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Thread: Output Wiring & Configuration Questions

  1. #1

    Default Output Wiring & Configuration Questions

    I'm working on building the wiring harness for an install in a car that will have all new wiring from scratch. I'm familiar with a number of other OEM and aftermarket EFI systems, but new to Holley. Lots of good info here reading through the past posts, but I few things that don't seem to be covered.

    The system I'm using was bought before the switch to the touchscreen controller, so I'm working off of both the older and newer instructions. The older instructions have the diagram of the harness, the new ones do not.

    The older set of instructions show P1-A2 as "Fuel pump relay out (10A MAX)", which is used to trigger a relay that powers the injectors and fuel pump through a 20A fuse. The instructions say that the fuel pump output of the relay (shared with the injectors) shouldn't be used for more than 15 amps. That would imply that the draw for the injectors is 5A Max. My questions:

    1) Even though it's initially setup to run a relay and only has a 22 AWG wire, if the wiring is upsized is that output really capable of 10A? My thought is that the P1-A2 output could be better used for something that needs more current, but less than 10A, and one of the different, lower current outputs could be used for the fuel pump/injector relay.

    2. From what I've read, if I'm using the laptop software (which I plan to do from the start) I have a lot more flexibility with the outputs. For example, I'd like to have an output for an electric water pump (through a relay of course) that doesn't run while cranking, so I can set that to only go on over some RPM that is just below my idle RPM. Does P1A2 have that same flexibility, or is that strictly a fuel pump output with limited configuration?

  2. #2
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    1) All outputs are low current. Do not use them to power anything with a high current draw, always use a relay.
    2) P1-A2 is controlled by the Fuel Pump Prime, under Engine parameters.
    Download the program from the Holley site and look it over. Your Terminator ECU is a HP ECU, it just has a different sticker on it. I attached a wiring PDF, just in case you don't have this one. I moved my ECU to the trunk and rewired it.
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  3. #3
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    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS T/W 11R 205 heads, 232°-244° duration/.623" lift/114° LSA camshaft, 12:1 C/R, TFS R-Series FTI ported intake, BBK 80mm T/B, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 200A 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, -6AN fuel system plumbing, Walbro 255 LPH pump, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/3000 RPM converter, B&M Hammer shifter, 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 M/T Street Comp tires.

  4. #4

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    The harness that came with mine, and is documented in the older instructions (pre-touchscreen, rev 8), isn't the same as the 4BBL TBI that's in the the wiring manual. Mine only has a 3-pin I/O connector (Outputs 1, 3, and 4), no knock sensor, no oil pressure, and uses an inline connector that puts everything for the TB on a sub-harness (MAP/IAC/MAT/TPS/Injectors).

    The harness in the documentation for the current Terminator (rev 10) looks the same as mine, but that version doesn't actually have a wiring diagram in it anymore. It seems that the harness that is depicted in the wiring manual is for if you bought a HP or other stand-alone system, so it's more complete. Pinouts are the same, of course.

    One of the things I'm trying to accomplish is to reduce the electrical load during and right after starting. I think I have a plan to accomplish this, but would appreciate a sanity check:

    The P1-A2 (fuel pump) output will run two relays; one powers the fuel pump/injectors, the other runs the coil. These are active during ignition & cranking. For this output I'm limited to the "Fuel System" configuration parameters (basically just fuel pump prime).

    Two outputs will be used to run a 2-speed fan. By using the advanced configuration instead of the canned one, I can make the fans not run unless the engine is running, and put a delay on it of a few seconds after startup to allow the electrical system to recover from starting.

    One output will be used to run an electric water pump. This will be setup similar to the fans so that it doesn't run unless the engine is running, with a shorter delay so they don't both (pump and fan) go on at once if started hot.

    Questions:
    After the Fuel Pump Prime, what actually triggers the fuel pump output to come back on? As soon as it sees RPM?

    In the built-in fan controls, does it run the fans during crank? From what I can tell it will run the fans with key-on/engine-off, didn't know if it had any logic to detect cranking and turn them off. Obviously with the advanced configuration I can easily do this.

    On a different tangent. It appears that even if you have a fuel pressure sensor installed, it doesn't use that for feedback and runs off of the "Actual System Pressure" in the config? I have a somewhat cramped car and engine compartment, so I'd prefer to run a semi-returnless system by putting a regulator back at the tank. Since that extends the lines and pressure drop between the regulator and the injectors, it'll vary more with fuel flow. With a fuel pressure sensor you can base the fueling off of actual pressure, but I don't know if this can be done with the Holley EFI? The other advantage is that I wouldn't have to use a vacuum reference for the regulator, it could be fixed absolute pressure.

  5. #5
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    Quote Originally Posted by Jeff F View Post
    After the Fuel Pump Prime, what actually triggers the fuel pump output to come back on? As soon as it sees RPM?
    Yes.

    In the built-in fan controls, does it run the fans during crank?
    Yes, however, read section #2: https://forums.holley.com/showthread...Fan-Holley-EFI (Electric Cooling Fan Wiring - Holley EFI)

    On a different tangent. It appears that even if you have a fuel pressure sensor installed, it doesn't use that for feedback and runs off of the "Actual System Pressure" in the config?
    http://forums.holley.com/showthread....ents-Read-This (Initial Checks & Adjustments - Read Step #2)

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    Have you looked into PWM for the fans, it's a lot easier on the alternator. I used three separate relays for the fuel pump, injectors & coils. You want the highest volts going to the fuel pump. Voltage drop at the fuel pump can cause issues. The alternator post has the highest voltage. Take your power for the fuel pump from there.

  7. #7

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    Quote Originally Posted by Danny Cabral View Post
    http://forums.holley.com/showthread....ents-Read-This (Initial Checks & Adjustments - Read Step #2)
    So that confirms that there's no pressure feedback, and implies that there's no way to do this? I didn't know if like the fan controls, there was a basic function, and more advanced function available or something hidden in the fuel menus. Fixed pressure actually isn't all that hard to do with MAP, you just have to scale the Base Fuel Table to account for it. Probably a better subject for a different post.

    Quote Originally Posted by 81 TransAm View Post
    Have you looked into PWM for the fans, it's a lot easier on the alternator. ... Voltage drop at the fuel pump can cause issues.
    Hadn't looked into PWM for the fans, but now I have! Will definitely consider it. I'll be using a Walbro 255 LPH fuel pump that pulls less than 10 amps, and it's way more pump than I need, so I don't have much to worry about there.

  8. #8

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    Fuel pressure feedback and running fixed (non-vacuum referenced) fuel pressure regulator actually seems quite easy to do with a 2D Table (Advanced ICF). Even with a vacuum referenced fuel pressure regulator, it seems like it'd be a good idea to do anyway, just in case your regulator isn't always exactly 1:1 with manifold vacuum or the base setting drifts.

    This is a table for use with a 50 psi base setting. I have a spreadsheet that can make one for any base fuel pressure/fuel pressure range/MAP range.
    Click image for larger version. 

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  9. #9
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    I run a fixed fuel pressure with my regulator and return in the fuel tank. I do not run an Advanced ICF table to Offset Fuel Flow. The Holley ECU has no problems running it this way. Don't over think it.

  10. #10

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    Quote Originally Posted by 81 TransAm View Post
    Don't over think it.
    I'm an engineer, it's what I do. I don't doubt that with the self-tuning/Learning it will eventually figure it out, but a couple of advantages to doing this:
    1. It'll make the initial calibration closer to correct.
    2. It'll make any areas of the tables that don't get covered during self-tuning closer to correct.
    3. It'll make the VE% or Fuel Flow tables sensible if you're trying to look at them. Otherwise, the VE% and Fuel Flow numbers will be right at very low vacuum/high MAP, but skewed everywhere else.

    On that last point, when I load in one of the Base Fuel Tables (I have a file I'm using just to play around with, and loaded "TBI, up to 409 ci, cam stock - 215° @ .050"), it seems that it only works if you load it with speed density selected? If I load it while I have "VE Based" selected it loads the Fuel Flow numbers into the VE% Table, which makes for a goofy looking VE% Table.

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