Engine/Transmission (1998.5 - 2002) Cold Air and increased power....

[hammersley]

It seems to me that there would be a difference in HP and or efficiency when there is a great difference in the air temperature being driven into the turbo, thus the air exchanger. Wondering then what a graph looks like in relation to air temperature, and at what point it bottoms out. For example I'd assume that operating at 100 degreew would yield a different result than at say 10. Is there any truth to this????

 

[Hohn]

It's not really COLDER air that makes more power. It's actually the DENSER air that does. It just so happens that colder air IS denser.



You can actually lose power if the air gets too cold because the engine can't heat it enough to burn all your fuel. You want nice cool air, but not ICE COLD air going into your engine. Where the line is drawn is anyone's guess. This is not like a gasser engine, where colder intake air is ALWAYS better.



The charge air cooler was actually added more for the emissions reduction than for the power increase. Cooling the charge air lowers the formation of certain kinds of pollutants (NOx if I remember).



At higher air flow levels, it's possible that the charge air cooler becomes such a restriction that the disadvantage of this restriction outweighs the benefits of the cooling effect it has. Some truck puller run without such a cooler for that reason.



Remember, density is what you want in your air. Cooling the intake air is only one way to make it more dense.



Justin

 

[JR2]

My very unscientific testing has confired that cooler air is better. In the summer my truck smokes on 5x5 during a wot run. In the winter with cooler air being drawn in the truck will hardly smoke and feels like it has a bit more power. Its hard to test because with the cooler air comes ice and snow... ... and sliping and sliding in 5x5.



I really like the early winter here in AK, temps in the 20's, no snow, dry roads and big power.





JR2

 

[RustyJC]

Colder (actually, more dense, as Justin says) intake air for a diesel engine is fine, up to a point. Smoke will indeed decrease and power may go up as air temperatures go down and density increases - since the air is more dense (more mass of air per cubic inch), there's more air available to burn with the fuel, and combustion will tend to be more complete, thus reducing the partially-oxidized "soot" particles and extracting more power per BTU of fuel injected.



That having been said, remember that a diesel is a compression ignition engine. This doesn't mean that the compression pressure in the cylinder ignites the fuel; rather the heat generated in the charge air in the cylinder during the compression process ignites the fuel. The final temperature of the compressed air is a mathematical function of (among other factors) the initial temperature at the beginning of compression (in effect, IAT) and compression ratio. Under extreme conditions, IAT can get so low that the temperature of the compressed air when the fuel is injected is too low to support efficent combustion. Therefore, there is a limit regarding how low one would want IAT to go.



Large industrial diesels that are sold for extremely cold climates often have a second heating coil in each liquid-to-air intercooler for just this reason - to keep the inlet air manifold temperatures from getting too cold.



Rusty