Horsepower

Looking for horsepower? Lots of it? Easy to install and maintain? What? And it has to be cheap, too? Racers can be a pretty tough crowd to please! Since World War I, Nitrous Oxide has been in use to significantly increase horsepower production from internal combustion engines. As we all know, combustion is a process that automagically happens when the right amounts of Oxygen, fuel, and heat come together. In our case, the Oxygen that feeds our internal combustion engines comes from the good old atmosphere. And we all know that the earth's atmosphere is far from "perfect", from a performance automotive standpoint. This is why Nitrous Oxide is packaged in an aluminum bottle. It's like carrying your own little supply of chemically perfect atmosphere specially for your car...so it can make horsepower. Lots of it. Easily installed and maintained. Oh, and cheap, too.

What Is Nitrous Oxide?

Nitrous Oxide is a combination of two parts Nitrogen to one part Oxygen, which is approximately 1.5x more Oxygen than atmospheric air; atmospheric air contains 23% Oxygen, and Nitrous Oxide contains 36% Oxygen. Why don't we simply carry a bottle of pure Oxygen, you ask? Simple; we want our engines to last more than about 2 seconds of extremely high power production. The Nitrogen content is to dampen the combustion process. Bolt-on Nitrous Oxide systems are available from several companies, the most popular brands amongst racers are Nitrous Oxide Systems(NOS), Nitrous Express, Top Gun and Nitrous Works.

The theory

Engines burn 14.7 parts atmospheric air to every one part gasoline on every power stroke. (More or less.) Remember all the fractions you've done in the 7th grade? Believe it or not, your grade school knowledge is about to come in handy. We must remember in fractions, that whatever happens to the numerator also happens to the denominator. So if we burn two parts gasoline, we must add 29.4 parts air. Let's keep this simple ratio in mind. Remember when I told you that Nitrous Oxide is 36% Oxygen? Well that would affect our ratio of 14.7:1 now, wouldn't it? With Nitrous, it's more like 24:1.6. What's this? MORE fuel? Ah, so we see the key reason to using Nitrous. The additional Oxygen allows us to burn more fuel. And with more fuel comes more power. (Keep in mind that 24:1.6 is not a literal ratio; we are still aiming for 14.7:1 but the Nitrous Oxide significantly increases the Oxygen concentration in the combustion chamber.)

Enough theory! I want to burn some rubber

There are 3 basic types of systems; "wet" manifold, "dry" manifold, and direct port.
Let's discuss wet manifold first. In a wet manifold system, Nitrous Oxide and fuel are delivered by an injector that manufacturers call a "Fogger". A Fogger is just a fancy name for a nozzle that combines your fuel and Nitrous into a cool "fog", and sprays it right through the throttle body. (You should know where it goes from there.) Since all engines are different, you can maintain our 14.7:1 air/fuel ratio by adjusting the orifices located on the Fogger, known as jets. While the jet itself is not adjustable, it is replaceable with another jet that will have a larger or smaller metering orifice, depending on what you need. (This is also how you adjust how much power the Nitrous system will help your engine make.) Where do the fuel and Nitrous come from, you ask? The Nitrous side of the fogger plumbs to the Nitrous bottle itself, through an on/off solenoid. The fuel side also goes through an on/off solenoid and into the stock fuel system. We'll discuss this in greater detail a little later.
The dry manifold type of system is the easiest to install. In this case, Nitrous is delivered not by a Fogger, but by a simple nozzle. The fuel is provided by the stock fuel injectors. The crude-but-effective way to make the fuel injectors deliver enough fuel to match the increased Oxygen in the combustion chamber is to increase the fuel rail pressure. The fuel rail pressure is increased by pinching off the fuel return line (bypassing the stock fuel pressure regulator), also done with an on/off solenoid. A Nitrous Oxide system isn't smart enough to hold the injectors open longer. Kinda like watering more of your lawn by opening the spigot more, instead of adjusting the speed of the sprinkler head. Got it?
Direct-port systems are considered by racers as the ultimate in reliability and power. This type of system uses one Fogger per cylinder; one located right at the head's intake port. This is the toughest to install, necessitating removal of the intake manifold. It is also difficult to adjust. But if you are into the racy-racy thang, the work will be well rewarded. By kicking just about anyone's ass that dares race you.

Installation simplified

Okay, so you've purchased your Nitrous Oxide system. Now what? Read the directions! But seriously folks, keep in mind that Nitrous should only be used at wide open throttle above 2,500 RPM. Anything less would be uncivilized. And cause what's known as a lean-out backfire, where too much Nitrous fills the cylinder, dramatically offsetting our nice 14.7:1 air/fuel ratio. Unless you like fire and explosions, do be careful. NOS and Jacobs manufacture special controllers that can cut in and cut out nitrous flow at specifed RPM points, and only at WOT. They are not expensive; and are cheap insurance! If you think you need a custom job, racers have had great luck using RPM operated accessories from MSD, Mallory, and Jacobs Electronics. But for most people, an out-of-the-box system will do the job nicely. If you've paid attention to half of this article, you'd already know that you need to plumb the Fogger(s) or nozzle. Then the Nitrous and fuel lines go from your Fogger/nozzle to their respective on/off solenoids, and attach to your Nitrous bottle and splices into your fuel line, respectively. In the case of the dry-manifold system, the fuel solenoid simply shuts off the fuel return line. Since the solenoids are simply on/off devices, you can wire them to a thumb button, or to a floor switch, or whatever you like!

Some Tips On tuning

Nitrous behaves much like a turbocharger; once it hits, you may have to make adjustments to your ignition timing and mixture. With Nitrous Oxide systems, the mixture adjustment is handled in the Foggers and nozzles. The ignition is still controlled by your distributor, unless you use an opto-ignition timer from Jacbos Electronics. If you need tips on which jets to start with, refer to the May 1996 issue of Turbo and High Tech Performance magazine (714-962-7795). A good rule of thumb is to start tuning from a fuel-rich and timing-retarded environment. This will help protect your hardware while you incrementally increase nitrous concentration and spark timing. Racers have had pretty good luck retarding base ignition timing 2 degrees per 50 horsepower of nitrous. If your car has a built-in knock sensor, so much for the better! The ECU will retard the timing for you when the nitrous comes on-line. (Integra GS-R, Eclipse GS-T, etc.) If you are luckier, your ECU will have a "wide band" oxygen sensor, which means it'll make up for slight errors in your jetting. (Audi A4) But be careful if you're not sure whether or not your car has these wonderful features. Do adhere to these guidelines, and your engine will enjoy many kick-ass runs down Main Street, er, the sactioned drag strip. To make sure your mixture and timing are correct, read your sparkplugs. A light tan coating means that you are spot-on. A black plug indicates too much fuel for peak power production, and a white one means there's not enough fuel. Be aware of mechanical damage to the plug, too, such as blistering. This (or knocking) may indicate your base ignition timing needs to be backed off. If you think your timing is too retarded, advance it in 1 degree increments until the engine knocks. At WOT, it'll be hard to hear knocking, so use caution. Ah, the sparkplugs. Don't forget that when you pack more air and fuel into a cylinder, it's a lot harder for a spark plug to fire. You may want to either upgrade your ignition system with an MSD, Jacobs, or Crane ignition unit. Nology spark plug wires give excellent results when used with Nitrous. Or,you can simply keep the stock ignition setup and reduce your plugs' gap by 0.005". The latter is "no buck", but will also hamper power production when you are not using the Nitrous.

The limitations