Car seems Fast when cold

I've just been running off of my wastegate since I got the car back together and have noticed quite a variance of boost depending on temps. It a .9bar spring, and when its REALLY cold, I see as much as 13.8psi at the manifold. When its warm, it will be 12-12.5 psi. And thats just with the a mechanical spring.

I can't wait for link to open up the closed loop boost control on my ECU. It should be pretty sweet, as they've taken long enough for development. :roll:

 

Err umm, forgetting that cold air is denser -> higher pressure? Cold Air = Dense Air = High Pressure.... I see an extra pound or two of boost in the STi when it is this cold. Hell, I can hit my boost gauge "alarm" in 2nd gear. In the summer, I am lucky to hear it in 4th gear.

 

Denser air does not directly correlate to higher pressure. What we measure as pressure is relative to atmospheric pressure. Density is its own quantity, as in number of mols per unit volume. A compressor will be more effective at a higher air density since each revolution will "grab" more molecules of air. Since there are more molecules introduced into the system for each rotation of the compressor, they will stack up faster and you will reach a certain pressure quicker. hmmmmm...



I might just be over thinking all of this. A spring will be stiffer in the cold. That could also contribute to higher boost in cold temps.

 

Higher density in a given volume equates to higher pressure... PV=nRT A turbo has a fixed volume over temp.

 

I realise that. The only thing is the temp is not constant in the system, so the ideal gas law doesn't necessarily provide all the answers. You cannot just look at the turbo by itself. There is much more going on than just a compressor. The much lower temperature is going to affect everything from where the air enters the intake to how efficient the IC is to how the wastegate and spring works, and everything else.

Maybe I think too much?