General IAC Info & Ford PWM IAC Wiring

[Danny Cabral]

It depends on how well the idle quality is tuned.
A good idle will only fluctuate the Idle Spark control about ⁺/₋ 2°-3°.
A poor idle can fluctuate the Idle Spark control as much as ⁺/₋ 8°-9°.
http://forums.holley.com/showthread....e-Tuning-Notes (Read "Idle Spark Control Tuning".)

[Rage]

So ⁺/₋ 8°-9° spark timing is the maximum the Holley will use to control idle speed. The engine's previous Mercruiser PCM555 would use about four times that, is why I asked. Thank you.

[Bullshark]

Can any one tell me the PID IAC control values used when "FAST", "MEDIUM" or "SLOW" is selected in Advanced Idle Control? Thanks, Bullshark.

[Danny Cabral]

The Slow, Medium & Fast IAC PID/Blanking values are now listed in post #1.

[Jay@HAP]

When using the Ford 2-wire IAC, should Advanced Idle Control be "5.0L Ford" or something else?

[Danny Cabral]

Not necessarily. Select the setting that best fits your engine application.

[jeff@califon]

Are 18 gauge wires suitable for the Ford IAC motor, or can I use something smaller?

[Danny Cabral]

Yes, 18 AWG is fine. Always refer to the Holley EFI Wiring Manual. You'll see the IAC motor wiring is 22 AWG.

[jeff@califon]

I did see that, but thought that was for the Holley IAC, wasn't sure if the Ford unit I will be using needed a larger size. Thanks.

[Danny Cabral]

You're welcome, 18 AWG is fine.

[gorfgorf]

Anyone know the purpose of the setting for “Low Side Enabling RPM” on idle control parameters? What's a scenario it would be used for?

[Danny Cabral]

Originally Posted by Danny Cabral EFI Software Help Information/Instructions: ‒ On the top Toolbar, click "Help" & "Contents". This opens all Help topics. ‒ When navigating the software, click "Help ?", drag it to any parameter and click again. ...This automatically opens the definitions for that specific parameter. ‒ Tuning information can be read by clicking the F1 key, when you're viewing any screen. http://documents.holley.com/techlibrary_199r10544.pdf (Holley EFI Help/Instructions Overview) http://documents.holley.com/techlibr...r10546rev1.pdf (Holley EFI Quick Start Guide) http://documents.holley.com/techlibr...10555rev17.pdf (Holley EFI Wiring Manual & Diagrams) http://forums.holley.com/showthread....ents-Read-This (Initial Checks & Adjustments - Read Steps # 1- # 6!) Open the Holley EFI software "Help" Contents ("Help" drop down menu), and read "Step-By-Step Beginners Tuning". Ensure the EFI software is set to run as an "Administrator" (right click for Properties/Advanced). Set it and forget it.

[gorfgorf]

My Help Contents system only opens a TerminatorX.pdf. That PDF doesn’t contain any information about “Low Side Enabling RPM”. Anyone have it?

[Danny Cabral]

Originally Posted by Holley EFI Software Help Contents Idle ICF Tuning – Settings All of the settings in this area deal with the control of the Idle Air Control motor (IAC). Three functions are programmed in this area: 1) Engine Idle Speed 2) IAC Position when the engine is cranking and immediately after it starts 3) IAC Position when an engine returns back to idle These parameters can be altered such that the engine operates as desired. This is one area of tuning that is very specific to an individual’s preferences. Tuning Idle Speed The “Idle Speed” tab is the target idle speed an engine will be held at based on engine coolant temperature. Typically, an engine will idle at a slightly higher speed when cold, but this doesn’t have to be the case. It is very important that the throttle plates be adjusted to the proper setting so that the Idle Control routines operate properly. To adjust the throttle plates properly, allow the engine to reach operating temperature. With the transmission in neutral, open or close the throttle plates so that the “IAC Position” seen in the data monitor is between 5 and 15%. If it is stuck at 0, the plates are too far open and the ECU can’t command the idle speed low enough. If the position is too high, there won’t be enough IAC airflow for when the engine is cold or in gear, as well as the other IAC parameters won’t be in a proper range. IAC Parked Table This table determines the position of the IAC when an engine is cranking and immediately after it starts. If is too high, the engine will rev to too high of a level after it starts. If it is too low, an engine may not have enough air to start well and struggle for a second after it starts. If either of these problems exists, raise or lower values in this table at the engine coolant temp the problem occurs at. Idle Parameters Idle Spark – If the ECU is controlling the ignition timing, Idle Spark control can be enabled. It allows the ECU to vary timing at idle to stabilize the idle. Raising or lowering the “P Term” will change the speed at which the timing is allowed to change. Monitor the timing on the data monitor to help optimize what is best for your engine. Understand that if this is enabled, the timing will fluctuate a lot at idle if you are viewing it with a timing light. IAC Ramp Down – The IAC Ramp Down parameters control what the IAC does when the engine TPS is moved past and returns back to idle. These parameters are intended to be used such that when the engine returns back to idle, the engine speed can return quickly or “softly”. This is up to the preference of the individual. Adjusting these parameters can greatly alter how this occurs. The “IAC Hold Position” is the position the IAC will freeze at when the TPS increases past 0%. For most street applications, this value will be between 30-40%. When an engine returns to idle, the IAC will decay from this value until the idle speed returns to target. The point which the IAC ramps back down is dictated by the “RPM Above Idle to Start Ramp”. This is typically 600-1000 RPM. The amount of time this ramp takes to decay back to idle is dictated by the “Ramp Decay Time”. A time of 3-4 seconds is usually a decent value. There's an easy way to set these quickly. Perform the following: With the engine at operating temp and in neutral, determine the engine speed where you want to start the IAC ramp-down (for example 1500). Set the engine idle speed to this speed (1500 for this example). Look at the position of the IAC when the engine is running at 1500. For this example, it is 38 (then set the idle speed back to the normal value). Subtract 5 from this value and enter that value for the “IAC Hold Position” (38 – 5 = 33 for this example). Subtract the target idle speed from the ramp down speed above (in this example 1500 – 800 = 700). Enter this value (700) for the “RPM Above Idle to Start Ramp. Then enter a “Ramp Decay Time” as desired. A larger number will take longer to set the engine back to idle speed, a smaller one will return it quicker. Performing this method will optimize these parameters. If these values are not set correctly, it can cause the IAC to not “count down” and return back to idle. If this is the case, either one of the following needs to be done: Lower the “IAC Hold Position” Raise the “RPM Above Idle to Start Ramp” NOTE: Before modifying these values, make sure that the steps outlined above in “Tuning Idle Speed” are performed. Startup IAC Position – The startup IAC position is used to hold the IAC at the “IAC Parked Position” for a certain amount of time after the engine starts. The “Hold Time” is the time that the engine is held at this higher RPM. This is usually about two seconds. The “Decay Time” is the time it takes to ramp the IAC back to a position of zero. These parameters can be adjusted to suit ones preferences. Advanced Idle Control – “CUSTOM” – If “CUSTOM” is selected for the “Advanced Idle Control” setting, it will open up the PID and other parameters for idle. Modification of these parameters is only recommended for people that understand them. The other pre-defined dropdowns should be used by those that do not clearly understand PID tuning. The following are some examples of the pretuned definitions. They indicate a solid baseline to start with. It should be noted that these PID values are “scaled” from 1-100 from the raw values. Due to this, one should not use formulas such as the Ziegler Nichols to calculate them. IAC Blanking Window – This is a very useful parameter for engine with either a noisy RPM input signal or one with a large camshaft that causes a lot of fluctuations. If an engine has a “normal” RPM variance of +/-30 RPM for example, a value of 60 can be put in. This will “mask” this area and as long as the RPM stays within +/-30 of the target, the IAC will not react, which causes a much better idle. Engines like a stock LS1, can operate with a value close to 0, as they have an excellent crank signal and a stock cam allows for the engine to operate very smoothly. D Blanking Window – Similar to the IAC Blanking Window above, this value masks D Term “noise” and stops the IAC from chasing “noise”. Experiment to find what is best on specific applications. Low Side IAC Operation – These 4 parameters allow for a different PID term set to be used if the engine speed should drop below a certain RPM. If an engine is tuned well, the engine speed should not fall to the point where these terms are active. The “Low Side Enabling RPM” is the engine speed below target idle speed that these values will take over until the speed returns above that value. The following is a list of the values used for various predefined drop downs. They provide a good starting point if one wishes to deviate from them. Holley 4BBL TB Holley 4 BBL MPFI GM LSx GM DBW 5.0L Ford Main P 18 16 18 6 4 Main I 32 32 32 8 14 Main D 60 60 60 45 80 IAC Blanking Window 40 40 25 30 40 D Blanking Window 40 40 40 40 40 Low Side Enabling RPM 100 100 100 100 100 Low Side P 30 30 25 7 5 Low Side I 50 50 40 11 17 Low Side D 60 60 60 60 80 PID Definitions: P Term – (Proportional) is the speed/gain of the system when there is a large deviation in the target idle speed. Raising this value increases the speed at which the IAC moves in order to remove target idle speed error. If this value is too high for a specific application, the IAC position will oscillate (be out of control) and cause the engine speed to surge up and down. If the value is too low for a specific application, the IAC will be slow to react to quick changes in idle speed deviation. However, it is much better for this term to be conservatively slow, rather than too fast. I Term – (Integral) is the speed of the system when the engine speed is near the target idle speed. Raising this value increases the speed at which the IAC moves when the engine speed is close to target idle speed. If this value is too high for a specific application, there may be “too much IAC activity” around the target idle speed. If the value is too low for a specific application, the IAC will be slow to react to changes near target idle speed. However, it is much better for this term to be conservatively slow, rather than too fast. D Term – (Derivative) higher derivative terms reduce the tendency of idle speed overshoot. Smaller derivative terms slow down the IAC movement as target idle speed is approached. NOTE: The PID terms are scaled values between 1-100. They are not the raw PID terms, so do not use conventional PID calculation equations to calculate these terms. The scaled values are such that both the high and low limits still maintain reasonable control.