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Consistent results from your nitrous system require consistent bottle pressure. Nitrous injection rate is directly related to bottle pressure. NOS nitrous systems are designed for nitrous bottle pressure between 900 and 1,000 PSI. A bottle with lower pressure will spray less nitrous than a bottle with proper pressure. In other words, the bottle pressure directly affects the effective "jetting." Inconsistent bottle pressure yields inconsistent performance.
Low bottle pressure results in a performance-killing double-whammy: not only is less nitrous injected, but the fuel side of the nitrous system injects the same fuel regardless of bottle pressure. The result is an overly-rich mixture—further depressing power.
How do you increase bottle pressure? Warm up the bottle! High school physics told us a gas's pressure and temperature are directly related. Increase a gas's temperature, and the pressure goes up. Reduce the pressure, and the temperature goes down. This is especially relevant to nitrous systems because even a bottle that's at the proper temperature and pressure will cool off during a pass because the pressure is going down in the bottle as the nitrous is used up.
The safe way to warm a bottle is with an electric bottle heater. You may have seen racers warm bottles with other methods, but they're quite literally playing with fire. An aluminum bottle is heat treated for strength. Using any localized heating method can alter the heat treatment and compromise the bottle's structural integrity. With nearly 1,000 pounds pushing on every square inch of bottle surface area, skimping on a bottle heater is a dangerous gamble.
NOS offers bottle heaters that are powered either by your car's electrical system or an external 110V AC power source. To avoid overheating the bottle, heaters are either temperature-activated or pressure-activated. Since the goal is to maintain the bottle at 900-1,000 PSI, a pressure-activated bottle heater is ideal.
A bottle heater not only brings the bottle pressure into the needed range for the first pass, but re-warms the bottle for the next pass because each pass cools the bottle as it's emptied. An NOS bottle heater is the best, safest way to maximize NOS nitrous system performance.
NOS offers bottle heaters that run on 12 volts DC and 110 volts AC. Thermostatically and pressure-activated methods are available.
We'll show you how we installed and tested the NOS Automatic Nitrous Bottle Heater (P/N 14169NOS) on a nitrous-injected 1991 Mustang GT.
NOS bottle heaters warm the bottle using a flexible electrical element that wraps around the bottle and is secured with hook-and-loop straps. Here's how we installed an NOS Automatic Nitrous Bottle Heater (P/N 14169NOS) on a Foxbody Mustang.
We installed the pressure switch between the bottle nut and the -4 supply hose using the supplied swivel adapter. (Note that the nitrous bottle valve must be open for the pressure switch to sense bottle pressure!)
We used the excellent instructions included with the NOS Automatic Nitrous Bottle Heater (P/N 14169NOS) as a guide for making the electrical connections.
NOS recommends placing the included electrical relay close to the heating element. We tucked the relay behind the interior taillight trim panel of this Mustang.
The taillight harness ground screw next to the hatchback latch provided a convenient and secure electrical ground for our heater.
We ran the relay's red trigger wire to the included switch which we mounted next to the NOS system's arming switch and piggybacked the power and ground for the switch off of the arming switch's wiring.
The orange supply wire for the relay went along the rocker panel, up through the kick panel and out of the firewall grommet shared with the fuel injection wiring.
We connected the relay's orange supply wire to the battery side of the starter solenoid.
With the electrical connections finished, we were ready to warm the bottle. Even with the nitrous bottle at a warm ambient temperature (74.5 F), the bottle pressure was low.
Our bottle was still relatively full, but the bottle pressure was only 825 PSI—below the 900-1,000 PSI target range.
We opened up the bottle valve and turned on the heater.
The NOS bottle heating element warms to about 130 degrees F (depending upon supply voltage).
Speaking of supply voltage, we wanted to see how much the NOS bottle heater taxed our battery, so we monitored the battery voltage. Our reading of 12.43 V was with the engine off. If we wanted to warm our bottle faster, we could run the engine to get the voltage up to 13.8 V.
After using the heater for 27 minutes, the NOS bottle heater raised the bottle temperature 15 degrees F.
Right on cue, the NOS Automatic Nitrous Bottle Heater's pressure switch shut off the heating element when the bottle pressure reached 975 PSI. Perfect! (Remember to turn off the heater before closing the bottle valve!)
Here's what we recorded while warming our bottle. With the battery around 12.4 volts, the NOS Automatic Nitrous Bottle Heater (P/N14169NOS) increased the bottle temperature 15 degrees F and raised the bottle pressure 150 PSI. Now we can bring our bottle pressure back up between passes quickly, easily, and safely for consistent nitrous performance!