Cold air density?

[srt20]

I am on another non-sled forum. Over there people are talking about a diesel that has been seeing higher boost levels since its been colder out. Makes sense to me, cold air is less dense, less oxygen and less moisture.

Anyway there is about 20 posters that say something is wrong with the truck. The boost level is only slightly higher, couple of psi. They all say that cold air is more dense than warm air. All of them! Maybe I am missing something? I just dont believe they are right, but how can 20 people be wrong? These are predominately older people as it is a RV site.

So am I wrong? Or are all 20 or so of them wrong?

 

[zimmbob]

cold air sinks and shrinks.... thus it's more dense. when gases heat up, they expand, making them less dense, and rising. ie - hot air ballon......

I know nothing about diesel engines... I just know for sure that cold air is more dense, just like me when I get cold.... but luckily I'm warm right now!

 

[snow_monkey]

makes sense to me.

 

[dcsnomo]

Cold air is more dense. Think of it in terms of a fixed volume, say a cubic yard of air. When things cool, they compress, right? So, if you cool the cubic yard of air, it will get "smaller", thus more air will rush in to fill the void (wind), which will cool, more air will rush in till an equilibrium is reached. Thus, in the fixed volume there is more air, therefore it is denser.

 

[yamadooed]

Cold air is denser than warm air thus increase'n your volumetric efficiency. (basically more oxygen molecules stuffed in the same size container) Also what their prolley see'n is its a turbo diesel and the exhaust air density drive'n the turbo will also be increased thus spool'n the turbo up higher which in case would give you the increased boost numbers...

 

[roam]

Colder, denser air is the reason for jetting according to temperature. when the air is colder, the engine needs more fuel to prevent a lean condition. I guess the extra boost they are seeing could be because the turbo is forcing the denser air (which means more air) that expands when heated..causing high psi

 

[srt20]

Ok I gotta. I was mixing up elevations, with cold air. So while air is less dense in higher elevations, that is not the case at sea level. I was just going off of cold air is less dense because cold air in the mountains is less dense. But its because of the elevations not the cold air. Thanks guys