Words And Photos: Richard Holdener

No matter what you drive or where run, drag racers have one thing in common: everyone wants to go faster. There are obviously many ways to improve the performance of the average internal combustion engine, ranging from basic bolt-ons to a boat-load of boost. No matter what route you choose, the concept of power improvement is pretty simple. Just add more oxygen and fuel.

The bolt-on route adds more power-producing oxygen molecules by increasing airflow through the motor. This is accomplished with a high-flow intake manifold, ported cylinder heads, and revised cam timing. Boost adds the necessary oxygen by force-feeding the engine more air than it can ingest of its own accord. Regardless whether it comes from a turbo or supercharger, extra air equals extra oxygen, which in turn equals more power.

Though both bolt-ons and boost add power, there is one final method of power enhancement used by racers all over the world. In fact, it can be combined with one or both of the other two forms for maximum performance. Of course, we are talking about adding the extra oxygen with the chemical compound known as nitrous oxide.

When it comes to bang for the buck, nothing on the street (or track) compares to nitrous oxide. Toss in a few fun facts like it is inexpensive, easy to install (and conceal) and (like forced induction) offers adjustable power gains, and, it’s easy to understand the popularity of nitrous oxide among street and drag racers. Short of a well-prepared turbo or blower motor, nothing runs harder than an LS on the juice.

The cost and concealment factors make nitrous oxide a natural for street racers, but so too does the ability to adjust the available power level. Much like cranking up the boost pressure on a turbo, jet changes on a nitrous system allow you to literally dial in extra power. Naturally, there is a limit to the amount of nitrous that can be added to any combination, something usually dictated by the strength of the internal components and the original power output of the motor. It doesn’t take a genius to figure out a “stock LS2” was sporting something more than stock when it pumps out more than 600 hp.

For those new kids on the block, the little blue bottle is not a fuel, but rather an oxidizer. Despite the infernos depicted in movies like the The Fast & The Furious, nitrous oxide does not burn nor is it likely to incinerate a car. Explosions of the magnitude depicted on the big screen are caused by the special effects people in Hollywood, not the compound contained in your shiny blue bottle. What happens when you crack open a bottle of nitrous and touch a match to the spray? There are no thunderous explosions, no massive fire balls, just an anticlimactic wisp of smoke as the flame is extinguished by the high-pressure, ice-cold stream of nitrous oxide.

If nitrous oxide doesn’t burn, how then, does it increase the power output of your LS motor so dramatically? The answer is simple, as nitrous oxide adds power by releasing free oxygen molecules contained in the compound. Since oxygen molecules are a key ingredient in power production (the more oxygen present the greater the power potential), the release of these oxygen molecules adds to the power potential of the motor. More nitrous equals more free oxygen molecules, which in turn, when combined with additional fuel, equals more power.

Naturally, there is a limit to just how much nitrous, and the attending free oxygen molecules, that can be added to any combination. While most stock LS motors, even those equipped with cast or hypereutectic pistons, will happily withstand a 100-150 hp shot (depending on the original power output and displacement), adding even more power brings the strength of the internal components into play.

Building a high-horsepower nitrous motor is not much different than building a high-horsepower turbo or supercharged motor. Short blocks typically include forged rods, cranks and pistons, with MLS head gaskets, head studs, and even possibly o-ringing of the block. Nitrous and forced induction motors do, however, differ in their cam timing and cylinder head porting. Nitrous motors tend to like a lot of exhaust flow, since the nitrous adds all the necessary intake oxygen molecules. All that improved intake efficiency must now be allowed to escape, thus the need for greater exhaust port flow and wilder exhaust cam timing (relative to a turbo), but we are getting ahead of ourselves.

This test involved running a little blue on a mild LS2, but the additional power can be added to just about any combination, mild or wild.

To illustrate the power gains offered by adding the NOS nitrous kit, we installed a system designed for the GM LS2. The NOS kit featured all the components required to add as much as 175 hp to an LS2 application. A dedicated throttle body adapter designed to flow the fuel and nitrous was sized for installation between the factory (or aftermarket) throttle body and intake manifold. The kit also included a pair of solenoids, one for fuel and one for nitrous, along with jetting to adjust the supplied power gain.

We set our jetting to increase the power output of the LS2 test motor by 100 hp. The LS2 used for testing was internally stock but featured a FAST (manual) 92-mm throttle body, COMP 54-459-11 cam and long-tube headers. Run with a Holley HP EFI system controlling the stock injectors, the mild LS2 produced 493 hp and 459 lb-ft of torque. After installation of the NOS LS2 kit (with 100-hp jetting), the peak power numbers jumped to 602 hp and 632 lb-ft of torque.

Credit proper NOS bottle prep (to ensure optimum pressure and flow) and precise control of the A/F mixture for the 100-hp jetting adding 110 hp.

Adding 100 hp is as easy as pushing a button. We installed the NOS LS2 EFI nitrous kit on this mildly modified LS2 with excellent results. Mods to the LS2 included a FAST 92-mm throttle body, COMP cam and long-tube headers. The final upgrade was obviously the NOS nitrous kit. Run on the dyno in normally aspirated trim, the LS2 produced peak numbers of 493 hp at 6,200 rpm and 459 lb-ft at 5,000 rpm. After equipping the adjustable NOS system with jetting to provide an additional 100 hp, the peak numbers jumped to 602 hp and 632 lb-ft of torque.

Sources

COMP Cams
compcams.com

FAST
fuelairspark.com

Holley/Hooker/Weiand/NOS
holley.com