The power adder page

Just thought I would tack on some thoughts and notes on power adders, since I get lots of questions on some of the setup's on these pages...

First off, what am I calling power adders? Well they usually fall into 2 basic groups. Mechanical supercharging, or nitrous oxide injection. Both are designed to add extra air, which allows more fuel to be burned, which equals more horsepower. Any of these can be a basically simple bolt-on, or a complete engine and support system upgrade. They will add 50-500+ hp.

Of course, we have all heard "nitrous kills engines", or " a supercharger puts too much wear on the crank".. etc., etc.! You also shouldn't be playing jacks on the freeway at rush hour, so I will assume you possess a little common sense!

For all but the most basic system, ignition and fuel upgrades will be required, as well as forged pistons, better valves, exhaust, cams... well, you get the idea? No free lunch, but that is how this hobby goes!

Mechanical Superchargers

This breaks down into 2 categories, either a belt driven supercharger (Vortech, ATI, Paxton, Power dyne, 471 - 671 - 871), or an exhaust driven supercharger, known as a turbocharger. Both are designed to do the exact same thing, that is to inhale air, compress it, and pack it into your cylinders. There are so many different ways to compress air (snail, screw type, twin or three rotor) that I won't even try to break them all down. Suffice it to say there are plenty of options for whatever you want to do.

The belt drive takes some horsepower to drive, which increases as the boost goes up. At high boost levels it will also add loads to the crank nose that they were never designed to see, and also try to twist the balancer/pulley on the crank. That is why you see big block snouts on small block cranks, and double keyways.

You also have three basic types of s/c; centrifugal (Vortech, Paxton), Roots (671) and the screw type (Kenne Belle comes to mind)
The centrifugal and screw are like a turbo in that they compress the air in the housing, whereas the roots packs it into the intake manifold.

The turbo will add heat and more piping under the hood, as well as some restriction to the exhaust. You also have added weight on the exhaust manifolds, which tends to break bolts and blow out gaskets. Most turbo specific headers have thick flanges and piping to offset that. You can cure some of the exhaust restriction by going to a larger exhaust housing or a smaller impeller, but then you induce more lag. Newer ball bearing turbos spin up easier to help offset that. Lots of research is required before you jump off into it.

Either type of supercharger adds extra weight to the nose of the car, so plan for that. You�ll also be rerouting hoses and wire to get them away from the heat on a turbo, since you have so much more exhaust piping under the hood.

Nitrous Oxide

First off, NOS is a brand, not the buzz word. Now so far as naaawwwzzz, well, we'll just blame that on the FTF crowd and move along.. (2 bottles, the big ones!!)

This is "oxygen in a bottle", stored under pressure, that is introduced into the intake along with extra fuel to do the same thing as the supercharger does. It is a combination of oxygen and nitrogen, which released into the atmosphere expands and releases the oxygen. A by product is that it also freezes the air as it expands, which lowers your intake temperature. We'll go into advantage/disadvantage later on. Some manufacturers are NOS, ZEX, Wilson, Compucar, NX.. and most have kits for carbureted and FI cars, and you can also build your own, using nozzles, jets and solenoids from the various lines.
You have two styles, nozzles or plates, and jettable or non-jettable. The carb systems run at 5-7 psi, and the FI systems are around 43-45 psi. With a plate, you have two spray bars (one fuel, one nitrous) that are either metered by the size and number of holes, or jets. The nozzles always use jets.

FI systems come in two variety�s: wet or dry. The wet kit uses two jets or bars, one for fuel and one for nitrous. The dry kit simply injects nitrous, and increases your fuel pressure or injector cycles for the extra fuel. The new FI manifolds are designed to flow dry air, so some don�t distribute the fuel well. That is when you go to a direct port system.

You can�t just keep going to bigger and bigger jets. At some point you will reach saturation, where the cylinder can no longer compress the mixture, or the spark cannot fire it. Or, you will just break something.

The other thing to note is since you are adding raw oxygen, you don�t want to be using any oil! It will act just like oil on a oxy/ace setup, and become a blow torch (or bomb)

Most nitrous systems are designed to have bottle pressure around 900-950 psi. More will lean the mixture out, less will richen it up. Too much and the nitrous solenoid may not open. NEVER HEAT THE BOTTLE WITH AN OPEN FLAME!!!!! This will crystallize the aluminum, and create a weak point. Also known as a hand grenade in the trunk.

All nitrous systems are jetted �safe�, or rich, so you have a little room to fine tune.

It is not recommended to ever engage the nitrous below 3000 rpm, or at part throttle openings. There is just too much cylinder pressure involved. An average 150 hp system will spike the torque over 160 ft/lbs, so think of the instant load that puts on the motor. I have personally seen a 302 Ford break two rocker studs and bend 4 pushrods when the button on a 100 hp system was accidently touched at idle. He was lucky (and had good parts) that was all he had break! WOT throttle switches are cheap insurance.

Ignition and fuel requirements

Any time you try to burn more fuel, or raise the compression, you will need to start the spark sooner. You also want a colder plug to lessen the chances of detonation in the hot chamber.

So you�ll need to go a couple steps colder on the plugs, but if it is a street car they tend to foul. So keep an extra set for the track. Occasional use on the street won�t hurt the stock ones.

Timing will vary by your combination, for spray most say around 2 degrees retard per 75 hp. On boost, � to 1 degree retard per pound of boost will be a good start. The electronic ignitions that are available make this super easy. Most use a plug in chip or dial.

Speaking of ignitions, more cylinder pressure needs a hotter/longer spark, so a quality aftermarket ignition and wires is a must.

You�ll also need extra fuel for the extra air to burn, so a quality fuel system is a must. All high end systems (150 hp and up) should use a stand alone system for the nitrous. Most FI cars can handle higher levels of spray due to their fuel system design. On the superchargers you will need more fuel as the boost goes up, so you either run a FMU (Fuel Management Unit) which increases your fuel pressure exponentially, or a boost referenced regulator and in the FI world, and modified injector map.

Safety

See the note about never heating a nitrous bottle with an open flame. Remember that this is also outlawed by ALL sanctioning organizations (like NHRA), and grounds to be asked to leave the track.

WOT switches, boost retard, water or alcohol injection, fuel pressure safety switches are all excellent add-ons. Depending on your system, you should seriously look into them.

Always be aware of the extra power under foot, and that the rest of the drive train needs to be up to the task. Traction can become very limited!