`The buzz is all about whether those nitrous camshafts are worth the effort. The skeptics in the crowd say the cams are just a marketing ploy and they don't work. Their point is that if you want more power, just add more nitrous--you don't need a different cam. There may be some truth to that since several companies list cams merely with wider lobe-separation angles as "turbo" or "supercharger" cams. It seems to us there is more to a nitrous cam than just that, so we decided to find out.
All About the O
The "O" in "N2O" is oxygen, and that's the oxidizer that nitrous adds when you squeeze the button. Adding more oxygen allows the engine to oxidize more fuel. Burning that additional fuel is what makes the power.
The performance key is the huge torque gain that comes from a given amount of nitrous added to the engine. For example, most nitrous companies using a 0.063-inch nitrous jet for a single-stage system will rate the package at 150 hp at 6,000 rpm. What many enthusiasts don't realize is the major torque gain created by this combination. That same volume of nitrous at 3,500 rpm is worth a stout 225 additional lb-ft of torque. If an engine is capable of making 400 lb-ft, add the squeeze and the twist jumps to 625 lb-ft, which is monstrous torque at that engine speed.
We talked with Comp Cams cam designer Billy Godbold, and his contention was that since nitrous already adds a ton of torque, why not improve the cam to make more horsepower as well? Ironically, the details of that cam design tend to reduce midrange torque, which is generally considered to be a main area of concern for a street engine. So in theory a nitrous cam will trade torque for a better top-end horsepower number. That's what we wanted to test.
We decided to use a Nitrous Pro-Flow plate similar to the one that won our recent test ("Nitrous Plate Shootout," Nov. '05). This 1-inch-tall plate utilizes Pro-Flow's directed nitrous spray bars combined with Pro-Flow's patented burst plates. The plate assembly and solenoids come prewired using quality Weatherpak connectors.
Cams For Nitrous
Most street-oriented performance cam grinds tend to include a significant amount of overlap. This is the period of cam timing when the piston is coming up toward the end of the exhaust stroke, the exhaust valve is closing, and the intake valve is just opening. As overlap increases, it tends to improve midrange and top-end power by starting the intake process sooner. It also tends to hurt power down low but help it on the top end. This overlap is what produces that distinctive choppy idle quality when reversion forces the exhaust and intake charges to mix.
The problem with lots of overlap when using nitrous is that the additional air and fuel is often lost since some of what is pushed into the cylinder immediately exits past the exhaust valve. One way to prevent this situation is to widen the cam's lobe-separation angle, which decreases the amount of overlap.
This Comp Cams graph does a great job of illustrating the concept of valve overlap. Note the triangle area created by the convergence of the exhaust closing point with the intake opening point. This illustration is of a different cam than the one we are running, but the effect of overlap is the same. By widening the lobe-separation angle from 110 degrees on the XE 274H cam to 113 degrees on the nitrous cam, we reduce the overlap and hopefully improve power.