CHP: What's your advice about tuning a nitrous combo?
SJ: The one thing I'd say is to work your way up in steps, from smallest tune to largest. Guys bolt the thing on, try a 100-shot, then try 200, then jump all the way to 500 without learning key things like what timing each step really likes. With all the cylinder heads and engine combos, there's never two guys that have the same base timing. So start small and work your way up. Learn where it wants to be. Make a run, take out 2 more degrees, fine-tune fuel pressure, watch your e.t. and mph-especially mph-and see how it changes. Don't try to take a shortcut to the end of the tune-up sheet without going in the middle and learning, and watch your bottle pressure.
CHP: Why do you mention bottle pressure?
SJ: Any change over 25 psi will show a difference, but if pressure makes a dramatic difference, you really need to look at your tuneup. If a guy runs 900 psi, then raises it to 1,000 psi and it seems to help, it tells you the system may be too rich, since higher pressure moves more nitrous.
CHP: Any final words?
SJ: Nitrous, to a degree, is a balancing act, but guys tend to go overkill. The simpler you keep things the better off you'll be. Pay attention to the instructions provided with your kit or work with only one tuner-not everyone in the pits who will talk to you
Q&A: Jamie Wagner, Edelbrock Performance
CHP: Edelbrock is known for a lot of things, but how heavily involved is the company in nitrous?
Jamie Wagner: We've got a pretty decent nitrous program, and it's increasing every year. Our direct-port and plate systems are doing pretty well.
CHP: So how much nitrous can you use on an engine?
JW: It's more of what you know. If you're shaky on tuning the car, you could hurt the engine. You should talk to somebody familiar with tuning nitrous-and follow the directions. You can call us for help, but you have to go through the steps.
CHP: So is there a guideline as far as a number?
JW: We say about 100 hp on a street car. Then you need to get the proper components, like forged pistons, and get the ignition timing worked out. You need to make sure you're matching the engine components with performance level.
CHP: Can you give us an example?
JW: If you've got a 350 and you want to do a 150-shot on it, you should have decent pistons, the correct timing and spark-plug range, and the correct fuel delivery, whether you tap into your existing system or mount an external pump. If you have hypereutectic pistons, you have an issue. You should leave a margin for error. With a good set of pistons, you can rattle the engine and not hurt it. But as long as the tune-up is right, go 150 or more.
CHP: You mentioned fuel delivery in particular.
JW: All our jetting specs our based on 6.5 psi for carbureted systems; with a wet system, you're working off the base fuel pressure. But what you want is consistent, stable pressure. If you've got a 400hp motor that uses 80 percent of your fuel system's capacity and you want to do a 200-shot, you have to make it up. It's the same thing if a fuel system is marginal at best to begin with. Overcapacity is better than undercapacity.
CHP: What are the considerations when choosing between a plate and a direct-port system?
JW: It depends on what you're after. A direct-port system provides max gains and better individual tuning regardless of power level. You could do a 100-shot direct-port and have much better control. The benefit of a plate system is simplicity. They're easy to plumb in, easy to get up and running, and easy to tune, but not as efficient.
If you're gonna play with nitrous, you'll want good tools when you're disconnecting bottles for changes and refills. NOS' bottle nut wrench makes quick work of line adapters; Nitrous Pro-Flow's Nutbuster attaches to the line fitting with a set screw for quick line removal and comes in AN-4 and AN-6 sizes. Edelbrock's slick Bottle Nut Combo Wrench can handle three AN sizes and standard 1 1/4-inch bottle nuts.