LS2 Crate Motor - The Great Crate Update, Part 3

In the first installment of our Great Crate Update series (Nov. '06), we upgraded our GM Performance Parts LS2 crate motor with two different sets of roller rockers, a Comp Xtreme Energy cam, and a Fuel Air Spark Technology LSX intake manifold. The next article (Dec. '06) covered the installation of a new cam profile from Crane, along with seven different carbureted and EFI intake setups. The motor was configured with a FAST XFI stand-alone engine-management system for both tests, allowing us to dial in air/fuel ratios and timing curves to match each new modification. To optimize output on the engine dyno, we also replaced the factory water pump and exhaust manifolds with a Meziere electric pump and a set of Hooker long-tube headers. Finally, for convenience, the factory drive-by-wire throttle body was yanked in favor of a conventional 90mm version from FAST.

As in our last test, our LS2 was configured with a Crane Z-series cam that offered a 0.551- to 0.551-inch lift, a 216- to 224-degree duration split, and a 115-degree lobe-separation angle. The otherwise-stock long-block was fed by a FAST LSX intake and matching 90mm throttle body. Thus equipped, the LS2 produced 500 hp at 6,100 rpm and 487 lb-ft of torque at 4,800 rpm. After running the baseline power numbers, we took the XFI system out of closed-loop operation so the only fuel compensation would be from the fuel jetting. We tried a pull with the nitrous engaged. Despite the nominal 100hp jetting, the NOS kit improved output by 133 hp and 161 lb-ft of torque, yielding totals of 633 hp and 648 lb-ft. Even better, the kit added more than 100 hp from 4,400 rpm all the way up to 6,300 rpm, where we turned off the system. An extra 100 hp or more at the push of a button from a system that can be installed in an afternoon? No wonder nitrous is so popular among budget-conscious drag-race aficionados.

For this issue, we've decided to step up the power output significantly with a pair of power adders, starting with a nitrous-oxide kit from NOS. When it comes to bang for the buck, nitrous stands alone. In fact, a properly tuned nitrous system can add an easy 100 hp or more, for less money than you'd spend on, say, a set of ported heads. Designed specifically for the Gen III/IV EFI motors, our NOS kit featured an aluminum plate sandwiched between the throttle body and intake. Feeding the plate on this "wet" system were a pair of solenoids, one for fuel and the other for nitrous. Once activated-either manually or via a full-throttle micro switch-the solenoids provide both nitrous and the necessary enrichment fuel through the intake manifold. The amount of supplied fuel and nitrous is controlled by small jets that can be adjusted from 100 to 150 hp. For more serious applications, the solenoids and adapter plate will support up to 250 hp. For this test, we selected jetting designed to deliver an extra 100 hp.

To ensure the safety of our motor during tuning, we added a can of Lucas Oil octane booster to the same 91-octane Rocket unleaded pump gas we'd been using for all of our previous testing. As a further hedge against possible detonation, we also retarded the total ignition timing by 4 degrees. While this may seem contrary to our search for power, the fact is that the extra cylinder pressure created by the oxygen molecules in nitrous oxide means less timing is required for optimum performance.

After hooking up the electrical connections and braided feed lines to the two solenoids, we plumbed in the nitrous-feed line from the 15-pound bottle. Since the flow rate of the nitrous is dependent on bottle pressure-more pressure equals more nitrous flow-we took the liberty of raising the pressure to 900 psi with a bottle heater available from NOS.