The Sprint Booster is one of those products that are a bit difficult to explain in words. In 2000, Porsche did away with the traditional cable that connects the gas pedal to the throttle body, and replaced it with what is known as drive-by-wire. Basically, an electronic sensor on the gas pedal tells the main computer (DME) how much the driver is pressing down the pedal, and then the computer opens the throttle body on the engine by the correct amount. Some people claim that the electronic throttle (also known as E-gas) is less responsive than a normal cable throttle. I have both types of Carreras (pre-2000 and post-2000), and I haven't been able to detect a difference between the two.
The pedal has a variable sensor on it that senses the exact position of the pedal as your foot presses on it. This position is read by the computer and then used to open the throttle body. A fully depressed gas pedal makes the computer throw the throttle body fully open. Likewise, with the gas pedal at resting position, the throttle body is almost completely closed (open about 6 percent to allow the engine to idle). As you press the gas pedal toward the floor, the computer opens the throttle body somewhat proportionately to how much "gas" you're giving the carÃÂ¢ÃÂ"pushing down the gas pedal halfway means that the computer opens the throttle body enough to allow air into the engine at half its maximum capacity. It's interesting to note that the relationship between the pedal and the throttle body is not linear--for example, when the pedal is pushed down 50 percent, the throttle body is only open about 27 percent. When the pedal is pushed down 85 percent, the throttle body is open 74 percent, and when the pedal is pushed 100 percent down to the floor, the throttle body is open 100 percent.
So, how does this Sprint Booster device work? Basically, I like to call it a "short shift kit for your gas pedal." It takes the signals from your gas pedal and changes them so that the computer is tricked into thinking that you've stomped down on your gas pedal when you really haven't. Basically, you reach about full throttle when the pedal is roughly halfway to the floor. The device does not increase horsepower or overall performance of the car, however the car "feels quicker." The resulting effect is real, even if the horsepower gains are not.
It's very difficult to explain the effect to someone who hasn't actually driven the car with the unit installed. It does actually feel a lot quicker. For my last book, I had an old BMW 318is project car that had about 50 or so less horsepower than my 325is. But the car was high-revving, and because of other mind tricks, it just "felt quicker" and was generally more fun to drive. I liken the effect of the Sprint Booster to that experience. It takes a little bit of getting used when you first install it, but after a few days it will feel like second nature.
There are a few potential downsides to the Sprint Booster, however. The first one is the price--at $330 from PelicanParts.com, it's definitely not cheap. The relatively high price combined with the fact that it's very difficult to explain what exactly this unit does is probably one of the reasons why the manufacturer offers a 30-day money back guarantee on it. So, if you don't like it, the risk is about 30 minutes of your time. Another potential drawback is the fact that you may experience a decrease in gas mileage. Common sense seems to indicate that if you're an "electronic lead foot" more of the time, your gas mileage will decrease. However, an informal search on the Internet seems to indicate that most people have not experienced any decrease in gas mileage. This is one of the last projects for this book (installed spring of 2012), and I have not had enough personal drive time with the device to determine what it's impact on gas consumption might be.
One more thing to note--since this is purely an electronic modification, if you are having your DME remapped (see Pelican Technical Article: Updating Your DME with Performance Software for the Porsche 911 Carrera), then you can also have the software reprogrammed to offer the same effect as the Sprint Booster. If this is something you're interested in, you might want to discuss it with the provider of your software map before you complete your purchase.
Installation is really a snap. All you do is disconnect the connector to the gas pedal, and plug in the Sprint Booster so it's now in-line with the harness. The toughest part is squeezing your body underneath the dashboard so that you can reach the connections (see Figure 1). I was able to do it and take photos without disconnecting any of the duct work under the dash, but it takes some patience and dexterity.
Here's a shot under the dash of the Sprint Booster installation. The plug for the accelerator is up under the dashboard--simply unplug it and insert the Sprint Booster device in its place. Then, reconnect the plug that connects to the chassis. The Sprint Booster is sandwiched between these two connectors. On the 2005 and later Carreras the gas pedal has been redesigned. Installation of the Sprint Booster attaches directly on the accelerator pedal between the pedal and the cable that comes off of it.