A pretty strong case can be made for Chevy's modern machinery. While we all look back fondly on the musclecars of yesteryear, the reality is that nostalgia has altered our perception somewhat. As great as some of these classics were, time and technology have marched on-to the extent that a modern LS-engined Corvette not only offers every bit as much performance (or more), but does so while delivering a combination of driveability, fuel economy, and reduced emissions only dreamed of by its carbureted forebears.
But while these modern motors are plenty potent, there are always ways to improve their power output. One route-nitrous oxide-was pioneered by the German Luftwaffe, which used the power-enhancing compound to improve the speed and flight ceiling of its WWII fighter aircraft. For those unfamiliar with nitrous oxide-or simply "nitrous," as it's commonly known-the compound contains both nitrogen and oxygen, not unlike the air you and your motor already breathe. It is actually the oxygen contained in this compound that's responsible for the additional power.
Before we proceed, let's dispel one persistent nitrous myth. Contrary to what you might have seen on TV, touching a lit match to a stream of nitrous will result in very little drama. In fact, the match will simply go out. But while the compound itself is not flammable, the oxygen contained within it is. Fortunately for enthusiasts, it requires a great deal of heat (572 degrees F) to liberate these oxygen molecules. In an internal-combustion engine, this heat is supplied by the gasoline-fueled combustion process, which, in turn, is greatly enhanced by the freed oxygen molecules.
Our nitrous came from this...
Our nitrous came from this Zex wet system. The Zex kit supplied both fuel and nitrous through a common fogger nozzle.
As if the release of power-producing oxygen molecules weren't enough, additional power gains are realized by an accompanying reduction in inlet-charge temperature. For automotive use, nitrous is stored, under pressure, as a liquid. When injected, the nitrous is converted into a gas, a process called "boiling." The liquid-to-gas conversion absorbs a great deal of heat from the surrounding area-in this case, the inlet air. While we normally associate boiling with extreme heat, the boiling point of nitrous oxide is actually a chilly -129 degrees. Cooler inlet air is rich in oxygen molecules, which, as noted earlier, enhance combustion and, in turn, power. Not surprisingly, the combination of extra oxygen molecules and a cooler inlet charge can produce some pretty impressive power gains.
One of the great things about nitrous is that it doesn't require expensive supporting upgrades to the engine. By cooling the inlet charge, nitrous not only improves power output, but it also helps suppress harmful detonation. The separation of the nitrogen and oxygen molecules during combustion also helps minimize detonation. This built-in "detonation control" allows impressive power gains without fear of component damage-even on a stock motor with cast pistons.
Comp Cams supplied this Xtreme...
Comp Cams supplied this Xtreme RPM XR265HR hydraulic roller. Don't let the name fool you: This relatively mild cam offered impressive midrange and low-end torque gains to go along with the additional high-rpm power. Its 212/218-degree duration split improved output throughout the rev range and proved a perfect match for our nitrous kit.
Keep in mind that the power gains and life expectancy of a motor are directly related to its tuning, as a proper air/fuel mixture and ignition timing are critical in a nitrous application. Applied and tuned properly, a modern nitrous system can provide safe, effective, and reliable power gains.
While nitrous will definitely wake up a stock LS1, there are ways to further improve its power-enhancing properties. This is where cam timing can play a part, as increasing exhaust lift and duration relative to intake will help rid the combustion chamber of all those extra oxygen molecules. To illustrate the gains offered by both cam timing and nitrous oxide, we set up an engine-dyno test using a mild LS1 equipped with a stock long-block, a FAST LSX intake and throttle body, and a set of Hooker headers.
The idea was to subject the LS1 test mule to nitrous oxide using the factory cam, then again with a slightly wilder-but still streetable-cam profile. Given the stock nature of the long-block and the fact that all of our tests would be conducted using 91-octane gas, we kept the nitrous shot at a conservative 100 hp. Such a combination could easily be duplicated on a typical street Vette.
This trick aluminum controller...
This trick aluminum controller was responsible for engaging the nitrous. The sophisticated circuitry built into the controller monitored the throttle-position sensor to ensure that the motor was at wide-open throttle before the nitrous could be activated. Part-throttle nitrous activation can produce catastrophic results.
The motor was equipped for dyno use with a FAST engine-management system and 36-pound injectors. The FAST system allowed us to dial in the timing and fuel curves to optimize the power produced by each camshaft. We tuned the combinations to produce a 13.1:1 air/fuel ratio and 30 degrees of total timing (any more or less reduced power). Thus configured, the LS1 produced 419 hp and 414 lb-ft of torque without nitrous. Before engaging our Zex wet fogger system, we retarded the timing by 4 degrees to reduce the chance of detonation.
This change dropped the power output to 402 hp. Activating the Zex system increased the peak power output to 528 hp, while peak torque shot to 559 lb-ft (see the accompanying graph for full details). Overall, the nitrous improved power output by 109 hp and torque by 137 lb-ft. With well over 500 hp, our LS1 was squarely into LS7 territory-and we had yet to change the cam.