How To

Gassing A Hemi

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  • This universal kit from ZEX (#82023) includes the bottle, activation solenoid, nitrous lines and wiring. Accessories include a purge system (#82005), along with an LED light (#8270R). The light (offered in different colors) illuminates the purge spray, creating an eye-catching visual display. Nitrous oxide bottles typically are shipped empty and must be filled prior to use. - 1
  • Step number one is mounting the bottle. In LX cars, there is plenty of room in the trunk to mount the bottle in the preferred elevated front-to-back manner, which will help the bottle’s siphon tube always stay immersed in liquid nitrous during acceleration. - 2
  • Next, at the front of the car, the nitrous nozzle was installed in the straight section of the air intake tract. The intake required removal for this step; it is shown here reinstalled. - 3
  • A concern with mounting the nozzle so close to the throttle body was the proximity of the nozzle to the air temperature sensor, which hangs down in the air stream (seen here). Paul’s High Performance turned the sensor element approximated 180 degrees, which helped shield the element from the cold blast of the nitrous oxide and, with hope, will prevent the sensor from icing. Also, a too-cold reading from the sensor would cause the computer to add too much fuel to the mixture. - 4
  • Next, the fuel system must be tapped to provide a fuel mix with the nitrous oxide when it is sprayed into the engine; this makes it a “wet” nitrous system. The passenger-side fuel rail was removed for modification. - 5
  • A hole in the end of the fuel rail was drilled and tapped for compatibility with a –4 AN fitting, which will connect the fuel supply to the nitrous controller. The bung for the fuel line was screwed into the fuel rail and welded in place. After a shot of silver paint on the rail’s tip, the fuel rail was reinstalled. - 6
  • The fuel supply line was then attached to a 90-degree fitting and routed beneath the throttle body and over to the area on the driver-side of the engine compartment where the nitrous system management unit would be mounted. - 7
  • One of the best traits of the ZEX nitrous system is the self-contained management unit, rather than separate solenoids. The feed lines for both fuel and nitrous enter and exit the electronically controlled box, making for an extremely easy and straightforward installation. - 8
  • Next, the appropriate jets for a 75-horsepower boost were added to the nitrous nozzle. More than a 75-horsepower shot would require taking at least 2 degrees of timing out of the tune – which cannot be done without programming. Programming was not available for this engine at the time the installation project took place. - 9
  • The purge system tees into the bottle supply line. This allows a quantity of nitrous to be vented to the atmosphere so that the system can be purged of trapped air. - 10
  • An activation solenoid for the purge system is mounted. A universal mounting flange included with the purge kit allowed the solenoid to be attached to the rear corner of the intake manifold. - 11
  • The purge outlet was located at the center of the cowl. The purge light slips over the outlet tube. A hole drilled in the plastic cowl allows the necessary wires and purge line to run into the engine compartment. Conveniently, when the hood is closed, the purge light housing is inconspicuous. - 12
  • With the supply lines routed, attention turns to the system’s wiring. This is mostly a straightforward endeavor – at least until it comes time to find the throttle position voltage output wire. Other wiring concerns the arming/activation switches and the purge light. Here, a connection is crimped to one of the nitrous system’s wires in order to mate with the vehicle’s wiring. - 13
  • The system power (“arming”) switch and the purge switch must be wired for the driver’s use inside the car. The arming switch powers the nitrous system, allowing it to be activated as long as the bottle is open. The purge button would be located in the ashtray, so it was removed for drilling and wiring. - 14
  • The red button is for the purge. The other switch and light are for unrelated accessories already installed on the project vehicle. - 15
  • Rather than a hard-mounted arming switch, Paul’s High Performance installed this simple plug-in switch. It is wired to the nitrous system and simply requires plugging into a lighter/auxiliary power socket. Then, a rocker switch on the tip is pushed to the “on” position. When the light is illuminated, the nitrous system is ready to rock. - 16
  • Because the bottle was shipped empty, it required filling. This is done with the bottle resting on a scale. The empty bottle weighs approximately 15 pounds; when the scale reads approximately 25 pounds during filling, the bottle is full. - 17
  • With the bottle full, it was placed back in the trunk and secured to the mounting straps. Then, the supply line was connected. In preparation for testing, the bottle was heated to bring its pressure up to the optimal 900 psi. The battery for heating was removed after the bottle was warmed up. - 18
  • Want to impress your friends and frighten fellow motorists? Hit a red-lit purge system at the next stoplight. It’s quite a sight! - 19
  • Paul’s High Performance baselined the 300C SRT8 on their chassis dyno. In stock trim, it made 375.5 horsepower and 369.8 lb.-ft. of torque at the rear wheels. With nitrous, peak output jumped to 409.1-horsepower and 508.1-lb.-ft. at the wheels – but offered greater percentage increases at different rpm levels. - 20
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by Barry Kluczyk  More from Author

How To Install Nitrous Oxide On A Late-Model Magnum, Charger or 300C

No longer considered the cheater’s power adder, nitrous oxide systems have become a popular and cost-effective method for boosting the power output of late-model vehicles. In fact, a carefully matched nitrous oxide system delivers an excellent performance-per-dollar value, as well as the benefit of no affect on drivability when the system is off.

In short, nitrous is there when desired and invisible when not. A nitrous system also is comparatively easy to install, as we found out with the installation of a ZEX ( system, including an LED-lit purge system, as it was adapted to a Chrysler 300C SRT8. The installation was performed at Paul’s High Performance (, in Jackson, Mich.

Nitrous oxide is a compound of nitrogen and oxygen – two nitrogen atoms and one oxygen atom per molecule – and is 66 percent nitrogen and 33 percent oxygen by volume. It is a very “cold” compound; it boils at -129 degrees F (-89 degrees C) and is a gas at room temperature; it requires 760 psi to squeeze it into a liquid.

More important than its volumetric properties is nitrous oxide’s oxygen content by weight, which is 36 percent. The atmosphere is 23 percent oxygen by weight. N2O also is about 50 percent denser than the atmosphere, so a cubic foot of nitrous oxide contains more than twice the oxygen of the air inhaled by humans – or automotive engines.

Like other power adders, such as a supercharger, turbocharger or even a set of high-flow cylinder heads, the optimal air/fuel ratio of the engine must be maintained, as well as spark timing. Simply put, a large increase in cylinder pressure, such as that delivered by nitrous oxide, will likely cause severe detonation without a corresponding change (retarding) of timing. Adequate fuel supply also is a must, as a super-oxygenated air/fuel mixture will go too lean without a matching boost in fuel.

Fortunately, the engine construction and sophisticated controls of most modern vehicles – including 5.7L and 6.1L Hemi-equipped vehicles – are very adaptable to low-to-medium doses of nitrous oxide. The biggest caveats are working with vehicle’s engine controller and being cognizant of the engine’s durability limit.

What does that mean on the Hemi engine? Without any computer programming that drastically retards timing, the horsepower “hit” of the nitrous is limited to about 75 horsepower. For a 100-horsepower “shot,” 2 degrees of timing would have to be taken out – and the factory computer won’t do it. Generally speaking, timing should be retarded 2 degrees for every 50 horsepower of nitrous power.

The performance of the 75-horsepower baseline is somewhat misleading, as the nitrous system doesn’t simply add 75 additional horsepower across the rpm range. Because engines make different horsepower and torque at different rpm levels, based on airflow and other factors, the nitrous-boosted engine simply does the same. As for the practical limits of the Hemi engine, it’s pretty durable. In stock trim it can generally handle more nitrous than allowed by the computer’s limitations. That said, however, both the 5.7L and 6.1L engines have cast pistons. They aren’t as hard or durable as forged pistons and would likely be the weak point with sustained, high-horsepower hits of nitrous – more than could be handled with the stock computer.

Dedicated kits marketed specifically for Hemi-powered vehicles were few. Luckily, the basic components of all nitrous systems are, for the most part, universal – such as the ZEX system used in this story. They include a storage tank for the nitrous (usually a 10-pound bottle), braided steel lines to carry the nitrous, activation solenoids, a fuel line tie-in and activation switches.

An advantage of the Hemi – car, pickup or SUV – is its electronic throttle control, which eliminates the need for a micro-switch to be installed near the throttle. Instead, the nitrous system’s activation switch can be spliced into the throttle control wiring harness. By tying in to the throttle position sensor (TPS) output voltage wire, the TPS voltage signal determines when the nitrous system engages – below wide open throttle, no activation; at wide open throttle, the nitrous system engages.

The biggest hassle with a “general” kit, such as the one used in the installation outlined here, is the trial-and-error procedure required to determine the correct TPS voltage wire among the numerous wires in the electronic throttle’s wiring harness. This is done by depressing the throttle pedal with the power on and the engine off. A handheld voltmeter is used to test the wires in order to determine which one is the correct voltage output carrier. Determining the correct TPS voltage wire requires manual activation of the throttle blade while testing a wire with a test light and depressing the pedal. Once the TPS voltage wire is located, a connection from the nitrous controller simply attaches to the wire and enables the wide-open throttle activation.

From there, an instant rush of power is just a press of the throttle away.


Editor’s note: This story is excerpted from author Barry Kluczyk’s new book, “New Hemi High-Performance Builder’s Guide,” from CarTech Books (




Paul’s High Performance

3715 Commerce Street

Jackson, Mich. 49203

(517) 764-7661



3418 Democrat Road

Memphis, Tenn. 38118

(888) 817-1008


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