We are the only magazine in our segment that provides full vehicle performance testing. We think it's important to call out vehicle manufacturers and tuners alike and print real numbers, so our readers can make informed purchase and modification decisions. However you use this information, be it for fun or for guidance, our testing methodology should be crystal clear. As engineering editor, I will attempt to make it so...
Theory and PracticeTesting is a lot hotter and less sexy than you might imagine. It takes at least two people all day at the race track or stadium parking lot to set up cones and timing gear and test and test and test until we have repeatable results we're satisfied with. That's just for one test on one car.
Our testing mindset and method is different from mainstream books like Motor Trend and Automobile. Not only are the cars we test different (we don't count test minivans or count cupholders), our aim is to gather real-world results and data that's relatable-and repeatable. Indeed, it's more likely an SCC reader will dyno or quarter-mile their own project car to see how it stacks up against one of ours.
Now that test equipment like data acquisition systems, GPS-based telemetry recorders and even dynos have become cheaper and accessible to the average guy, quantitative performance measurements by readers are possible. But testing still requires time, financial resources, and most of all, experience that few people outside of race teams or engineers possess. Simply having the right equipment isn't enough-you need to have the right track, driver and geek to generate useful data.
Things get even more hairy with aftermarket tuning. There are countless variables that testers of stock vehicles can ignore. But anything that can be tweaked usually is. Things like boost curves, fuel, tire pressure, spark plug gapping, suspension settings and so on add to the long list of things we have to put into the equation.
Tuners can spend hours making minor changes at the dyno or track, playing with tire pressures, alignments or even cool-down times trying to squeeze out that last 10th. We test each car we receive from a tuner as-is. We expect them to have enough common sense to bring a car that's dialed-in and ready. That rarely happens, but our job is to provide the fairest conditions we can as we try to generate repeatable numbers from usually inconsistent tuner cars.
Our core tests and procedures have not changed since the day SCC got its first radar gun and timing lights, even though we constantly explore new ways of making our tests faster, more accurate and (most importantly) relatable. Here are some standard tests SCC performs:
Dyno TestingThe fact we measure power on a chassis dyno should tell you that this is a flawed means of measurement already. But drivetrain loss variables aside, we stick with Dynojet's 248 series two- or four-wheel inertial dyno because it is the simplest, non calibration-dependent and abundant dynamometer around. All our dyno graphs show wheel-horsepower numbers generated on these dynos, even though other eddy current dynos-like the Maha-may be more sophisticated in how they acquire an accurate power figure.
For the uninitiated, the Dynojet is just a large drum roller of known properties that the car has to spin like a giant gerbil wheel. The faster a car can accelerate this heavy drum, the more power it makes. It's simple and leaves little guesswork or variability.
But there are problems. One we frequently run into is airflow. The fact that the car is stationary means it's not getting enough cold air for cooling or the intake charge. Few dyno facilities have fans that come close to replicating true airflow at 80mph. So to cope with this unrealistic scenario, we perform dyno pulls with the hood open and spray down intercoolers, then wait a minimum of five minutes between runs. It's a compromise, but it helps even out the numbers.
We've also never used SAE (Society of Automotive Engineers) horsepower correction. Long story short, when we started working with Dynojet's Winpep software, it didn't offer SAE atmospheric corrections as an option. Since then, we've stuck with it to keep our dyno charts consistent, even though it corrects to a higher ambient pressure compared to SAE.