Not really a performance question but a general Q

[tony1963]

I'm not sure why we would table this discussion as we had to settle the idea that hotter has less oxygen, an obvious error.

Clearly, the incoming air temperature should not be the source of problem solving.

 

[69.5Mav]

Absolutely Last Post on this subject

From Wikipedia

Temperature and pressure

The density of dry air can be calculated using the ideal gas law, expressed as a function of temperature and pressure:

where ρ is the air density, p is absolute pressure, R is the specific gas constant for dry air, and T is absolute temperature.
The specific gas constant for dry air is 287.05 J/(kg•K) in SI units, and 53.35 (ft•lbf)/(lbm•R) in United States customary and Imperial units.
Therefore:
• At IUPAC standard temperature and pressure (STP) (0 °C and 100 kPa), dry air has a density of 1.2754 kg/m3.
• At 20 °C and 101.325 kPa, dry air has a density of 1.2041 kg/m3.

One cubic meter (m3)of air has a mass of, at STP, 1 m3 X 1.2754 kg/ m3 = 1.2754 kg.
Air is composed of many molecules 20.9% of which are Oxygen or 0.209 x 1.2754 kg = 0.26656 kg of Oxygen.
The mass of one Oxygen atom with 8 neutrons is 2.67803909 x 10-26 , the number of Oxygen molecules in .26656 kg is .26656/( 2.67803909 x 10-26 X 2) = 9.9535 x 1024 molecules.

One cubic meter (m3)of air has a mass of, at 20 °C, 1 m3 X 1.2041 kg/ m3 = 1.2041 kg.
Air is composed of many molecules 20.9% of which are Oxygen or 0.209 x 1.2041 kg = 0.251657 kg of Oxygen.
The mass of one Oxygen atom with 8 neutrons is 2.67803909 x 10-26 , the number of Oxygen molecules in .251657 kg is .251657/( 2.67803909 x 10-26 X 2) = 9.39706 x 1024 molecules.

Subtracting the two gives 9.9535 x 1024 - 9.39706 x 1024 = 5.56441 x 1023 or 5.59% less molecules.

 

[tony1963]

I do not disagree that there are less parts of the air. But, there is not necessarily a disproportionate less amount of oxygen content as a percentage of the total.

Less air drawn through will pull less fuel. I don't believe that the heated air will make that much of a difference, unless you have a high-performance engine.

 

[Lazy JW]

..... I don't believe that the heated air will make that much of a difference, unless you have a high-performance engine.

Oh, but it will.

Before I got all of the pieces scrounged up to make the thermostatically controlled air cleaner on my 81 F-150 functional I just hooked the flapper door up direct to manifold vacuum in the winter to maintain warm air to the carb in order to prevent carburetor icing. This worked fine until springtime when the mornings were cool 35º-40º but the afternoons were 80º+. I have a 44 mile commute and must pass through a small town about halfway; after 20 miles of highway driving with the heat to the carb it would barely run at idle while creeping through town, then when leaving town it was VERY sluggish until it got up to cruising speed and still didn't have the oomph it normally had. For a while there I was switching the vacuum line morning and afternoon until I got both vacuum modulators purchased and installed properly.

If those things didn't "make that much of a difference" the factory wouldn't have spent the money for R&D or the money to install them. I want mine fully functional, thank you very much.
YMMV
Joe

 

[rbohm]

I do not disagree that there are less parts of the air. But, there is not necessarily a disproportionate less amount of oxygen content as a percentage of the total.

Less air drawn through will pull less fuel. I don't believe that the heated air will make that much of a difference, unless you have a high-performance engine.

remember that when you heat a gas, it expands and thus becomes less dense. and while the amount of air drawn into the system doesnt change, the density does, and the less dense the air is, the less oxygen is available for combustion. the reverse is also true in that the colder the air the more dense it is and thus the more oxygen is available for combustion. it is a know fact that if you drop intake air temperature 10 degrees you pick up 1% horsepower. this doesnt mean much for the average street engine in so far as its power goes, but it does affect its drivability, and rather substantially.

 

[69.5Mav]

Positively Ralf

Ant progress?

 

[Positively Ralf]

Yup, I got that sucker rebuilt. I'll be getting it back on Saturday so I'm going to go burn some gas all day. I told myself no need for some high performance C4(it would've cost a lot anyways). Seeing as I'm new to cars in general and this being my first car, I may as well just go along for a mild build and work from there.