Timing at idle - requesting some help
04-26-2011, 11:29 AM
#41
You get the numbers that you get. That's what the procedure is for.
Your VE table varies in the idle region. Pick the VE that's best for YOUR engine at idle (22 right?) and make them all the same. You're driving your PID loop nuts as it has to deal with a varying mixture as RPM and MAP changes. VE is completely dependent upon YOUR engine, YOUR injector cc's, YOUR "Req. Fuel" setting, etc. It is of no concern that I'm using 38 and you're using 22.
Follow the procedure. Don't skip steps.
You can run 17° if you like. I run 20° when my AC compressor is engaged. 10-15 is the compromise that people with a lot of experience running MS tend to prefer. Difference between 17° and 10° . . . your idle screw will be a little more open (which helps the car catch itself).
You can also get more aggressive with the dashpot to help catch the engine. That's what the dashpot is for.
However, I need to stress doing things in order. The mistake people make is diving directly into messing with closed loop when the fundamentals (primarily, idle mixture and minimum air flow) aren't set. That will get you nowhere.
Your VE table varies in the idle region. Pick the VE that's best for YOUR engine at idle (22 right?) and make them all the same. You're driving your PID loop nuts as it has to deal with a varying mixture as RPM and MAP changes. VE is completely dependent upon YOUR engine, YOUR injector cc's, YOUR "Req. Fuel" setting, etc. It is of no concern that I'm using 38 and you're using 22.
Follow the procedure. Don't skip steps.
You can run 17° if you like. I run 20° when my AC compressor is engaged. 10-15 is the compromise that people with a lot of experience running MS tend to prefer. Difference between 17° and 10° . . . your idle screw will be a little more open (which helps the car catch itself).
You can also get more aggressive with the dashpot to help catch the engine. That's what the dashpot is for.
However, I need to stress doing things in order. The mistake people make is diving directly into messing with closed loop when the fundamentals (primarily, idle mixture and minimum air flow) aren't set. That will get you nowhere.
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04-26-2011, 12:13 PM
#42
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You get the numbers that you get. That's what the procedure is for.
Your VE table varies in the idle region. Pick the VE that's best for YOUR engine at idle (22 right?) and make them all the same. You're driving your PID loop nuts as it has to deal with a varying mixture as RPM and MAP changes. VE is completely dependent upon YOUR engine, YOUR injector cc's, YOUR "Req. Fuel" setting, etc. It is of no concern that I'm using 38 and you're using 22.
Follow the procedure. Don't skip steps.
You can run 17° if you like. I run 20° when my AC compressor is engaged. 10-15 is the compromise that people with a lot of experience running MS tend to prefer. Difference between 17° and 10° . . . your idle screw will be a little more open (which helps the car catch itself).
You can also get more aggressive with the dashpot to help catch the engine. That's what the dashpot is for.
However, I need to stress doing things in order. The mistake people make is diving directly into messing with closed loop when the fundamentals (primarily, idle mixture and minimum air flow) aren't set. That will get you nowhere.
Your VE table varies in the idle region. Pick the VE that's best for YOUR engine at idle (22 right?) and make them all the same. You're driving your PID loop nuts as it has to deal with a varying mixture as RPM and MAP changes. VE is completely dependent upon YOUR engine, YOUR injector cc's, YOUR "Req. Fuel" setting, etc. It is of no concern that I'm using 38 and you're using 22.
Follow the procedure. Don't skip steps.
You can run 17° if you like. I run 20° when my AC compressor is engaged. 10-15 is the compromise that people with a lot of experience running MS tend to prefer. Difference between 17° and 10° . . . your idle screw will be a little more open (which helps the car catch itself).
You can also get more aggressive with the dashpot to help catch the engine. That's what the dashpot is for.
However, I need to stress doing things in order. The mistake people make is diving directly into messing with closed loop when the fundamentals (primarily, idle mixture and minimum air flow) aren't set. That will get you nowhere.
just fyi .. i tried to follow your directions step by step .. making slight modifications as i went .. like keeping timing at 17 and fuel at 22.
i was running in warm-up only mode too. image only shows closed-loop is selected so i could display the closed loop extra settings as well. i didn't run in closed loop last night.
reason for the VE table now jumping all over the place is that i used tunerstudio's autotune feature and that changed the VE table around. i did have it set to 22 below 54kpa and 1500rpms. but when i started going a little faster, AFR spiked lean to 15-17. so that's when i tried to use autotune .. i'll have to find a good mix.
i know very little about the dashpot.. wanna talk a little about that?
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04-26-2011, 01:36 PM
#43
However, no matter what you have, the basics are the same:
1. Start by setting the car up so that you control idle air -- no closed loop variability.
2. Tune fuel at idle for maximum vacuum and make all idle region cells the same for stability.
3. Set idle spark to something between 10 and 15 and make all idle region cells the same for stability. Also, make sure that cranking spark is constant.
4. Set your minimum mechanical idle air for a target RPM.
5. Now, you can return to closed loop idle control and mess with it at your leisure. Closed loop is used to handle loads, not your basic idle.
1. Start by setting the car up so that you control idle air -- no closed loop variability.
2. Tune fuel at idle for maximum vacuum and make all idle region cells the same for stability.
3. Set idle spark to something between 10 and 15 and make all idle region cells the same for stability. Also, make sure that cranking spark is constant.
4. Set your minimum mechanical idle air for a target RPM.
5. Now, you can return to closed loop idle control and mess with it at your leisure. Closed loop is used to handle loads, not your basic idle.
One thing I noticed is that your VE RPM columns jump from 900 to 1800. 1800 is not in the idle region. It would help if you changed your VE RPM columns to be like your spark advance RPM columns so you could focus on that idle region. My columns go "800," "1200," "1800" and I limit my idle adjustments to the "800" and "1200" columns.
Dashpot mimics the effect of a physical dashpot (think shock absorber) on the throttle. Basically, it "closes" the throttle slowly by adding duty cycle to your IACV. This helps the engine catch its breath at idle. The first two parameters ("TPS Threshold" and "Idle Activation Adder") arm the dashpot. In your case, the dashpot is armed when you increase throttle position above 40 counts or when your RPM is 450RPM above your current idle speed (which depends upon CLT). Once armed, the "Dashpot Adder" DC is added to your Minimum DC when you return to idle. The "Dashpot Adder" DC fades out over the "Dashpot Settle Time." In your case, when you first get off the throttle, your effective "Minimum DC" is 12 (11 + 1). It reduces to 11 over 0.44 seconds. You have plenty of room to get a lot more aggressive with this. However, I recommend you work Dashpot after you achieve a stable closed loop idle.
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04-26-2011, 02:50 PM
#45
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to find the operating range of the valve. turn on warm-up only mode, and increase and reduce the DC until there is no longer a change in idle speed.
voila. you now know the operating range.
voila. you now know the operating range.
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04-26-2011, 03:40 PM
#46
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on a 1999 engine (1995 throttle body, wiring).. is the idle valve frequency still 26?
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04-26-2011, 03:51 PM
#47
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forgive me because I have zero experience in idle control with MSI, but IIRC...
the minimum dc is the duty cycle just below a normal warm idle without any a/c or headlights.
the closed dc is the duty cycle the valve closes at.
so i see you have warm idle set to 900RPM. You'd want to find the duty cycle the valve likes to maintain a 900rpm idle...you're kinda helping the software along by being asked to enter this in.
you would do this by using warm-up mode only, when the car was warm, and manually change the DC value until you get to 900RPM. Enter the DC minus say 1-2 into that box.
think of DC as the % the valve is opened or closed. Say you determine the valve operates between 20-60dc.
so then think of 20dc as closed and 60dc as fully open. any number in between will bring your idle speed somewhere in between the two.
the minimum dc is the duty cycle just below a normal warm idle without any a/c or headlights.
the closed dc is the duty cycle the valve closes at.
so i see you have warm idle set to 900RPM. You'd want to find the duty cycle the valve likes to maintain a 900rpm idle...you're kinda helping the software along by being asked to enter this in.
you would do this by using warm-up mode only, when the car was warm, and manually change the DC value until you get to 900RPM. Enter the DC minus say 1-2 into that box.
think of DC as the % the valve is opened or closed. Say you determine the valve operates between 20-60dc.
so then think of 20dc as closed and 60dc as fully open. any number in between will bring your idle speed somewhere in between the two.
Last edited by Braineack; 04-26-2011 at 05:15 PM.
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04-28-2011, 08:12 AM
#49
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after messing with this some more, i have a steady idle at around 900rpm in the warm-up only mode
fuel table in idle is now down to 15.
spark table in idle is now down to 14.
MAP is 33kpa.
AFR is 13.3ish
Vacuum: -19 in. Hg.
Timing: 14°
when i switch to closed-loop, the engine likes to rev/settle/rev/settle for about 40 seconds until it settles around 900rpm. then a couple minutes it rev/settle/rev/settle for about 40 seconds until it settles again around 900rpm. the rev/settle cycle range is about 850-1100rpm. this cycle seems to happen every couple minutes.
in closed-loop, the above numbers are the same, except AFR has bumped to 14.3ish
the whole time I was messing with the car, it was on flat ground and I didn't touch the gas pedal (or drive around.. simply trying to figure out idle). also, no AC and no PS and no touching any buttons in the car.
my actual question in all this, is, is the closed-loop rev/settle/rev/settle cycle that i'm seeing normal? or should i be doing more tweaking not have that happen.
actually, now that i think about it, the radiator fan did automatically come on every now and then. would that cause the rev/settle/cycle i'm experiencing?
fuel table in idle is now down to 15.
spark table in idle is now down to 14.
MAP is 33kpa.
AFR is 13.3ish
Vacuum: -19 in. Hg.
Timing: 14°
when i switch to closed-loop, the engine likes to rev/settle/rev/settle for about 40 seconds until it settles around 900rpm. then a couple minutes it rev/settle/rev/settle for about 40 seconds until it settles again around 900rpm. the rev/settle cycle range is about 850-1100rpm. this cycle seems to happen every couple minutes.
in closed-loop, the above numbers are the same, except AFR has bumped to 14.3ish
the whole time I was messing with the car, it was on flat ground and I didn't touch the gas pedal (or drive around.. simply trying to figure out idle). also, no AC and no PS and no touching any buttons in the car.
my actual question in all this, is, is the closed-loop rev/settle/rev/settle cycle that i'm seeing normal? or should i be doing more tweaking not have that happen.
actually, now that i think about it, the radiator fan did automatically come on every now and then. would that cause the rev/settle/cycle i'm experiencing?
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04-28-2011, 09:52 AM
#51
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Dashpot mimics the effect of a physical dashpot (think shock absorber) on the throttle. Basically, it "closes" the throttle slowly by adding duty cycle to your IACV. This helps the engine catch its breath at idle. The first two parameters ("TPS Threshold" and "Idle Activation Adder") arm the dashpot. In your case, the dashpot is armed when you increase throttle position above 40 counts or when your RPM is 450RPM above your current idle speed (which depends upon CLT). Once armed, the "Dashpot Adder" DC is added to your Minimum DC when you return to idle. The "Dashpot Adder" DC fades out over the "Dashpot Settle Time." In your case, when you first get off the throttle, your effective "Minimum DC" is 12 (11 + 1). It reduces to 11 over 0.44 seconds. You have plenty of room to get a lot more aggressive with this. However, I recommend you work Dashpot after you achieve a stable closed loop idle.
My car has always shot up to 3300 RPM at crank and I had no idea why! It's because the minimal DC was set to 22 to keep my car from stalling, therefore my cranking had to be 22 or higher. I've now set my cranking to 16 my minimal to 15 and my dashpot adder to 7 over a 46 ms time period. Lets see if that helps!
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04-28-2011, 10:07 AM
#52
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dashpot prevents idle droops when coming back to idle. it's not a hard concept 
reading the msextra manuals helps. Think of it as a shock absorber for your idle..the more the valve is open the higher your idle speed. So it lets you open the valve before you settle into an idle speed.
a dashpot adder of 7 means it idle valve will be opened 7% more duty cycle as you come down to idle, then it will taper off to your normal duty cycle amount. This allows you to stop the rpms at like 1000-1200RPM when you hit the clutch, then dorp down to 900rpm or whatever you have set. Otherwise the idle might droop low, and then have to recover up to 900.
Shooting up to 3000RPM at cranking is not a funciton of dashpot.
reading the msextra manuals helps. Think of it as a shock absorber for your idle..the more the valve is open the higher your idle speed. So it lets you open the valve before you settle into an idle speed.a dashpot adder of 7 means it idle valve will be opened 7% more duty cycle as you come down to idle, then it will taper off to your normal duty cycle amount. This allows you to stop the rpms at like 1000-1200RPM when you hit the clutch, then dorp down to 900rpm or whatever you have set. Otherwise the idle might droop low, and then have to recover up to 900.
Shooting up to 3000RPM at cranking is not a funciton of dashpot.
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04-28-2011, 10:22 AM
#53
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dashpot prevents idle droops when coming back to idle. it's not a hard concept reading the msextra manuals helps. Think of it as a shock absorber for your idle..the more the valve is open the higher your idle speed. So it lets you open the valve before you settle into an idle speed.
a dashpot adder of 7 means it idle valve will be opened 7% more duty cycle as you come down to idle, then it will taper off to your normal duty cycle amount. This allows you to stop the rpms at like 1000-1200RPM when you hit the clutch, then dorp down to 900rpm or whatever you have set. Otherwise the idle might droop low, and then have to recover up to 900.
Shooting up to 3000RPM at cranking is not a funciton of dashpot.
reading the msextra manuals helps. Think of it as a shock absorber for your idle..the more the valve is open the higher your idle speed. So it lets you open the valve before you settle into an idle speed.a dashpot adder of 7 means it idle valve will be opened 7% more duty cycle as you come down to idle, then it will taper off to your normal duty cycle amount. This allows you to stop the rpms at like 1000-1200RPM when you hit the clutch, then dorp down to 900rpm or whatever you have set. Otherwise the idle might droop low, and then have to recover up to 900.
Shooting up to 3000RPM at cranking is not a funciton of dashpot.
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04-28-2011, 10:26 AM
#54
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should add to the min DC%. if your min is set to 12%, then it will add 7% to that...so your valve will be operating at 19%DC until it decays out and the closed loop gets it back down to your target RPM.
in MS3 it adds to the last known idle duty cycle. The ECU actually remembers where you were idling last and tries to target that...kinda cool.
in MS3 it adds to the last known idle duty cycle. The ECU actually remembers where you were idling last and tries to target that...kinda cool.
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04-28-2011, 04:33 PM
#55
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should add to the min DC%. if your min is set to 12%, then it will add 7% to that...so your valve will be operating at 19%DC until it decays out and the closed loop gets it back down to your target RPM.
in MS3 it adds to the last known idle duty cycle. The ECU actually remembers where you were idling last and tries to target that...kinda cool.
in MS3 it adds to the last known idle duty cycle. The ECU actually remembers where you were idling last and tries to target that...kinda cool.
This is good info though. I went out at lunch and fixed my idle based on info from this thread. Someone should Sticky this.
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04-28-2011, 07:45 PM
#56
after messing with this some more, i have a steady idle at around 900rpm in the warm-up only mode
fuel table in idle is now down to 15.
spark table in idle is now down to 14.
MAP is 33kpa.
AFR is 13.3ish
Vacuum: -19 in. Hg.
Timing: 14°
when i switch to closed-loop, the engine likes to rev/settle/rev/settle for about 40 seconds until it settles around 900rpm. then a couple minutes it rev/settle/rev/settle for about 40 seconds until it settles again around 900rpm. the rev/settle cycle range is about 850-1100rpm. this cycle seems to happen every couple minutes.
in closed-loop, the above numbers are the same, except AFR has bumped to 14.3ish
the whole time I was messing with the car, it was on flat ground and I didn't touch the gas pedal (or drive around.. simply trying to figure out idle). also, no AC and no PS and no touching any buttons in the car.
my actual question in all this, is, is the closed-loop rev/settle/rev/settle cycle that i'm seeing normal? or should i be doing more tweaking not have that happen.
actually, now that i think about it, the radiator fan did automatically come on every now and then. would that cause the rev/settle/cycle i'm experiencing?
fuel table in idle is now down to 15.
spark table in idle is now down to 14.
MAP is 33kpa.
AFR is 13.3ish
Vacuum: -19 in. Hg.
Timing: 14°
when i switch to closed-loop, the engine likes to rev/settle/rev/settle for about 40 seconds until it settles around 900rpm. then a couple minutes it rev/settle/rev/settle for about 40 seconds until it settles again around 900rpm. the rev/settle cycle range is about 850-1100rpm. this cycle seems to happen every couple minutes.
in closed-loop, the above numbers are the same, except AFR has bumped to 14.3ish
the whole time I was messing with the car, it was on flat ground and I didn't touch the gas pedal (or drive around.. simply trying to figure out idle). also, no AC and no PS and no touching any buttons in the car.
my actual question in all this, is, is the closed-loop rev/settle/rev/settle cycle that i'm seeing normal? or should i be doing more tweaking not have that happen.
actually, now that i think about it, the radiator fan did automatically come on every now and then. would that cause the rev/settle/cycle i'm experiencing?
Now, it's time to mess with the closed loop settings. Do the following:
1. Make sure that the Closed-Loop "Minimum DC" matches the "Idle Duty at Upper Temp DC" that was working well for you in warmup mode.
2. Set your "Fast Idle Speed (RPM)" as desired. Mine is set to 1400.
3. Set your "Slow Idle Speed (RPM)" to the stable RPM that you were holding in warmup mode.
4. Let's skip "Dashpot Settings" for now.
Moving on to the exciting world of "Closed Loop Settings." To begin with, note the following definitions:
"Deadband Range" is the range around your target idle speed in which the closed loop algorithm makes no change to DC.
"Upper Limit" is the threshold above which closed loop corrections are made at the "Fast Recovery" rate.
"Lower Limit" is the threshold below which closed loop corrections are made at the "Fast Recovery" rate.
"Fast Recovery" and "Slow Recovery" determine how often a new idle DC is calculated. The more often a new idle DC is calculated, the faster the DC changes (whether or not the engine is keeping up).
To illustrate the relationship among the above, let's use the following values for an example (assuming a target idle RPM of 900):
Deadband Range = 50
Upper Limit = 250
Lower Limit = 75
Fast Recovery = 10 (0.1 seconds or 10 corrections per second)
Slow Recovery = 150 (a correction every 1.5 seconds)
This gives the following thresholds:
Lower Limit = 900 - 75 = 825RPM
Bottom of Deadband = 900 - 50 = 850RPM
Top of Deadband = 900 + 50 = 950RPM
Upper Limit = 900 + 250 = 1150RPM
These settings will cause the MS to react as follows based upon different idle RPMs:
750RPM: You are below the Lower Limit AND below the Bottom of the Deadband. The MS will be calculating a new idle DC 10 times per second to aggressively raise your idle RPM.
830RPM: You are below the Bottom of the Deadband but above the Lower Limit. The MS will be calculating a new idle DC once every 1.5 seconds to gently raise your idle RPM.
875RPM: You are above the Bottom of the Deadband and below the Top of the Deadband. The MS does nothing . . . it's happy.
1000RPM: You are above the Top of the Deadband AND below the Upper Limit. The MS will be calculating a new idle DC once every 1.5 seconds to gently lower your idle RPM.
1200RPM: You are above the Top of the Deadband AND above the Upper Limit. The MS will be calculating a new idle DC 10 times per second to aggressively lower your idle RPM.
Got all that? Good. Here are some recommendations for tuning closed loop:
1. We want to be aggressive with the low RPM situation. Therefore, make the Lower Limit close to your deadband and make the Fast Recovery aggressive.
2. The high RPM situation is less worrisome -- you won't stall. Therefore, give the engine some breathing room and be generous with the Upper Limit. This allows the engine to have a decent RPM range in which it is using a Slow Recovery.
3. Make the Slow Recovery slow. This gives the engine plenty of time to catch up to the DC change. Oscillations, such as those you are seeing, means that the DC is changing too fast for the engine to catch up.
4. Keep your Deadband relatively tight. So long as your Slow Recovery is gentle and has room to operate, you'll be fine.
FYI, my closed loop settings are:
Deadband Range = 30
Upper Limit = 250
Lower Limit = 30
Fast Recovery = 10
Slow Recovery = 150
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04-29-2011, 12:06 PM
#59
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Hornet- when you said to disable the valve to set your mechanical idle. This made sense to me but my issue is:
1) What should our valve frequency be? If i use something in the 30's 8-9 DC is closed. If i use 62 18-19 DC is closed?
2) Once the valve is closed should I set it to the low, good sounding 950 idle? Even if this means that my car stalls when I rev it and let go? Or should I crank the idle until it can recover from falling RPM's?
1) What should our valve frequency be? If i use something in the 30's 8-9 DC is closed. If i use 62 18-19 DC is closed?
2) Once the valve is closed should I set it to the low, good sounding 950 idle? Even if this means that my car stalls when I rev it and let go? Or should I crank the idle until it can recover from falling RPM's?
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