Does anyone know how to calculate or determine what the optimal air temperature is for optimal combustion? This would obviously have to take into account that the A/F mixture is also optimal. Another way to say this is: What is the point when the air becomes too cold and will hinder combustion? Any ideas on what equipment would be needed to test and verify this? What are the indications that the inlet temperature is too cold? Let the thinking and analysis begin.

 

I didn't know air could get too cold to combust. As long as there is oxygen, it will burn. The colder the air, the more dense, the more oxygen to burn.

 

It would have to be so cold that it thickens the oil. You aren't even going to see that in Antartica.

 

OK, this is not going where I thought it would. Or maybe it is - that's the point. What I'm after is: Is there an optimal air temp that will get the most air(mass) in and still get complete combustion. Is complete combustion not attainable? Is there always going to be fuel that doesn't get burned. If so, can the air temperature effect how much is left unburned?

 

I've never heard of an optimal air temp. Just optimal mixture based on density. At some point I would imagine, air temp's (density's) benefits would be limited by the ability to measure airflow and add correct amounts of fuel. Although, some race cars have a volumetric efficiency over 100% at room temp? So what do I know.

Here's a website that can help you calculate hp increase from air density. This explains the relationship between, humidity/pressure/temperature and density and how it affects horsepower. Hope this helps.


http://wahiduddin.net/calc/calc_hp_dp.htm
http://wahiduddin.net/calc/density_altitude.htm

 

Air keeps getting denser as it gets colder, at least in the temp range you're driving your car. Like you said, there will come a point where the ECU can no longer compensate for the more dense air charge, but I'm really not sure how cold you would have to drop it. Usually the ECU gets out of its range from a mod like a plenum or headers, which allow you to flow more air regardless of the temp.

Let us know what you dig up.

Hey moog -

I read an article on that dude in your avatar. You know he has his own website now?

 

0 degrees kelvin (provided there's no moisture)? just a guess.

 

Actually 0 Kelvin can never be reached, and if it did all motion would stop. Secondly, at a low enough temperature oxygen will condense to its liquid state which would not be helpful for obvious reasons.

I actually learned about this in chemistry today. The changes in enthalpies (energy) of reactions change very little with changes in temperature. So the reaction ( Fuel + O2 --> CO2 + H20 ) will essentially yield the same amount of enthalpy ( energy at constant pressure), which will be used for work (driving pistons down the cylinder).

The fact that you get more power on colder days is simply due to the fact that you are getting more O2 into your engine, because the air is denser. This just enables your engine to combust more fuel with the increased amount of oxygen in your engine. This has nothing to do with the temperature of air and the amount of energy that is produced in the combustion of a specific amount of fuel and oxygen.

Dam and I thought I would never apply this stuff in my life!!