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Thread: EFI Idle Tuning Notes

  1. #1
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    Default EFI Idle Tuning Notes

    I recently spent several days reading (books) about EFI idle tuning and improving my engine's idle quality. I finally achieved, what I consider, an excellent idling engine...but it wasn't easy. In fact, I believe the Holley HP/Dominator ECU is more sensitive to idle tuning (idle algorithm), than the Commander 950 is; meaning it's easier to achieve a good idle with the C950. I tried to disregard what I thought I knew about idle tuning and start with a fresh mindset...I'm glad I did. Every engine will idle slightly different and the engine combination (components) will affect the idling characteristics, especially the camshaft. These ECU parameters influence the idle quality:

    Target Idle Speed RPM
    Increasing the idle RPM provides a smoother idle. This doesn't mean your engine has to idle at 1000 RPM, however, don't expect a race engine with a radical camshaft to idle at 700 RPM. Generally, the bigger the camshaft the more idle RPM it needs. Most mild performance engines should idle well at 700-800 RPM and most potent street performance engines should idle well at 800-900 RPM. Serious race engines with radical camshafts will need to idle at 900-1000+ RPM, due to the camshaft's tight LSA which causes a high overlap period (not efficient at idle & low RPM). Also, ensure the Target Idle Speed RPM scale is properly programmed. If the hot engine idles in between two temperature cells on the Target Idle Speed scale, set the temperature cell before & after the target idle, to the same RPM; so the ECU doesn't vary the idle speed.

    Target Air/Fuel Ratio
    Most high performance engines will idle well with a target air/fuel ratio between 13.5:1 & 14.2:1. This surprised me, and I wasn't comfortable with it at first, because I thought the idle should be leaner at a stoichiometric 14.7:1 AFR. However, when I tried it, my engine responded so favorably, especially when I shifted it in gear. This became one of the three most significant aspects of my idle quality improvement (the other two being timing advance & Fuel Table tuning). This isn't as detrimental to fuel economy as one might think, because at idle, there are less injection events (engine cycles) over time, than at higher RPM. Remember to also check the idle in gear, and allow the engine to idle for at least a minute with each change. (LINK)

    RPM & kPa Axis Configuration
    When an engine is idling, there's a 'target idle cell' on the Fuel & Timing Tables. It's important to identify this single cell, in order to properly configure the RPM (X) axis & kPa (Y) axis. Ideally, the target idle cell should be in the center of the RPM & kPa range the engine idles in. Some engines exhibit better idle stability than others, as seen on the Fuel & Timing Tables. The goal is to configure the idle area so the idle has equal range above & below the target value. Fuel & Timing Tables should have three RPM columns and three kPa rows; one column/row above & below the target column/row. The values programmed above & below the target, depend on how the engine idles and the resolution of the Fuel & Timing Tables (e.g. 16x16 vs. 31x31). Typically, the RPM axis (idle area) has increments of 100-150 RPM, and the kPa axis (idle area) has increments of 2-8 kPa. Adding idle resolution to the kPa (Y) axis can resolve issues with a radical camshaft and/or a forced induction application (with naturally less resolution in the off boost regions of the table). Remember to check the idle in gear, to verify the kPa axis configuration above idle, is acceptable. (LINK)

    Base Fuel Table
    Most people I help, don't know how to tune the idle area of the Fuel Table (Commander 950 EFI or Avenger/Terminator/HP/Dominator EFI). It has a big impact on the idle stability. The Base Fuel Table should not be totally flat (except the Fuel Graph); meaning you can't have the same numbers in the idle area. Unlike the Base Timing Table & Target A/F Ratio Table, which should be flat in the idle area. Below are sample Fuel Table idle tuning scenarios for the Commander 950 EFI. The Fuel Table values are a pulse-width, as opposed to the Avenger/Terminator/HP/Dominator Base Fuel Table, which is in pounds-per-hour (lbs/hr). This means the Commander 950 Fuel Graph will look like the engine's torque curve (LINK), and the Avenger/Terminator/HP/Dominator Fuel Graph will look more like the engine's horsepower curve. The bold numbers indicate idling with no load (13) & idling in gear and/or accessories on (15). The surrounding cells direct the engine idle back to the target idle cell (center). Study the diagonal pattern of the idle numbers; that's the secret to good Commander 950 Fuel Table idle tuning. Notice how the values increase with higher load & less RPM, and decrease with lower load & more RPM. Example (Commander 950 EFI):
    MAP
    62...16...15...14
    56...15...14...13
    50...14...13...12
    44...13...12...11
    .....700..800..900 RPM
    The Fuel Table example above is a good one, however, it illustrates the idle segment of a Commander 950 Fuel Table with large injectors. On Commander 950 Fuel Tables, smaller numbers mean larger injectors, and larger numbers mean smaller injectors. Therefore, if your idle values (numbers) are larger than what's illustrated above (typical injector sizing), then the number pattern should change in increments of two or maybe even three. Example (Commander 950 EFI):
    MAP
    62...31...29...27
    56...29...27...25
    50...27...25...23
    44...25...23...21
    .....700..800..900 RPM
    Since the new Avenger/Terminator/HP/Dominator ECUs self-tune, why does the idle area of the Base Fuel Table need to be adjusted? Because the Learn function can only self-tune to the Target Air/Fuel Ratio Table in a floating 3x3 cell (9 block) pattern; and it does so very well. When the Learn table self-tunes, it's adjusting the entire idle area the same amount; just like it's supposed to. In other words, the Base Fuel Table is responsible for idle quality, and the self-tuning is responsible for WBO2 compensation. So the idle area of the Base Fuel Table needs to be blended smooth (using the Fuel Graph) to promote a smooth idle, for the same aforementioned reasons. When Holley engineers create the base calibrations, it's impossible to know exactly where anyone's engine will idle on the Base Fuel Table. The engine has to be idling to tune the idle. Therefore, the base calibrations must gradually increase the lb/hr values (MAP & RPM) for the Learning to self-tune. The Avenger/Terminator/HP/Dominator EFI Base Fuel Tables use "lbs/hr" unit of measure, so the number incrementation won't be as equally spread as the C950. The point is to manipulate the engine to idle well, by having a smooth Base Fuel Table.
    Ensure the Base Fuel Table is smooth by viewing & blending the Fuel Graph. It's very important to have a smooth Fuel Graph.
    One aspect of viewing the Fuel Graph: It's better to zoom in, by highlighting segments of the Base Fuel Table (left click & drag), and click "Graph".
    This method offers much greater detail. Looking at the entire "Fuel Graph" will almost always look smooth, because it's not as magnified.
    TIP: When the Fuel Graph is smooth, click "Conversion" (VE% Conversion mode) and continue smoothing the general contour of the VE Fuel Graph.

    • If you'd like to manually tune the Base Fuel Table (even while the engine is running), read below:
    Left click & drag to select a group of cells, then use the CTRL & Arrow keys (▲►▼◄) to change the highlighted cell values.
    The ▲ & ▼ arrow keys adjust the Base Fuel Table slowly (one tenth at a time). The ◄ & ► arrow keys adjust it rapidly.
    Or you can left click & drag a group of highlighted cells, and right click "Offset Selected" to adjust the entire cell group.
    • When the engine is tuned & running well, you should decrease the Closed Loop and Learned Compensation Limits % to lock in a good tune.
    I decreased my Learned Compensation Limits to 2% in the idle area (10% elsewhere). My Closed Loop Compensation Limits are 50% or less.
    When the Learn Table values stop making significant changes, the ECU is finished self-tuning. (LINK - Read this Learn Table thread, especially posts #2, #6 & #11.)
    http://forums.holley.com/showthread....2523#post62523 (Holley EFI Tuning Tips & Information)
    https://www.youtube.com/watch?v=y17MClF7SYA (Base Fuel Table/Fuel Graph Tuning - Part 1)
    https://www.youtube.com/watch?v=aRn3A5_ecpo (Base Fuel Table/Fuel Graph Tuning - Part 2)

    Closed Loop/Learn Compensation ±
    ECUs without Learning capability will have a Closed Loop Compensation Limit of around ±25%, and must be tuned so the ECU is subtracting about 5% from the Fuel Table. With a limit of only ±25%, the initial tuning procedure will most likely need to be repeated each time the tuning is applied to the Fuel Table. You won't notice the ECU subtracting fuel, but you can notice it adding fuel. For initial tuning purposes, allow the maximum value in the idle area, due to coolant & air temperature modifiers. ECUs with Learning capability will have a virtually infinite Closed Loop Compensation Limit; as much as ±999%. The reason why, is so the ECU doesn't need to repeat the entire modification to the Base Fuel Table (if the O2 Compensation was limited), every time it returns to idle or any other area for that matter. The Learn Table modifies the Base Fuel Table by applying its Learned amount to the Base Fuel Table values.
    • In some stubborn cases, a better idle may be attained by limiting the amount of Closed Loop Compensation or Learning, added or subtracted from the idle area. Also, large duration (race) camshafts will exhibit a fluctuating AFR/false lean condition at idle & low RPM, due to their significant amount of overlap, and/or a WBO2 sensor near the end of an open exhaust pipe. To rectify this, enter Closed Loop Parameters and set the "Enable RPM to Enter Closed Loop" high enough to ignore this condition. You'll then need to manually tune the idle area in Open Loop mode.
    • Also, the Advanced Control (1-5) sets how fast the Closed Loop control operates. 1 is the slowest and 5 is the fastest. (The Avenger & Terminator hand-held controller calls this the "Closed Loop Speed".) This depends heavily on where the WBO2 sensor is located in the exhaust system. The further away the WBO2 sensor is (away from the engine), the lower the number should be. If Advanced Control 4 or 5 is selected, one must ensure the ECU isn't oscillating the Closed Loop operation. Viewing a datalog is helpful. I experienced a condition where the actual AFR often "lagged" momentarily, behind the Target AFR. I fixed it by changing the Closed Loop Advanced Control to 5. My WBO2 sensors are located in full-length header collectors. Sometimes it's best to start at a lower value, especially with a fresh base calibration.
    • When the engine is tuned & running well, you should decrease the Closed Loop and Learned Compensation Limits % to lock in a good tune. (LINK) I decreased my Learned Compensation Limits to 2% in the idle area (10% elsewhere). My Closed Loop Compensation Limits are 50% or less. When the Learn Table values stop making significant changes, the ECU is finished self-tuning.

    Ignition Timing Advance
    First, ensure the ignition timing is synchronized (LINK). The Base Timing Table must be flat in the idle area, meaning it's the same value in the entire idle area (especially if using Idle Spark Control). Most street performance engines will idle well with 15°-25° of timing advance. (Stock cam - 20°, performance cam - 25°, radical cam - 30°). The exact amount depends heavily on the camshaft specifications. Generally, tighter LSA - lobe separation angles (overlap) and larger lobe duration figures, require more timing advance at idle. 106°-108° is considered a tight LSA (idle quality suffers with less idle vacuum), 108°-110° is moderate, 110°-112° is moderately wide, and 112°-114° is wide (idle quality improves with more idle vacuum). One must pay close attention to how much timing advance is used at idle. Resist the urge to use too much; I've made this mistake in the past. Advancing the timing, offers better fuel efficiency and raises the idle speed, however, excessive timing creates an unstable idle speed due to the engine having too much torque at idle (Idle Spark control becomes ineffective). Retarded timing lowers the idle speed, decreases engine torque and increases the coolant temperature. Excessively retarded timing also causes the exhaust headers to glow red hot. Remember to check the idle in gear, to verify the amount used is also acceptable. (LINK)

    Idle Spark Control Tuning
    The Idle Spark Control basically fine tunes the idle speed by manipulating the timing (quickly increasing & decreasing in accordance to RPM). The idle quality must be well tuned before adjusting these two parameters. If the idle is well tuned (fuel & IAC), the Idle Spark PID control can actually help determine the optimum timing advance at idle (LINK & LINK). It may help to datalog various P & D combinations (name the datalog by the two numbers to decipher them), and look for the straightest RPM line. This is because you can't watch the idle RPM on the Data Monitor, since they change too fast and the tachometer usually isn't an accurate enough indicator of idle stability. I've found values of 20 (P term) & 40 (D term) are a good start with Holley EFI systems.
    P & D Definitions - Excerpt from Holley EFI manual:
    • P Term – The speed at which the ignition timing is varied to maintain target idle.
    • D Term – Eliminates the overshoot.

    IAC Control Tuning
    The PID terms must be fine tuned to each particular engine. Start with all three PID parameters at 10. Tune the Proportional first, the Derivative second, the Integral last, then fine tune the three together. Temporarily disable the Idle Spark Control while tuning the idle PID parameters, and ensure the Fuel Map is well tuned in the idle area. It may help to datalog various PID combinations (name the datalog by the three numbers to decipher them), and look for the straightest RPM line. This is because you can't watch the idle RPM on the Data Monitor, since they change too fast, and the tachometer usually isn't an accurate enough indicator of idle stability. Of course, you don't have to datalog the number combinations that obviously make it idle worse. Typically, slower IAC control promotes better idle stability.
    PID Definitions - Excerpt from the Holley EFI manual:
    • P Term – (Proportional) 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 & 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) 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.
    http://forums.holley.com/showthread....neral-IAC-Info (General IAC Information - Read "IAC NOTES")

    IAC Counts or Position (%)
    The throttle blades must be set so the engine is breathing sufficient air on its own (without excessive IAC intervention), for idling & starting. The IAC motor/valve is supposed to regulate the idle airflow to help maintain the idle speed. IAC motors have an IAC Position range of either 0-255 counts or 0%-100% (each 1% is the equivalent of 2.55 counts). The throttle blades (idle speed screw) is often set to position the IAC motor at 8-12 counts or 15%+ at hot idle. I've found this to be too much IAC control when it's closing (toward zero). I prefer to further open the throttle blades to achieve a IAC position of 3 counts or 5% at hot idle. This only allows a minute amount of airflow reduction, which always seems to promote a more steady idle speed and improve starting. Remember to perform another TPS AutoSet, whenever you adjust the idle speed screw on the throttle body. In the Idle ICF, the "Target Idle Speed (RPM)" must be programmed to the desired RPM speed at hot idle. If the idle speed screw is unscrewed too far, the engine is inhaling air from an additional source - vacuum leak. Ensure the proper type of Advanced Idle Control is selected in Idle Settings. "Slow" may provide the best idle quality. (LINK)
    FYI: The Commander 950 EFI system uses IAC Position Counts, not IAC Position %, so don't try copying the Commander 950 IAC values. IAC motors have an IAC position range of either 0-255 counts or 0%-100% IAC Position (each 1% is the equivalent of 2.55 counts).

    Injector End Angle
    I also spent some time tuning the injector end angle timing. ECUs have different end angle software parameters, so there's an excerpt of how Holley does it below. I like the idea of injecting fuel a little earlier during the intake stroke. The end angle has a diminishing effect as the injector duty cycle reaches 90% (since the injectors are "on" for most of the engine cycle), however, it's nice to tune this for optimum idle quality and low to mid RPM torque. Torque, economy, emissions & idle quality are all effected by the injector timing. The optimum value depends on the engine RPM & load. To notice a difference, the end angle must be adjusted in large increments, such as −45° or −90°. The injection timing can be plotted on paper, if the user knows the injector duty cycle in question, and the intake valve opening (°BTDC) & closing (°ABDC) events. Good technical description from Motec: LINK.
    • Excerpt from the Holley EFI manual:
    "Injector End Angle - This is the crankshaft angle in degrees when the injectors will finish their injection event. A value of 0° will end the injection event at BDC (Bottom Dead Center) before the compression stroke. A negative value moves the event before BDC, and a positive value moves the event after BDC. There could be some improvements in cylinder to cylinder fuel distribution by tuning this parameter. If modifying, it is best to move this value in a negative direction to start."
    • For reference (in Holley EFI software), a 0.0° Injector End Angle value, ends the injection event at BDC (Bottom Dead Center) of the intake stroke, before the compression stroke. This is 540° in the four stroke cycle. A negative value moves the injection event before BDC, and a positive value moves the injection event after BDC. So a −180° Injector End Angle value will end the injection event at TDC (Top Dead Center) of the intake stroke (as the intake valve is opening). Obviously, a −90° Injector End Angle value will end the injection event in the middle of the intake stroke.
    FYI: The Holley V4 EFI software/ECU firmware now has much more sophisticated Injector End Angle/Phasing parameters. We discussed it in depth HERE (MPFI engines only).

    Injector Pulse-Width
    It's important to use the proper size fuel injectors. Injectors that are too large for your application, won't idle well due to low pulse-width operation. Don't decrease fuel pressure in order to increase pulse width times at idle. Decreasing fuel pressure results in less than optimum injector spray patterns. Holley suggests the pulse-width at idle shouldn't be lower than 1.7 msec (which won't be an issue when using the appropriate size injectors), and that it shouldn't fluctuate more than .3 msec. Also, large injectors will idle better when sequentially injected, for reasons mentioned in this LINK.

    Minimum Injector Opening Time
    This parameter can be especially useful for very large injectors that have poor low pulse-width linearity (such as the Bosch 160 lb/hr injectors). This msec value programmed by the user, will prevent the injector pulse-width from fall below the setting, which promotes a much more stable idle speed (idle quality). A good starting value is 1.00 msec. However, unless the injectors are too big or the fuel pressure is too high, most injectors won't reach this setting anyway.

    Injector Voltage Offset
    All injectors have a voltage off-time/voltage curve, and this needs to be correctly entered into the ECU's software. Sometimes this data can be difficult to find, and contacting the manufacturer is the only way to acquire it. The injector off-time values don't have to be exactly correct. In fact, some aftermarket ECUs just provide generic values. Adjusting the fuel pressure will skew the results somewhat because increasing the fuel pressure does increase the injector off-time values. If the data sheet you find or receive is a short list, you can mathematically find the value in between any two consecutive data points, by averaging.
    Example - The data sheet gives you the values for 8 & 10 volts, but you want to find the value for 9 volts: 1.669 (8V) + 1.057 (10V) ÷ 2 = 1.363 (9V).
    If your injector data sheet only provides values up to 15 volts, divide that value by 7, and use that subtraction factor for the last six cells. (LINK)
    • Another aspect of proper voltage is the alternator. Ensure the alternator can maintain the battery charge at idle. This is a big problem with older alternator designs, even if it's a high amp alternator (and they output a lot of electrical noise). However, modern design alternators are capable of producing most of their power (amps) at idle speeds. These modern designs simply have larger stators, more windings, better rectifiers, etc for greater idle speed output. Ford owners can retrofit a Ford 3G alternator (LINK). GM owners can retrofit a CS-144 alternator (CS-130 for high RPM racing use). I believe Mopar owners can retrofit a certain model Denso alternator.

    Alpha-N Idle Fuel
    Alpha-N Idle Fuel ("Combo" Load Sensing in Engine Parameters) is a fuel injection strategy, based on TPS Position & RPM. It's for serious race engines with radical camshafts that can't maintain a steady kPa value because it fluctuates too much. Alpha-N Idle Fuel still has the benefits of O2 compensation, however, it can't sense load because it doesn't use the MAP sensor at idle. In Alpha-N mode, most ECUs use the MAP sensor as a Barometric sensor. Alpha-N Idle Fuel should only be used as a last resort. Adding idle resolution to the kPa (Y) axis usually resolves issues with a radical camshaft. Of course, forced-induction applications must use speed-density mode (MAP sensor), since they need to measure load points under boost.
    • I once helped a user with their "Alpha-N Idle Fuel" tune. We programmed the Max Alpha-N TPS parameter (TPS axis) at 3%, and the Max Alpha-N RPM (RPM axis) at 1200 RPM. The Fuel Flow (lb/hr) table ranged from 8.5 to 9.0 lb/hr. (Alpha-N was only necessary at actual idle.) The default Alpha-N Idle Fuel table didn't have realistic TPS & RPM values, so program it to your specific application.
    May God's grace bless you in the Lord Jesus Christ.

    '78 BRONCO: 508" stroker, TFS heads, 11:1 comp ratio, Dominator MPFI & DIS, cold air induction, Spal dual 12" fans/aluminum radiator, dual 3" exhaust/Magnaflow mufflers, Moroso vacuum pump, Accusump, engine oil & trans fluid coolers, 100HP progressive dry direct-port NOS, A/C, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, traction bars, 4" Skyjacker lift, 35" mud tires

  2. #2
    Join Date
    Aug 2012
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    Fort Myers, Florida
    Posts
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    ^Info was helpful for getting my 427" SBF w/ATI ProCharger F1-R to idle. Thanks.

  3. #3

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    Ultimate useful topic, thanks!
    Chevy Blazer Full Size 1994, 383ci, twin turbocharged, Holley Stealth Ram, Dominator ECU.
    Swap this engine and transmission to Chevy Vette C3!

  4. #4

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    Just found this, I don't understand much of it, but it certainly gives me points to look for & learn. Thanks for the write-up!

  5. #5
    Join Date
    Dec 2009
    Location
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    This is rarely an idle problem, but I'll mention it anyway. I once helped a friend with an fluctuating (erratic) idle, and we found his PCV valve was intermittently failing; not metering properly. Large camshafts can also cause PCV valve malfunctions, due to unstable idle vacuum. Anyway, I like the "fixed orifice" type of PCV valve, better than the conventional "variable orifice" PCV valve; especially for EFI applications. I like knowing the predetermined vacuum draw (PCV orifice) is always the same. I think the idle is more consistent too. FYI: For naturally aspirated engines only.
    http://mightyautoparts.com/MightyCat...arts/3-915.pdf (Fixed orifice vs variable orifice PCV valve.)
    https://www.mightyautoparts.com/docu...a0?version=1.1 (Fixed orifice PCV valve document.)

    "Fixed Orifice" PCV Valve Part Numbers:
    GM OEM 12572717
    ACDelco CV4000C
    NOVO 2377
    FRAM FV410
    BWD PCV484
    Wells PCV371
    Airtex 6P1241
    CarQuest 76-2698
    MicroGard PCV2377
    NAPA/Echlin 2-9485
    AutoZone/Duralast PCV1009DL
    Standard Motor Products V372
    (If you need the 90° version, simply reuse your old plastic 90° plastic barb fitting. Yes, it pops off & on the PCV valve.)

    Dual Flow Adjustable PCV Valve - M/E Wagner Performance:
    http://mewagner.com/?page_id=444 (DF-17 Dual Flow PCV Valve)
    http://mewagner.com/wp-content/uploa...-Manual-R3.pdf (Dual Flow PCV Valve Manual)
    FYI: This aftermarket PCV valve can also operate in "fixed orifice" mode (for low idle vacuum camshafts), and still
    retains backfire & reverse flow protection (check valve) for use on naturally aspirated & forced induction engines.

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    UPDATE 1: I no longer use a PCV valve (LINK). I installed a Moroso Enhanced Design 4-vane crankcase vacuum pump with their on-pump adjustable vacuum regulator, 5" diameter vacuum pump V-belt pulley (no crank mandrel), -12AN hose kit & breather tank/breather tank. All high quality components, and it works great. I modified two vacuum pump mounting brackets (LINK/LINK) for pivot mount eyelet holes, with an aluminum spacer in between & long bolt. (I used the idler pulley for something else.) I used two heim joints (1 male, 1 female) threaded into each other, so it adjusts belt tension like an alternator. Quick & easy disassembly if it ever needs cleaning. The AEM 30-2130-30 2 bar stainless steel MAP sensor is a great crankcase pressure sensor. It's 1/8" NPT & more compact than a conventional MAP sensor (additional details - LINK). It's installed vertically at the top of my timing chain cover, on the abandoned front sump dipstick tube with a very short piece of 3/8" hose - perfect mounting point. (My engine has a rear sump oil pan with it's own dipstick tube.) I programmed my Holley EFI 553-106 Digital Dash to display it as vacuum - inHg (inches of mercury). To convert kPa to inHg (vacuum gauge) on the Digital Dash (Math Multiplier/Channel Math):
    x^2 Term (a) 0
    Multiplier (b) 0.2961
    Offset (c) −29.61

    UPDATE 2: This Moroso Enhanced Design 4-vane crankcase vacuum pump is just fantastic! I've been street running it for two years now (at 130% engine speed, driven off a dual groove alternator pulley), and the vanes have only worn .002". I've periodically disassembled the vacuum pump for inspection (which is extremely easy since the pump body remains on the engine), however, I've never had to actually clean it. The vacuum pump pulls in just enough oil vapor to keep it lubricated, and there's never too much oil in the breather tank (there's a good baffle in the valve cover). It draws such a strong vacuum, I had to remove two of the four vanes internally, and restrict the suction hose I.D. to 7/32" (.2187") with an custom made orifice insert. I also had to add a secondary vacuum relief valve on a 5/16" hose off the suction hose elbow fitting. The on-pump adjustable vacuum regulator is set to 3.5 inHg at idle, and the system pulls 7 inHg at WOT (safe for a wet sump big block Ford). My only complaint against Moroso, is they offer only one 5" diameter V-belt pump pulley. We need more (larger) diameter options, because the future of vacuum pumps is not crankshaft driven. Moroso, think outside the box.

    UPDATE 3: The vacuum pump system's 2-stage vacuum regulator installation works great. The secondary vacuum relief valve is operational during normal driving (2nd stage further bleeds off & maintains a preset amount of vacuum). I later realized that I can temporarily disable the secondary vacuum relief valve when my nitrous oxide system is enabled/armed (full vacuum from adjustable on-pump regulator). I do this with a simple cap plug over the vacuum relief valve (of course, a manual open/close valve would work too). The small increase in combustion blow-by from the forced induction/power adder, slightly decreases the amount of crankcase vacuum at WOT. When the secondary vacuum relief valve is disabled, the crankcase vacuum is maintained under full vacuum from the adjustable on-pump regulator only. So there can be two different crankcase vacuum settings, selectable with a simple cap plug, a manual open/close valve, or even a +12V solenoid valve (LINK/LINK) automatically controlled by a custom +12V or Ground Output programmed in the Holley EFI ECU. The amount of crankcase vacuum each stage pulls is user adjustable, since both the vacuum regulator & relief valve is fully adjustable.

    UPDATE 4: The only other issue I initially addressed, was the smell. Vacuum pump systems stink a little bit because they pull crankcase gases out of the engine, and vent it into the engine compartment via the breather tank vent filter. Of course, this doesn't matter on a race only vehicle, but it's unacceptable for a street driven vehicle. I solved this issue by removing the Moroso vent filter off the breather tank, and attaching a male -10AN fitting using a short piece of 1⅜" I.D. hose. This hose is routed to a PCV air/oil separator (probably not necessary if using the Moroso 85467 air/oil separator type breather tank, as opposed to their conventional 85500 breather tank). This completely stops 100% of any oil vapor from passing through. I then routed 5/8" heater hose from the PCV air/oil separator to the rear of the vehicle (along the inside of the frame rail with P-clamps), next to one of my tailpipes. Now I don't have to smell it, or periodically clean a vent filter. I drain the primary breather tank a few times a year, and drain the secondary air/oil separator once a year. In my estimation, the primary breather tank catches about 85% oil vapor, and the secondary air/oil separator easily catches the rest of it.
    May God's grace bless you in the Lord Jesus Christ.

    '78 BRONCO: 508" stroker, TFS heads, 11:1 comp ratio, Dominator MPFI & DIS, cold air induction, Spal dual 12" fans/aluminum radiator, dual 3" exhaust/Magnaflow mufflers, Moroso vacuum pump, Accusump, engine oil & trans fluid coolers, 100HP progressive dry direct-port NOS, A/C, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, traction bars, 4" Skyjacker lift, 35" mud tires

  6. #6

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    Danny, can you elaborate some more on the issues that might occur when using Drive-By-Wire, since there is no IAC motor in a conventional sense. Also, since I have two big throttle bodies, what might be some challenges that I might face? I have the car idling pretty well right now, but I don't like how slowly it settles back to idle after blipping the throttle. Which parameter effects this? Andrew

  7. #7
    Join Date
    Nov 2013
    Location
    Chicago IL
    Posts
    1,958

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    Even though you don't have an actual IAC motor (DBW), you will still adjust the IAC Ramp Down in the Idle ICF.
    -Scott
    Don't forget to check out progress on my Race Car:
    Project Blasphemy - 8.07 @ 171
    Low 8 Second Street Car

  8. #8

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    Thanks Scott. In the IAC Ramp Down section, I see 4 parameters:
    IAC Hold Position, Ramp Decay Time, RPM Above Idle To Start Ramp, and RPM Above Idle To Re-Enable Idle Control.
    Would you mind elaborating on those four parameters, and how changing them effects things, especially with dual throttle bodies? Andrew
    Last edited by andrewb70; 07-04-2015 at 12:40 PM.

  9. #9
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    Dec 2009
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    Connecticut
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    Quote Originally Posted by andrewb70 View Post
    Would you mind elaborating on those four parameters, and how changing them effects things, especially with dual throttle bodies?
    As S2H stated, the IAC Control Parameters still apply for a Drive-By-Wire application. It all tunes the same way.

    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/techlibr...10555rev17.pdf (Holley EFI Wiring Manual)
    May God's grace bless you in the Lord Jesus Christ.

    '78 BRONCO: 508" stroker, TFS heads, 11:1 comp ratio, Dominator MPFI & DIS, cold air induction, Spal dual 12" fans/aluminum radiator, dual 3" exhaust/Magnaflow mufflers, Moroso vacuum pump, Accusump, engine oil & trans fluid coolers, 100HP progressive dry direct-port NOS, A/C, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, traction bars, 4" Skyjacker lift, 35" mud tires

  10. #10
    Join Date
    Nov 2013
    Location
    Chicago IL
    Posts
    1,958

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    Quote Originally Posted by andrewb70 View Post
    Thanks Scott. In the IAC Ramp Down section, I see 4 parameters:
    IAC Hold Position, Ramp Decay time, RPM Above Idle To Start Ramp, and RPM Above Idle To Re-Enable Idle Control.
    Would you mind elaborating on those four parameters, and how changing them effects things, especially with dual throttle bodies?
    It's very simple, and it doesn't matter if you have a single throttle body, or dual, or a 4 hole, or a mono-blade. The IAC function is the same for all.

    IAC Hold Position is basically a reference to how much air to allow in when you crack the throttle.
    It aids in barely off idle throttle response and gives the IAC a wait position for when you close the throttle.
    The IAC will always go to this position while the throttle is open.
    The idea is that you want enough air to allow the idle to come down smooth, but not so much as to make it hang or rise when you first close the throttle.

    IAC Ramp Down has to do with how fast it returns back to zero (idle).
    In general, we try to make it so that your IAC Position is as close to zero as possible when at idle.
    The Ramp Decay is how long it takes to get from the Hold Position to zero.

    The RPM Above Idle To Start Ramp & RPM Above Idle To Re-enable Idle Control, is basically
    when you want the previous two parameters to start, and to go back to normal idle routines.
    So let's say an example:
    40% IAC Hold Position
    2 seconds Ramp Decay Time
    1000 RPM Above Idle To Start Ramp
    200 RPM Above Idle To Re-enable Idle Control
    Idle at 1000 RPM for easy math.

    So I open the throttle, and the IAC goes to 40%. When I let off the throttle, the 40% is low enough that RPM comes down, at 2000 RPM, the ramp begins and over the next 2 seconds it will decay from 40% to 0% until it gets to 1200 RPM. At which time, it exits the Ramp Down no matter where it is percentage wise, and starts normal idle routines.

    If it returns to idle too fast (and potentially overshoots and dips below desired idle RPM), I would raise the IAC Hold Position first, as it's a direct relation to how much extra air there is. If it starts to fall slowly, and the suddenly falls too fast, change the Ramp Decay Time. If it falls too slow and you adjust the Decay Time, and it still falls too slow, try changing the RPM Above Idle to Start Ramp, or just try decreasing the IAC Hold Position some.
    It all plays together, there's no exact answer to what works, as every combo is different. Some like more IAC Hold Position, some like less. Some like longer Delays, some like shorter.
    -Scott
    Don't forget to check out progress on my Race Car:
    Project Blasphemy - 8.07 @ 171
    Low 8 Second Street Car

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