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Thread: Dual IAC

  1. #11
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    Quote Originally Posted by S2H View Post
    No, when you have to set the TPS/IAC for In Gear, you also need to setup base spark for In Gear as well.
    You're right about the IAC Position. I understand that, but I think he can use the same timing for in gear as in neutral. (Either way, I can't argue over tuning an engine that's not here in front of me.)
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/3000 RPM converter, FPP aluminum driveshaft, FPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 MT tires.

  2. #12
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    Quote Originally Posted by Danny Cabral View Post
    You're right about the IAC Position. I understand that, but I think he can use the same timing for in gear as in neutral. (Either way, I can't argue over tuning an engine that's not here in front of me.)
    The problem lies with the fact that he can only command Idle speed for one or the other.
    (Unless he has a PRNDL Switch of some sort and can monitor Park/Neutral or in gear.)
    So let's say you get it to Idle at 900 RPM in gear...Under Load.
    Then when you put it in Neutral (no load), it idles up a few hundred RPM.
    And Idle Spark control tries to take care of knocking it down.
    And Idle Spark can knock it down to that 900 RPM pretty easily in Neutral/Park.

    You don't do it the other way around because adding spark to bring the idle up in gear will lead to an unstable return to idle (which he was already experiencing).

    If you have a switch to tell the ECU when the vehicle is in Neutral/Park, you can build an Advanced Table to take care of the changes needed in Idle or Park vs Gear. (I do this on every car I can.)
    -Scott
    Don't forget to check out progress on my Race Car:
    Project Blasphemy - 8.07 @ 171
    Low 8 Second Street Car

  3. #13
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    Quote Originally Posted by S2H View Post
    So let's say you get it to Idle at 900 RPM in gear...Under Load.
    Then when you put it in Neutral (no load), it idles up a few hundred RPM.
    And Idle Spark control tries to take care of knocking it down.
    And Idle Spark can knock it down to that 900 RPM pretty easily in Neutral/Park.
    When you do this, do you still leave the Base Timing Table flat in the idle area?

    You don't do it the other way around because adding spark to bring the idle up in gear will lead to an unstable return to idle...
    What do you mean by an unstable return to idle? The idle hangs/prolonged return to idle, or it wants to stall/die?

    If you have a switch to tell the ECU when the vehicle is in Neutral/Park, you can build an Advanced Table to take care of the changes needed in Idle or Park vs Gear. (I do this on every car I can.)
    The neutral safety switch should be able to provide this capability. The old Commander 950 Pro EFI had an optional Park/Neutral Input wire that commanded the IAC to a user programmable value to prevent stalling in gear. Some users really need a higher stall torque converter upgrade to match their engine combination.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/3000 RPM converter, FPP aluminum driveshaft, FPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 MT tires.

  4. #14
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    Quote Originally Posted by Danny Cabral View Post
    When you do this, do you still leave the Base Timing Table flat in the idle area?
    Yes, absolutely.

    What do you mean by an unstable return to idle? The idle hangs/prolonged return to idle, or it wants to stall/die?
    If you set Idle for Neutral, and it really has to work when it's in gear, it would try to die in gear as it
    would not have enough air for in gear, because it will try to return to the Idle airflow set to in Neutral.
    This may manifest itself as a small Dip before the idle stabilizes, or it could be a complete stall.

    If you setup idle properly for in Gear, it won't hang or stall.
    And neutral won't matter because you shouldn't really be revving it way up in neutral anyways.

    The neutral safety switch should be able to provide this capability. The old Commander 950 Pro EFI had an optional Park/Neutral Input wire that commanded the IAC to a user programmable value to prevent stalling in gear.
    Good to know.
    Basically you can take your neutral safety switch and split it off to the ECU (regular input, not the A/C IAC Kick Input).
    You would then set it up for Idle in Neutral, and an offset for in gear.

    But if that's not an option, you set it up for in gear and deal with neutral being a little higher idle, as we spend most of our time in gear.

    And reasons to not be able to add the neutral safety into the ECU could be as simple as no more inputs available, or even just the wrong kind of inputs left in your Pin Map.
    And of course the most horrible reason would be because you don't have a neutral safety switch at all. In which case (as a business practice) I refuse to work on your car till you add one and make it safe.
    -Scott
    Don't forget to check out progress on my Race Car:
    Project Blasphemy - 8.07 @ 171
    Low 8 Second Street Car

  5. #15
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    Thanks for a very informative post, Scott. I understand how you're using the EFI system to manipulate the idle to benefit Park/Neutral idle and in gear idle. However, I've got to say, I can't even imagine my engine having this "return to idle" problem. It seriously never even hints toward stalling. If it ever did, I'd be shocked and assume an ignition related failure. Some users really need a higher stall torque converter upgrade to match their engine combination.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/3000 RPM converter, FPP aluminum driveshaft, FPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 MT tires.

  6. #16
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    Quote Originally Posted by Danny Cabral View Post
    Thanks for a very informative post, Scott. I understand how you're using the EFI system to manipulate the idle to benefit Park/Neutral idle and in gear idle. However, I've got to say, I can't even imagine my engine having this "return to idle" problem. It seriously never even hints toward stalling. If it ever did, I'd be shocked and assume an ignition related failure. (Some users really need a higher stall torque converter upgrade to match their engine combination.)
    I've tuned a LOT of cars, and it's a more common problem than people realize.
    -Scott
    Don't forget to check out progress on my Race Car:
    Project Blasphemy - 8.07 @ 171
    Low 8 Second Street Car

  7. #17

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    You can also try taking away some timing in the idle area. This will require a larger throttle opening to maintain the same idle speed. This may help your idle consistency. Mike
    1967 Camaro. 5.3L L33 swap, Holley Dominator EFI. 10.65 @ 128 so far.
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  8. #18
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    Quote Originally Posted by silverbullet9 View Post
    You can also try taking away some timing in the idle area. This will require a larger throttle opening to maintain the same idle speed. This may help your idle consistency. Mike
    This is a problem is between in gear and out of gear. It's not solved by taking away timing. It's a problem compounded by too much throttle body on top of a converter that grabs too hard at idle (converter needs to be loosened up).
    -Scott
    Don't forget to check out progress on my Race Car:
    Project Blasphemy - 8.07 @ 171
    Low 8 Second Street Car

  9. #19

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    Thank you very much, that's just the sort of answer I'm after.
    So for setting up an Advanced Table, I assume it's a 1D Table? What parameter would be best to use on the X axis?
    If it was done the other way using the Idle Spark control, would you then need to increase the P & D Terms?

  10. #20
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    Quote Originally Posted by James Taylor View Post
    So for setting up an Advanced Table, I assume it's a 1D Table? What parameter would be best to use on the X axis?
    There's more than one way to accomplish this, but an Advanced 1D Table with an RPM X Axis should do it (especially since you can also select an Advanced Enable for activation when TPS is below 2%, or whatever works best). The Switched Enable is your custom created Park/Neutral Input signal from the neutral safety switch (Inputs/Outputs ICF). Then you can increase the 'in gear' RPM using the Target Idle Speed Offset table. The IAC Position Offset might not work well, because the IAC Position constantly changes and it doesn't always repeat the same when shifting into gear, which could cause it to vary. However, try it both ways and determine what works best on your engine.

    I like additional options, so I'd create an Advanced 2D Table with an RPM X Axis & MAP Y Axis, so I could isolate this function to just the idle area. In fact, there's another way to do this without a custom created Park/Neutral Input. Using an IAC Position Offset table with an RPM X Axis (I.E. 650-800 RPM) & MAP Y Axis (I.E. 30-50 kPa) - Advanced 2D Table, add the IAC Position Offset % only to the 'in gear' area of the table (below target RPM & above target kPa). Only 3-5% of IAC Position Offset should be necessary to prevent the RPM dip. However, it's important to keep a couple RPM columns below target idle (about 30 RPM) at zero, and a few kPa rows above target idle (about 4 kPa) at zero. Select the Advanced Enable for activation when TPS is below 2%, so it's only active at idle. Now when the idle tries to dip down 'in gear', it will immediately hit the increased IAC Position Offset % cells (momentarily bumping the idle speed a bit) and will be forced toward the target idle RPM.

    Name:  IAC Gear Kick.jpg
Views: 148
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    https://beta-static.photobucket.com/...080&fit=bounds (Advanced 1D/2D Table For In-Gear Idle Control)

    If it was done the other way using the Idle Spark control, would you then need to increase the P & D Terms?
    Leave the Idle Spark control enabled either way. P & D Terms of 30 & 50, or 40 & 60 are typical values.

    Originally Posted by Danny Cabral
    Park/Neutral Input − '87-'93 Ford Fox Mustangs, Automatic Transmission (preferably not for TFI ignition):
    For reference: http://www.fuelinjectedford.com/file...ng_1988-22.gif ('87-'93 Ford Mustang 5.0L SEFI Start/Ignition Wiring Diagram)
    There's a CIS (clutch interrupt switch) jumper wire connector located above the brake pedal, laying on the steering column mounting bracket. The chassis harness side of this connector has two Red/Light Blue wires (neutral safety switch & TFI ignition module) on one terminal, and one Red/Light Blue wire on the other (starter relay). This jumper harness/connector is easily routed to the driver's side kick panel, which is easily removed with one Phillips screw and one plastic push pin (LINK).

    Also behind the kick panel is a 4-wire harness routed down to the transmission. Two wires (Purple/Orange & Black/Pink) for the reverse lights, and two wires (White/Pink & Red/Light Blue) for the NSS (neutral safety switch). The White/Pink is the +12V wire from the Start position on the ignition switch, to the NSS. The Red/Light Blue wire is the return from the NSS, to the aforementioned CIS jumper wire connector. The NSS is closed in Park & Neutral. The NSS, connector & its transmission wiring remains as-is. The Park/Neutral Input wiring modification is performed entirely behind the driver's side kick panel.

    This Park/Neutral Input requires the NSS converted to a Ground circuit with a typical 4-pin automotive relay LINK/LINK. (If using a 5-pin relay, terminal #87A isn't used.) So working only from the removed driver's side kick panel, locate the White/Pink +12V Start wire routed to the NSS. In a suitable location, cut the White/Pink wire. The +12V end of the White/Pink wire (from ignition switch) connects to relay terminals #86 & #30. (Relay terminals #86 & #30 can be connected with a short jumper wire, so there's only three wires actually routed to the 4-pin relay.) The NSS end of the White/Pink wire is simply grounded to the body with an eyelet crimp connector.

    The CIS jumper wire connector can be unplugged and modified on a workbench. Cut the Red/Light Blue jumper wire loop in half to access both sides of the connector/circuit with butt crimp connectors. Orientate the CIS jumper wire connector to correspond with the two Red/Light Blue wires on the chassis harness side of the CIS connector. This cut CIS jumper wire connects to relay terminal #85. The other cut CIS jumper wire connects to relay terminal #87, which powers the starter relay. The 4-pin automotive relay can be wire tied to the harnesses behind the driver's side kick panel, so the additional relay wiring is very short.

    The actual Park/Neutral Input wire to the Holley EFI ECU is that 2nd Red/Light Blue wire routed to the TFI ignition module. (FYI: If TFI ignition must be retained, then cut & splice this 2nd Red/Light Blue TFI wire onto the other single Red/Light Blue starter relay wire to maintain +12V Start activation.) This 2nd Red/Light Blue wire can be cut & tapped into anywhere along its run into the engine compartment (depending on how the Holley EFI system is installed). This is a Ground Type Input, so program it accordingly in the Holley EFI software (Inputs/Outputs ICF & Pin Map). It's Grounded in Park & Neutral, so program any custom I/O (Switched Input Trigger) or Advanced ICF 1D/2D Table (Switched Enable - Activate when Park/Neutral Input is Disabled) properly.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/3000 RPM converter, FPP aluminum driveshaft, FPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 MT tires.

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