The first day of Autumn has passed and gone. Here in Florida we still have beach weather and scorchingly beautiful heat lol. But for most of the country, Autumn is the foreshadowing of winter with temperatures starting to fall. Still it’s not too bad and by most standards it’s quite enjoyable (as one of my friends likes to put it, Shorts and Hoodie weather).
And with Autumn, comes Halloween, and Pumpkin Spice Lattes, and fall foliage, and most importantly Turbo Season. It’s during this part of the year that our forced induction brethren can strive. Cool temperatures means cold intake air, low engine temps, and ultimately more power. But what exactly comes into play for making this ideal Turbo weather?
So Turbochargers work by compressing incoming air and basically forcing as much air as possible into the intake chamber for combustion. By doing so you assume more air means more oxygen and therefore a stronger combustion for more power. So ideally you want as much oxygen as possibly. The same concept applies to Naturally Aspirated engines, but since a turbo compresses more air, the change is greater for them.
Now the Ideal Gas Law (PV=nRT) states that Pressure X Volume is equivalent to the number of Molecules X Ideal Gas Constant X Temperature. So for Turbocharged cars this means the following:
- Pressure is basically your Boost
- Volume is fixed as you only have a fixed volume in your combustion chamber
- number of molecules in this case is Air/Oxygen, which should be maximized
- Ideal Gas Constant stays constant
- Temperature is well more or less intake temperature
At max boost, pressure and volume are constant. You can’t physically control the number of air/oxygen molecules, therefore temperature is the variable factor. In order to keep the equation equivalent, to increase oxygen molecules your temperature has to decrease. Therefore colder air has more densely packed air and oxygen molecules.
To summarize, cold air means more oxygen, and more oxygen means more power!