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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, 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.
Electric Nitrous Bottle Heaters
One of the most common ways to heat a bottle is to use an electric bottle heater. Most of these heaters wrap around the bottle and 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 new 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. Many manufacturers such as Nitrous Express (NX), Nitrous Oxide Systems (NOS), ZEX, Texas Nitrous Technologies (TNT), Edelbrock and others have DC models available for sale. 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.
Peltier Junction Nitrous Bottle Heater & Coolers
A new bottle heater has come into favor among racers here in the last year or so 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's website indicates a price of around $450 which is a bit more that NX's Fire & Ice system - though the fact that it is fully enclosed and maintains a tighter temp/pressure window, may be enough to justify the added cost.
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, however the company is working on a 15lb capable model.
Nitrous Express has a combination heater/cooler that is unique. The Fire & Ice 12vdc device has the ability to both heat or cool the bottle as needed. Like most of NX's heaters, this one is controlled by bottle pressure using a pressure switch but doesn't have the ability to control the temperature as closely as the Nitrousaurus-X which uses a temperature probe and a more sophisticated temperature control. NX advertises that it can maintain bottle pressure within a 5psi window, but we have not been able to verify that from any independent sources. Typically bottle pressure switches vary far more than that. The Fire and Ice unit sells for around $380*.
No wattage or heating time data is available that we have found, however Peltier Junction devices such as this generally have the ability to cool small objects like a can of pop down to 25 degrees below ambient temperature and have about 50 watts of power available for heating. This unit probably is a bit slow for heating a bottle up as compared to the higher wattage traditional heaters.
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.
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 100 degrees. It lasts for about an hour 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.
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" and you should find all kinds of sources. The 8x12 one shown in the picture was available for $25 at Amazon.com and ebay.com.
Other Quick and Dirty Bottle Heating Methods
There are lots of other ways to heat a bottle that don't require a torch. For example before going to the track heat your bottle up in the kitchen sink with warm water for an hour or two. That will get the bottle good and heat soaked and you won't need as long to get it warmed up at track. No heater at the track? Use the exhaust from your tow truck or generator - just keep an eye on the bottle pressure, don't walk off and leave it there heating up. In the last year we've seen and heard of several guys sticking their bottles in the generator compartment only to walk off and forget them. One of these had the generator compartment closed and the generator sucked in the nitrous, resulting in a engine letting go and catching the trailer on fire.
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.
Many racers that use a lot of nitrous like to keep several bottles hot and ready to go when they need them. There are several different styles of 110 AC multi-bottle water heaters available from different sources or you can build your own using a water heater element. The biggest advantage to the water tank style heaters is very uniform bottle heating and a heat soaking ability, the main drawback is having to fill the tank full of water.
For you low buck guys out there building your own hot water style heater, consider using a heated livestock bucket which sell for around $35. They are thermostatically controlled and preset for around 100 °F.
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.