Ryan Manson of Clampdown Competition handled our Holley Sniper 2 EFI installation. While the installation was straightforward, success lies in the details. This is especially true when converting from Sniper 1 to Sniper 2; don’t skip any steps, and don’t make any assumptions.
Technology advances in leaps and bounds these days. With a new smartphone coming out every week, it seems that features so advanced in modern vehicles were unheard of only a few short years ago. So, it should come as no surprise when a company like Holley announces a new system that modernizes what’s been available for over a decade—and that system is the Holley Sniper 2 EFI. Designed as an upgraded replacement for the original Sniper system, the Sniper 2 features upgrades in many of its electronic components with built-in features and factory settings based on 10-plus years of developmental data from the original Sniper system.
The original Sniper EFI system on our Corvette has served us well, but we were excited to try the new Sniper 2. At first glance, we noticed some differences between the two that will need to be addressed during our retrofit.
While the Sniper 2 EFI system features many built-in upgrades, it really shines in the ecosystem of the Sniper family of components. Simple plug-and-play functionalities allow the Sniper 2 to directly connect, communicate, and control a variety of fuel and ignition components, even outputting information that can be displayed on a digital dash.
One of the features found on the original Sniper throttle bodies that is not on the Sniper 2 is the integrated fuel pressure regulator. For the Sniper 2 install, an external regulator will need to be added to the existing fuel system.
The installation of a Sniper 2 system is similar to that of other EFI systems, with the required high-pressure fuel pump, regulator, lines, and a handful of necessary wiring connections. On a carbureted vehicle, an EFI install can be slightly daunting, which is where Holley’s Sniper 2 ecosystem shines: it combines all the necessary components required to make the upgrade in one kit.
The new Sniper 2 EFI System (PN 550-511-3AE) is available with either a black or polished throttle body, capable of 800 cfm and providing enough air/fuel to support 650 hp naturally aspirated and 575 in a boosted application. The rear-exiting harness makes for a “stealth” installation, while the side-mounted inlet and outlet fuel fittings mean our current hardlines will need to be modified. Other less obvious features include the relocation of the ECU from the front of the throttle body on the Sniper to the side on the Sniper 2. At the same time, the ECU itself has been redesigned as a more robust unit with increased RFI shielding to help protect it from electronic interference, a common problem on older vehicle ignition systems, radios, and so on.
Our project Corvette already had an older Sniper throttle body installed, so the swap from that to the new Sniper 2 is about as easy as it can get since Holley offers an adapter harness that plugs the existing Sniper wiring harness into the new Sniper 2 throttle body, plug-and-play. We did have to modify the fuel lines at the throttle body since the original Sniper locates those on the rear while the Sniper 2 feeds from the side like a traditional 4150 4-bbl carb.
Since our Corvette was already equipped with a Sniper EFI system, adapting the Sniper 2 is a simple plug-and-play affair, utilizing this adapter harness from Holley (PN 558-489). For non-Sniper upgrades, wiring requirements are simple: 12V+, 12V- to battery, 12V+ ignition, fuel pump power, and rpm signal.
With the removal of the original Sniper system in the morning, by that afternoon, we were already up and running with the Sniper 2, making minute, on-the-fly adjustments on our first testdrive. After inputting only a few parameters into the handheld following the Sniper Wizard, it’s amazing how well the car ran with a simple base map tune. No doubt, as more miles are put on the car, the Sniper 2 system will continue to make changes to the fuel table and base map, further improving the driving experience.
When ordering a Sniper 2 system from Holley, you have many options. One of those options we chose was the addition of an EFI Bypass Fuel Pressure Regulator Kit, which included a length of 3/8-inch hose and clamps. This will ensure that Sniper 2 receives the required 60 psi of fuel pressure.
When it comes to programming and controlling the Sniper 2, once again, there are several options. We went with the base option of the tried-and-true 3.5-inch handheld touch screen, but there is also an option for a larger 5-inch handheld. A Bluetooth Module dongle can be added to allow the end user to access the Sniper 2 on their smartphone or similar device using Holley’s Sniper 2 app. The Sniper 2 can also support a standalone digital dash display, such as Holley EFI’s 6.86-inch Pro Dash (PN 553-117).
The Sniper 2 EFI throttle body features a 4150-style mounting flange, which means it can bolt to nearly any intake manifold that accepts that pattern. In addition to the more robust ECU, Holley upgraded the throttle position sensor on the Sniper 2 with a contactless unit, resulting in increased durability and reliability. Holley also revised the throttle linkage for an improved pedal feel while incorporating more kickdown mounting options for a myriad of transmissions.
Getting the throttle body plumbed using the existing fuel lines required a little rework, including mounting and plumbing the external fuel pressure regulator. Since the Corvette was already equipped with an EFI system, including a Sniper EFI fuel tank, adjusting the routing of the existing feed and return lines to the regulator and throttle body was a simple matter.
Holley has a vast line of retrofit EFI fuel tanks that come ready to go with an EFI-compatible fuel pump installed in the tank, making the upgrade to EFI super easy.
Holley offers a line of fuel pumps, like this In-Tank RetroFit Fuel Module (PN 12-132), for those who want to keep their original tank.
Installation of the Fuel Module is simply drilling a hole in the tank, measuring, adjusting the pickup depth, and dropping the unit in.
After loading a base map with information input into the handheld related to our engine setup, a quick turn of the ignition key finds the small-block roaring to life, with Holley’s Sniper 2 quickly going to work. After allowing the engine to warm up to operating temperature, it’s time to address the IAC position, which is too high at the moment.
To do so, the curb idle speed screw is turned until that IAC Pos percent number is between 2-10 percent, TPS is still at 0, and the engine idle speed is at the preset rpm.
Those parameters look good here, so it’s time for a testdrive!
Since our SBC is well past its break-in period, logging the miles was a simple matter. You will need to drive in all the popular everyday driving conditions, such as steady freeway speeds, acceleration, and stop-and-go around-town traffic. The more conditions you put the Sniper 2 in, the more it will learn and the better it will perform. We have 500 miles on our new EFI, and all seems to be running well.
