How Much Can I Run?
It's a loaded question, and the one we all want answered the most: How much nitrous can I run? We all want the most bang for our buck without literally going bang, right? So the answer is...it depends. The biggest thing is to know what you have in your engine. Is it bone stock, with a cast crank and pistons? What kind of cam and heads do you have? What kind of shape is your motor in? Is your motor properly tuned for non-nitrous operation? According to NOS, a small-block should be able to take about a 140hp shot, while big-blocks can handle 125-200 extra. If you're looking for more than that, it's time to start looking into forged pistons and an overall stouter bottom end. Our man Steve Brul at Westech Performance recommends not going higher than 35 percent of your engine's power output; in other words, the limit on a 300hp engine would be 105 hp extra. "You're rolling the dice at 50 percent," Brul tells us. "And I've never seen someone run 50 percent and not blow something up." This may sound conservative to some, but given that most of you will want to run your engine on nitrous more than once, we think it's advice worth considering, especially when dealing with stock engines. One of the best tips we've heard, however, is this: If you're planning to run nitrous on a regular basis, build your engine as if it will run at all times at the power level you intend to reach with juice. For example, if you're cooking up a 450hp small-block and want to hit it with a 150-shot, build the engine as if it will always be making 600 hp.
What You Must Do
Despite all the talk about whether engine internals can handle a certain amount of squeeze, most nitrous mishaps come from improper tuning, especially failure to pay attention to those most crucial of factors, spark and fuel. "People don't take enough care about their timing," says Zex's Matt Patrick. With nitrous, cylinder pressure isn't just higher, but it peaks earlier as well, meaning ignition timing must be retarded-if it isn't, detonation can quickly ruin your day. Each manufacturer will provide guidelines (they're in your instruction booklet), but reducing advance by 1.5- 2 degrees per 50 hp is a good rule of thumb. And while you're working to fight detonation, don't forget your spark plugs. In general, plugs that are one to two heat ranges colder than normal should be used when nitrous shots up to 150 hp are in play, and the gap should be reduced to 0.025-0.030 inch to help the spark travel across in this high-pressure atmosphere. Remember, by adding nitrous to an engine, you're really adding enormous amounts of oxygen-and without the proper amount of fuel mixed in, an engine can go lean and disaster can result. A nitrous system will need a minimum amount of fuel pressure to work properly-usually 6-10 psi for carburetor systems. The instruction manual for your kit will spell how much pressure is needed, and you really should make sure you have it. You also need to make sure your fuel system has enough capacity to support your goals-we'll give you a formula elsewhere, but the engine-building guidelines above work here too: If you have a 450-horse engine you plan to squeeze with a 150 shot, your fuel system must be able to support 600 hp.
For many, nitrous comes off as a risky proposition. But if we learned anything from this investigation, it's that a properly installed-and tuned-system can provide the huge power gains we all crave without making engines go boom. And the way to get there, according to every manufacturer and tuner we talked to, is to read the directions and follow their recommendations. Remember, it's all about air, fuel, and spark. If you take the time to control these factors as the experts suggest, chances are you'll quickly get addicted to the instantly gratifying, kick-in-the-pants power that comes from hitting the juice
You've got to arm your nitrous system before you run it-a covered toggle switch like the NOS piece here does the job with a bit of flair. Because it increases cylinder pressure rapidly, nitrous should only be engaged when an engine is over 2,500 rpm and at wide open throttle. A WOT ensures activation at the proper time. A simple switch like the one up front will get the job done, but beefier pieces, such as NOS' Billet Microswitch and Nitrous Pro-Flow's laser-cut piece keep the switch in place and look trick. The item at the back is an NOS waterproof microswitch, which may come in handy in marine applications.