there is several different type of air intake systems out there. several for performance and other options. From what I've experienced from automotive experience most people want a cold air intake vs a stock box. Well theres several different reasons with that. Air to fuel ratios are tricky to read depending on what your going for. MPG vs Performance. Most civics and four cylinder accords have a warm air induction from stock. Thats a induction method of hot air from the engine bay into a resonator box under front passenger fender well then flowed thru the filter to the intake hence the mpg effiecency. Most acura integras have ram air induction from a vented air induction hose in the front bumper to allow performance. hence why integras have terrible gas mileage. now to explain this futhermore by definitions.


A warm air intake or WAI is a system to decrease the amount of the air going into a car for the purpose of increasing the fuel economy of the internal-combustion engine.(wiki)

A cold air intake is a device used to bring lower temperature air into a car's internal-combustion engine, to increase engine power...(wiki)

A ram-air intake is any intake design which uses the dynamic air pressure created by vehicle motion to increase the static air pressure inside of the intake manifold on an engine, thus allowing a greater massflow through the engine and hence increasing engine power.(wiki)


I prefer a warm air induction versus the cold air and ram air. I have modded several cars and greatly improved gas mileage by a warm air induction. I have gotten 62 hwy /38 city in my 1991 honda crx dx 1.5l. I have gotten 42 city 72 hwy mpg in my Mini me swap 1991 EF hatch with the stock warm air induction box and resonator box removed. I have installed a cold air intake on both models and gradually experienced loss of gas mileage due to more air/more fuel. Crx = 32 city / 38 hwy with cold air intake. EF= 28 city/ 36 hwy. I have modded other honda air intake systems and seen a great amount of fuel mileage increase. 2001 honda accord ex coupe bone stock 27 city/ 32 hwy. F23a engine. I dropped in a h22a1 single cam vtec into it and a proper tune up and increased the temp up by removing exhaust heat shield. 32city/ 40 hwy. but without doing engine swaps for fuel efficency its all how your air induction is setup and tune up. I have modded other peoples vehicles and increased fuel mileage in other hondas as well.


Now back to the physics of it all. Warm air is more dense than cold air. denser the air the less fuel you'll use. more air/ more fuel.

 

say what now?

 

think of a fire in a jar. Light a piece of paper in a mason jar and close the lid the air becomes thicker smoldering the fire out. hence warm air is more dense. as you increase air flow into your engine the map sensor and o2 has to calcuate more fuel to ignite with the increase in air. there is more sensors in a obd 2 car to calculate fuel ratio.

Engines that use a MAP sensor are typically fuel injected. The manifold absolute pressure sensor provides instantaneous manifold pressure information to the engine's electronic control unit (ECU). The data is used to calculate air density and determine the engine's air mass flow rate, which in turn determines the required fuel metering for optimum combustion (see stoichiometry) and influence the advance or retard of ignition timing. A fuel-injected engine may alternately use a mass airflow sensor (MAF sensor) to detect the intake airflow. A typical configuration employs one or the other, but seldom both. (Wiki)

Automotive oxygen sensors, colloquially known as O2 sensors, make modern electronic fuel injection and emission control possible. They help determine, in real time, if the air–fuel ratio of a combustion engine is rich or lean. Since oxygen sensors are located in the exhaust stream, they do not directly measure the air or the fuel entering the engine. But when information from oxygen sensors is coupled with information from other sources, it can be used to indirectly determine the air-fuel ratio.(Wiki)

A throttle position sensor (TPS) is a sensor used to monitor the position of the throttle in an internal combustion engine. The sensor is usually located on the butterfly spindle so that it can directly monitor the position of the throttle.(wiki)


You also have IAC sensor and other calculations going to the ECM.


Air–fuel ratio (AFR) is the mass ratio of air to fuel present in an internal combustion engine. If exactly enough air is provided to completely burn all of the fuel, the ratio is known as the stoichiometric mixture, often abbreviated to stoich. AFR is an important measure for anti-pollution and performance-tuning reasons. The lower the excess air, the "richer" the flame.(wiki)


The reason why if you live in a high elevation with colder temperatures you use more fuel. but when terrains get involved hills curves mountains etc. Your ecm has to calculate all this to run fuel properly to burn. optimum air to fuel ratio is 14.7:1 which means it takes 14.7 grams of air to burn 1 gram of fuel. Its a very complicated scientific process. Just like if you cool your gas lines on carburated cars they got better gas mileage but thats muscle/ v8s. new school is all computer based mapping thru sensors to run the engine at optimum performance.

4 yrs automotive technician schooling comes in handy with 12 years of in the field work. Need more explaination please ask.

 

i would think the fire goes out because it's burned up all it's available oxygen. but i'm no expert.

 

 

true the fire goes out because all the oxygen is used up. but do you realize the whole concept?

 

Cold air is more dense. Meaning more parts oxygen per air in a controlled space. Basically when air is colder you can pack more into your cylinders. Making yourself more power with a tune. That's why temp comes into play on a dyno day. That's also why you use intercoolers, etc. To keep the air cooler. I don't know how this will help fuel economy, but i've seen people get tunes and be around 45mpg highway on built engines. NA of course.

 

You've got your physics backwards.

Warm air is less dense than cold air because oxygen molecules move around much more at higher temperatures and as a result less molecules can be packed into a given area. You can pack more cold molecules into a given area than you can hot molecules so by the laws of nature, cold air is more dense than hot air. The denser the air is the more fuel you need.

You were correct until you decided to contradict everything you had written at the end.