Holley's Wet Nitrous System - Wet Scream

Holley's new NOSzle wet-nitrous kit (PN 08100NOS) is made specifically for '96-through-present Mustang 4.6 Two-Valve applications. The kit is shipped with two sets of jets rated for either a 100 or 125hp shot over stock. Increasing jet size for anything beyond this power level would best be accompanied by fuel system, and possibly internal engine, upgrades.

Horse Sense: A dry-nitrous kit supplies only nitrous and relies on the factory fuel system for any additional fuel, while a wet kit contains the hardware to supply both nitrous and supplementary fuel.

If you like your strength to flow from a bottle, we have good news. The giggle gas gnomes at the Nitrous Oxide Systems division of Holley Performance have introduced their NOSzle wet nitrous kits. One is specifically engineered for '96-through-present 4.6 Two-Valve Mustangs and will be shipped with two full sets of nitrous and fuel jets for your choice of a claimed power boost of either 100 hp or 125 hp. The primary distinction of this revolutionary design is that it feeds both nitrous and extra fuel almost directly to the combustion chambers without requiring the intake modifications of a typical race-fogger system. This design, claims Holley, also avoids the backfire threat caused by the poor mixture distribution and fuel puddling of wet systems that simply add fuel at or near the throttle body.

The system is named for these patent-pending anodized billet aluminum NOSzles, which sandwich between each fuel injector and the intake manifold to meter stock injector-supplied fuel, supplementary fuel, and nitrous to the stock location. The extra gasoline and nitrous flow through axial passages surrounding the central outlet for the factory injector's fuel. This arrangement is said to ensure proper nitrous and fuel distribution, optimum fuel atomization, and ensure proper combustion.

On this topic of backfires and other untimely explosions, the NOSzle system encompasses a number of electronic safeguards designed to ensure a long and peaceful relationship with your engine. As with most nitrous systems, it is shipped with master arming and wide-open-throttle switches, so that it can only engage when switched on and with the gas pedal nailed to the floorboard. But it also features a black box that limits operation to a window between 2,600 and 6,000 rpm. The reasons for this? Nitrous injected at too low an rpm can be damaging, and on the other end of the rev scale, if N2O flow isn't shut off before the factory rev limiter begins to cut back on fuel delivery, it can be even more destructive. Lastly, a pressure switch is incorporated, preventing system engagement if fuel pressure drops below a preset limit. That, an explicit instruc-tion manual, and color-coded and clearly labeled hardware fittings make the system about as idiot-proof as possible.

Going beyond the specific Mustang kit for a moment, Holley says the basic NOSzle design lends itself to being configurable as either a one-stage wet system of up to 500 hp or a two-stage dry system for up to 1,000 hp, and the NOSzle fits all fuel injector brands.

Underhood installation begins by disconnecting the negative battery cable and relieving fuel pressure via the Schrader valve on the passenger-side fuel rail. Then, the airbox-to-throttle-body duct is removed, and the fuel line, along with various electrical harnesses and vacuum lines, is disconnected, as detailed in the kit's well-illustrated instruction booklet.

Sean Hyland Motorsport received one of the first available production Mustang kits and promptly installed it on one of its in-house '01 GTs, with us peering over the shoulder of technician Mike Lester. Installation was fairly straightforward, and the result was peak-to-peak rear-wheel power gains of 91.5 hp and 144.6 lb-ft on this otherwise completely stock modular. Check out our dyno sidebar for the complete power story.

On The Dyno
Our test vehicle was a Sean Hyland Motorsport show car, a prettied-up '01 GT that was mechanically bone-stock right down to its exhaust system. In this form it produced 221 hp and 269 lb-ft on SHM's Dynojet. Afterward, these peaks had jumped to more than 312 hp and 414 lb-ft. The system seemed to particularly favor the 3,500-rpm mark, where power was up by 101.9 hp and no less than 153 lb-ft.

We had to leave before the car was buttoned up for the street, but Sean Hyland reports that it drove like a supercharged car, with a smooth and progressive power delivery, and a fat and juicy torque curve.

The kit's preassembled, 16-port distribution block routes supplementary fuel from a Cheater solenoid and nitrous from a Super Pro Shot N2O solenoid to each NOSzle. Solenoid actuation is limited not only by a wide-open-throttle switch, but also by an rpm window switch, which allows nitrous flow only between two preset rpm points.

The upper intake/throttle-body assembly is unbolted after disconnecting the throttle cable, the speed-control actuator, and the return spring.

The eight fuel-injector electrical harnesses are disconnected, and the fuel rail is unbolted and removed as an assembly, complete with injectors. Before removing injectors, it's a good idea to blow any dirt clear of the intake's injector bosses, as any loose grit can end up right in the cylinder.