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Nitrous Bottle Heaters - Kiss that Torch Good Bye!
Get those bottles up to pressure the safe way...
To get peak performance from your nitrous system it's a well known fact that nitrous bottle pressure plays an important role. If your bottle pressure is too low, your nitrous system tune up will be pig fat and have less than desired results. Too much bottle pressure and you may be getting into a lean tune up, unable to activate the nitrous solenoids, or in a worst case situation run into safety issues with the bottle itself. Most nitrous companies recommend a nitrous bottle pressure around 900-950 PSI, and many racers run upwards of 1000 PSI depending on the volume they are using and other factors . The tricky part is getting that bottle up to the correct pressure and maintaining it there for during the run. Ideally you want to avoid your nitrous pressure droppping below 750-800psi during a pass to avoid the liquid nitrous turning to a gas.
Take a minute and study the Pressure Vs. Temperature chart on the right side of the page. As you can see if you're going to be racing in 60 or 70 degree weather you're going to be way low on bottle pressure. If you're racing in the heat of the summer, you'll need to be cooling the bottle down to get it to the recommended manufacturer's pressures.
According to Ricky Dyer of O2-Technology
Ricky also states that above 102°F Nitrous is 100% gas. This has a big effect on your tune up as the difference between gaseous and liquid nitrous affects how much you're putting in your engine! On the low pressure side, you want to stay above 760 psi to maintain Nitrous as a liquid, lower than that and it starts to turn into a gas again.
It's easy to cool a bottle down, just soak a towel in your cooler and lay it on the bottle and it will bring the temperature down quickly. Heating up the bottle is a bit more controversial subject, let's take a look at the methods people use to heat up their bottles...
Heating Bottles with a Propane Torch
Even though heating bottles with a propane torch is a popular method among some racers, it's dangerous and can get people hurt.
Aluminum starts to melt around 800 degrees and applying that much heat for too long in any one spot can weaken the bottle causing it to rupture. Think!!! We're talking about an aluminum (which melts easily) nitrous bottle filled with an oxidizer at high pressures and applying a torch (filled with fuel) to it - not a wise idea. Don't even consider using a torch on a carbon fiber bottle.
There are more reasons, besides the obvious safety issues, to not use a torch to heat your bottles. Many tracks have outlawed this practice and some sanctioning bodies such as IHRA, AMA/Pro-Star have as outlawed it as well. Those telltale scorch marks on a bottle may also prevent you from getting the bottle refilled at many locations.
Wrap Around Electric Nitrous Bottle Heaters
One of the most common ways to heat a bottle is to use a wrap around style electric bottle heater. Most of these heaters are powered by the cars 12 volt power system. The good systems utilize either a thermostat or pressure switch to turn the heater on and off. A heater without a pressure switch or thermostat can be a safety risk because the pressure will keep climbing to unsafe levels if the heater isn't turned off at a safe level. Even with a thermostatically or pressure switch controlled heater, it's a good idea to keep an eye on the bottle pressure during the heating process.
Even a 400 watt heater can take quite a while to bring a bottle up to racing temperatures in cool weather. If you're racing on a cool day, say 64 °F (700 PSI) and want to bring your bottle up to say 88 °F (900 PSI), you're looking at right around 18-20 minutes minimum to get it there. With this short amount of heating time, the bottle isn't going to be evenly heated either, we'll talk about that further in this article.
The other drawback to most nitrous bottle heaters is they run on 12 volt DC current and draw a lot of amps which can run your battery down quickly when trying to heat a cold bottle. The folks at Applied Racing Components have a great solution for that problem with their combo 12 volt DC / 110 volt AC Nitrous Bottle heater.
This $175* combination model is hot because you can get your bottle fully up to temperature by just plugging it into your generator without draining your battery. If you have to sit in the staging lanes for an extended time you can also use the 12 volt heater to keep the bottle at pressure. Getting the bottle up to temperature is the hard part, keeping it there is far easier for the heater to do. Most DC bottle heaters are rated around 240 watts, while not as fast as a 110 volt model, they will do an adequate job of heating a bottle in warmer weather. We highly recommend using the style of heater that utilizes a pressure switch instead of the ones that use a thermostat for quicker pressure buildup. Many Nitrous racers use these style of heaters in conjunction with a Water Bath Heater. The Electric heater is used to bump up pressure in the staging lanes if they have to sit for long, especially in cold weather.
Peltier Junction Nitrous Bottle Heater & Coolers
A new bottle heater has come into favor among racers here in the last few years is called the Nitrousaurus-X by Carnivore Performance Products. It's the as first fully enclosed nitrous temp control system for use inside the car. The 11lb Nitrousaurus-X provides both heating and cooling functions and, according to Carnivore, will maintain the exact temperature that you want within one degree F! Carnivore advertises that the unit includes a built-in overheat thermostat protection with automatic system shutdown.
Carnivore also claims that the unit will operate on both 12VDC or 16VDC charging systems and only draws 4 - 5 amps while heating or cooling. That's a huge difference from regular bottle heaters that draw as much as 20 amps or more! Once the set temperature is reached, the unit will only draw .06 DC amps. This makes it very attractive for keep the bottle at set pressures even while the car is in the staging lanes without running down the battery.
The company hasn't documented the recovery time of the bottle temp after use but they do indicate that the unit can restore the temp to the current setting "easily between rounds". The biggest drawback to the product that we can see at this time is that it's only offered in a 10lb version.
Chemical Heaters for Nitrous Bottles
One of the newest ideas that have came out lately is these little reusable chemical heater packs. These things are awesome if you need a temporary source of heat for maintaining bottle temp - notice we didn't say heating a bottle up, they're not really powerful enough to do that.
Say you've got your bottle nice and warmed up and are sitting in the lanes waiting to run and somebody oils the track down. That can easily take an hour of down time or more, and the whole time you're sitting there your bottle is cooling off. You can cover it with a blanket, which will delay it some, but it's still going to cool off.
With these handy dandy little pads, you poke the metal disc and a chemical reaction occurs which generates heat and brings the pack up to around 130 degrees. It lasts for about about 15 minutes or so in open air strapped to a bottle with a bungee cord, which isn't a lot but it's better than nothing, and is a heck of a lot easier than yanking the bottle out and taking it back to the pits to warm up when an oil down occurs. When you get back home, put them in boiling water and let them cool, and they are ready to go again! They are supposed to be good for thousands of cycles. We suggest experimenting with these some before you get to the track to see how well they hold temp and ways to secure them to the bottle.
These things are available many places online like Amazon.com as they are used in Spa's and Massage Therapy. Just do some searching for "Reusable Instant Heat Pad" "Heat Wave" is one brand name - you should find all kinds of sources. The 8x12 one shown in the picture was available for $25 at Amazon.com and ebay.com, we highly recommend getting the larger sizes vs the smaller 5x9 models.
Neal Performance Innovations
Hot Water Bottle Heater
Nitrous Bottle Water Heaters
Almost all class racers use heated water tanks to keep bottles at the exact "Ready to Race" pressure so at least two bottles are ready to go when they get the call to the lanes. There are several different styles of 110 AC multi-bottle water heaters available from different sources, however the quality of the control systems will vary and that is very important to maintain tight bottle temperatures.
One of the best in the industry is the one made by Neal Performance Innovations which maintains the water temperature very tightly, which is quite important. Note there are some that look similar to the Neal Nitrous Bottle Heater, but may not be capable of holding as tight a temperature range, so do your research if you're looking to buy another brand. Neal's unit also is equipped with a sensor thermowell to protect the temperature sensor, something many others don't use. This prevents the sensor from water damage, just like most industrial applications.
The biggest advantage to the water tank style heaters is very uniform bottle heating and the ability to heat soak the entire contents of the bottle, they are a must-have for the serious nitrous Racer.
When heating a nitrous bottle always keep safety in mind. Nitrous bottles are normally equipped with a safety burst disc in the bottle valve to prevent over pressurization of the bottle, However it is possible that the disc may not open as planned which could lead to a bottle explosion. It's a real good idea not to fully rely on automatic thermostats or pressure switches to regulate your bottle pressure. When heating your bottle, manually monitor the nitrous pressure or the tank temperature and don't leave bottles heating unattended.
Fundamentals of Nitrous Bottle Heating
Heating up a bottle takes time, the chart below shows how long it takes to get a 15lb bottle heated up to 1200 PSI from 64 degrees. An important point is EVEN heating of the nitrous, you can get the pressure up to 1000 PSI fairly quickly with most heaters, but it will quickly fall when you remove the heating element because the entire nitrous volume is not yet at an even temperature. To do that, you need to heat soak the bottle for an extended period of time.
*Please note that this test was conducted with a good bottle heater that puts out 400watts BUT it used a thermostat to switch it on and off. That thermostat, due to hysteresis (the differential between when the thermostat opens and closes), increased the time to heat up the bottle because the blanket was not on constantly. I have not tested the same heater with a pressure switch style setup yet, but you should find that pressure switch controlled heaters are considerably faster than thermostatically controlled heaters because the element stays on until the pressure is reached. Unlike a thermostat style which cycles on and off as it heats. That said, because the bottle heats up quicker with a pressure switch control, you still have the issue of how long it takes to heat soak all the nitrous in the bottle.
In the chart above it took us only 15 some minutes to get the nitrous up to 1000 PSI (99°F), but at the bottom of the bottle it was 13 degrees cooler than at the top half of the bottle. This indicates that the bottle isn't fully heat soaked. Removing the heater at this point would cause the bottle temp to quickly drop. Bottle blankets do help to reduce this, but to keep your pressure up during the run it helps a lot to have the entire contents of the bottle heated evenly to your desired pressure.
To get the bottle close to fully heated at the top and the bottom using a blanket style heater you're talking about 2 hours at temperature. Note that in the above chart, once we got the bottle fully heated to a little over 100 degrees, it held temperature for about 1 hr after the heater was turned off in 63 degree air. That's why you see the Pro's using the multi-bottle heaters in the pits. They get their bottles fully up to racing temperature and can always cool them down quickly if necessary. Then they purge the bottle down to the pressure they have their tune up set for. Remember it's far easier to cool a bottle than to heat it up. Ideally your bottle pressure should just be a little above your launch pressure when you stage the car. Excessive purging to get the pressure down reduces the volume of nitrous in the bottle and will result in higher pressure drops during the run.