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Holley Sniper EFI

Sniper EFI Stealth 4500 - Shiny Finish

Sniper EFI Stealth 4500 - 8 Injector - 800-1500 HP

Part # 550-841
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Estimated shipping date: 12/27/2021
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Introducing the Sniper Stealth 4500 EFI System! Wanting to convert your Dragster or Pro-street vehicle to Fuel Injection? Look no further! The Sniper Stealth 4500 EFI system from Holley features 8, 100LB/HR Fuel Injectors capable of supporting 800 to 1500 HP naturally aspirated, or 800-1250 HP on forced induction applications. The Sniper Stealth 4500 also features multiple Input and Output options for sensor inputs and switched outputs to control external relays. This system also comes with a USB to CAN tuning cable and free downloadable Sniper EFI Software give you unlimited control of your engine


  • Supports up to 1500 HP Naturally Aspirated or 1250 HP Forced Induction with Eight 100 Lb/Hr Injectors
  • Compatible with Draw through or Blow through forced induction applications
  • 2.125” Throttle Plates, Flow 1440 CFM for large cubic inch engines
  • 2.5Bar MAP Sensor
  • Integrated ignition timing control
  • Programmable launch control via 2-step and timing retard. Both can be triggered by a trans-brake input
  • Gen 3 Ultra Dominator Style 4 Bolt Air Cleaner Flange
  • -8AN Fuel Inlets
  • High Resolution Full Color Touchscreen for Initial Setup, Tuning, and Gauge Displays
  • Simple Calibration Wizard (Answer a few questions about your engine and it creates the base map, then starts tuning on its own!) - NO laptop required
  • Self-tuning ECU means you don’t have to be a computer/tuning wiz to have EFI!
  • The included Genuine Bosch LSU 4.9 Wideband Oxygen Sensor provides realtime Fuel Map Learn
  • Built-in Single Stage Wet or Dry progressive nitrous control
  • Three Programmable 0-5V Sensor Inputs for Oil/Fuel/Dome or Nitrous Pressure or other critical information
  • Six Programmable Ground Outputs, Five programmable ground inputs. These can be used to trigger or control external devices such as nitrous solenoids, boost control solenoids. Or to provide the ECU with an Input to turn on function such as an ignition timi
  • One +5v Reference Output - +5V Power Supply for 0-5v Sensors, One Sensor Ground – Ground supply for 0-5v Sensors
  • Throttle body mounted ECU – no extra boxes to mount
  • Only 4 Wiring Connections Required! (Battery +, Battery - , Switched Ignition & RPM)
  • Required external fuel pressure regulator, 12-848 is recommended
  • Customizable secondary fuel pump output (TPS, RPM or Boost enabled)
  • User friendly Boost Control with handheld adjustability
  • Free Software included comprehensive datalogging tool to help you maximize the performance of your engine
  • Real-time datalogging to the included 3.5” Touch Screen, allows you to save information to the SD card without needing a communication cable
  • Programmable Target Air Fuel Ratios per Boost level
  • Advanced boost control available via free Sniper EFI tuning software, including Boost vs RPM and Boost vs Time
  • OEM Style TPS/IAC, for years of dependable service
  • Included clamp-on oxygen sensor kit ensures a leak free oxygen sensor installation, with Stainless Steel T-Bolt clamps and a Stainless Steel (Weldable) oxygen sensor flange
  • Patent Pending
United States Coast Guard Approved
Certified to ISO 8846, SAE J1171 Requirements
Brand Holley Sniper EFI
Coast Guard ApprovedYes
Emission Code3
Flange Size4500
Flange Style4500
Fuel Pressure58.5 PSI
Injector Size100 lb/hr @ 58.5 PSI
Inlet / Outlet Size8AN
MAP Sensor2.5Bar
Max Horsepower Rating1250 Forced Induction
1500 Naturally Aspirated
Product TypeSniper EFI 4500
Throttle Bore2.125 inch
Part Number550-841

This part is legal for sale and use on Uncontrolled (Non-Emissions Controlled) Vehicles and Racing Use Only Vehicles.

The following vehicles are considered Uncontrolled (Non-Emissions Controlled) Vehicles:

  • 1965 and older U.S. manufactured California Certified vehicles
  • 1967 and older U.S. manufactured Federally Certified vehicles
  • 1967 and older Foreign manufactured vehicle

The following vehicles are considered Racing Use Only Vehicles:

  • Racing Use Only Vehicles are vehicles that are used exclusively for competition and that are not registered and that may never be used on the street

WARNING: It is against the law to install this part on an Emissions Controlled Vehicle

The following vehicles are considered Emissions Controlled Vehicles:

  • 1966 and newer U.S. manufactured California Certified vehicles
  • 1968 and newer U.S. manufactured Federally Certified vehicles
  • 1968 and newer Foreign manufactured vehicle
Not for use with engines producing less than 800 horsepower Gasoline Only Use of leaded race fuels may shorten the service life of the WBO2 sensor

Have a question about this product?

  • Question

    A couple of years ago I was looking at Fi-Tech 1200hp set up but just wasn''t sold on it working well on my set up. I talked to some fellow Drag Week folks and the general thought was my junk would not be happy with the 4 injector Sniper so I waited on the 8 to come out BUT I do run a 4500 with 2" spacer now with a 1050 and am happy, BUT the start up on cold days is HORRIBLE. I have had a 850 mech. sec. Demon, 950 cfm Quick Fuel, a used 1050 3-circuit and now a factory reconditioned 1050 2-circuit on the truck. It LOVES the 1050 and runs low 12''s high 11''s @ 108 - 112. Do you recommend the 4150 sniper or the 4500 sniper for my set up. (I also plan to spray a 150 shot in the future) Have you done any testing on the street with the 4500. Sure wish Drag Week would get back to Bowling Green. I LOVED that track.

    By Jesse M. on May 26, 2018

    The 8 Injector 4150 Super Sniper would be a better application match to your engine combination than the 4500. The 4500 is 1440 CFM and really isn''t well suited on engines that produce under 800HP. Both systems have dry and wet progressive or non progressive nitrous control.
  • Question

    I Have a Merlin 2 BBC 540. It is hard to start. Both carbs that I have used do not have a choke circuit. My engine is around 700+ HP. I was wondering if I installed the Sniper EFI if that would make it any better on starting? any help would be much appreciated !!! Thank you

    By Johnny D. on January 4, 2020

    Without knowing what is causing your hard start, I cannot say if the EFI system will make your startup process easier. What I can say is that you can easily add or remove more fuel during startup with the handheld. Additionally, the EFI system has data logging capabilities to help you diagnose the issue. Generally speaking in regard to high performance engines, an EFI combo will start up more consistently than a carbureted combo.
  • Question

    Ok on the new sniper 4500 which fuel pump do you recommend? engine puts out 800 hp with a 300 shot on top of that, going to run Q16, I have a Atech account and plan on making a purchase as soon as I can, thanks, keith

    By Keith E. on May 17, 2018

    The 12-1500 would be the recommend fuel pump for that horsepower range. If you have a fuel cell we have some drop in fuel cell EFI conversion kits also that you might be interested in.
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Some parts are not legal for use in California or other states with similar regulations.