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Ships within 48 hours · Estimated delivery Jul 11 - Jul 16
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Description
HP EFI ECU & Harness Kits - 550-601NOverview: 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
Overview:
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:
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 injector flow for Water/Meth tuning precision unmatched in the industry
Application:
| Year | Make | Model | Submodel | Engine Size |
|---|---|---|---|---|
| Universal |
Specs:
| Brand | Holley EFI |
|---|---|
| Emission Code | 3 |
| Ignition Type | Coil - (No Timing Control) |
| Ignition Type | GM HEI Small Cap |
| Ignition Type | Holley Dual Sync Distributor |
| Injector Connector | Jetronic / Minitimer (Bosch) |
| Product Type | HP EFI Kit |
Shipping Notes
- Free Standard Shipping on $100+ Orders to the USA.
- Except Preorder products are shipped in 48 hours.
- Delivery to the USA:
- 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
4.2 ★★★★★
Based on 1989 reviews
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Product Reviews
★★★★★ 5
Give the green light to the green oil.
Size: 5 Liter, Style: 1 Pack, Configuration: 0W-20
Great oil. I've used Liqui-Molly in all my vehicles and it always performs. Theres very little burn off between changes and I noticed cleaner, quieter engine. I've used this in many different car brands, it never disappoints.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on May 17, 2026
★★★★★ 5
Car Runs Smooth, Less Friction, and Improved Performance at Start Up and Underload.
Size: 5 Liter, Style: 1 Pack, Configuration: 0W-20
I kept hearing things about this oil from a few friends that work on cars and from my "go-to" mechanic. I was previously using Mobile 1 0w-20 on my 2024 4Runner and my wife's 2025 Outback Onyx, and this time around I decided to try it on both cars as they needed an oil change. So far I am happy with the change for both cars. This is good oil quality, smooth engine running, and noticeable oil lubrication at cold start. I am getting better MPGs mileage on both cars. Also noticeable engine is running with smoother. I had to lower my car window to check that my 4runner was on as it was quiet. I will update my review after a second oil change with this oil on both cars.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on December 12, 2025
★★★★★ 5
Liquid Gold for Your Engine! 🛢️💥
Size: 1 Liter, Style: 1 Pack, Configuration: 5W-40
I didn’t think I’d get excited about motor oil, but here we are—Liqui Moly Molygen 5W-40 has officially made me feel like a car enthusiast. If you're serious about keeping your engine purring like a kitten, this stuff is like giving it a spa day with an energy drink chaser.
First off, this isn’t just any old motor oil—it’s high-tech motor oil. We’re talking German engineering at its finest. The neon green color? Oh yeah, it looks as cool as it sounds, and trust me, when you see that green oil running through your engine, you know you're in for some serious performance. 🟢💯
Why do I love it?
Engine protection: This oil is like a security blanket for your engine. It reduces friction like a champ, so parts glide smoothly, which means less wear and tear. Translation: your engine will thank you with better performance and a longer life.
Fuel efficiency: You’re not just getting a smoother ride; you’re also saving some bucks at the pump. The way this oil cuts down on friction helps with fuel economy. It’s like the gift that keeps on giving.
Cold start-ups? No problem. Whether you’re dealing with a chilly morning or scorching summer, this oil handles temperature extremes like a boss. It maintains its viscosity so your engine stays protected regardless of the weather.
And did I mention the Molygen technology? It’s not just a fancy name—this oil has additives that coat your engine in a protective film, keeping it running smooth and reducing the risk of damage, even during high-stress drives.
Final thought: If you're looking for an oil that’s as serious about your car’s performance as you are, the Liqui Moly Molygen 5W-40 is it. Your engine will run smoother, quieter, and stronger, and you’ll feel like you’ve just upgraded your car’s lifeblood. 🚗💨 Plus, that neon green color? Total conversation starter at the garage. 😉
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on September 23, 2024
★★★★★ 5
Near OEM quality at 1/4 cost
Near OEM performance at 25% of the cost! Bosch Quality replaced NGKs/Toyota OEMs. Great value and now the engine is running smoothly! I have seen a slight improvement in my mpg @1mpg overall in mixed driving conditions.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on April 22, 2026
★★★★★ 5
Very Expensive
Had one cylinder misfiring so replaced coil and spark plug. Runs fine now, but old plug looked shot after only 5 months so I think the coil was the problem. Really good plug so far but very expensive.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on February 12, 2026
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