Do cold air intakes hurt gas mileage?

Question

The idea is colder air is denser > More O2 > More power. That will obviously make more emissions, but does it hurt your MPG?
Warm air intakes do the opposite to "improve fuel efficiency" according to wikipedia.
Anyone got data?

Answer 1

Improving fuel efficiency and improving power often go hand in hand. The reason your efficiency drops when you use cold air is that the fuel doesn't atomize well at low temperatures. The same issue causes power to drop. That's why production air plenums are designed to keep charge temperature constant.

If you think your cold air intake has improved your performance, test it on a dyno and post the numbers. Usually the advantage is only experienced at higher ambient temperatures. In a normal range of driving conditions, you will average less fuel economy AND less power.

Answer 2

Years ago there was a thing known as a cool can. Using an empty coffee can. Coil fuel line inside, leaving the center empty. Make it so you can connect it to your existing fuel system line. After it's hooked up, fill the can with dry-ice, and put on the lid. That will improve performance, not for use on the road. It's poor man's N2o.
You also buy gasoline early in the morning for the same reasons.
Condensing air on an injected system that is newer than1996 is futile to begin with. If you are actually seeking ways to regain those controls, you need a carburetor.

Answer 3

Cold air intakes allow more oxygen to the engine and the computer adjusts the air fuel mixture. At normal speeds nothing will happen to fuel economy. Under hard power, the added oxygen will increase power but anytime you hammer it, your fuel economy goes out the pipe.

Answer 4

Actually I would think that a cold air intake would be more efficient & produce less emmissions under normal circumstances... its basic air fuel ratio mix equations... (nothing works well at -20 degrees though LOL)

Answer 5

Hello. there is a tremendous amount of misinformation on the benefits of a CAI. I have one installed on my RSX-S. I passed on installing one on my miata, which has very short gearing to begin with.

To begin with, the simple answer is, lower the temp of the intake charge (whether it is a CAI or driving in cooler weather such as winter), increases the density of the charge, which means more oxygen. the denser charge is sensed by your vehicle's MAF (mass airflow sensor) and the onboard computer compensates for the denser charge-air with increased fuel delivery via the fuel injectors.

You can measure this increase in fuel usage using a scangauge II, or any OBD-II computer, which will provide the temp of the intake air. Temperature for the purposes of determining any chemical reaction is measured in Kelvin, which is 273 + celsius.

For example. My RSX-S commuting in the summer was getting about 35mpg. given the same driving but in the dead of winter with a cold intake installed, i'm only getting about 30mpg. 15% drop in fuel economy.

let's break that down. typical intake charge temp without a cold air intake is maybe 80 celsius. that is 273+80 or 353Kelvin. if you could somehow cool the intake charge to 177K, you would double the power and halve the fuel economy. Installing a cold-air intake (located in the bumper) and driving in the wintertime, might reduce the average temp down to 280-300K, max.

let's call it a one-sixth reduction in the temp of the intake charge. ie, temp has dropped by 1/6th. new temp is 5/6th. thus intake charge density has increased by 6/5th, or 20%. as a result, fuel consumption will increase by 20% also, as with each rpm of the motor, 20% more oxygen is drawn in, the intake charge is 20% more massive, and the MAF will signal a 20% increase in the fuel injected.

this is great on a track car, as you need as much power as you possibly can, and economy is not an issue. however, on a commuter car, for regular commuters, steady-state commuting is usually in top-gear with an excess of power being produced by the motor, as rolling and aero -drag is modest relative to the power the engine is producing. as a result, for the average driver, adding a cold air intake will increase fuel use under every circumstance, thus reducing fuel economy.

also, it is my experience that a cold-air intake will increase power most significantly for those that live in cold climates. ie, there isn't a huge benefit to installing a CAI when in california as the difference between outside and underhood temp is modest. if you live somewhere where it is very cold, then you can in fact get a significant reduction in the temp of the intake charge, and as a result, you can get more power, but at the expense of increased fuel use.

other comments relating "cooler air" to "more efficient burn" are non-sensical and completely wrong. fuel use is based on the amount of air/oxygen you can force thru a motor. Either you pressurize the intake charge using forced induction (turbo or supercharger), or you lower the temperature of the intake charge, or both.

period.

Answer 6

The whole reason for the optimum tempature in your car is to have the best gas mileage for your vehicle.when you wake up you do have the best reflexes when your body is at it,s peak temperature,so does your car,this is called open loop close loop system,the warmer the air the car atomizes the gasoline and improves the stoiciometric ratiofor your vehicle,that is the reason the auto industry went from feedback carburetors to secuential fuel injection systems,I drove from New York to Savannah Georgia,about 1,080miles,with my regular intake filter,sucking in regular intake air and spent$210 on gas,same trip and same price I retrofitted the intake to feed hot air off the exaust heat and saved $50.00 in gas proving to myself that warmer air into the intake does improve a whole lot your gas mileage,another thing is to find ways to warm the gasoline before it enters the combustion chamberthis is obviously more dangerous but the rewards can save you a bundle if done properly,thank you for the question.

Answer 7

25MPG is optimal conditions and likely highway driving. If you are doing any stop & go driving around the city, you will get much lower. My car has an expected 26MPG highway, but I overall average 22 combined city/highway, so it goes to show that what is written in the ratings is not always what you will get in real life. Also realize, the car is empty when they drive it, and anything you add to the car weightwise will reduce gas milage. As for the add-ons, look at what the others said.

Answer 8

fuel injection adjusts fuel to air mixture...it doesnt cause more emissions..it helps mpg by bring cooler air which promotes efficiency

Answer 9

1

Answer 10

Actually a cold air intake will improve you milage.