CAI Question

[jrs21]

I know it might sound stupid, but I have to ask .net to end my curiosity here.

OK. So CAI does work better for cars since it give denser air (cold = denser since the specific volume decreases as temp goes down)

Now, the car's engine uese mixture of gas and air to perform. And the best ratio of air to gas is 14.1:1? (I just looked up)
and oxgen sensor located at the exaust decides whether the mixture is 'rich' or 'lean'? and this feedback corrects the amount of gas needed.. so far right?

Now, I know that most websites says that CAI improves the MPG.
And simply thought, denser air will give more oxygen, which will give a better combustion so it improves the MPG.

After my friend told me about this, I am thinking..maybe he could be right on this.
Here's what he thought: more oxygen coming in will result more gas to come in because of the oxygen sensor, which will eventually give a worse MPG.
More air comes in, more gas will be used.
(if I exagerate, your intake gives you 100 times of air coming in, the engine will need 100 times of gas fuel to match up and it will be done by the oxygen sensor)

Now, perhaps, the oxgen sensor has some offset that allows different ratios of the mixture (e.g. 13.9 to 14.3 : 1 instead of exact 14.1:1 and no sensor is perfect, thus it will have some offset of course)
The intake might maximize the ratio which will give a slightly "lean" mixture. which will result a better MPG.....Maybe not. I don't know..

So does mass air inflow improves the MPG? Or not?

Anyways, you see my point hehe... sorry for posting such a boring subject. I didn't expect this to be this long, I guess I should end it here.

Thanks in advance

[02 Joe]

I am not sure that is completely correct. I think that to some extent it is true, especially once you get a CAI and drive like aggressively which in turn uses more fuel.

However more air would make the fuel burn more efficiently, meaning a bigger explosion and allowing your engine to make more HP/TQ with less gas and moving the more easily. That would be where you MPG would increase.
So using your 100 times more air would make 100 times more explosion and burn the same fuel 100 times more efficiently and making some serious HP/TQ. (100 times is obviously an exaggeration) and would move the car 100 times easier.

What does anyone else think??

[jrs21]

Dang only one person replied? Thanks Joe.. Come on people. I want some good answers..

[Osiris]

I think what happens with an intake and the MAF is yes your car will probaly lean out a little but not to the degree your thinking. But they say it will improve fuel economy because your using less throttle to achieve the same amount of speed. Meaning that your not using as much as gas to get up to the same speed because the your fuel is being burned more effieciently. But we're probaly talking very small changes in the numbers with just a intake. I may be way off but this is what I understand it to be. So to answer your question yes it will improve mpg under light driving conditions. Driving hard will probaly negate in positive affects a intake will have.

[cjbaldw]

OK, I'll take a shot at this question.

First off, while the ideal a/f ratio is somewhere around 12-14:1 depending on circumstances, most of the engine CPU's will either run rich or lean as the revs get higher. Just an FYI that often the a/f ratio is not ideal from the factory.

OK, now to your question. While ambient air temp could affect MPG because of the air pressure (barometric pressure), I don't think that any increase in MPG is because of the air temp. I know people with WAI's that also see a slight MPG increase as well. MPG is really a function of how hard the engine must work in order to provide a certain level of power/performance. The primary reason that people see an increase in MPG when installing a WAI/CAI is because in so doing, all of the baffles, resonance enhancing stuff, etc., are removed from the intake path, which means less restriction. This means the engine doesn't have to work as hard to produce power. You get this improvement at the expense of more noise, and more risk (CAI's for instance, with water being sucked into the filter worst case). Here's what the K&N website says:

Results will vary depending on your vehicle, driving habits, load on the engine (towing for example), existing air system restriction, and other factors. Many K&N users report an increase in miles per gallon. See our testimonial page. K&N air filters and intake kits provide less restriction on your engine’s air intake than typical original equipment manufacturer (OEM) filters and air box systems. Less restriction can provide for more efficient combustion. Our internal testing is performed using employee and customer vehicles. We usually have the cars for a short period of time that will only allow for fit checks and dyno (power curve) testing. If you take advantage of added power by driving harder, you will not see much of a gain, if any, in MPG. Also if you add a K&N filter and the primary source of air restriction in the OEM system is the air box, you won’t see much of a difference in power or MPG unless you add a K&N intake kit to reduce the restriction.