Michael Galimi
December 1, 2006

Warning: What you are about to read can be labeled as cheating. This article is for entertain-ment purposes (and for the less fortunate who need a little help taking down the neighborhood bully). It may also give you an edge in grudge racing at the local racetrack. For those who might attempt running this setup in your class-legal racer-beware, many tech officials read this magazine!

Ed. Note: We threw caution to the wind with this installation by disregarding the NOS-supplied instruction manual. Holley-NOS has designed this system to work correctly when it is properly installed. Our installation/usage was successful despite not following the instructions step-by-step. But that's not to say there isn't some sort of risk involved when deviating from the NOS installation manual. Not installing this system properly as designed can cause failures and/or other problems.

A secret nitrous system is a time-honored tradition on the most hard-core grudge-racing scenes. When winning is everything and your morals are thrown out the window, follow these steps and you'll have a nitrous system that is virtually undetectable to most would-be competitors. We know there are bullies around your neighborhood and at grudge night at the track. Hiding a nitrous kit just might be the solution to your problems, and the best part is that your competitors won't have the slightest clue that your car is jugged.

There's nothing new about hiding a nitrous system. For as long as nitrous has been a known commodity in the racing world, there have been those willing to conceal its usage. MM&FF performed a test many years ago using a nitrous bottle hidden in a gym bag. After that story hit, street racers across the country started mimicking the installation. We are here today to offer a crazier, more devious way to hide your juice kit. It raised more than a few eyebrows at MM&FF Command Central, and we think it's the most detailed hidden-nitrous install in the history of automotive enthusiast magazines.

Orchestrating our installation was Justin Burcham of JPC Racing (Glen Burnie, Maryland) and his crew. They spent the better part of the day tearing into a virtually stock Mustang (headers, x pipe system, after-cat exhaust, and pullies). The coupe spent many years in the NMRA Factory Stock class with Justin's wife, Melanie, behind the wheel. It was recently sold, and a bone-stock engine (from the junkyard) was installed along with a stock AOD transmission.

By sundown, the go-fast juice was adapted (read: hidden) inside the vacuum system of this Mustang, all done under a veil of secrecy. Even casual shop visitors were baffled when we asked them to find the nitrous. The first place these bystanders checked was the area around the air filter. Over the years, the airbox area has become the common location to shoot the nitrous, so naturally we chose a different place to get the sauce into the engine. The second spot most people checked was under the manifold-another easy-to-install location where the injection point is a nozzle (usually painted black) that is drilled into the main runner on the underside of the upper intake manifold. The drawback is that the nozzle is easily detectable, especially when the people checking the car have a flashlight. Our entry point was under the manifold, but it was undetectable.

Burcham's ideas for this installation were great. The concept was to mount a 5-pound bottle and the nitrous solenoids inside the door, and to use one wire to power both small solenoids. We used the defroster switch as our on/off arming switch. We then ran two nylon lines (like the ones used for gauges) through the door via the wiring duct. One nylon tube carries nitrous to the manifold and the other tube was connected to the fuel pressure gauge. The nylon tubes/lines are rated at high pressures, upwards of 2,000 psi, making them safe for use with nitrous since the system runs optimally at a bottle pressure of 900 psi.

Mmfp_0612_01z Hidden_nitrous_system Nos_dry_manifold_system
For this exercise, we used an NOS single-stage, dry-manifold system (PN 05115NOS). A dry-nitrous system sprays nitrous through the manifold and extra fuel is added through the fuel injectors. A spike in fuel pressure is used to increase fuel flow.
Mmfp_0612_02z Hidden_nitrous_system Fitting_nitrous_bottleMmfp_0612_03z Hidden_nitrous_system Fitting_bottle
Our first task was fitting the bottle in the door. We ran it in the middle where the door naturally bulges outward. It was wide enough to hold the NOS bottle. Initial attempts at putting it on the lower half of the door failed because the door cuts inward.
Mmfp_0612_04z Hidden_nitrous_system Bottle_bracket_cut_down
Burcham used a bandsaw to cut down the bottle bracket. We had to modify the bracket to fit in the door with the 5-pound NOS bottle.
Mmfp_0612_06z Hidden_nitrous_system 5_pound_nos_bottle
Here is the standard 10-pound nitrous bottle that NOS includes in the kit. We selected a smaller 5-pound NOS bottle because it was easier to hide.

The nylon tubes are concealed in wire loom and run behind the dashboard and up to the firewall on the driver side. From there we drilled into the cowl area and then popped through the firewall right behind the vacuum tee. The lines entered the vacuum tee and went their separate ways. One nitrous line runs inside an A/C vacuum line that goes to the bottom of the intake. The other went out the vacuum port labeled "B/R" and into a vacuum hose that ran to the fuel-pressure regulator. We used a T-fitting hidden under the manifold to pipe in the regular vacuum line that goes to the fuel-pressure regulator.

Nitrous pressure must be run to the fuel-pressure regulator to add the nitrous. When the juice is flowing, the nitrous puts pressure on the fuel-pressure regulator diaphragm and restricts the fuel return, thus increasing fuel pressure. Running the extra fuel through the fuel injectors is what classifies this as a dry-type system. Only nitrous is sprayed into the intake manifold, and it does not mix with the fuel until they meet at the bottom of the intake ports.

What makes this system hard to detect is that it uses existing lines so nothing is out of the ordinary. The only addition is one extra vacuum line and T-fitting to properly route the nitrous to the fuel-pressure regulator. But it was done with the utmost care and looks ordinary enough that no one should notice-especially Brand X racers who are not familiar with Mustang engine compartments. Let's be realistic, there are a lot of hoses and wires running around in these engine compartments. It's easy to lose track of what goes where.

This install is certainly harder to perform than others and there are some sacrifices that had to be made. For instance, the passenger-side window could not be lowered when the bottle was in place. To fit the bottle in the door, we had to hack up the doorframe a bit. Just be careful when using a Sawzall as there are some sharp edges remaining. Since the rear-defroster switch was used as our arming button, the rear defrost was disconnected-just one of life's little sacrifices. Otherwise the install was fairly simple.

Throughout the install we bench raced about various combinations that would be unbelievable sleepers. "I would build a 347ci engine and use the stock heads-ported, of course-and intake manifold," Burcham says. "Of course, the intake would be Extrude Honed and the ports enlarged until the intake was paper-thin. The camshaft would be mild, maybe even stock. I would have a few nitrous systems on the car; one shown and two hidden ones. That way you disconnect the one but still have a few good shots of nitrous hidden. The car would be perfect for the TV show Pinks." Your author has visions of a 375ci engine (based on an 8.2-deck block from World Products) with a mild-sounding camshaft and a pair of aluminum heads. Of course, two hidden shots of nitrous would work wonders. Running nines in a lightweight notch wouldn't be a problem with this combo.

Back to reality-the results from our test subject were predicable, to say the least. In stock trim, the AOD-equipped Stang spun a Mustang dyno to the tune of 194 hp and 259 lb-ft of torque. With a 0.047-inch jet in place (80 hp, according to the NOS instructions), the power shot up to 260 hp and 352 lb-ft of torque-at the rear tires, of course. That was a 66 peak-horsepower increase. Timing was set at 10 degrees. What was even cooler was no one in the dyno cell, except for Burcham and us, knew this LX was running on the sauce.

Mmfp_0612_07z Hidden_nitrous_system Nos_solenoids
We mounted the NOS solenoids to the door using the supplied bracket from NOS. The aluminum block in the middle of the solenoids sends nitrous to the back of the fuel-pressure regulator to help spike fuel pressure. The second solenoid is normally attached to a Hobbs safety switch that shuts down the system if the fuel pressure doesn't spike. We didn't run the safety switch for fear of exposing the nitrous system.
Mmfp_0612_08z Hidden_nitrous_system Braided_line
Burcham's solution to going from braided line to the nylon tubing was to use a NOS flare jet fitting (PN 17952NOS). It is used on NOS nitrous plates to connect the plate to the nitrous/fuel lines. We used it to house the nitrous jet (0.047 inch) and then connected it to a brass fitting that converts to the nylon tubing. We sourced the brass fitting from an Auto Meter boost gauge. The white line on the right of the photo is the nylon tube we used to carry the nitrous. Everything fit perfectly. We used this setup on both the nitrous solenoid and aluminum block.
Mmfp_0612_09z Hidden_nitrous_system Nylon_tubingMmfp_0612_10z Hidden_nitrous_system Hidden_nylon_tubes
The nylon tubes were hidden in wire loom that we snaked through the duct that leads from the door to the body of the Mustang.

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