[-Josh-]

I was reading through one of my old Hot Rod Magazines and found some really good tech articles in the January 2004 issue. This one in particular i thought would be a good post since everyone's always talking about peak numbers on here. It's a good article for gear heads...


HR January 2004, pg. 46
Area Under the Curve

Notice we said "the rpm range where the engine spends most of its time." Merely considering peak numbers is misleading. In almost every case, it is better to look at the average area under the power curve rather than simply at peak numbers, because a broader, flatter curve generally delivers superior performance to a peaky curve. As superflow's Harold Bettes puts it, "Some engines have a power curve that looks like a table top instead of a mountain range in profile are pure pleasures to drive." Comp cams Scooter Brothers adds, "If its a comp elminator, pro stock, or Winston Cup car, maybe peak power is the answer," because these engines operate in a relatively narrow RPM band. "But for the dual purpose car, torque must be flat for an extended period of time."

According to David Reher, "We look at the average horsepower within the RPM range we run in; we dont look at the peak number. Anytime you can pick up the average, that's an increase. But you dont want to lose power somewhere else."

"The wider the powerband, the better the acceleration," says turbo wizard Ken Duttweiler. "The best exacmples are variable cam engines like the Honda VTEC - they'll pull down to 500 RPM and accelerate to 7,000!" And Norm Brandes at Westech Automotive (of Wisconsin) adds that high strung, peaky motors "are easier to get out of tune. A carb on a good 'torque' motor sees a much stronger manifold signal, so it's more forgiving. The same holds true with electronic engine management; the computer will be much happier with a broad curve."

Generally the RPM range that is most important is the area between peak torque RPM and peak power RPM. The car should be geared so that you shift 400-500 RPM beyond peak power, and the engine "falls back" to just beyond the peak torque point. Assuming a similar operating range, the engine with the greater area under the power curve between the power and torque RPM peak points makes for the better combination. On an engine with the most "area under the curve," the torque falls off less rapidly after hitting its peak, so in that sense you are always building for the best overall torque, in order to produce the best overall power. This is where Scooter Brothers of Comp Cams gets his axiom, "build for torque, and horsepower will take care of itself," but remember the end goal is always to generate maximum power within your engine's operating RPM range. "There's not one thing that isn't a tradeoff," David Reher points out. "That's the most critical thing in engine building: deciding where and when to make those tradeoffs." Harold Bettes adds, "It is teh package with the greatest area under the power curve that has the advantage. Remember, you cannot have horsepower without torque, but you can have torque without horsepower!" It's called a dumptruck. HR