Good things may come to those who wait, but when it comes to horsepower there’s nothing better than a little instant gratification. That’s exactly why we love nitrous systems. It’s power at the flick of a switch, there just when you need to cut a few tenths off your ET.
But nitrous isn’t just for dedicated drag cars. In fact, it makes a perfect addition to a powerful street/strip hot rod because it can add significant amounts of horsepower even when you’re on a tight budget. Best of all, it does all of this with no effect on drivability or gas mileage during regular cruising.
For this tech installment, we took one of Nitrous Oxide System’s (NOS) Powershot 125 carbureted nitrous plate (Part #05001NOS) for Carter and Holley carbs, and installed it on a very nice classic Challenger. We did some before and after dyno testing to see exactly how much horsepower and torque the system can add to a typical street/strip musclecar.
The Nitrous System
It’s a common misconception that nitrous is some kind of a “super fuel,” but it really builds power by working on the opposite side of the combustion process. Nitrous is actually a non-flammable gas that has been compressed down into a liquid. When injected, it acts as an oxidizer and introduces huge amounts of extra oxygen into the combustion process.
With all that extra oxygen there needs to be a proportionate amount of fuel added to match it. That’s why most carbureted plate systems like the Powershot 125 utilize two solenoids – one is plumbed into your existing fuel system for adding extra fuel, and the other is connected to the nitrous oxide. Both solenoids allow the additional fuel and the nitrous to be injected into the intake tract.
To get the extra juice into the intake the Powershot 125 system uses NOS’s simple injector plate that bolts directly under the carburetor. The injector plate sprays the nitrous directly over the stream of additional fuel right as it enters the intake plenum. It’s a simple and extremely effective delivery system that can be used on virtually any mechanically sound, carbureted vehicle, with a strong fuel system and an extra ½-inch of hood clearance.
Another huge benefit of a system like the Powershot 125 is that they are extremely inexpensive considering the type of power gains we are talking about. The kit comes ready to go with every component you need to install it on your musclecar; from the 10-pound bottle all the way down to the gaskets. In fact, you can pick up the ready-to-roll Powershot 125 system for just a little over $400 from most retailers like Summit Racing. “Nitrous is one of the most cost effective ways to safely add horsepower to an application,” says Blane Burnett from NOS. “NOS is pleased to be able to offer these power adding solutions to racers who don’t want to spend the coin on a forced induction setup in order to add more horsepower and torque to their vehicles.”
Major Benefits of the NOS Powershot 125 Nitrous System
- Relatively low cost
- Big horsepower and torque gains
- Easy installation
- Perfectly safe when properly installed and maintained
- Horsepower when you need it, normal drivability when you don’t
The Car/Before Test
Nitrous is one of the most cost effective ways to safely add horsepower to an application. -Blane Burnett
Our workhorse for this install and test session is Adam Miles’ gorgeous 1972 Dodge Challenger, which you’ll likely recognize from our recent feature on the car. The Challenger is powered by a 360 small-block that has been bored and stroked out to 408 cubic inches. It was built to do two things: look good, and go fast.
With a host of underhood goodies, including a 750 cfm Demon carb, the goal here was to give the engine a little assistance with the flip of a switch, without having to do a lot of modifications internally. The car combined the classic look of the early Challenger with a few upgrades to help it perform like the modern car, without giving up its musclecar heritage.
Dynojet to see how much power it was starting out with. The Dodge churned out a respectable 295.9 horsepower and 321.8 pound feet of torque at the rear wheels as our baseline.Before we got busy with the install we strapped down Miles’ Challenger to our in-house
Overall the install of the Powershot 125 system is fairly straight forward, but it does require attention to detail and a mindset focused on safety. The best place to start is deciding where to mount the bottle. You can mount it in just about any location you want as long as you keep a few things in mind.
First, the orientation of the bottle has to be taken into account. The pickup tube inside the bottle is angled down towards the bottom corner of the bottle so that the combination of the car’s motion and the angle of the mounting brackets will always keep it covered even when the bottle is almost empty.
So how do you know if you have the pickup tube aimed correctly? Easy – the NOS label on the bottle is your clue to how the pickup tube inside is aimed. If the bottle is mounted straight forward, then the label goes straight up. If you have to mount your bottle at a bit of an angle or even horizontally, you simply turn the bottle in its brackets to aim the pickup tube towards the bottom rear of the bottle where the nitrous will pool when the car is moving. We couldn’t mount the bottle perfectly straight in the Challenger because of the trunk hinges, so we slightly angled it and gave the bottle a very slight twist in the brackets to put the pickup where we needed it.
The second consideration in bottle mounting is ease of access. You’ll have to remove the bottle regularly for refills so make sure you mount it in a place where you can get to the mounting brackets easily, and that you can maneuver the bottle in and out of the car without banging it around. Beyond that, just find a place that is solid and flat, mark your holes, and drill away. We used 5/16-inch nuts and bolts along with washers on both sides to keep the hardware from pulling through the floor.
Running The Feed Line
The next step in the install is to run your feed line to the engine bay. When you’re laying out your line find a path that avoids any sharp edges, moving components, and hot exhaust. NOS says it’s fine to run the feed line through the passenger compartment if you need to. We decided to follow the trans tunnel and secured the -4AN stainless line under the Challenger. The included 14-foot long line was just the right length to get to the top of the intake manifold taking this route. However you route your line, it’s important that you give yourself enough slack to be able to remove and replace the bottle easily.
From here it was time to go back to the rear of the car and get the bottle completely squared away. We put the white Teflon washer in the bottle adapter, tightened it up to the bottle valve, and connected our feed line to the adapter.
Under The Hood: Injector Plate and Solenoids
Moving back to the engine bay, we removed the air cleaner and carburetor, installed the longer carb studs, and dropped in the injector plate. The important thing here is to make sure the plate has the spray bar holes aimed down into the intake manifold. If they aren’t aimed down, well let’s just say this would be a less than optimal situation for both safety and power production. An easy way to tell if you have the plate oriented correctly is if the NOS logos cast into the ends of the mounting surface are facing up – simple as that.
From there you can decide where you want to put your fuel and nitrous solenoids and turn the injector plate accordingly. We decided to put the fuel solenoid (red) on the back of the engine and tap into the fuel system at the end of the fuel feed line on the secondary side of the carburetor, and to put the nitrous solenoid (blue) on the front side of the carburetor.
Wiring Up The Solenoids and Switches
Next we moved on to wiring up the solenoids, arming switch, and the micro switch used to trigger the system. The wiring is fairly simple. In fact, only one hot wire needs to be tapped using the included fused link and connected to the arming switch. We decided to mount the arming switch inside the Challenger’s ashtray to keep things stealthy and for easy access by the driver.
The hot wires to the solenoids and micro switch trigger are then ran from the arming switch. Then it’s really just a matter of making good grounds, and following the easy to use instructions included with the kit.
Mounting up the micro switch trigger is one of the most important parts of the install. The micro switch is designed to be clicked by your carb linkage and trigger the Powershot 125 system while you keep both hands safely on the wheel. Burnett tells us, “The kit comes with a universal bracket – meaning it may need to be modified slightly in some applications – to install the micro switch in close proximity to the throttle linkage in such a way that the switch activates when the throttle is at 90% or wide-open-throttle. It’s important to note that when installing the micro switch to make sure you don’t obstruct the path of the throttle linkage in any way.”
After we reinstalled the carburetor, we bolted the micro switch bracket to the rear carburetor stud on the driver’s side, and bent the bracket how we needed it and made sure that it was engaging at the correct point.
The “After” Test
When we had the entire Powershot 125 system wired and plumbed we did a thorough final check for functionality and safety. After just a few short hours of careful and deliberate work it was time to put the Challenger back on the Dynojet and see just how much our new magic switch had given us. We armed the system, went to wide open throttle in third gear, and the micro switch worked flawlessly triggering the spray. The difference in how aggressively the challenger spun the drums, as well as how it sounded at WOT was instantly noticeable.
We knew that the car had significantly more power, but we also knew that the 125 shot of nitrous wouldn’t translate directly to an instant 125 at the wheels. The dyno graphs revealed 386.0 horsepower and 380.6 pound feet of torque from the Challenger. We had gained a total of 91.1 horsepower and 58.8 pound feet of torque at the wheels. It’s enough to shave a little time off the big Dodge’s quarter mile time. That’s a great gain, especially considering that the car still has the same street manners as before, and no extra encumbrances like it would with a supercharger or turbos.
The Final Dyno Results
- Before – 295.9 RWHP and 321.8 LB./FT.
- After – 386.0 RWHP and 380.6 LB./FT.
- Total Power Gain – 91.1 RWHP and 58.8 LB./FT.
The Final Gear
Nitrous is the very definition of bang for your buck. The horsepower-per-dollar, and even the horsepower-per-minute-of-install-time ratios are absolutely through the roof with. In fact, it would be difficult to come up with another power adder for a musclecar that will yield 90 rear wheel horsepower for just over $400 bucks and an afternoon worth of install time – and still keep the street manners intact at that. We call that a definite win-win situation.