The information provided by data acquisition is a reference to itself; there is no magic number other than your e.t. and mph based on changes you've made and the relationship between graphs of each variable against overall acceleration. More importantly, the data can be carefully evaluated using graphs and hard numbers in the pits so you can make the right moves.
Reading the DataEngine and Driveshaft RPMGraph A (page 72) illustrates a near perfect run from a Pro Stock five-speed car. A slower street machine would create similar curves, just not as steep! Note that the driveshaft rpm (blue) follows the engine rpm (red). As each shift occurs, there is a small rpm spike before the two curves converge at the end of the run. Pro Stock racers monitor this area carefully to avoid bogging the engine between shifts and to adjust tire pressure and suspension for the launch and 60-foot time. A spike in driveshaft rpm can only mean tire spin or component failure. Since the graphs are time based, it is easy to determine where and when tire spin is occurring.
Another use for this information is transmission analysis. Since the best torque converter in the world keeps you close to peak horsepower for the greatest amount of time, knowing how much it's slipping can be used to increase acceleration. If you are trying to optimize your pass, you want to go through the lights at peak hp with the converter putting all the power on the ground. The program automatically compares engine versus driveshaft rpm and determines the percentage of torque converter slippage. A high engine rpm and low relative driveshaft rpm (high percentage of slippage) for example, would tell you to use a tighter or lockup converter.
Finally, this info can be referenced to engine rpm to determine if the clutch is slipping in a manual trans, and abnormal spikes in rpm at the shift points will indicate an auto transmission that is slipping between shifts on its way to failure.
Battery Voltage and Fuel PressureGraph B shows the load that is placed on the fuel and electrical systems during a run. It might be a bit of a surprise to learn that the Racepak guys encountered a drop in voltage as one of the main reasons racers fail to realize the full potential of their vehicles. A typical example is the racer who moves the battery to the back of the vehicle or disconnects the alternator for more speed thus increasing the resistance between the battery and the charging system and reducing available voltage from the battery. Laying the curves over the rpm curve, any drops in rpm that correspond to a drop in voltage is an indicator of a problem. A downward curve could indicate that the ignition is starved for electrical power. The overall voltage curve is important especially when using high-end ignitions that can draw upwards of 35 amps that require a minimum voltage to operate. On a nitrous car, for example, the nitrous solenoid draws more amperage than the fuel solenoid. If the alternator fails on a run, the fuel solenoid will bog the engine with fuel and possibly backfire.
What Does It All Mean to You?If you are serious about what you are doing, there is a basic system that will help you analyze tire spin and transmission, voltage, and fuel pressure. As the car gets faster, the system is easily upgradeable to add items like a g-meter or air-fuel ratio monitor. Getting the results you want is a matter of going to the racetrack, building a database, and learning your way around the data. It will add a whole new dimension to the Friday night drags and give you a real advantage.