How do you go about tuning the lower end of the VE table? 400 800 and 1200?
03-22-2008, 11:05 AM
#1
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How do you go about tuning the lower end of the VE table? 400 800 and 1200? Its not like I can get down to 400 rpm very easily but maybe I can. The tune procedure shows to start off from the rpm and roll into and off of the throttle.
Is it the same for these low end portions of the table?
Im trying to get my idle spot on here which is the reason I am doing this.
Is it the same for these low end portions of the table?
Im trying to get my idle spot on here which is the reason I am doing this.
03-22-2008, 08:33 PM
#3
My idle is at 725, so the 800 column is the main one I care about.
To get near 400, the engine has to be on the verge of dieing, and the map goes way up when that happens, so you still can't get a good reading for 400 at a real map reading.
To keep things simple, I just set my 400 column to match the 800 column. Otherwise, if the rpms start going down, the fueling gets reduced, and when the rpms come back up fuel gets increased, which just sets up an oscillation in the idle speed.
You can change the rpms you're logging, depending on what your idle rpm is. For example, if you're idling at 600, you could log 500, 600, 700, 800. Now you will have numbers to look at, to see how (if any) your VE changes in the rpm range your engine operates in. Then you can figure out what makes sense to put in the 400 column so when the pcm interpolates between 400 and 800, you end up with the number you want at the speed you actually idle at.
Also the 400 column really doesn't matter at any map ranges outside of your idle range. In decel the rpms will never go there because the wheels will be pushing the engine to higher rpms, and you'll never be at 400 rpms at wot either.
One more thing to think about. The exhaust gas flow is much slower at idle. If your idle is oscillating, there will be a lag between an rpm peak or valley, and what the wideband is telling you. Depending on the frame rate and the lag, and the rate of the oscillation of the idle, the numbers you get from logging may be telling you the opposite of what you need to do. If the lag is timed just right, the rpms will already be peaking again when the wideband is reading the exhaust from the valley, and the rpms will be hitting a valley again when the wideband is reading the peak. This can lead you to dropping the VE in a lower numbered map row, and increasing the VE in the next higher numbered map row, making the two rows start getting further and further apart. If you see the oscillation get worse, then start pulling the VE values back closer together again in those 2 or 3 rows that cover your idle kpa.
I repeated 41 as the VE in a six-cell block. My 400 and 800 columns for 50, 55, 60 kpa. The 50/55/60 rows start spreading apart only after I get to 1200. That settled my idle down a whole lot. The wideband was telling me to spread them at idle, and it kept getting worse when I strictly followed the afr error from the wideband. (more pronounced in mine because the wideband is in the tailpipe and the delay is even longer)
To get near 400, the engine has to be on the verge of dieing, and the map goes way up when that happens, so you still can't get a good reading for 400 at a real map reading.
To keep things simple, I just set my 400 column to match the 800 column. Otherwise, if the rpms start going down, the fueling gets reduced, and when the rpms come back up fuel gets increased, which just sets up an oscillation in the idle speed.
You can change the rpms you're logging, depending on what your idle rpm is. For example, if you're idling at 600, you could log 500, 600, 700, 800. Now you will have numbers to look at, to see how (if any) your VE changes in the rpm range your engine operates in. Then you can figure out what makes sense to put in the 400 column so when the pcm interpolates between 400 and 800, you end up with the number you want at the speed you actually idle at.
Also the 400 column really doesn't matter at any map ranges outside of your idle range. In decel the rpms will never go there because the wheels will be pushing the engine to higher rpms, and you'll never be at 400 rpms at wot either.
One more thing to think about. The exhaust gas flow is much slower at idle. If your idle is oscillating, there will be a lag between an rpm peak or valley, and what the wideband is telling you. Depending on the frame rate and the lag, and the rate of the oscillation of the idle, the numbers you get from logging may be telling you the opposite of what you need to do. If the lag is timed just right, the rpms will already be peaking again when the wideband is reading the exhaust from the valley, and the rpms will be hitting a valley again when the wideband is reading the peak. This can lead you to dropping the VE in a lower numbered map row, and increasing the VE in the next higher numbered map row, making the two rows start getting further and further apart. If you see the oscillation get worse, then start pulling the VE values back closer together again in those 2 or 3 rows that cover your idle kpa.
I repeated 41 as the VE in a six-cell block. My 400 and 800 columns for 50, 55, 60 kpa. The 50/55/60 rows start spreading apart only after I get to 1200. That settled my idle down a whole lot. The wideband was telling me to spread them at idle, and it kept getting worse when I strictly followed the afr error from the wideband. (more pronounced in mine because the wideband is in the tailpipe and the delay is even longer)
03-22-2008, 10:09 PM
#4
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well I have it close right now, my idle with the AC off is pretty darn close to perfect, no surging at anytime at all, when I turn the AC on I still don't get the surging it just dies for some reason, but this does not even happen all the time only sometimes and its hard to predict, I'm thinking possibly that its happening in open loop mode but I need to confirm with more logging.
I tried giving my idle trims more room to learn, I tried giving the under speed rpm spark table a little room for correction but I think in the end the AC is just bogging the engine down too much for the little air that is in the cyls.
At least I think,
My wideband is on the way in the mail as we speak but in the meantime I'm trying to work on this idle, what could cause the idle to die only with the AC on and not because of surging it just loses rpms and dies.
I tried giving my idle trims more room to learn, I tried giving the under speed rpm spark table a little room for correction but I think in the end the AC is just bogging the engine down too much for the little air that is in the cyls.
At least I think,
My wideband is on the way in the mail as we speak but in the meantime I'm trying to work on this idle, what could cause the idle to die only with the AC on and not because of surging it just loses rpms and dies.
03-24-2008, 11:01 PM
#6
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My idle is at 725, so the 800 column is the main one I care about.
To get near 400, the engine has to be on the verge of dieing, and the map goes way up when that happens, so you still can't get a good reading for 400 at a real map reading.
To keep things simple, I just set my 400 column to match the 800 column. Otherwise, if the rpms start going down, the fueling gets reduced, and when the rpms come back up fuel gets increased, which just sets up an oscillation in the idle speed.
You can change the rpms you're logging, depending on what your idle rpm is. For example, if you're idling at 600, you could log 500, 600, 700, 800. Now you will have numbers to look at, to see how (if any) your VE changes in the rpm range your engine operates in. Then you can figure out what makes sense to put in the 400 column so when the pcm interpolates between 400 and 800, you end up with the number you want at the speed you actually idle at.
Also the 400 column really doesn't matter at any map ranges outside of your idle range. In decel the rpms will never go there because the wheels will be pushing the engine to higher rpms, and you'll never be at 400 rpms at wot either.
One more thing to think about. The exhaust gas flow is much slower at idle. If your idle is oscillating, there will be a lag between an rpm peak or valley, and what the wideband is telling you. Depending on the frame rate and the lag, and the rate of the oscillation of the idle, the numbers you get from logging may be telling you the opposite of what you need to do. If the lag is timed just right, the rpms will already be peaking again when the wideband is reading the exhaust from the valley, and the rpms will be hitting a valley again when the wideband is reading the peak. This can lead you to dropping the VE in a lower numbered map row, and increasing the VE in the next higher numbered map row, making the two rows start getting further and further apart. If you see the oscillation get worse, then start pulling the VE values back closer together again in those 2 or 3 rows that cover your idle kpa.
I repeated 41 as the VE in a six-cell block. My 400 and 800 columns for 50, 55, 60 kpa. The 50/55/60 rows start spreading apart only after I get to 1200. That settled my idle down a whole lot. The wideband was telling me to spread them at idle, and it kept getting worse when I strictly followed the afr error from the wideband. (more pronounced in mine because the wideband is in the tailpipe and the delay is even longer)
To get near 400, the engine has to be on the verge of dieing, and the map goes way up when that happens, so you still can't get a good reading for 400 at a real map reading.
To keep things simple, I just set my 400 column to match the 800 column. Otherwise, if the rpms start going down, the fueling gets reduced, and when the rpms come back up fuel gets increased, which just sets up an oscillation in the idle speed.
You can change the rpms you're logging, depending on what your idle rpm is. For example, if you're idling at 600, you could log 500, 600, 700, 800. Now you will have numbers to look at, to see how (if any) your VE changes in the rpm range your engine operates in. Then you can figure out what makes sense to put in the 400 column so when the pcm interpolates between 400 and 800, you end up with the number you want at the speed you actually idle at.
Also the 400 column really doesn't matter at any map ranges outside of your idle range. In decel the rpms will never go there because the wheels will be pushing the engine to higher rpms, and you'll never be at 400 rpms at wot either.
One more thing to think about. The exhaust gas flow is much slower at idle. If your idle is oscillating, there will be a lag between an rpm peak or valley, and what the wideband is telling you. Depending on the frame rate and the lag, and the rate of the oscillation of the idle, the numbers you get from logging may be telling you the opposite of what you need to do. If the lag is timed just right, the rpms will already be peaking again when the wideband is reading the exhaust from the valley, and the rpms will be hitting a valley again when the wideband is reading the peak. This can lead you to dropping the VE in a lower numbered map row, and increasing the VE in the next higher numbered map row, making the two rows start getting further and further apart. If you see the oscillation get worse, then start pulling the VE values back closer together again in those 2 or 3 rows that cover your idle kpa.
I repeated 41 as the VE in a six-cell block. My 400 and 800 columns for 50, 55, 60 kpa. The 50/55/60 rows start spreading apart only after I get to 1200. That settled my idle down a whole lot. The wideband was telling me to spread them at idle, and it kept getting worse when I strictly followed the afr error from the wideband. (more pronounced in mine because the wideband is in the tailpipe and the delay is even longer)
man I reread this and what you said is sinking in, I get the valley peak thing but the one thing that I don't necessarily get is why you made all the idle kpa's the same value? wouldn't the airmass be diff for any kpa?
Explain more if you don't mind.
03-24-2008, 11:05 PM
#7
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Also whats the specs on your setup? like cam size engine size etc.
My VE table is waaaaaaayyyy lower than yours at those values you mentioned in the 6 pack range, like half as much.
My VE table is waaaaaaayyyy lower than yours at those values you mentioned in the 6 pack range, like half as much.
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03-25-2008, 01:00 PM
#8
After seeing all that stuff again that I typed, I had to re-read it too... 
Engine is 5.7, heads are TEA 5.7 "touched up" (not milled for compression).
16cc dished pistons, so my compression ratio is low, around 8.7.
Cam is 224/228 .581/.588 on 115.
LS6 intake, MAC mid-length headers.
60 lb mototron injectors with return-style fueling.
SD tune (no MAF in the mix).
Rear mount turbo.
I think that's all the high points from a tuning perspective.
My idle was "hunting" a lot. I was mostly confined to the 50-60 kpa region, but once it broke out of there it would swing from 500-1500 rpms and all bets were off. I figured if I could tame it down there in that region, I'd be ok and it wouldn't break out, and I wouldn't have to do anything out of the ordinary in a broader region.
I was thinking about the older carb cars, with a constant size idle jet and a idle screw, and those cars didn't surge and start swinging the idle with a moderate cam. So I worked at flattening the fueling response in that narrow area.
I'm still letting timing adjustments handle a lot of the idle control.
So my map, in a much tighter rpm window now, stays in the 50-60 kpa area, and I decided to treat it all the same, instead of my fueling jumping all around in there, which was just confusing the issue that much more.
You'll have to watch and see (when it's idling at the right rpms) where in the MAP range it's riding 90% of the time. It may be a little higher or lower MAP depending on the cam and the idle speed. A bigger cam and/or higher idle speed will shift it around. A bigger cam will pull less vacuum (and be a higher kpa). If I turn my idle speed up, I pull more vacuum (up to a point anyway) and the MAP number is lower.
Engine is 5.7, heads are TEA 5.7 "touched up" (not milled for compression).
16cc dished pistons, so my compression ratio is low, around 8.7.
Cam is 224/228 .581/.588 on 115.
LS6 intake, MAC mid-length headers.
60 lb mototron injectors with return-style fueling.
SD tune (no MAF in the mix).
Rear mount turbo.
I think that's all the high points from a tuning perspective.
My idle was "hunting" a lot. I was mostly confined to the 50-60 kpa region, but once it broke out of there it would swing from 500-1500 rpms and all bets were off. I figured if I could tame it down there in that region, I'd be ok and it wouldn't break out, and I wouldn't have to do anything out of the ordinary in a broader region.
I was thinking about the older carb cars, with a constant size idle jet and a idle screw, and those cars didn't surge and start swinging the idle with a moderate cam. So I worked at flattening the fueling response in that narrow area.
I'm still letting timing adjustments handle a lot of the idle control.
So my map, in a much tighter rpm window now, stays in the 50-60 kpa area, and I decided to treat it all the same, instead of my fueling jumping all around in there, which was just confusing the issue that much more.
You'll have to watch and see (when it's idling at the right rpms) where in the MAP range it's riding 90% of the time. It may be a little higher or lower MAP depending on the cam and the idle speed. A bigger cam and/or higher idle speed will shift it around. A bigger cam will pull less vacuum (and be a higher kpa). If I turn my idle speed up, I pull more vacuum (up to a point anyway) and the MAP number is lower.
03-25-2008, 01:04 PM
#9
Oh yeah, and the other reason for flattening that area, is I'd never be able to get real numbers with my wideband to account for 1-3 percent differences in VE from 50-60 kpa. And that's about all the percent would vary in that range anyway. So instead of guessing (and not having a good way to know if I was guessing right), or letting the wideband tell me the wrong thing to do, I flattened them. Much simpler for me in this case, and took one more variable out of the equation.
03-25-2008, 03:01 PM
#10
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ok gotcha, nice setup you got there btw !
mine idles in the 60 to 65 kpa area so I'll need to concentrate there, I really find it amazing how much changing the VE table can affect so much stuff so drastically.
mine idles in the 60 to 65 kpa area so I'll need to concentrate there, I really find it amazing how much changing the VE table can affect so much stuff so drastically.
03-25-2008, 06:18 PM
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03-25-2008, 09:37 PM
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03-27-2008, 01:03 AM
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well I have it close right now, my idle with the AC off is pretty darn close to perfect, no surging at anytime at all, when I turn the AC on I still don't get the surging it just dies for some reason, but this does not even happen all the time only sometimes and its hard to predict, I'm thinking possibly that its happening in open loop mode but I need to confirm with more logging.
I tried giving my idle trims more room to learn, I tried giving the under speed rpm spark table a little room for correction but I think in the end the AC is just bogging the engine down too much for the little air that is in the cyls.
At least I think,
My wideband is on the way in the mail as we speak but in the meantime I'm trying to work on this idle, what could cause the idle to die only with the AC on and not because of surging it just loses rpms and dies.
I tried giving my idle trims more room to learn, I tried giving the under speed rpm spark table a little room for correction but I think in the end the AC is just bogging the engine down too much for the little air that is in the cyls.
At least I think,
My wideband is on the way in the mail as we speak but in the meantime I'm trying to work on this idle, what could cause the idle to die only with the AC on and not because of surging it just loses rpms and dies.
Mike K. if your using hpt look under Torque management> engine torque> ac torque and look at the max retard table. I usually just zero it out and it helps a bunch on cammed cars when turning the a/c on.
03-30-2008, 01:15 PM
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yeah I did 0 that out and times the tq also by 1.25, changed the LTIT range for AC, tuned in my RAF, I also zeroed out the cat lightoff spark as well as the startup enrichment table. I did all this and it did help but what helped alot was changing the vE tabe down low. I am intalling a wideband today but from what you guys have said its all unreliable at low rpms due to pulsing so the 400 and maybe 800 rpm ranges are gonna be a bit of trial and error.
FWIW I do have it close now even with AC on, Its getting there slowly but surely.
FWIW I do have it close now even with AC on, Its getting there slowly but surely.
03-31-2008, 12:13 PM
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If you are doing a VE tune, it will change down low when the maf is plugged back in. If you're trying to bring the idle ltrims down with a maf plugged in...not the way to do it...but you'll have to change the maf table down low since it will override the VE table once the maf is plugged back in.