lol ok, but dyno charts dont lie, neither did my 1.3 mpg inprovement.... I drive 325 miles ever other weekend, I know EXACTLY what kind of mpg I get..

 

[QUOTE=chester8420]I can't drive 55!

I think the 55mph constant is the source of confusion here.

Pinch the hose or restrict air flow enough, and your engine will simply quit.

I think we're trying, but.......................

I'm about to press the ejection button. Seriously, I think the PCM will adjust itself to whatever situation you present it, within its limits of doing so, so you will eventually have to depress the pedal just as much.

More restriction=less fuel burned? If the engine could fire on air, I'd agree. You're compensating for the wrong variable.

You're missing the element of time frame. In a split second, a certain amount of fuel and air is required to maintain a certain level of power. If that air is coming in more freely and less restricted in that split second, power is increased without increasing fuel consumption.

Frankly, your point boils down to more restriction is better as regards mileage. Let's carry it to the extreme. COMPLETELY restrict the air supplied to the engine, and see what kind of mileage you'll get. ZERO. ('Cause it won't run!)

 

THANKS! I Hope he understands now...

 

You're all right but each one of you is looking at a different part of the problem and focusing on different variables. The computer controls the a/f ratio based upon your throttle position. Changing the air filter should change the throttle position at which x amount of power is made and possibly improve throttle response. Because there is less resistance to each pistons intake stroke (not loading stroke, the air is pulled, not pushed) it is possible to create horsepower gains and mileage gains, not because you are feeding more air or fuel but because you've decreased resistance. Parasitic loss isn't only external. The engine has to use some of the power created to keep it self running. Why do you think we have a flywheel? It's not just to engage the starter. Decrease the resistance to the air flow and less of that power is used to suck air in through the intake tract. Yes, gas engines are controlled by restricting air flow but a minimum volume is required. If that minimum volume can reach the piston quicker or with less restriction then less of the power created has to be used to draw in the needed air. We can argue all day but it seems to me that we are all right. Everybody is just looking at it from a different angle.

 

"05" STX 4.6 What a great debate, All i know, I put a drop in k&n filter in my truck I lost mpg. Now I don't know if it is from me going faster than before to get to my cruising speed or what. so i've baby it still seems i lost a little. But I do Know THIS SITE ROCKS I've learned so much from yall KEEP THESE GREAT FORUMS GOING.

 

probably because you have a heavier foot.

 

I have had a K&N dropin for over 35,000 miles. I don't believe it did anything to the gas mileage at all, but I have saved dollars on filters.

 

u guys want to know the best ways to save gas granny drive it (best way) clean injectors, less restrive filiter or drop in, keep tire properly air'd

 

I think a few people here need to go back to physics and chemistry class. I don't know why everyone can't understand that the restriction of an air filter at part throttle, doesn't decrease fuel mileage.

"Part throttle" means (in a gas engine) that you don't want the engine to get all the air it can. Because if it did get all the air it wanted, the PCM would inject enough fuel to maintain stoich (or near to it) and the engine would takeoff! (hopefully )

So in a cruise situation, it is necessary to restrict the airflow to maintain stoichiometric conditions (equal ammounts of fuel and air), and a constant power level suitable for steady speed.

Now, when the piston goes down, there is a negative pressure created in the combustion chamber. The ammount of negative pressure is directly porportional to the ammount of air molecules in the chaimber. You can verify this using the equation PV=NRT..

P= Pressure in ATM
V= Volume in Liters
N= number of moles of molecules of air
R= Ideal gas law constant... equal to 8.3145 J/mol K
T= Temperature in Kelvin.... convert from degrees celsius... K= *C + 273

Using this equation, you see that the more pressure you have, the more air you have. This equation also illustrates why colder air gives more air molecules.(but that's an intercooler discussion) Plug in some numbers, and you'll find that anytime you increase pressure, you're gonna have more air. And if you have more air, then more fuel will be added, and you will speed up.

Any gasoline engine at part throttle (supercharged or not) experiences the same conditions: As the piston travels down, the pressure in the cylinder decreases, and the engine has to work harder to pull the piston down. If you have a high flow filter, or a supercharger, it doesn't make it any easier to pull the piston down, because the throttle body is restricting the intake in an attempt to maintain a constant number of molecules of air in the combustion chamber. And the resistance associated with part throttle driving comes directly from the piston's unwillingness to pull a vacuum in the combustion chamber. It has nothing to do with what happens before the throttle body, because the throttle body controls the ammount of air being let through. If you have a supercharger giving 25 lbs of boost, then you will only have to crack the throttle body to allow enough air through. Because the equation PV=NRT states that the same ammount of negative pressure is required for a supercharged engine as is for a N/A engine. So you see, a gasoline engine is throttled by controlling air. More air in = more fuel used. Hence a supercharger

I know what everybody is thinking, the air has a harder time going through a stopped up air filter, so the engine has to pull harder, etc... And that's true in a WOT situation, (hence a supercharger again) but for part throttle, that isn't the case. Even in a forced induction situation the engine still works hard for it's air in part throttle conditions. Cause the equation PV=NRT demands that the same vacuum must be present for the engine to produce the same power.

An easy breakdown of the equation I mentioned follows:
PV=NRT
(Pressure * Volume) = (Moles * R * Temperature)
Whether you inject the air, or you let the engine pull it in, it doesn't matter except at WOT. Cause at any other time, the same negative pressure will exist regardless.

I am not trying to make anybody feel bad, or stupid. I'm just trying to explain why Ford isn't a dumbass for not putting a better intake and air filter on their trucks!!!! That's because they have engineers that know how engines work, and they build their intakes accordingly. True, you can put a high flow filter in, and you may a couple more horsepower, but Ford isn't concerned about that. They are concerned about filtering the air properly, and making maintenence easier. But when it comes to fuel mileage, they would be idiots to let 1 or 2 mpg get away if it was as simple as a better air filter. Or by letting the engine breathe hot air from behind the radiator instead of cold air from the fender.

Using PV=NRT you will also see that the hot air from behind the radiator will decrease the moles of air available unless you increase pressure or volume. This won't make a difference at part throttle, cause you can "give it more gas" (eg. open the throttle body more) That's why your truck gets the same gas mileage regardless of whether or not it's warm weather. And regarless of barometric pressure.

 

Sorry guys but Chester8420 is correct here! However, the ideal gas law does not take into consideration all of the variables. This equation will give us all the thermodynamic information about the system.

equation at the following URL: http://en.wikipedia.org/wiki/Helmholtz_equation
This equations is know as the Helmholtz equation.

In a nutshell no matter how we try to look at it in this system potential will always be affected by pressure. Efficiency in this case is not correlated to AT ALL to potential. Furthermore, more air(O2) in a system that has the optimal amount of air will not increase efficiency. Notice that the gas is the limiting factor and if you add more gas to reach the optimal reaction you only increase pressure(ie: speed up) not affect the efficiency of the reaction. Well that’s from my chemistry point of view(BS,MS, ACS certification)

 

OH THANK GOD!!!!

 

No it doesn't. And it isn't a perfect fit for all the gasses in "real life" because it doesn't take into account the mass of the actual air molecules. But for our argument, it suits the purpose. It effectively demonstrates how pressure, temp, volume, and the number of molecules of air are all related to each other.

You got me with the Helmholtz equation. I don't know anything about it.

 

All the physics stuff, I agree with 100%. It's these statements that you're trying to validate with physics that I'm not buyin'.

There is no way that a "high flow" air filter is going to cause you to get worse gas mileage. It may not have a noticable positive affect but it will not decrease fuel efficiency.

 

Chester8420 the Helmholtz equation just takes into consideration Van der Waals equation (environmental factor) and the combination of the Helmholtz equation and the ideal gas law will give you the a better representation of the Energy for the system. But you are correct it’s easier to explain the ideal gas law.

Turtle313:
You have to be open-minded about this to be able to understand reason.
Let’s call it the “air pedal” because that what it is. As we both have said, As more air(O2) is taken into the engine the vehicle will increase the amount of fuel into the engine to maintain a proper ratio. This will create more pressure which will speed up the vehicle. However, you will decelerate to maintain the initial velocity. This will produce the EXACT amount of fuel and air intake as before! (If not at the same ratio of air and fuel, the engine would run lean or rich depending on if the ratio is decreased or increased) I have no idea who Chester8420 is and today is the first time I have seen this site, but his intention is not to start an argument. He is just illustrating the point (assuming the vehicle’s computer system adjusts to maintain a constant air fuel ratio) more air WILL NOT require less fuel. Assuming it didn’t adjust it would be equivalent to a vehicle with a bad fuel pump and run lean.

So what it boils down to is that it is physically impossible for an intake that provides more air to an engine to be more fuel efficient. However, it can produce more horsepower due to an increase in pressure, but this will require the addition of more fuel. So you are wasting money if you are buying it solely for increased efficiency, but can produce extra horsepower.

 

You don't agree with this, turtle? Well how do you explain the increased top end horsepower? What is it burning more of, if not fuel?

Under part throttle driving, it doesn't decrease fuel mileage. But if it does flow better, then it would give more horsepower at WOT. Thereby decreasing fuel mileage!