Dale Amy
July 1, 2002

Step By Step

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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.
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.
The NOSzle design atomizes fuel-injector fuel, nitrous, and enrichment fuel into a wide, low-inertia spray pattern aimed right at the intake valve. There is no spray bouncing back into the intake plenum that could cause cylinder-to-cylinder fueling variations.
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.
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.
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.
With their O-rings lubricated by a little fresh engine oil or equivalent, the eight NOSzles are gently seated into the injector bosses on the manifold. The “F” on the NOSzle indicates the supplementary fuel inlet, while the fitting labeled “N” is for nitrous.
The rail assembly can then be reinstalled with the injectors carefully inserted into the top of the NOSzles, but only after fitting the four supplied 3/4-inch aluminum spacers between the manifold and rail. These compensate at the attachment points for the height of the NOSzles.
To clear the heightened fuel rails, a 1/2-inch aluminum spacer (with gasket) goes between the upper and lower intakes, with another supplied for the forward jutting leg of the upper intake. By the way, it’s easiest to reconnect the EGR tube to the upper before inserting the spacer.
The kit includes a bracket to mount the solenoids/distribution block via the driver-side two bolts of the alternator upper support bracket. The smaller fuel solenoid goes to the front. This shot also shows the fuel rail and intake spacers in place with the upper intake bolted back down.
The fuel solenoid feeds the upper of the two distribution blocks, while the giggle gas is dispensed via the lower. In a departure from tradition, rather than rigid steel lines, the NOSzle kit uses 1/8-inch flexible poly lines that are extremely easy to work with and route. No sealant is necessary on the line’s AN fittings.
The fittings on the other ends of the 16 lines are color coded: red for fuel, blue for nitrous. Before threading them onto their respective marked NOSzle fittings, the appropriate fuel and N2O jets are slipped onto the lines. SHM technician Mike Lester used the kit’s larger 0.018-inch nitrous and 0.010-inch fuel jets for a 125hp shot, and he also installed a fresh set of spark plugs, one range colder than stock with gap set at 0.030.
Fuel is supplied to the solenoid off the passenger-side rail after removal of the stock Schrader valve and insertion of a brass T fitting. A fuel-pressure safety switch is plumbed to one side of the T; it sends a signal to shut off the nitrous supply if fuel pressure drops below 35 psi.
Using supplied weatherproof Packard connectors, the kit’s WOT switch is wired into the car’s throttle position sensor harness. Further wiring interlinks the WOT switch, rpm window switch, and fuel-pressure sensor, restricting nitrous engagement to safe opera-ting parameters. The various electrical connections are the most tedious part of installation, but the kit’s manual contains a clear wiring schematic and explicit instructions.
The rpm window switch will permit system activation only above 2,600 rpm and below 6,000. This upper limit is specifically set below the factory rev limiter, which does its job by cutting fuel to the cylinders. Having nitrous in the cylin- ders without fuel can be catastrophic to your engine and wallet. The system also comes with an illuminated master arming switch, which should be wired at a convenient location in the cockpit.
The kit includes a 10-pound bottle, which was mounted in the trunk in normal fashion and plumbed to the nitrous solenoid via the supplied 16-foot braided –4AN supply line. Also included is a 12-inch –4AN line to connect the fuel rail to the fuel solenoid and color-keyed 90-degree adapter fittings for each solenoid. At this point, the installation is complete except for neatening up the 16 poly lines with cable ties, and testing for leaks.

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.

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. 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.

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.