dpasseto

As most of you know, It's fookin' freezin' out these days. I don't know how many of you took your fd's out but I got tired of looking at it in the garage and took it out for a little while. What I noticed is that My boost pattern is a little different then on days with normal temps. My guage read 12-10-12 almost everytime that I stomped on it. I also got a pretty big overboost to 14psi when my first turbo kicked on. Is it normal to get different boost readings when the outside temp is 26F????

RTS3GEN

Yes,
very normal, cold air is denser and thus fills up space faster than warmer less dense air, simple physics really.
Art

dpasseto

I guess that would also explain the big overboost at WOT. Does this mean we should take it easy when the weather is this cold?

karken29

RTS3gen... said it well.... Air density changes in the course of any given day depending on the weather patterns; i.e. if you local area is experiencing a high or low pressure area or atmospheric changes such as cold fronts or warm fronts. Further, if you keep your eye on the Barometric pressure you'll be able to determine if air density is up or down and thus how you car will perform. Temperature plays in all this in that when it's cold you cooling system and IC more efficiently manages and tranfers BTUs of heat from you compressed charge to the cars surroundings. Put another way, a one inch column of air weighs 14.7psi and approximately 18% of that is comprised of oxygen. That's the oxidizer that enables your fuel to burn. So, if you take 18% of the air present, based on its' density, you get the "Partial Pressure" of O2 present. That's what you want to know. In the final analysis though, all that really counts is maintaining good air to fuel ratios.