Cam-Only LS1 Nitrous Engine - Zex Appeal

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.

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.

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.

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.