When it comes to bang for the buck, nothing compares to nitrous oxide. Toss in the fact that it is easy to install (and conceal) and the power output is adjustable (as with forced induction). It’s easy to see why nitrous oxide is all the rage among street racers and enthusiasts. Short of a well-prepared turbo or blower, nothing runs harder than an LS engine on the juice.
Nitrous oxide offers a number of benefits, including 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 the extra power. However, there is a limit to the amount of nitrous that can be added, something usually dictated by the strength of the internal components and the original power output of the engine.
In addition to the adjustable power, street racers like nitrous because it can be easily hidden. Of course, it doesn’t take a genius to figure out that a stock 2010 Camaro was sporting something more than the stock when it knocks out consistent 11s at the track. Further improving upon the adjustable power and concealment is the cost. Compared on the basis of available power gains, nitrous offers far and away the best bang for the performance buck.
As you know, nitrous oxide is not a fuel, but rather it’s an oxidizer. Despite the automotive infernos depicted in movies such as The Fast and the Furious, nitrous oxide does not burn nor is it likely to incinerate a car. You could literally open the bottle of nitrous and touch a match to the spray and the only thing that would happen is that the match would go out. 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, then how does it increase the power output of the engine? The answer is simple: Nitrous oxide adds power by releasing free oxygen molecules contained in the compound. Because 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 engine. More nitrous equals more free oxygen molecules, which in turn equals more power.
Nothing wakes up an LS3 or LS7 application like a small shot of nitrous. Combine the right amount of nitrous and fuel through a single (or multiple) fogger nozzle(s) and you have instant horsepower.
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There is, however, a limit to the amount of nitrous and the number of attending free oxygen molecules that can be added to any combination. While most stock engines, even those equipped with cast or hypereutectic pistons, withstand an increase of 40 to 50 percent (depending on the original power output and displacement), adding more power brings the strength of the internal components into play.
Building a high-horsepower nitrous engine is not much different than building a high-horsepower turbocharged or supercharged engine. Short-blocks typically include forged rods, cranks, and pistons, with MLS head gaskets, head studs, and possibly O-ringing the block. Nitrous and forced induction engines do, however, differ in their cam timing and cylinder head porting. Nitrous engines prefer big port volumes and a lot of exhaust flow because the nitrous adds all the necessary intake oxygen molecules. All those extra oxygen molecules must now be allowed to escape, thus the need for greater exhaust port flow and wilder exhaust cam timing.
Adding power through nitrous is different than adding the same amount of power through forced induction. Sure, both add an easy 75, 100, or even 150 hp (or more) to an average LS engine, but how they add the power differs. Both forced induction and nitrous increase the amount of oxygen molecules available to produce power. Forced induction does so by increasing the mass flow of air. Pressurizing the air increases the mass flow, thus force-feeding the engine more air than it could ingest on its own or otherwise in NA form.
The unfortunate side effect of the pressurization of air (boost) is that the pressure causes heat. Turbochargers and superchargers heat the inlet air, something not desirable from either a power (less oxygen molecules per volume) or a detonation threshold standpoint. The hotter the air, the easier it is to ignite. In some cases, the heated inlet air can self-ignite before the spark plug initiates the burn. The result is an expansion of the air/fuel mixture while the piston is still on its way to TDC. As a result, the expanding gases resist the upward moving piston. The result of this struggle is sometimes not very pretty. The same thing can happen with excessive ignition advance.
Nitrous, on the other hand, does not resort to pressurizing the inlet air, but rather the extra oxygen molecules are carried in the pressurized compound. Once delivered to the inlet tract from a pressurized bottle, the liquid nitrous quickly turns into a gas. This liquid-to-gas vaporization requires an input of energy; in this case the energy is heat. The vaporization of the liquid nitrous absorbs heat from the surrounding inlet air, desirable in any performance application (especially a turbo or supercharged engine).
Although you associate heat with boiling (for example, water turning from a liquid to a gas), the vaporized nitrous does not produce heat (at least not to the inlet air). Although vaporized, the temperature of the nitrous oxide is still at or near minus 129 degrees F (the boiling point of nitrous oxide). Mixing the inlet air with a gas that is even that cold still provides a dramatic cooling effect. This double cooling reduces the chance of detonation and increases the density of the inlet air. Denser air equals more oxygen molecules, which in turn (potentially) creates more power.
Nitrous kits can be pretty elaborate but most feature the components illustrated in this NOS kit. The components include a bottle, solenoids, fogger or plate, jetting and arming, and activation switches.
Nitrous oxide (such as in this Zex kit) can also be used on carbureted LS applications with the Perimeter Plate system. This system was designed to evenly distribute the fuel and nitrous to all cylinders to maximize (safe) power.
Test 1: Modified LS3: NA vs Nitrous Using 100- and 150-hp Shots
The great thing about nitrous oxide is that it can be added to any engine, but big doses of nitrous are best used on modified engines designed to take the abuse. After all, nitrous kits can easily increase the power output of an NA engine by 100 hp or more.
This test was run on a modified LS3. Starting with a GM LS3 crate engine from Gandrud Chevrolet, the short-block was augmented with a set of CP forged, flat-top pistons and 6.125-inch connecting rods. The piston and rod upgrade were combined with the stock crank (more than strong enough for this level of nitrous). I retained the stock LS3 heads, but they were treated to a valve spring upgrade from BTR. Comp Cams supplied a 459 cam for this test that offered a.617/.624-inch lift split, 231/239-degree duration split, and 113-degree LSA. The stock heads were retained using Fel-Pro MLS head gaskets and ARP head studs. This test relied on the stock LS3 intake, but I swapped on a manual 90-mm throttle body to replace the factory drive-by-wire unit. Run with long-tube headers, a Meziere electric water pump, and FAST XFI management system, the modified LS3 produced 552 hp, and 520 ft-lbs of torque.
To illustrate the power gains offered by nitrous oxide, I selected one of the affordable Sniper Kits from NOS. Because one of the benefits of nitrous is the ability to easily increase power with a simple jet change, I decided to run two different power levels on this engine. The Sniped Universal EFI kit featured a 10-pound bottle, two solenoids, and a single fogger nozzle designed to inject the nitrous and fuel together. Because nitrous oxide is an oxidizer, extra fuel is a critical component to add to the extra oxygen molecules supplied by the compound. Using the supplied jetting, I set up the system to provide an extra 100 hp. Activating the nitrous at 4,300 rpm resulted in a jump in power to 687 hp and 684 ft-lbs of torque. The Sniper system provided a nice, smooth power curve. After the success of the 100-hp shot, I stepped up to 150-hp jetting and was immediately rewarded with 732 hp and 730 ft-lbs of torque. I made sure to heat the bottle properly to ensure adequate bottle pressure prior to testing.
Because the stock valve springs did not accept the available cam lift, I replaced them with a dual-valve spring upgrade from BTR.
In addition to forged rods and pistons, the LS3 also received a Comp 459 cam upgrade.
The Sniper universal wet EFI system offered plenty of bang for the buck. Applied to this modified LS3, the nitrous system increased the power output from 551 to 687 hp using the 100-hp jetting. This increased to 732 hp with the 150-hp jetting. Thanks to the forged internals from CP and Carillo, I felt confident adding this much power to the LS3.
The torque curves illustrate how easy it was to increase power on the nitrous-injected LS3. Simple by chang- ing jets on the Sniper system, I was able to increase torque production first from 520 ft-lbs to 684 ft-lbs, then up to 730 ft-lbs with the 150-hp jetting. Note the 300-rpm earlier activation (4,300 versus 4,600) on the 100-hp shot.
Test 2: 408 Hybrid Stroker: NA vs Zex Wet EFI Nitrous Using a 100-hp Shot
Aluminum LS3 engines are expensive and more difficult to come by than iron 6.0 truck blocks, and as a result, building your own 6.0 LS3 hybrid has become common practice. This works especially well if you bore and stroke the 6.0 to 408 ci as with this test engine.
The 6.0 iron block was fi rst bored .030 over then treated to a stroker assembly that included a Scat forged steel crank and 6.125-inch rods combined with JE forged (asymmetrical) pistons. Finishing the stroker was a Comp cam (PN 277LrHR13) that offered a .614/621-inch lift split, 227/235-degree duration split, and 113-degree LSA. Making this a hybrid was the fact that I topped off the .030-over iron block with a set of as-cast LS3 heads treated to a Comp beehive valve spring (PN 26918) upgrade. The engine was run with a stock LS3 intake, FAST injectors, and a Holley HP management system. As always, I replaced the drive-by-wire throttle body with a 90-mm manual version. Equipped as such, the NA LS3 hybrid produced 577 hp and 526 ft-lbs of torque.
After running the NA hybrid stroker, I installed the Zex Wet EFI nitrous kit. The cool thing about the Zex kit is that not only was it adjustable with different jet- ting, but the single fogger nozzle could be applied to just about any fuel-injected application. The kit included the purple 10-pound bottle, a digital controller, and a single fogger nozzle designed to combine the nitrous and fuel before injecting it into the engine.
After filling the bottle at Westech Performance, I hooked up the system, went through the WOT learn procedure for the throttle position sensor (TPS), then purged the system. With plenty of bottle pressure, I activated the Zex nitrous at 4,500 rpm, and the power jumped immediately. It soon settled in with gains that exceeded 100 hp. Credit the extra power offered by the kit to tuning and bottle pressure above 1,000 psi. Increased bottle pressure works like a larger nitrous jet, and this Zex kit worked amazingly well on this hybrid stroker.
The test engine started as a 6.0, but the iron block was upgraded with a 4.0-inch SCAT stroker crank and K1 6.125-inch rods.
JE supplied the necessary forged flat-top pistons for the LS3-headed 6.0 stroker.
Nothing adds instant power like a good nitrous system. The Zex Wet EFI kit offered impressive power gain, upping the power output of the 408 hybrid stroker from 577 hp to 702 hp using 100-hp jetting. I did take the necessary steps to ensure proper nitrous pressure and delivery by preheating the bottle.
It is not unusual to see a massive torque gain on the initial activation of a nitrous system. The Zex kit added more than 200 ft-lbs to the stroker engine at 4,900 rpm but settled in to a more real- istic torque gain thereafter. Remember, the lower you activate the nitrous, the more torque you gain, but care must be taken not to become too greedy.
Test 3: Mild LS3: NA vs Nitrous Works Using a 100-hp Shot
I ran this test to illustrate that it is possible to not only add nitrous to any LS3 or LS7 combination (even a stock one), but do so safely. Forget the horror stories and explosions shown on TV, movies, or YouTube, nitrous is not even flammable, nor does it hurt stock pistons or rods if tuned properly. Nitrous is simply an oxidizer that adds extra oxygen molecules. Extra oxygen means extra power, but the oxygen must have additional fuel to support the burn. Combine the two properly and inject into the engine and that’s when the magic starts to happen.
To illustrate how well nitrous companies have perfected their systems, I ran nitrous on an LS3 equipped with stock internals, meaning powdered-metal rods and cast pistons. The only upgrades made to the LS3 were a BTR cam and valve springs. Run with headers, a Meziere electric water pump, and Holley HP management system, the cam-only LS3 produced 544 hp and 514 ft-lbs of torque. (See Chapter 3 for some serious cam-only information from BTR.).
As much as I love how well an LS3 responds to more aggressive cam timing, it responds even better to nitrous oxide. This includes an old, out-of-date system no longer available. Rummaging through the cabinets at Westech Performance, I ran across an old Nitrous Works kit from Barry Grant. No longer available, the system was complete and ready to run. The Nitrous Works system included the usual array of solenoids, lines, and a single fogger nozzle, along with a 10-pound bottle, activation switch, and various hoses and fittings.
To test the system, I installed jetting to provide a 100-hp increase to the cam-only LS3. Despite not being available for some time, all the components worked well and the 100-hp jetting increased the power output of the LS3 from 544 to 660 hp. The torque gains were equally impressive; the nitrous increased torque production from 514 to 655 ft-lbs. Even on a near-stock engine, nitrous oxide works wonders.
The power output of the GM LS3 crate engine was increased by replacing the factory cam with a higher lift cam from BTR.
The cam swap necessitated replacement of the stock LS3 valve springs. BTR supplied a set of double springs to accommodate the higher-lift and increased engine speed of the new cam.
Starting with a GM LS3 crate engine from Gandrud Chevrolet, I installed a mild BTR cam (and springs), then an old Barry Grant Nitrous system that I had laying around. Running jetting to supply an extra 100 hp, the single fog- ger system increased the power output of the mild LS3 from 554 hp to 660 hp. Nitrous offered nice, smooth, consistent gains.
Activation of the Nitrous Works nitrous system at 4,500 rpm resulted in impressive torque gains. I made sure to retard the timing by 4 degrees to eliminate any chance of detonation. Nitrous can transform a mild LS3 into a wild one with one push of the button.
Written by Richard Holdener and republished with permission of CarTech Inc
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