SKU: 5270546285

Holley HP EFI ECU and Harness Kits 550-604

Sale price$1237.47 Regular price$1374.97
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Ships within 48 hours · Estimated delivery Jul 18 - Jul 23

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Description

Holley HP EFI ECU and Harness Kits 550-604MPFI HP ECU AND HARNESS KIT Looking for a plug and play alternative for your stock or built late model factory EFI engine? How about a replacement ECU for your older Holley C950? Holley has you covered. HP EFI ECU and harness kits are designed to be used with popular factory EFI engines as an alternative to the factory ECU and harness or as a replacement for your C950 ECU. The HP allows you to accurately control the fuel and ignition of your engine

MPFI HP ECU AND HARNESS KIT

Looking for a plug and play alternative for your stock or built late model factory EFI engine? How about a replacement ECU for your older Holley C950? Holley has you covered. HP EFI ECU and harness kits are designed to be used with popular factory EFI engines as an alternative to the factory ECU and harness or as a replacement for your C950 ECU. The HP allows you to accurately control the fuel and ignition of your engine along with additional controls for nitrous, boost or water meth.

Features:

  • Optional 5.7” full-color touchscreen LCD allows easy on-the-fly tuning, data-logging or can be used as an easy to see graphical gauge panel
  • Eight sequentially driven 8:2 peak and hold injector drivers, capable of driving up to 16 low or high impedance injectors as a standard feature. Multiple staged injector strategies
  • Eight channel Distributorless Ignition (DIS)outputs capable of directly driving “Smart” ignition coils or Holley DIS coils. Will drive 2 wire coils with the addition of PN 554-112 high current coil driver module
  • Integrated single channel wide band oxygen sensor control. Works with NTK or Bosch sensors
  • Internal data-logging standard with a huge 2GB of memory
  • 4 Stage progressive nitrous control
  • Turbo boost control
  • Integrated water/methanol injection control
  • Self-tuning fuel table strategy greatly simplifies tuning process
  • Individual cylinder fuel and spark control allows you to unlock your engine’s potential
  • Works with 4, 6, 8 cylinder engines
  • Unique lb/hr based fueling strategy greatly simplifies and commonizes tuning
  • Advanced idle, closed loop, and enrichment strategies allow for very stable operation
  • ECU is fully potted and can be mounted in the engine compartment or interior
  • Sealed automotive and marine grade connectors
  • Allows for use of common OEM sensors as well as customer sensor calibration input
  • Ignition Plug and Play with GM HEI, Ford TFI, magnetic and hall effect trigger, and other ignition systems. New Plug and Play applications in process. Custom settings can be configured to allow many other applications
  • 1-5 Bar MAP sensor capability
  • Two channel knock control sensor Inputs for both one or two wire knock sensors
  • Dedicated fuel and oil pressure inputs
  • Controls both stepper and PWM Idle Air Control (IAC) motors
  • Speed density, Alpha-N, or combination fueling strategies
  • 4 Programmable high or low Pulse Width Modulated (PWM) outputs and 4 fully configurable inputs can be configured for use
  • 4 Stage nitrous oxide control
  • Fully featured nitrous control eliminates the need for a separate nitrous controller device
  • Can be configured “Wet” or “Dry” with closed loop feedback
  • Progressive control based on time, RPM, or boost, requires part # 554-111
  • Lean or rich safety cutoff
  • Full timing retard/control configurability per stage based on RPM or time
  • Integrated Water/Methanol injection control
  • Uses Holley Water/Meth solenoids specially designed and calibrated for use with this EFI system to allow the user to enter Water/Meth flow as a percentage of fuel injector flow for Water/Meth tuning precision unmatched in the industry

Application

  • Universal

Specs

Brand Holley EFI
Emission Code 3
Ignition Type Coil - (No Timing Control)
Ford TFI
GM HEI Small Cap
Holley Dual Sync Distributor
Injector Connector Jetronic / Minitimer (Bosch)
Product Type HP EFI Kit
Part Number 550-604
Shipping Notes
  • Free Standard Shipping on $100+ Orders to the USA.
  • Except Preorder products are shipped in 48 hours.
  • Delivery to the USA:
  1. Standard Shipping : 3-10 business days
  • If time is of the essence, please consider selecting expedited delivery for faster service.
Exchange/Return Notes
  • We offer a 30-day return/exchange service after receiving.
  • Final sale items are not eligible for returns or exchanges.
  • To process your return/exchange, please contact us at [email protected]
  • Please click here for more details>>> Return & Exchange Policy
SKU: 5270546285

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Reviewed in the United States on April 22, 2026
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Reviewed in the United States on March 14, 2026
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Phoenix, US
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Size: 11, Color: Optic White/Optic White
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Reviewed in the United States on February 18, 2026
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Jimmy
Carnegie, US
★★★★★ 5
Takes a Licking and Keeps on Ticking
Color: Green/Black
I love this watch despite the fact that it is really a toy. I love the look of the watch, I love how lite the weight of the watch is on my wrist, and it really does keep good time if you manage the solar charge properly. Other than looking cool on your wrist, this watch has absolutely no functions other than time keeping. The black plastic bezel is molded into the case and does not turn, so don't plan on using that. The watch has no light, the dial numbers are non-luminous and the hands are very limited in terms of luminosity. No buttons. All you can do is adjust the time and date by pulling out what used to be a winding stem in the good old days. The small tag on the strap with Geographic coordinates shown on it indicate the location of the old Timex manufacturing facility (SW of Waterbury, CT). I have a nice ledge at my bedroom window and it gets good western sun for a good part of the day regardless of the time of year. On this ledge you will find a half dozen solar powered watches (mostly Casio) properly aligned to maximize the charge they may receive each day. Note that the description for this Timex watch specifically states that a lightbulb won't charge this watch. You need direct sunlight for several hours if you want to get more than a 3-week charge into this watch. So, I'll leave you with a couple of tips, my friends; 1.) If you are looking for a first watch to give your outdoorsy oriented Son or Daughter, then give them this one. Why? Because it is cool looking, fairly well built, and it actually works, 2.) After you receive your Timex watch, be sure to keep the display mount it is packaged with. It makes a great fixture to mount your watch on for charging and allows you to maximize the position of the solar cells on the dial so that you can optimize charging time. Have Fun! Jimmy
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Reviewed in the United States on February 28, 2026
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Nuka Shroom Soup
Lowell, US
★★★★★ 5
Excellent value, flawless performance for well over a year and no signs of quitting.
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Excellent value, had this for well over a year and it still keeps perfect time, still water resistant. No worries about having to change batteries. Owned a fancy expensive (battery) watch once and the dept. store repair intentionally sabotaged the watch in the hopes I would purchase another from them. Yeah, good luck with that, lost my business forever. This is the 21st century, cell phones are the new time pieces, but solar is totally reliable and Timex makes it happen. Holds a charge for many months, although I prop it in a bright window for a few days every few months or so just to make sure the cells are always fully charged, although it's probably unnecessary, just being over cautious. I haven't actually experienced this watch ever running out of power even after months of use. Damn impressive, as it should be.
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