Let's play a little game of car-component-free association. It's quite simple: I throw out a few descriptive features of a car, and you identify it. Ready? Full-frame construction, two-door, six-cylinder, turbocharged, and intercooled, produced in limited amounts for a few years. You knew that was a Grand National or Turbo Regal. Here's another one: Four doors, available in only three colors, 350 ci of LT1 power, makes new Mustangs quiver with fear in their tracks, 400-plus horsepower. Did I stump you? You were doing so well up until the last part. You may think there is no such car, but there is; and it could be in your driveway right now. If you are a lucky owner of an Impala SS, you too can have a 400hp family hauler with some help from NOS.
What should we do after all of our favorite bolt-ons have been added? Take the next step perhaps? In this case, Anthony Castorina from Queens, New York, has been doing some performance hunting for his '96 Impala SS of the green-gray metallic hue. After taking delivery of the car he began adding the usual power-augmenting parts that would drop ETs and raise eyebrows. An MTI cold-air induction system, a Hypertech crank pulley, and a chip add some ponies to the mix, while Dynomax mufflers permit a free-flowing path for the exhaust to exit the car. With these minor bolt-ons, his best time on radials is 14.64 at 95 mph. It's quick enough to impress us, considering it is an OBD-II car, but not enough for Mr. Castorina. He felt this was the limit for the factory naturally aspirated combination.
Aside from lifting off the heads or changing the camshaft and intake, he was in search of an easy way to lower his ETs. He gave each option consideration. Supercharging would require a large initial amount of money, but that wouldn't be the end of the costly route. Tuning and living with the cloud of high maintenance over his head nixed that idea. Turbo systems were also deemed too complex and expensive. So, for a fraction of the cost of any of those power adders, nitrous was given the nod.
The benefits of the NOS system make it worth the investment. Its uncomplicated parts layout, ease of installation, and low initial cost make it the obvious choice. Let's take a closer look at how nitrous works and why the NOS system works so well.
One could conjure up images of instant horsepower, cheap initial purchase price, and low maintenance when the "N" word comes to mind. However, your thoughts could also revolve around engine component failure, such as piston damage, blown head gaskets, or other forms of powertrain carnage. With modern nitrous technology we can eat our cake and have it, too. Gone are the days of supertuning to get the extra kick in the pants that you were looking for at the cost of engine longevity. Today we can practically bolt on and go.
All internal-combustion engines consume air and fuel. The horsepower and torque potential of the engine is based on how much air can go into the cylinders for combustion, as long as there is adequate fuel present. Using a supercharger or turbocharger forces more air into the cylinders, making more power, but nitrous uses a different principle.
Nitrous is stored in a bottle as a liquid. Like most gases, when it is compressed, it turns into aqueous form, allowing us to store it safely in the infamous blue bottle. As nitrous is released into the engine, it goes from 1,000 psi to atmospheric pressure, returning to a gaseous state due to the sudden pressure drop. Although there are two nitrogen atoms present for each oxygen atom in each molecule (N20), the nitrogen is not what is actually burned to give the added power, contrary to popular belief. As the engine inhales the nitrous, only the oxygen atom from N2O is used for combustion. Nitrogen is known as a "spectator" atom and simply goes along for the ride, exiting the engine unused. This technically makes nitrous a form of artificial aspiration because there is more oxygen going into the cylinder than the atmosphere can offer.
Dry manifold is the term NOS uses to describe the system's operation. Instead of injecting the nitrous and fuel together at the intake manifold like other kits, only the nitrous is injected so that the manifold is not wet with fuel. Rex Uraki, Tech Consultant at Nitrous Oxide Systems, elaborated for us: "Using this method, the additional fuel is added through the existing fuel injectors. Their flow capacity is increased by raising the rail pressure to approximately 80 psi so that the injectors provide more fuel with the same pulse width. This is accomplished with a NOS regulator valve, which is plumbed with the solenoids. When the solenoids are activated, nitrous is sent from the regulator valve to the fuel-pressure regulator and works against the diaphragm to increase injector rail pressure. This way, nitrous is carried airborne into the cylinder, and the added fuel finally meets it when the combustion process is taking place in the cylinder. The result is a 150-horsepower increase."
Parts are PartsIt was refreshing to see that this kit was complete before we actually installed it on the car. In our case, kit PN 5176 for LT1s has everything needed for a neat and complete installation. Although originally designed for Camaros and Firebirds, it also fits the B-body Impala without any drama. Aside from the bottle and solenoids, we were happy to discover a fuel pump assembly in the package. The NOS pump is a pusher-type that goes inline. It works in conjunction with the stock in-tank pump to increase the fuel system's total capacity.
For all of these parts to come together, we enlisted the services of Manny Boumakis of DynoSport Performance in New Hyde Park, New York. Manny provided us with the installation and dyno sessions with and without the nitrous flowing.
The tools and fabrication required are minimal. However, since professional equipment was available, Boumakis elected to make a custom mount for the nitrous spray nozzle. He cut a 1-inch piece from a section piece that resembled a plug. The nitrous nozzle was then mounted into this aluminum plug and they were both clamped into the inlet pipe, right where the factory air silencer once entered. This gave the nitrous nozzle a straight shot toward the throttle body and allowed us to acquire some desired underhood space.
The solenoids and the pressure regulator were then assembled on the bench. With all of the fittings sealed with liquid Teflon paste, they were brought over to the car to be mounted. Boumakis again fabricated an aluminum piece, this time, a bracket to support the solenoid and regulator assembly on the firewall. The nitrous line to the rear of the car was installed next. DynoSport's Nick Pezoulas decided to route the high-pressure braided hose down the passenger side of the engine compartment. Underneath, it was fastened to the inside of the framerail and entered the rear cargo hold through a small hole into the trunk. The bottle brackets were then bolted into the trunk floor. After leaks were checked with bottle pressure, the knob was closed until it was time to squeeze the nitrous.
Lastly, the wiring was left to complete the day's work. Castorina wanted an activation switch location that would be undetectable. This would keep curious eyes away from it. We found a spot for the arming switch-a small coin cup located below the headlight switch-that keeps it out of plain view. Once it was wired in we checked for operation. The full-throttle switch was then aligned and tested. Now it's time for dyno testing.
We first baselined the car to see how much horsepower the car had in non-nitrous-injected form. With the car strapped down onto DynoSport's Dynojet model 248C chassis dynamometer, we disarmed the nitrous system and tuned the rollers. The Dynojet computer calculated the correction factor for the 59.5 F air and 29.92 inches of Hg at .96. This meant that any numbers measured by the dyno were to be automatically multiplied by .96 to compensate for the SAE standard of dyno test. This results in corrected horsepower and torque, which is what we will use throughout.
With the number crunching all figured out, we were rewarded with 237.4 peak horsepower at 4800 rpm. Torque registered at 285.6 lb-ft at 3800 rpm. A few additional runs were made to back up the original Dynojet numbers; they were repeated.
After 30 minutes of cool-down time we fired the LT1 back to life, this time with the bottle on and nitrous armed. With the Impala's 350 spinning at 3500, we punched it, initiating the test and the nitrous pull. The four-door roared on the dyno and sounded like a caged beast. The horsepower increase, whatever it was to be, was definitely noticeable; the car went through third gear with little sweat. The printout reported 327.8 hp at 5000 rpm and 393.7 lb-ft at 4000 rpm in increase of 90.4 hp and 108.1 lb-ft of torque. Dissatisfied with the numbers, Boumakis put his hand on the bottle and noted how cold it was. Pezoulas then warmed the bottle with a heat gun for approximately 15 minutes. Since we had no pressure gauge, Boumakis was sure that the lack of nitrous pressure was the reason we did not get the expected 125-horse increase at the rear wheels.
With the bottle warmed up and the engine cooled off, the results were more to our satisfaction. Horsepower jumped to 344.6 (at 4900 rpm) and torque responded with a 447.9 lb-ft reading for a total gain of 107.2 hp and 162.3 lb-ft of torque. Boumakis informed us that due to drivetrain inefficiencies and a lack of a bottle at optimum pressure of 1,100 psi, we could have expected more at the rear wheels. "On a car like this you have to add a 20 percent factor to measure power at the flywheel," he states. So, a little calculator tickling gave us a figure of 414 hp and 538 lb-ft. If that doesn't make a car move, we don't know what will.
What kind of tech story would not give you track numbers? Not this one, that's for sure. With a filled bottle mounted to the brackets and a warmed nitrous bottle installed, we were ready to go for the second portion of the test. Dyno numbers are great, but they don't prove much if they don't make an appreciable difference on the dragstrip.
Castorina took a baseline pass to the tune of a 14.79 at 93 mph. Traction was poor, so the BFGoodrich Drag Radial tires were mounted for the nitrous passes. As the car left the tree, we could see the car charge harder toward the traps as the Compulinks spat out a 13.10 at 106 mph.
For a 1.6-second drop in ET and a 107hp gain at the rear wheels, the NOS dry manifold system ends up being the best investment Castorina has ever made. "The Impala has proven to be very reliable and has no undesired affect on drivability," he tells us. Did somebody mention something about a 400hp four-door?