Idle air vs IAC park position
05-03-2004, 10:29 AM
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Idle air vs IAC park position Has anyone figured out the difference between these tables or how they relate?
Idle air seems to make sense to me but I'm unclear on what the IAC park position does. To add to the confusion, this is in relation to a c5 that does not have a IAC motor.
I've gotten my car idling pretty good, but I still get brief idle hunting under a few specific conditions and I would like to clear that up.
Idle air seems to make sense to me but I'm unclear on what the IAC park position does. To add to the confusion, this is in relation to a c5 that does not have a IAC motor.
I've gotten my car idling pretty good, but I still get brief idle hunting under a few specific conditions and I would like to clear that up.
05-04-2004, 09:06 AM
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Originally Posted by QuickSilver2002
Has anyone figured out the difference between these tables or how they relate?
Idle air seems to make sense to me but I'm unclear on what the IAC park position does. To add to the confusion, this is in relation to a c5 that does not have a IAC motor.
I've gotten my car idling pretty good, but I still get brief idle hunting under a few specific conditions and I would like to clear that up.
Idle air seems to make sense to me but I'm unclear on what the IAC park position does. To add to the confusion, this is in relation to a c5 that does not have a IAC motor.
I've gotten my car idling pretty good, but I still get brief idle hunting under a few specific conditions and I would like to clear that up.
05-04-2004, 01:09 PM
#3
Originally Posted by QuickSilver2002
Has anyone figured out the difference between these tables or how they relate?
Idle air seems to make sense to me but I'm unclear on what the IAC park position does. To add to the confusion, this is in relation to a c5 that does not have a IAC motor.
I've gotten my car idling pretty good, but I still get brief idle hunting under a few specific conditions and I would like to clear that up.
Idle air seems to make sense to me but I'm unclear on what the IAC park position does. To add to the confusion, this is in relation to a c5 that does not have a IAC motor.
I've gotten my car idling pretty good, but I still get brief idle hunting under a few specific conditions and I would like to clear that up.
Idle Air = Running Airflow
I monitored DESIAC, TPS% - Absolute, etc.
Here is what I found:
1 IAC Count (value) = 4 "Steps" = 1/5 % TPS
5 IAC Counts (values) = 1% TPS
20 Steps = 1%TPS
0.25 IAC = 1 "Step" = .05% TPS
MAX IAC = 63.99 (Edit), but real max value = 63.75 =255 steps.
RAF MAX = 31.99 but real max value = 31.75
MAX IAC + MAX RAF = 19.1 - 19.2 % Absolute TPS.
MAX IAC + MAX RAF + .9% Reserve = 20.0% Absolute TPS
RAF is added % TPS, added to IAC, in gear/Running.
There is 0.4% absolute TPS when my TB /Pedal are at Zero. Foot of
accelerator pedal.
There is an additional 0.4- 0.5 %, on top of the 0.4% - off pedal, that
the system uses as it attempts to reach the target RPM/TPS position.
The "DESIAC Steps" begin at 0.8 - 0.9% absolute TPS%.
So - foot off pedal it shows .8 - .9% absolute TPS. With throttle changes
the baseline for steps is 0.8-0.9%. As the throtlle closes it uses 0.4-0.5 %
TPS to buffer/dampen. It never goes into the reserved /bottom 0.4% TPS.
Basically IAC sets the blade for the amount of incoming air at idle. Idle Air is the Running Airflow - added to the IAC value when the car is moving. Idle Air/ RAF keeps the idle up to power brakes etc.
FWIW.
joel
Last edited by Bink; 05-04-2004 at 01:19 PM.
05-04-2004, 02:48 PM
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Originally Posted by Bink
Some info on fly- by wire....Vettes
Idle Air = Running Airflow
I monitored DESIAC, TPS% - Absolute, etc.
Here is what I found:
1 IAC Count (value) = 4 "Steps" = 1/5 % TPS
5 IAC Counts (values) = 1% TPS
20 Steps = 1%TPS
0.25 IAC = 1 "Step" = .05% TPS
MAX IAC = 63.99 (Edit), but real max value = 63.75 =255 steps.
RAF MAX = 31.99 but real max value = 31.75
MAX IAC + MAX RAF = 19.1 - 19.2 % Absolute TPS.
MAX IAC + MAX RAF + .9% Reserve = 20.0% Absolute TPS
RAF is added % TPS, added to IAC, in gear/Running.
There is 0.4% absolute TPS when my TB /Pedal are at Zero. Foot of
accelerator pedal.
There is an additional 0.4- 0.5 %, on top of the 0.4% - off pedal, that
the system uses as it attempts to reach the target RPM/TPS position.
The "DESIAC Steps" begin at 0.8 - 0.9% absolute TPS%.
So - foot off pedal it shows .8 - .9% absolute TPS. With throttle changes
the baseline for steps is 0.8-0.9%. As the throtlle closes it uses 0.4-0.5 %
TPS to buffer/dampen. It never goes into the reserved /bottom 0.4% TPS.
Basically IAC sets the blade for the amount of incoming air at idle. Idle Air is the Running Airflow - added to the IAC value when the car is moving. Idle Air/ RAF keeps the idle up to power brakes etc.
FWIW.
joel
Idle Air = Running Airflow
I monitored DESIAC, TPS% - Absolute, etc.
Here is what I found:
1 IAC Count (value) = 4 "Steps" = 1/5 % TPS
5 IAC Counts (values) = 1% TPS
20 Steps = 1%TPS
0.25 IAC = 1 "Step" = .05% TPS
MAX IAC = 63.99 (Edit), but real max value = 63.75 =255 steps.
RAF MAX = 31.99 but real max value = 31.75
MAX IAC + MAX RAF = 19.1 - 19.2 % Absolute TPS.
MAX IAC + MAX RAF + .9% Reserve = 20.0% Absolute TPS
RAF is added % TPS, added to IAC, in gear/Running.
There is 0.4% absolute TPS when my TB /Pedal are at Zero. Foot of
accelerator pedal.
There is an additional 0.4- 0.5 %, on top of the 0.4% - off pedal, that
the system uses as it attempts to reach the target RPM/TPS position.
The "DESIAC Steps" begin at 0.8 - 0.9% absolute TPS%.
So - foot off pedal it shows .8 - .9% absolute TPS. With throttle changes
the baseline for steps is 0.8-0.9%. As the throtlle closes it uses 0.4-0.5 %
TPS to buffer/dampen. It never goes into the reserved /bottom 0.4% TPS.
Basically IAC sets the blade for the amount of incoming air at idle. Idle Air is the Running Airflow - added to the IAC value when the car is moving. Idle Air/ RAF keeps the idle up to power brakes etc.
FWIW.
joel
joel 
05-05-2004, 02:23 PM
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Originally Posted by Bink
Some info on fly- by wire....Vettes
Idle Air = Running Airflow
I monitored DESIAC, TPS% - Absolute, etc.
Here is what I found:
1 IAC Count (value) = 4 "Steps" = 1/5 % TPS
5 IAC Counts (values) = 1% TPS
20 Steps = 1%TPS
0.25 IAC = 1 "Step" = .05% TPS
MAX IAC = 63.99 (Edit), but real max value = 63.75 =255 steps.
RAF MAX = 31.99 but real max value = 31.75
MAX IAC + MAX RAF = 19.1 - 19.2 % Absolute TPS.
MAX IAC + MAX RAF + .9% Reserve = 20.0% Absolute TPS
RAF is added % TPS, added to IAC, in gear/Running.
There is 0.4% absolute TPS when my TB /Pedal are at Zero. Foot of
accelerator pedal.
There is an additional 0.4- 0.5 %, on top of the 0.4% - off pedal, that
the system uses as it attempts to reach the target RPM/TPS position.
The "DESIAC Steps" begin at 0.8 - 0.9% absolute TPS%.
So - foot off pedal it shows .8 - .9% absolute TPS. With throttle changes
the baseline for steps is 0.8-0.9%. As the throtlle closes it uses 0.4-0.5 %
TPS to buffer/dampen. It never goes into the reserved /bottom 0.4% TPS.
Basically IAC sets the blade for the amount of incoming air at idle. Idle Air is the Running Airflow - added to the IAC value when the car is moving. Idle Air/ RAF keeps the idle up to power brakes etc.
FWIW.
joel
Idle Air = Running Airflow
I monitored DESIAC, TPS% - Absolute, etc.
Here is what I found:
1 IAC Count (value) = 4 "Steps" = 1/5 % TPS
5 IAC Counts (values) = 1% TPS
20 Steps = 1%TPS
0.25 IAC = 1 "Step" = .05% TPS
MAX IAC = 63.99 (Edit), but real max value = 63.75 =255 steps.
RAF MAX = 31.99 but real max value = 31.75
MAX IAC + MAX RAF = 19.1 - 19.2 % Absolute TPS.
MAX IAC + MAX RAF + .9% Reserve = 20.0% Absolute TPS
RAF is added % TPS, added to IAC, in gear/Running.
There is 0.4% absolute TPS when my TB /Pedal are at Zero. Foot of
accelerator pedal.
There is an additional 0.4- 0.5 %, on top of the 0.4% - off pedal, that
the system uses as it attempts to reach the target RPM/TPS position.
The "DESIAC Steps" begin at 0.8 - 0.9% absolute TPS%.
So - foot off pedal it shows .8 - .9% absolute TPS. With throttle changes
the baseline for steps is 0.8-0.9%. As the throtlle closes it uses 0.4-0.5 %
TPS to buffer/dampen. It never goes into the reserved /bottom 0.4% TPS.
Basically IAC sets the blade for the amount of incoming air at idle. Idle Air is the Running Airflow - added to the IAC value when the car is moving. Idle Air/ RAF keeps the idle up to power brakes etc.
FWIW.
joel
I'm trying to understand the purpose of the two tables and how they related.
Here is my understanding at this point:
It seems that Idle Air (running airflow) is basically the minimal airflow (g/sec) that will be demended at a given coolant temp. I'm assuming the PCM opens the TB enough to get this reading (on fly by wire cars) and uses the IAC motor on non fly by wire cars.
Now the IAC Park Position table looks similar, but I don't understand exactly when it comes into play. Do they combine together in some way? Is the Park position table only used before start?
A statement above says "RAF is added % TPS, added to IAC, in gear/Running." Can you clear up this statment.
Sorry for the confusion, but as we all know there has never been any clear documentation on this stuff to refer to.
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05-05-2004, 05:24 PM
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I've been thinking about my take on the Idle and limiters tables relating to fly by wire. This is probably a good place to get feedback.
Idle Speed - Only takes affect when the car is completely stopped.
IAC - Sets where the throttle blade wants to come to rest when your off the gas pedal, idling or moving. My opinion is that if this is set right the idle you set will be what actually occurs.
RAF - Controls the amount of air delivered by changing TPS. I think of it as a decay table by temperature. Set it too high and you get cruise and too low it searches or stalls.
P/N Airflow decay - Sets the rate of decay out of gear. Raising values speeds up decay.
Airflow decay in gear. - Sets decay by mph and by gear. Another way to set RAF. Raising values speeds up decay.
Throttle cracker - Sets decay by mph and rpm. Also another way to set RAF. Lowering values speeds up decay.
Reset IAC - I've tried changes the value and noticed no changes?
Idle air and the "other" decay tables All effect airflow, but for the various functions.
How IAC and RAF relate. - They relate in that they are both trying to set the TBlade position. If the IAC is set right then leave it alone and work on the rest.
This is my experience.
Idle Speed - Only takes affect when the car is completely stopped.
IAC - Sets where the throttle blade wants to come to rest when your off the gas pedal, idling or moving. My opinion is that if this is set right the idle you set will be what actually occurs.
RAF - Controls the amount of air delivered by changing TPS. I think of it as a decay table by temperature. Set it too high and you get cruise and too low it searches or stalls.
P/N Airflow decay - Sets the rate of decay out of gear. Raising values speeds up decay.
Airflow decay in gear. - Sets decay by mph and by gear. Another way to set RAF. Raising values speeds up decay.
Throttle cracker - Sets decay by mph and rpm. Also another way to set RAF. Lowering values speeds up decay.
Reset IAC - I've tried changes the value and noticed no changes?
Idle air and the "other" decay tables All effect airflow, but for the various functions.
How IAC and RAF relate. - They relate in that they are both trying to set the TBlade position. If the IAC is set right then leave it alone and work on the rest.
This is my experience.
05-05-2004, 06:24 PM
#9
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Yes, I was asking about the "RESET IAC". I have lowered that substantially but not raised it. No resulting difference....just curious what it's purpose is?
Also, more importantly, in regard to the throttle follower: P/N Decay and the Air Flow in gear how are these used in an M6 tranny? I would assume that when the clutch is engaged and the car is moving that the P/N decay would be used? Is the P/N decay only active if there is a delay value entered into the delay table? Same on the airflow in gear? I have been trying to tune the 90mm setup as you may have noticed in another thread and adjustments to these tables of 5% to 500% made no difference. So I returned them to stock values and added 2 seconds of delay. Have not tested yet but thought someone may know the answer. Also the throttle follower on this setup may not be functioning properly due to the
TPIS TB not being constructed correctly? I never adjusted this on my stock TB that is why I ask.
Also, more importantly, in regard to the throttle follower: P/N Decay and the Air Flow in gear how are these used in an M6 tranny? I would assume that when the clutch is engaged and the car is moving that the P/N decay would be used? Is the P/N decay only active if there is a delay value entered into the delay table? Same on the airflow in gear? I have been trying to tune the 90mm setup as you may have noticed in another thread and adjustments to these tables of 5% to 500% made no difference. So I returned them to stock values and added 2 seconds of delay. Have not tested yet but thought someone may know the answer. Also the throttle follower on this setup may not be functioning properly due to the
TPIS TB not being constructed correctly? I never adjusted this on my stock TB that is why I ask.
05-05-2004, 07:10 PM
#10
Originally Posted by gojo
I've been thinking about my take on the Idle and limiters tables relating to fly by wire. This is probably a good place to get feedback.
Idle Speed - Only takes affect when the car is completely stopped.
IAC - Sets where the throttle blade wants to come to rest when your off the gas pedal, idling or moving. My opinion is that if this is set right the idle you set will be what actually occurs.
RAF - Controls the amount of air delivered by changing TPS. I think of it as a decay table by temperature. Set it too high and you get cruise and too low it searches or stalls.
P/N Airflow decay - Sets the rate of decay out of gear. Raising values speeds up decay.
Airflow decay in gear. - Sets decay by mph and by gear. Another way to set RAF. Raising values speeds up decay.
Throttle cracker - Sets decay by mph and rpm. Also another way to set RAF. Lowering values speeds up decay.
Reset IAC - I've tried changes the value and noticed no changes?
Idle air and the "other" decay tables All effect airflow, but for the various functions.
How IAC and RAF relate. - They relate in that they are both trying to set the TBlade position. If the IAC is set right then leave it alone and work on the rest.
This is my experience.
Idle Speed - Only takes affect when the car is completely stopped.
IAC - Sets where the throttle blade wants to come to rest when your off the gas pedal, idling or moving. My opinion is that if this is set right the idle you set will be what actually occurs.
RAF - Controls the amount of air delivered by changing TPS. I think of it as a decay table by temperature. Set it too high and you get cruise and too low it searches or stalls.
P/N Airflow decay - Sets the rate of decay out of gear. Raising values speeds up decay.
Airflow decay in gear. - Sets decay by mph and by gear. Another way to set RAF. Raising values speeds up decay.
Throttle cracker - Sets decay by mph and rpm. Also another way to set RAF. Lowering values speeds up decay.
Reset IAC - I've tried changes the value and noticed no changes?
Idle air and the "other" decay tables All effect airflow, but for the various functions.
How IAC and RAF relate. - They relate in that they are both trying to set the TBlade position. If the IAC is set right then leave it alone and work on the rest.
This is my experience.
Okay ...here is how I see it.
Idle - is a target value. PCM will attempt to achieve this idle at the given IAC value. If either is set too low/high we get surging.Timing must be in synch also. Idle relearn synchronizes and stabilizes all three.
IAC is the opening of the blade at idle..car stopped. Can be monitored as TPS% or DESIAC/steps.PCM will attempt to achieve the set IAC and idle RPM.
Again, they must be synchronized.
RAF - TPS% added on top of IAC. The sum of the two provides the running airflow in and out of gear - as long as ithe car is mobile.. Too much RAF and we get "cruise control" - too little and it bogs/dies.
Throttle Cracker is added to RAF or is a multiplier of RAF - I don't think these are scaled properly in LS1edit. As gojo said - > Sets by MPH and RPM (fine tunes) reducing these values speeds the decay...RPM doesn't hold up as long or as high.
P/N Airflow Decay - I defer to gojo. But, I thought increasing the value up to 1.0000 ->decreased the rate of decay.. i.e. slows the descent to Idle speed in neutral? Increase the value holds the RPM up longer??
Airflow Deay in Gear - I defer to gojo, again. And again I thought increasing the value up to 1.0000 ->decreased the rate of decay.. i.e. slowed the descent to Idle speed in Gear? Increase the value holds the RPM up longer??
Reset IAC Park Position - the position the blade returns to after the engine is powered off.It moves from Reset position to IAC Park as you power up the PCM starting sequence.This is the position it assumes after an Edit and before an Idle Relearn procedure. I think it is part of the relearn procedure.
gojo is the expert on C5 Idle + Limiters!! (fly by wire)
18 - 24 months ago everyone said these tables, especially IAC, were not used with C5s - all the C5 Tuners said No Way
............gojo continued telling them that they do work........They eventually listened...gojo was right.
Thanks for your persistence, gojo
joel
05-05-2004, 11:25 PM
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Great info guys, but there still seems to be some uncertainty about how the two (RAF and IAC Park position relate). Is the scale in ls1edit (g/sec) totally off?
I don’t see how the car moving or not would make a difference on a manual tranny car. It seems that in gear would make a diff, but I'm not sure the PCM knows if in or out of gear. Maybe it has something to do with a time delay after the throttle position relaxed to relative 0.
Is it a good general practice to keep them scaled pretty close together?
I think I’ll do some more experimentation this weekend.
I don’t see how the car moving or not would make a difference on a manual tranny car. It seems that in gear would make a diff, but I'm not sure the PCM knows if in or out of gear. Maybe it has something to do with a time delay after the throttle position relaxed to relative 0.
Is it a good general practice to keep them scaled pretty close together?
I think I’ll do some more experimentation this weekend.
05-06-2004, 12:18 AM
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I added a 2 second delay, all the way out, to the throttle follower and drove for about 30 minutes. No changed was noticed. Keep in mind I have an M6 and currently setup with the 90mm TPIS. I have asked a friend to test the follower on his M6 C5 to see if his functions with the stock TB. None of my follower tables seem to function. I have adjusted them from the stock values @5% up to 500%.
I hope others will let us know about the M6 and fly by wire adjustments.
BTW thank you to
Bink and gojo for the helpful info as well as others.
I hope others will let us know about the M6 and fly by wire adjustments.
BTW thank you to
Bink and gojo for the helpful info as well as others.
05-06-2004, 06:50 AM
#14
Originally Posted by goodhands
I added a 2 second delay, all the way out, to the throttle follower and drove for about 30 minutes. No changed was noticed. Keep in mind I have an M6 and currently setup with the 90mm TPIS. I have asked a friend to test the follower on his M6 C5 to see if his functions with the stock TB. None of my follower tables seem to function. I have adjusted them from the stock values @5% up to 500%.
I hope others will let us know about the M6 and fly by wire adjustments.
BTW thank you to Bink and gojo for the helpful info as well as others.
I hope others will let us know about the M6 and fly by wire adjustments.
BTW thank you to
Bink and gojo for the helpful info as well as others.joel
05-06-2004, 06:59 AM
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the PCM calculates the IAC position or ETC position by calulating an "airflow" , it then converts this airflow to a number of steps for the IAC motor. There is a table in the PCM that calibrates the IAC motor steps to airflow.
All the Throttle cracker, throttle follower, idle airflow, plus a few others (such as AC on and trans in gear compensation) work together to give a final airflow number and hence position for the IAC/ETC. When the car is at idle the PCM adjusts both the IAC and SPKADV to get the desired idle, once you are off idle you are running on the other tables. The closer you have the idle airflow to the actual idle airflow the engine requires then the less the PCM has to compensate at idle.
the IAC reset position is only used after a hard reset of the PCM.
the IAC park position is used to set the initial IAC position such as when the key is off.
Hope that helps.
All the Throttle cracker, throttle follower, idle airflow, plus a few others (such as AC on and trans in gear compensation) work together to give a final airflow number and hence position for the IAC/ETC. When the car is at idle the PCM adjusts both the IAC and SPKADV to get the desired idle, once you are off idle you are running on the other tables. The closer you have the idle airflow to the actual idle airflow the engine requires then the less the PCM has to compensate at idle.
the IAC reset position is only used after a hard reset of the PCM.
the IAC park position is used to set the initial IAC position such as when the key is off.
Hope that helps.
05-06-2004, 08:05 AM
#16
Gameover- when my IAC was set too low , for my Idle/RPM value, I could scan and watch the PCM reduce the TPS% by 2 stepat a time .It would then stall and surge...RPM and TPS% would jump up and then slowly it would reduce the TPS% to the IAC ....then it would start allover. So I bumped IAC value and it settled into a steady idle. During all of this it would adjust the timing to lowest the advance without surging.
the IAC park position is used to set the initial IAC position such as when the key is off. - When I initially tuned my IAC the car would stall until I increased the values through the temp range. For example as coolant temp hit 80*C it would stall with IAC below 31. At or above 31*C it would adjust and continue running. So it must use this value for more than an idle park position.
How do the Decay values translate in terms of steps or TPS%?? For instance, with my Vette, 1.00 IAC = 4 Steps and 5 IAC = 1TPS%.
Are the Decay values simply added to IAC and RAF??
Are IAC and RAF the baseline for airflow when mobile??
Thanks for the info.
the IAC park position is used to set the initial IAC position such as when the key is off. - When I initially tuned my IAC the car would stall until I increased the values through the temp range. For example as coolant temp hit 80*C it would stall with IAC below 31. At or above 31*C it would adjust and continue running. So it must use this value for more than an idle park position.
How do the Decay values translate in terms of steps or TPS%?? For instance, with my Vette, 1.00 IAC = 4 Steps and 5 IAC = 1TPS%.
Are the Decay values simply added to IAC and RAF??
Are IAC and RAF the baseline for airflow when mobile??
Thanks for the info.
05-06-2004, 10:50 AM
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Originally Posted by gameover
the PCM calculates the IAC position or ETC position by calulating an "airflow" , it then converts this airflow to a number of steps for the IAC motor. There is a table in the PCM that calibrates the IAC motor steps to airflow.
All the Throttle cracker, throttle follower, idle airflow, plus a few others (such as AC on and trans in gear compensation) work together to give a final airflow number and hence position for the IAC/ETC. When the car is at idle the PCM adjusts both the IAC and SPKADV to get the desired idle, once you are off idle you are running on the other tables. The closer you have the idle airflow to the actual idle airflow the engine requires then the less the PCM has to compensate at idle.
the IAC reset position is only used after a hard reset of the PCM.
the IAC park position is used to set the initial IAC position such as when the key is off.
Hope that helps.
All the Throttle cracker, throttle follower, idle airflow, plus a few others (such as AC on and trans in gear compensation) work together to give a final airflow number and hence position for the IAC/ETC. When the car is at idle the PCM adjusts both the IAC and SPKADV to get the desired idle, once you are off idle you are running on the other tables. The closer you have the idle airflow to the actual idle airflow the engine requires then the less the PCM has to compensate at idle.
the IAC reset position is only used after a hard reset of the PCM.
the IAC park position is used to set the initial IAC position such as when the key is off.
Hope that helps.
Also, what is the exact definition of being at idle. I've noticed this transition as I drive. You put in the clutch and let off the gas and the rpms drop below normal idle and then you hear things start to level out. Is there a set delay count or something.
05-06-2004, 12:21 PM
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Joel,
My observations are pretty much the same as yours, except for the affect of changing the values in the P/N decay and Airflow decay in gear. I should be able to be more certain when I get my laptop back.
Regarding how the IAC and RAF tables relate. I also believe, as you do, that there is an impact on the airflow when moving. I've proved that to myself many times. You can cause the cruise affect or more drag when your foot is off the pedal, by changing IAC values. This is probably why there is confusion about what is the relationship. That's why I pointed out that I found it most effective to find the sweet spot for Idle and IAC values, then proceeding to RAF or any other of the tables that are meant to be adjusted for when the car is moving.
Joe
My observations are pretty much the same as yours, except for the affect of changing the values in the P/N decay and Airflow decay in gear. I should be able to be more certain when I get my laptop back.
Regarding how the IAC and RAF tables relate. I also believe, as you do, that there is an impact on the airflow when moving. I've proved that to myself many times. You can cause the cruise affect or more drag when your foot is off the pedal, by changing IAC values. This is probably why there is confusion about what is the relationship. That's why I pointed out that I found it most effective to find the sweet spot for Idle and IAC values, then proceeding to RAF or any other of the tables that are meant to be adjusted for when the car is moving.
Joe
05-07-2004, 12:01 PM
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[QUOTE=Bink]Some info on fly- by wire....Vettes
Basically IAC sets the blade for the amount of incoming air at idle. Idle Air is the Running Airflow - added to the IAC value when the car is moving. Idle Air/ RAF keeps the idle up to power brakes etc.
Bink, I thought you should know my recent experience:
While attempting to tune the 90mm setup, on start up for about 3 or 4 seconds the RAF's seem to be used. The rpm would shoot up to 3500 rpm then drop to the asked for 900 rpm idle. I had to reduce the RAF's about 50% from the setting that worked well with my H/C tune to correct for the rev up at start. Wierd huh????? Personally I think the RAF's are used to start the car. I have proven this to my self by watching how high my rpm rise when I start the car at different temps/RAF settings while keeping IAC's the same. What if the RAF's are used to fire the car until MAF is reporting then IAC's, P/N delay, spk adv and idle limiters take over until the car is moving. Then it's RAF's, cracker and in gear airflow with IAC as a base.
I still do not get all this yet but thought I would share.
Basically IAC sets the blade for the amount of incoming air at idle. Idle Air is the Running Airflow - added to the IAC value when the car is moving. Idle Air/ RAF keeps the idle up to power brakes etc.
Bink, I thought you should know my recent experience:
While attempting to tune the 90mm setup, on start up for about 3 or 4 seconds the RAF's seem to be used. The rpm would shoot up to 3500 rpm then drop to the asked for 900 rpm idle. I had to reduce the RAF's about 50% from the setting that worked well with my H/C tune to correct for the rev up at start. Wierd huh????? Personally I think the RAF's are used to start the car. I have proven this to my self by watching how high my rpm rise when I start the car at different temps/RAF settings while keeping IAC's the same. What if the RAF's are used to fire the car until MAF is reporting then IAC's, P/N delay, spk adv and idle limiters take over until the car is moving. Then it's RAF's, cracker and in gear airflow with IAC as a base.
I still do not get all this yet but thought I would share.
Last edited by goodhands; 05-07-2004 at 12:16 PM.
05-07-2004, 12:43 PM
#20
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Goodhands,
I've experienced the same thing. I think what we are seeing is that the functions are interrelated. Just as setting the IAC values too high effects results when the car moves, so will setting RAF's too high affect startup. I would think that the car you mention should have had bad cruise affect. At least that is my take. The tables do have a main function though and need to be set with that in mind. That's what seems to work for me. I do think the IAC has the major roll in start up and where the throttle blade wants to rest when we are off the gas pedal. The desired IAC is highest with the key on only. It comes down after startup and continues to come down. I agree the RAF will have an impact, but almost as a side affect. I don't think any of the tables get turned off when we change conditions such as starting to move or coming to a stop. They all affect tuning results but when set correctly I find they are more responsive to their major function. I have seen some posts saying the t. follower and cracker tables don't do anything for them. I had the same experiences and finding they work well when IAC and RAF are close to right.
Joe
I've experienced the same thing. I think what we are seeing is that the functions are interrelated. Just as setting the IAC values too high effects results when the car moves, so will setting RAF's too high affect startup. I would think that the car you mention should have had bad cruise affect. At least that is my take. The tables do have a main function though and need to be set with that in mind. That's what seems to work for me. I do think the IAC has the major roll in start up and where the throttle blade wants to rest when we are off the gas pedal. The desired IAC is highest with the key on only. It comes down after startup and continues to come down. I agree the RAF will have an impact, but almost as a side affect. I don't think any of the tables get turned off when we change conditions such as starting to move or coming to a stop. They all affect tuning results but when set correctly I find they are more responsive to their major function. I have seen some posts saying the t. follower and cracker tables don't do anything for them. I had the same experiences and finding they work well when IAC and RAF are close to right.
Joe