This NSX FAQ entry has been migrated to the NSX Wiki -> http://www.nsxprime.com/wiki/Nitrous
How Can I Learn More About Nitrous?
Q&A From Nitrous Oxide Systems, Inc.
Q: What are the advantages of using nitrous compared to other performance options?
Q: Can I simply bolt a nitrous kit onto my stock engine?
Q: Will nitrous affect engine reliability?
Q: How does nitrous work?
Q: Will the use of nitrous oxide affect the catalytic converter?
Q: Which is the best position to mount a nitrous bottle?
Q: How long can I hold the nitrous button down?
Q: When is the best time to use nitrous?
Q: Is nitrous oxide flammable?
Q: Will nitrous oxide cause detonation?
[LE - 99/9/13] There are three main types of nitrous kits. What is a good idea high HP levels is overkill for low, and what is safe at low levels can be dangerous with big HP boosts. Everything below applies to EFI cars, I'm not familar with nitrous on carbed engines.
Dry manifold kits are safe, cheap and easy for low HP applications like the RM kit which adds 70 HP to an NSX. The whole reason dry kits were developed was because people realized fuel and nitrous nitrous were not being delivered evenly with the single port fogger kits. No, the mixture is not 100% even but with a low HP kit it's good enough that you're not going to detonate. At 70 HP on an NSX you will simply not damage your engine and the stock injectors can deliver plenty of fuel. Period. There are a LOT of people who have been running the 70 HP NSX kit for YEARS and I've never heard of anyone having any problems. In fact there are NSXers using stock fuel injectors with a 100 HP dry nitrous shot with zero problems. You don't want to use a dry kit for high HP applications but but 70 or 100 HP on a 270 HP engine is not a big shot of nitrous at all.
Traditional wet single foggers are where you can end up with very uneven N20 and fuel distribution. But it's a cheap way to try and run more HP than a dry kit but less than a full direct port kit. I suspect the number of blown engines you hear about from single fogger kits is as much related to the fact that a bunch of kids who don't know what they're doing buy them because they're cheap and then try to run too much HP. They're also very flexible because it's quick and easy to change the nozzle. There are some new nozles out these days that are supposed to help with the mixture but I've never messed with them. Overall I would not recommend this type of kit. Either get a low HP dry kit or spend the money and go with a good wet direct port kit.
Wet direct port foggers are a lot more complicated to install but have good fuel and nitrous distribution. This is really the way to go for high HP applications but it's overkill if you're doing a small shot like the 70 HP RM kit. Even the 4-cylinder (think Civic, Prelude, Integra) direct port kits usually START around 80-90 HP. If you installed a kit like this on an NSX I would expect to see it running at least 175-200 HP, more if you went with new lower compression pistons and redid fuel, ECU, etc. To be honest I'm surprised there aren't several such cars out there already.
Some people manufacture plates for specific engines that will integrate with the intake manifold on those engines (i.e. the 2-piece manifold on the B18C engine). These are pretty popular because you don't have to really modify anything and the better ones do a pretty good job of atomizing the fuel/nitrous mixture to help prevent puddling.
What Nitrous Kits Are Available?
Nitrous Oxide Systems, www.nosnitrous.com
If you feel like doing it yourself, you can buy all the parts from NOS and save a little money. Most people prefer to buy a kit for the NSX so they don't have to figure it out, measure hose and wire lengths, etc. themselves.
RM Racing 70HP
[JF] NOS Kit produces 70 beautiful smooth horses at the rear wheels. Decisive power after 3500-4000 rpm I would call NSXhilaration! See Motor Trend Dec.97' for more on this subject by a pro driver... BTW, once the Nitrous System is armed, using the switches hidden behind the ash tray door, the Nitrous is then cleverly triggered using either horn button. Injection is very easy to control without any distraction to the business of driving.
RM's Dry Manifold NOS kit does not in anyway change stock NSX tuning data, plugs, ignition settings and so on. When NOS is disarmed you're Dr. Jekyll with a horn, but when NOS is armed out comes Mr. Hyde on "laughing gas".
What Performance Boost Does Nitrous Give?
[CEW] An NSX with intake, exhaust, headers, cat-bypass, Al flywheel, and 70Hp NOS can do 12.1's @ 117 - 119. If you go to 150Hp, you NEED slicks. Without slicks, expect 12.5+'s. With 150 NOS, spinning through second and third is VERY easy. This is from experience, not a guess. I will assume that 11.6 - 11.7 is possible with decent slicks + 150Hp NOS. Probable trap speeds may be low 120's.
As a side note, you may want to get a bigger fuel pump with the 100Hp NOS kit. You definitely have to have it for the 150Hp kit.
Do I Need A Bottle Heater?
[JF - 99/7/16] The summer heat is good because the higher temperatures keep the bottle pressure up above 900 psi and you will experience a huge performance difference between from 700 psi to 900 psi. If you live in a cooler/cold climate you will want to install a bottle heater kit to keep the bottle pressure up and consistent. The heater has a thermostat to turn itself on and off as needed.
Where Can I Get Nitrous Refills?
[RM] Call (800) 99R-EFIL for information on getting nitrous oxide tanks refilled.
What About Safety?
[JF - 99/7/16] If the NOS is installed with the proper safe guards it is very safe and EFFECTIVE system. I have been very pleased with my 70 shot RM NOS.
[AVE - 99/7/16] NOS packages come with a relief valve, should the pressure inside the bottle exceed a pre-set limit.
The steel bottles (sometimes called cylinders) are manufactured to DOT standards, and are typically rated for a maximum allowable working pressure on the order of 2000 PSI. I have heard of composite material bottles, but I personally am not convinced yet of long term exposure to pressure cycles. Also, composite material is not as impact resistant as steel.
The bottles are most often installed in the trunk laying down, or maybe at a slight incline. The top (where the shut-off valve screws into the bottle) of the bottle is pointed towards the front of the NSX, away from the rear bumper. If you get rear-ended and the shut-off valve breaks off, the bottle will instantly become a projectile, flying towards the person who hit you. Kind of a retribution for the idiot hitting you in the first place, no?