says in the tuning videos. Also since I do have fast torque exit off on my car my Wot now has zero timing drop its dead flat at wot on the timing and my shifts are .1 for every shift very quick and positive but not hard at all. I still see dips of torque but timing is flat and so is the throttle which is key to a faster pass on these cars I found vrs one that dips the timing like stock on every shift. I dont have it perfect but I see the direction it needs to go and spreading them apart at all is not what you want. I might even try much tighter to see what it does just so I know for future tuning on anything that uses virtual torque tables. Trial and error sucks if you dont know the direction to go and what the limit of an adjustment is or a ceiling to stay away from at least. Hope it helps.

[eficalibrator]

You refer to the mbt table a lot on these videos but its unclear how to properly set it up.

Many poeple won't like hearing this, but the right way to do it is to perform spark sweeps at each speed/load point (with stable AFR and temps) to find MBT timing by plotting it against delivered torque. It's honestly a very basic exercise, but it can be very time consuming if you need to hit a lot of points. In practice, I usually start with all the good factory values and spot-check it to make general adjustments to a wider area of the map.

And its really odd how gm puts all negative values in the flex mbt adder table. For instance on 93 and meth I make peak power around 24 degrees timing and on e60 its around 27 degrees yet even on stock gm flex vehicles they reduce the mbt table rather then add 3 more degrees to it. I feel like so much of this is just do what it takes to make it work vrs do whats right to make it work. So its very hard to look at any stock gm cal and try to understand what it is doing when values being used make no sense to what the car even makes in stock form. I feel more of this needs more depth to it for sure so to understand it better. I really want to tune my car to be correct and not just make it work out if that is even possible with what everyone knows.

Now you are confusing gasoline vs ethanol. If you don't have the gasoline (E0-E10) MBT values right, I wouldn't jump into flex fuel tuning yet. The flex tables are indeed adders to the base gasoline values (as we showed in the flex fuel tuning video). Ethanol has a different burn rate, so it requires LESS part throttle timing to hit MBT. But the octane number is higher, so it can tolerate MORE timing at high load before hitting the knock limit (which is now much closer to MBT).

GM has intentionally put more layers in the control, each with its own specific purpose to address one physical issue (gasoline MBT, ethanol flame speed, etc.) The trick is to perform your calibration work such that you are properly isolating each layer. Without a clear test plan, you will have a hard time getting each one right.

[lt1z350]

Many poeple won't like hearing this, but the right way to do it is to perform spark sweeps at each speed/load point (with stable AFR and temps) to find MBT timing by plotting it against delivered torque. It's honestly a very basic exercise, but it can be very time consuming if you need to hit a lot of points. In practice, I usually start with all the good factory values and spot-check it to make general adjustments to a wider area of the map.


Now you are confusing gasoline vs ethanol. If you don't have the gasoline (E0-E10) MBT values right, I wouldn't jump into flex fuel tuning yet. The flex tables are indeed adders to the base gasoline values (as we showed in the flex fuel tuning video). Ethanol has a different burn rate, so it requires LESS part throttle timing to hit MBT. But the octane number is higher, so it can tolerate MORE timing at high load before hitting the knock limit (which is now much closer to MBT).

GM has intentionally put more layers in the control, each with its own specific purpose to address one physical issue (gasoline MBT, ethanol flame speed, etc.) The trick is to perform your calibration work such that you are properly isolating each layer. Without a clear test plan, you will have a hard time getting each one right.

I drive the car on e60 and up 90 percent of the time why I started to work on that sooner then later. I got pretty much all my driving excellent now but the idle is kicking my ass. I have gone from it being ok or more so tollerable in park and in gear to now it wants to hunt in gear so bad I cant drive it. Pull it into park and its fine or more so ok. I never can get the timing into this I want. idles in park with around 0 up and down 5 degrees. It was fine in gear same basic thing actually it was adding a little timing to it but now it gets colder out side and now its going crazy hunting all over the place and no change is sending me in a good direction. I can ruin the park idle make it hunt and drop then go back to a decent in park idle and still hunts in gear.
What I dont get is why when I add the influence of pushing the pedal adding just 5 percent to the throttle it all starts to work fine. I can see the tps goes down timing goes up and idle becomes steady. But it takes me influencing the settings with adding throttle pedal into it. Trying to rationalize it I see torque go up and axle torque go up so I try to add torque to the vt and it gets worse. So I go down and it doesnt help either.
The fact the car drives good really it drives great I hate to start over on anything to fix the idle issues. Seems no matter what I do I cannot get the zero torque pid to go up other then when its hunting. No changes in the tune will make that go up against the setting of 86 thats in it other then if hunts and goes up over 1200 rpm. I had the vve really good at idle and now see its pulling fuel but its hunting so I hate to mess with something I had at -2 at idle when it was in open loop SD as right now im seeing -10 on the histogram.
I even tried to make vt tables flat from 550-950 and keep it really close from .300 to .500 trying to make it so that it out of the equation commanding different values. Something to do with adding the load of the car in gear is making it go nuts and yet to make sense of it staring at logs all morning.

[sevinn]

I drive the car on e60 and up 90 percent of the time why I started to work on that sooner then later. I got pretty much all my driving excellent now but the idle is kicking my ass. I have gone from it being ok or more so tollerable in park and in gear to now it wants to hunt in gear so bad I cant drive it. Pull it into park and its fine or more so ok. I never can get the timing into this I want. idles in park with around 0 up and down 5 degrees. It was fine in gear same basic thing actually it was adding a little timing to it but now it gets colder out side and now its going crazy hunting all over the place and no change is sending me in a good direction. I can ruin the park idle make it hunt and drop then go back to a decent in park idle and still hunts in gear.
What I dont get is why when I add the influence of pushing the pedal adding just 5 percent to the throttle it all starts to work fine. I can see the tps goes down timing goes up and idle becomes steady. But it takes me influencing the settings with adding throttle pedal into it. Trying to rationalize it I see torque go up and axle torque go up so I try to add torque to the vt and it gets worse. So I go down and it doesnt help either.
The fact the car drives good really it drives great I hate to start over on anything to fix the idle issues. Seems no matter what I do I cannot get the zero torque pid to go up other then when its hunting. No changes in the tune will make that go up against the setting of 86 thats in it other then if hunts and goes up over 1200 rpm. I had the vve really good at idle and now see its pulling fuel but its hunting so I hate to mess with something I had at -2 at idle when it was in open loop SD as right now im seeing -10 on the histogram.
I even tried to make vt tables flat from 550-950 and keep it really close from .300 to .500 trying to make it so that it out of the equation commanding different values. Something to do with adding the load of the car in gear is making it go nuts and yet to make sense of it staring at logs all morning.

What are your idle torque reserve settings like?

[lt1z350]

What are your idle torque reserve settings like?

they were up around 7 I tried up to 13 and got worse so dropped them to 3.50 and got better. That was before I redid the vt tables so got a lot of changes in that took a lot of time making sure airmass and map are reporting what the car is doing in the idle areas to test out now. Had to take a few days off it now getting back to it today to see if all this effort paid off. I do know I was going in the direction of this and it was getting better so I just started from scratch again. Ill report back once get it in the car and test it out.
Its just odd I see a lot of tuners going really high on that table to make the car they are working on idle yet my setup couldnt tollerate it going higher caused more hunting and was got worse when went from park to in gear.

[Ben Charles]

The idle reserve is the available idle tq it can “sway”.... I use to use higher numbers myself but the swings in Tq were quite a bit... lower reserve less tq management spark from my experience and tighter!

I can see both work, but I’ve always been a fan of making airflow as accurate as possible and not relying on spark to fix idle speed!
Sometimes I get customers that want small cams to “chop” and I tend to make airflow little less accurate and make spark jump

[sevinn]

they were up around 7 I tried up to 13 and got worse so dropped them to 3.50 and got better. That was before I redid the vt tables so got a lot of changes in that took a lot of time making sure airmass and map are reporting what the car is doing in the idle areas to test out now. Had to take a few days off it now getting back to it today to see if all this effort paid off. I do know I was going in the direction of this and it was getting better so I just started from scratch again. Ill report back once get it in the car and test it out.
Its just odd I see a lot of tuners going really high on that table to make the car they are working on idle yet my setup couldnt tollerate it going higher caused more hunting and was got worse when went from park to in gear.

I'm in the less than stock camp but I prefer a smooth idle so that it doesn't buck on the brakes as much. Care to send/share a log of your idle right now just so I can get an idea of what you're seeing?