I have been forced to drive my coupe in the cold alaska winters (-14F!)
and I have gotten used to what seems like a huge difference in acceleration!
Some of the roads around here don't have snow on them, so I can hook up (my tires)briefly and damn, it sure feels good.. Just wanting to know what mods I will have to do to get the same power in the summer?
Gary.

 

I have seen reports claiming 1% gain in power for every 10 degree drop in air temperature, due to denser air having more O2. Also a factor for SOTP gain is that the tires and road surface are cooler, lessening traction, making car feel faster 'cause you can light-um-up easier :D Enjoy. :cheers:

 

The density of air increases at 0.4% per degree Centegrade loss (ideal gass law).

 

Something else to remember about colder air is even though the relative humidity may be high, actual moisture content may be very, very low. Relative humidity is just a measure of how much moisture that air is holding, relative to it's maximum capability. The colder the air, the less the capability to hold moisture, therefore, the higher the relative humidity (with the same total moisture content in the air). So, even though relative humidity may be higher in the winter, and usually is, actual moisture content of that air, per unit mass, is lower.
Air holding a lot of moisture is less dense air. The water molecules in the air displace the oxygen molecules. In the winter you have two things helping you toward denser air...low temps and low moisture content. It sure works!:D
Ed

 

Gary,

If you’re interested in the physics behind this, it goes something like this. The engine produces hp by converting heat energy to mechanical energy in the form of expanding gases. The intake system limits are by air volume, where the heat energy available is a function of the oxygen present. Cooler air is more dense and has more oxygen molecules per volume. The ratio of temperature to volume is a direct one, double the temperature and double the volume. The base temperature in -459 degrees F. or absolute zero. The ratio from 70F to 0F is the ratio of 529 over 459. Depending on which way you want to express it 70F air has 86% of the available oxygen of 0F air OR 0F air has 115% of the oxygen of 70F air. All things being equal (and the never are) a car that makes 345 crankshaft HP in 70F air would make 397 crankshaft HP in 0F air. As you can see there is an almost unbelievable 50 HP gain from just cooler air alone. As I said, all things being equal. The rest of the story is this temperature change HP is more a function of inlet temperature than a function of ambient air temps. The place to measure this temperature is in the intake tract just before the mass air flow sensor. GM knew about this when they placed a temperature sensor in this very spot. Smart huh? GM went one better and used a sensor that measures air MASS and not volume to gage air flow into the engine. To calculate the volume of a gas we need to know both temperature and pressure. The C5 sensors measure inlet temps, air pressure inside the air plenum and the mass of the air flowing into the engine. This provides a redundant measurement system. The stock C5 air intake system draws air from the relatively warm engine compartment and is not impacted as much by outside air temps. Air screen like in the Z06 help to address this issue. An after market air intake system that draws air from outside the engine compartment will be more affected by the outside air temp. I have measured my inlet air temps using autotap and found with my after market system that the inlet temps will be only a few (2-3) degrees higher than ambient air temps. Cooler inlet temperature do in fact make large differences in real world horsepower.

Terry

 

Thanks Terry! Now I suppose I know what a 405hp/Z06? might feel like to drive.