I can remember being a kid and thinking, "why doesn't every car have a turbo?" Now, as an adult with a few years of HPDE experience under my belt, my motto has changed to "NA all the way" – let me clarify. This discussion pertains specifically to road courses and track driving in general. Also, there's a big difference between cars that come forced-inducted from the factory, and the world of aftermarket turbos and superchargers — I'm only talking about aftermarket applications.
Forced induction does have a place in some motorsports, such as drag racing, but I think it's most important role is allowing daily drivers with little engines to stay fuel efficient while still allowing the driver to have enough power to safely negotiate traffic.
I enjoy hearing a turbo blowoff valve or the whine of a supercharger as much as the next guy, but I don't think it's the best way to go on road course. There are simply too many disadvantages: they're expensive, add too much mechanical complexity, generate too much heat, and, in most cases, don’t have a linear throttle output.
I've heard that if you want to drive, get a naturally aspirated car, but if you enjoy tinkering and you are mechanically-inclined then you might consider forced induction. It isn’t as easy as just bolting on a turbo and hitting the track. Depending on how big of a turbo you get and how much boost you want to run, you may end up buying a new transmission, getting larger fuel injectors, re-map the ECU, and buying a larger cooling system to support all this newly added power. If you don’t buy a common setup, you will also spend many hours on a dyno trying to get the air/ fuel ratio perfect through the entire RPM range. If you get the engine too lean, you run a good chance of overheating the engine and breaking internals. If you get the engine too rich, you can gunk up the valves and waste a lot of fuel. All of this cost money and it adds up quick. Don’t forget to call AAA to make sure you can get a tow home if it's your daily driver.
For the professional racer on a team, having a FI car is no big deal. They have engineers and mechanics to prep the car before each race and the driver just has to drive. For the weekend warrior like myself, I would have to play all of those roles. I would consider myself mechanically-inclined, but I am not an engineer by any stretch of the imagination. Once you actually get the FI installed and tuned, the “fun” doesn’t stop there. Now that you have added many more points of failure, and you have increased the chance for a problem when you’re at the track. That is the worst case scenario, especially if that car is also your daily driver. Good thing you called AAA and got that policy.
Heat is the enemy. It is that simple. Whether it is your brakes, differential, transmission, or engine, too much heat will end your day. FI creates more power but it also creates more heat. Even cars with a factory FI engine have overheating issues during a 20 minute track session. I have seen everything from turbo Miatas to BMW 335s limping around the track with the driver’s arm out the window with a fist up to signal they're going into the paddock because their car has overheated.
Lastly, and this comes down to personal preference, but rolling into the power upon exiting a turn in a consistent linear fashion will allow a driver to stay on the edge of his friction circle without going over the boundary. Turbo cars tend to have no power from 0 to 3499 RPM, and then the power smacks you in the butt all at once at about 3500 rpm. It only increases exponentially from there. I've spent some time driving a modded Subaru WRX that was tuned so that if you wanted to have constant linear acceleration, you had to let off the gas pedal as the engine increased in RPMs. How can you learn to be smooth when your power delivery is anything but?
With that said, a good driver with a bundle of disposable income/credit, a tow vehicle, and a mechanical engineering background (they're out there, trust me), will have no problems with going to forced-induction. It's people like myself who just want to become better drivers that should stick with a naturally aspirated car so they can spend their money on consumables and more track time.
Dave Russell is an avid track goer, future Porsche 911 GT3 owner, and driver of naturally aspirated things. His remarkably active YouTube channel can be found here.