IAC park position + 90mm TB
01-11-2005, 11:06 AM
#1
IAC park position + 90mm TB I am assuming that the IAC park table refers to the gm/s that the TB will flow when the TB is in the parked position. What should this table do when you switch to a 90mm TB? I thought it should be increased since the area around the butterfly is greater and will allow for slightly greater airflow. Any thoughts?
Phil
Phil
01-12-2005, 07:55 AM
#2
6600 rpm clutch dump of death Administrator
Here you go Phil here is a screen cap from HPT.
You will see a couple of things. IAC park position is normally 320. Thats 320 "steps". I normally cut it about in half. This opens the blade of the TB less and parks it in a more closed position. You need this to keep the blade closed just a bit more to keep the same airflow as stock. In the cap I have included, its already stepped down to 130 from 320 which is stock.
You have throttle cracker. This is the air that is added once the car is under way. This often leads to idle hangs when the car is moving that are resolved when the car is stopped. You can either change the enable speed up really high, or 0 out the whole table. See below about the adaptive learning....
Idle airflow vs ECT. Is exactly that, airflow vs engine coolant temp. You simply log the data of the car idling as it warms up, and fill in those values.
Here is what HPT says about each one....
Idle
The PCM has a number of parameters that influence the idle behavior of the engine. These parameters specifically control the desired idle RPM and the behavior of the Idle Air Control (IAC) motor during idle conditions. The IAC is controlled via a desired airflow value that has many contributing factors, the PCM then translates this "Idle Desired Airflow" into a number of steps for the IAC stepper motor itself. For Electronic Throttle vehicles the PCM translates this into a TPS % for idle.
Idle RPM
Target Idle Speed vs. Coolant Temp vs. (Drive & Park, A/C On & Off): This table controls the desired idle RPM vs Engine Coolant Temperature. There are a number of settings depending if the transmission is an A4 or M6 (in gear or PN) and also is the AC is on or off. When the vehicle speed is below the Throttle Cracker speed, the PCM will enable adaptive, feedback-based, idle routines to achieve the desired idle RPM.
Base Running Airflow
Idle Air Flow vs. Coolant Temp vs. (Gear & P/N): This table is used to determine the base airflow (in g/sec) for the IAC motor control vs Engine coolant temperature. This is used as a base setting for the adaptive idle routines and also the base IAC position when the vehicle is moving.
Cooling Fan Airflow
Fan 1: This value is the extra airflow added to the base running airflow to compensate for extra electrical load when a single cooling fan is active.
Fan 1 & 2: This value is the extra airflow added to the base running airflow to compensate for extra electrical load when both cooling fans are active.
Throttle Follower
The throttle follower parameters are used to adjust decay and delay rates for the IAC motor during throttle closure to prevent stalling and make gear changing/selection easier.
Throttle Follower Airflow Decay vs. Speed (In Neutral): The decay value is the rate at which the IAC motor closes when the throttle is closed and the selector is in Park or Neutral. These values are subtracted from the current IAC Airflow value every 12.5 ms, hence higher numbers mean faster decay.
Throttle Follower Delay Time vs. Speed (In Neutral): This is the delay before the decay value begins to be subtracted in P/N.
Throttle Follower Airflow Decay vs. Speed (In Gear): The decay value is the rate at which the IAC motor closes when the throttle is closed and the selector is in gear. These values are subtracted from the current IAC Airflow value every 12.5 ms, hence higher numbers mean faster decay. The 4th Gear row is used for gears including and above 4th gear for M6 transmissions.
Throttle Follower Delay Time vs. Speed (In Gear): This is the delay before the decay value begins to be subtracted in gear.
TPS Tracker Step Size %: This is the rate at which the throttle follower tracks the current TPS value.
Throttle Follower Airflow vs. TPS: This is the throttle follower airflow value used as the throttle is opened. It is the value that is reduced to zero by the decay parameters if the throttle is closed. It is versus TPS %.
Throttle Follower Airflow Mult vs. RPM: This table is used to enable the throttle follower in relation to RPM.
Throttle Cracker
The throttle cracker parameters are used to open the IAC motor as vehicle operating conditions change.
Throttle Cracker Airflow vs. RPM vs. MPH: This table is used to open the IAC motor as RPM and MPH vary.
Enable Speed: MPH threshold to disable the adaptive idle and enable the throttle cracker.
Disable Speed: MPH threshold to enbale the adaptive idle and disable the throttle cracker.
IAC Park Position
IAC Park Position Airflow vs. IAT: This table is used to determine the Airflow to control the IAC motor when the IAC motor is in the park position. (ie. when the ignition is in the off position).
IAC Reset Park Position: This value is used to set the IAC motor park position after a PCM reset.
You will see a couple of things. IAC park position is normally 320. Thats 320 "steps". I normally cut it about in half. This opens the blade of the TB less and parks it in a more closed position. You need this to keep the blade closed just a bit more to keep the same airflow as stock. In the cap I have included, its already stepped down to 130 from 320 which is stock.
You have throttle cracker. This is the air that is added once the car is under way. This often leads to idle hangs when the car is moving that are resolved when the car is stopped. You can either change the enable speed up really high, or 0 out the whole table. See below about the adaptive learning....
Idle airflow vs ECT. Is exactly that, airflow vs engine coolant temp. You simply log the data of the car idling as it warms up, and fill in those values.
Here is what HPT says about each one....
Idle
The PCM has a number of parameters that influence the idle behavior of the engine. These parameters specifically control the desired idle RPM and the behavior of the Idle Air Control (IAC) motor during idle conditions. The IAC is controlled via a desired airflow value that has many contributing factors, the PCM then translates this "Idle Desired Airflow" into a number of steps for the IAC stepper motor itself. For Electronic Throttle vehicles the PCM translates this into a TPS % for idle.
Idle RPM
Target Idle Speed vs. Coolant Temp vs. (Drive & Park, A/C On & Off): This table controls the desired idle RPM vs Engine Coolant Temperature. There are a number of settings depending if the transmission is an A4 or M6 (in gear or PN) and also is the AC is on or off. When the vehicle speed is below the Throttle Cracker speed, the PCM will enable adaptive, feedback-based, idle routines to achieve the desired idle RPM.
Base Running Airflow
Idle Air Flow vs. Coolant Temp vs. (Gear & P/N): This table is used to determine the base airflow (in g/sec) for the IAC motor control vs Engine coolant temperature. This is used as a base setting for the adaptive idle routines and also the base IAC position when the vehicle is moving.
Cooling Fan Airflow
Fan 1: This value is the extra airflow added to the base running airflow to compensate for extra electrical load when a single cooling fan is active.
Fan 1 & 2: This value is the extra airflow added to the base running airflow to compensate for extra electrical load when both cooling fans are active.
Throttle Follower
The throttle follower parameters are used to adjust decay and delay rates for the IAC motor during throttle closure to prevent stalling and make gear changing/selection easier.
Throttle Follower Airflow Decay vs. Speed (In Neutral): The decay value is the rate at which the IAC motor closes when the throttle is closed and the selector is in Park or Neutral. These values are subtracted from the current IAC Airflow value every 12.5 ms, hence higher numbers mean faster decay.
Throttle Follower Delay Time vs. Speed (In Neutral): This is the delay before the decay value begins to be subtracted in P/N.
Throttle Follower Airflow Decay vs. Speed (In Gear): The decay value is the rate at which the IAC motor closes when the throttle is closed and the selector is in gear. These values are subtracted from the current IAC Airflow value every 12.5 ms, hence higher numbers mean faster decay. The 4th Gear row is used for gears including and above 4th gear for M6 transmissions.
Throttle Follower Delay Time vs. Speed (In Gear): This is the delay before the decay value begins to be subtracted in gear.
TPS Tracker Step Size %: This is the rate at which the throttle follower tracks the current TPS value.
Throttle Follower Airflow vs. TPS: This is the throttle follower airflow value used as the throttle is opened. It is the value that is reduced to zero by the decay parameters if the throttle is closed. It is versus TPS %.
Throttle Follower Airflow Mult vs. RPM: This table is used to enable the throttle follower in relation to RPM.
Throttle Cracker
The throttle cracker parameters are used to open the IAC motor as vehicle operating conditions change.
Throttle Cracker Airflow vs. RPM vs. MPH: This table is used to open the IAC motor as RPM and MPH vary.
Enable Speed: MPH threshold to disable the adaptive idle and enable the throttle cracker.
Disable Speed: MPH threshold to enbale the adaptive idle and disable the throttle cracker.
IAC Park Position
IAC Park Position Airflow vs. IAT: This table is used to determine the Airflow to control the IAC motor when the IAC motor is in the park position. (ie. when the ignition is in the off position).
IAC Reset Park Position: This value is used to set the IAC motor park position after a PCM reset.
