The following sensors are included:TPS - IAC - MAP - CTS - MAT - Wideband O2ECU is certified to ISO 8846, SAE J1171 And United States Coast Guard Requirements for Ignition Protection And Fire Resistance. Holley HP EFI systems are equipped with 4 programmable inputs and 4 programmable outputs that are ideal for most vehicles with a single power adder. This feature allows the user to configure the system to support a wide range of controls including boost control, progressive nitrous, water/meth injection, speed inputs, fuel pump control, AC inputs, timing retard inputs and various other uses. When selecting an ECU, users need to ensure their planned controls can be run with the 4 inputs and 4 outputs as certain combinations may use more I/Os than are available. If more I/Os are required, users should choose the Dominator VMS.
Software and firmware updates can be downloaded here for free.

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Holley 550-500 Details

Do you have a Mopar, Ford or other type engine you want to install multi-port fuel injection on? No, problem, the Holley HP universal retrofit EFI kits are designed to be used with any V-8 intake manifold. The kit comes with injector bungs and un-machined fuel rails so you can modify to fit any single plane 4bbl intake manifold. The HP universal retrofit kits also come with the necessary wiring, ECU, sensors and throttle body. Just select the fuel pump and injectors of choice and you are off and running.

Features:

NEW V2 SOFTWARE FEATURES

“Quick Start” ignition and fueling strategy for LS x Engines

Data Logger. Scalable axes, Smoothing, Multiple graph view ability, Pre-defined notes fields and many more

Strip Chart Real-Time Data Viewer

Integrated Boost Control - Boost vs Time, Boost vs Gear (Time or RPM), Boost vs RPM, Boost vs Speed, Launch control. Boost launch builder, Over-boost safeties, Boost scramble

Traction Control - Power reduction via timing, nitrous percentage or boost (Requires Davis Technologies Holley Module)

“Quick Start” fueling for all engines

Option for VE based fueling strategy

Fuel Map and Learn Function Smoothing

Configurable User Password Protection

Fully Configurable lap top Gauge Panel

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

Plug and Play control of factory GM 24x and 58x LSx engines

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 24x and 58x LSx engines, 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 Injectors flow for Water/Meth tu

Rebates

Holley Fuel Up Spring Savings Event 2026

Save 10% instantly on select products across the Holley family of performance brands during the annual Holley Fuel Up Spring Savings Event 2026. Instant rebate period runs from March 30, 2026 through April 19, 2026.

Guides & Documents

Choosing an Electronic Fuel Injection Retrofit for Your Street Rod or Muscle Car

Fuel Injection Systems Buyers Guide (425550500)

Fuel Injection Systems Installation Instructions (425550500)

CARB Warning

For use on pre-1966 vehicles only

Emissions warning: this part only legal for sale or use in California if installed in vehicles model-year 1965 or older; motorcycles model-year 1977 or older; or off-highway recreational vehicles (such as off-road motorcycles and all-terrain vehicles) model-year 1996 and older. ++any other use renders the vehicle tampered and not legal for use on California public highways (any public street or roadway, public dirt road, public park, or publicly maintained right of way open to the use of the public for vehicular travel). Violations subject to $37,500 penalty per violation per vehicle, revocation of registration, loss of use on California public right of ways, and proof of correction for tampering there are similar restrictions and penalties under federal law and the laws of all other states with penalties under federal law of up to approximately $45,268 per tampered vehicle and/or engine.

CARB warning

Holley 550-500 Specifications

KEY SPECS
MFG. Part #	550-500
Brand	Holley

GENERAL
GTIN Code	090127666883

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