Mustang GT and K&N air charger

"WindsorFox" wrote in message news:fnsl26$58c$ snipped-for-privacy@posting2.glorb.com...

Again, why do you believe this? Air flow into the engine is restricted by the throttle plate at anything less than wide open throttle. To achieve a particular level of power, you need a given amount of air. The flow of air into the engine is restricted if you are trying to develop anything but maximum power. Where in the intake this restriction occurs is irrelevant. The pumping losses (this is what you are talking about) are the same whether the restriction occurs at the air filter or at the throttle plate. For any power level less than maximum, a slightly more restricted air filter will just require a slightly more open throttle to compensate. And the difference will be tiny. You guys seem to have it in your mind that a normal air filter is very restrictive. It isn't. We are talking about a difference in restriction in the noise range (0.01 to 0.03 psi).

Which electronics do you thing will be affected? There are only two, possibly three, sensors in front of or concurrent with the throttle plate - the mass air flow sensor - MAF, throttle position sensor - TPS, and possibly the intake air temperature sensor (these are often combined with the MAF). The MAF is designed to measure the mass of air flowing through the intake tract. The trivial differences in pressure related to normal changes in air filter restriction are not going to affect the MAF operation beyond what would be considered a normal variation. The PCM can compensate for this based on feedback from the O2 sensors. The TPS is a gross throttle position measurement device. It is not highly accurate. Any minor changes in the position of the TPS for a given power output caused by a slightly more restricted air filter will be easily compensated for by the PCM based on feedback from the O2 sensors.

Again, I am not talking about grossly contaminated air filters. I am talking about filters serviced in a reasonable manner per the manufacturer's recommendations. Any air filter so restrictive that the PCM cannot adjust the A/F to compensate, should turn on the check engine light. And to be clear, I am talking about differences measurable by normal consumers. I wouldn't claim that there is no difference at the level that could be measured under tightly controlled laboratory conditions with precision equipment. I doubt there is any significant difference even in that case, but given the uncertainty of almost any complex system, I can't be absolutely sure that there won't be minor differences down in what would be the noise range for normal vehicle operation. Also, I am not claiming that a restricted air filter will have no effect on performance. It certainly can reduce maximum power. With the throttle wide open, other restrictions in the intake tract are what limits the air flow. The more air you can get into the engine the more power you can develop. A K&N filter may provide more power, but in most cases the differences will be trivial. For most cars, it is not the air filter that is the most restrictive part of the system, it is the actual plumbing (intake opening and connecting tubing). Air filters are usually sized to provide minimal restrictions. K&N provides a means of calculating an air filter size to minimize power loss due to air filter restrictions. See

used to provide a filter factor for their filters and for paper filters (they have dropped the paper filter number from the current web page, but I recorded it). They claimed that their filters would flow 6.02 cfm per square inch and that a paper filter would flow 4.38 cfm per square inch (they don't clue us in on as to the pressure drop needed to achieve these flow rates). You should use the K&N method to calculate the filter size needed for your engine. Then derate it by 73% (4.38/6.02). Compare the resulting filter size to the stock filter for your engine. I'll wager you that your stock filter is at least one and a half times the size this calculation suggest is required (assuming it is stock). And the calculation is very conservative. Working backwards through the K&N calculations for a 350 engine turning at 5500 it can be shown that they are assuming an air flow of 560 cfm. This much air flow should be sufficient for a 450 hp engine. So the K&N calculation is clearly for a very powerful engine - hardly a normal production engine.

It is not irrelevant. Almost anytime you can use less throttle (i.e. the engine is more efficient) to travel the same speed under the same conditions the mileage will increase. It is the same reason going with a less restrictive exhaust will also improve gas mileage. Why do under drive pulleys increase mileage? Think about it. They increase horsepower to the rear wheels across the ENTIRE rpm range which will result in a mileage increase in normal driving.

"Michael Johnson" wrote in message news:TtWdne2vKoBMYjzanZ2dnUVZ snipped-for-privacy@giganews.com...

This is hopeless. Air flow is what mattes, not the exact position of the throttle plate. You change the throttle position to adjust the air flow to achieve a certain power level. The fact that the air flow is restricted at the air filter instead of the throttle plate doesn't affect the fuel economy to any measurable degree for a modern fuel injected engine (at least as measurable by typical consumers). You seem to have the idea that you'll get more power for the same amount of air just because the restriction is at the throttle instead of because of the total intake tract flow restriction. This is simply wrong. If you remove the throttle from the equation, by completely opening it (i.e., WIDE OPEN THROTTLE), then yes the maximum air flow is controlled by the other parts of the intake tract and the air filter will be one of the factors limiting maximum power output. However this doesn't mean the engine is more efficient for a given power output than if the restriction is caused by a partially closed throttle. Unless you are at wide open throttle, there is no increase in horsepower across the rpm range. You are setting a power level by throttling the air flow. You are confusing measuring horsepower on a dynometer with driving a car on the highway. On a dynometer, you are at wide open throttle. To measure the power at different rpms, you load the engine up to slow it down to the speed of interest - you don't close the throttle to achieve the lower rpm. The power output of a gasoline engine is primarily a result of the amount of air flowing into the engine. I am not claiming that a less restrictive air filter won't affect the power output at wide open throttle. A restrictive air filter will reduce the maximum flow rate of air into the engine and this will reduce the maximum power at wide open throttle. But you cannot use this fact to claim that it will affect the fuel economy. Throttling the amount of air because of a restrictive air filter is no different that using a moving plate to throttle the amount of air. Until I can get you to understand this, I am not going to get you to understand the situation.

I'll try this analogy again - if I blindfold you and ask you to suck on a straw, and then partially block the straw, will you be able to tell where I am blocking the straw by how hard it is to suck in air? Certainly you will know I am restricting the air flow through the straw, but you won't be able to tell where, or even how I am restricting it (without looking). This is the situation with the engine when you are driving at anything but wide open throttle. As far as the engine is concerned something is restricting air flow into the engine and limiting the power to the level required to move the car. As a practical matter the engine doesn't care whether the restriction is due to the throttle position or a reasonable air filter restriction. There may be a slight difference in the position of the throttle plate because of a slight increase in the restriction in front of the throttle plate at the air cleaner, but the difference will be trivial as far as the TPS is concerned. We are talking percentage point differences and the PCM can easily handle this sort of drift based on feedback from the O2 sensor.

1) Do you believe that unless you are at wide open throttle that the air flow into the engine is restricted by the complete intake tract flow restriction (cumulative restriction of air intake, air filter, piping, throttle, valves, etc)? If you don't believe this, why not? Why is the restriction imposed by the air filter different than the restriction imposed by the throttle plate (assuming you are not at wide open throttle)? 2) Do you believe that to cruise at a given speed, or accelerate moderately, that you are not operating at wide open throttle? 3) If you are not operating at wide open throttle, do you believe that you can compensate for a "normally" restricted air filter with a slight increase in the throttle opening to achieve a given steady state speed or moderate rate of acceleration? 4) Do you believe that a modern fuel injection system can adjust for changes in the input parameters by adjusting fuel delivery based on feedback from the O2 sensor? 5) If you believe the answers to 3 and 4 are yes, why do you think the fuel economy is affected by a "normally" restricted air filter. And if you still think it is significantly affected, why wouldn't the PCM see this as an error and turn on the check engine light?

Ed

Haven't we beat this to death between us? I was replying to WF because you and I are never going to agree on this issue.

By this thinking if the car is at an idle and not WOT then putting your hand over the intake should do nothing. A clogged filter ads more resistance to what it already there.

ARRRRGGGGGGGGGGGGGGGGGGG -you really don't get it do you. What is so hard to understand here. The amount of air that flows into the engine is what determines the amount of power the engine developed. For a given speed, or moderate acceleration rate, you need a certain amount of power that is most likely less than what can be developed at wide open throttle (I know, some people claim to drive all the time at WOT). The total restriction to air flow is the sum of all the little restrictions that make up the inlet tract from the air intake to the actual cylinders (including the piping, air filter, throttle plate, etc). For a properly maintained engine, NOT at wide open throttle, the biggest single source of flow restriction is the throttle plate. If there is a minor increase in the restriction in another part of the intake system, you can decrease the total restriction of the entire intake system by opening the throttle a little more - as long as the additional restriction is not something outlandish, LIKE PUTTING YOUR HAND OVER THE INTAKE!!!!!!!!!!!!!!!!!!!!

If you guys want to argue that cramming a potato in the intake will affect fuel economy, I'll agree with you, although the results might not be what you expect. Assuming you don't block the intake so completely that the PCM can't properly adjust the A/F Ratio, it might even increase the fuel economy since you'll be reducing the available power . I have never claimed that an idiot with an air filter so clogged that the check engine light is on won't have fuel economy problems. I am just talking about the range of restrictions associated with a properly maintained air filter and an otherwise stock engine in good condition. If you want to talk about what happens if you do something stupid, all bets are off.

Ed

We beat it to death long ago. I just can't turn away. You clearly don't understand how modern feedback fuel injection systems work and because of this you are drawing bad conclusions. Foolishly, I hope I can make a subtle change in my arguments so that you can understand that unless you are at wide open throttle, the restriction of the air filter is largely irrelevant as far as the performance of the engine is concerned. Except at WOT, the throttle plate is the final adjustment to the air flow rate. If you increase the restriction in another part of the intake tract, you can open the throttle a little more to get the same overall flow restriction. This doesn't effect fuel economy because the PCM has the ability to correct the A/F ratio based on the output of the O2 sensors (as long as the restriction is not so gross as to set the malfunction indicator). The system is designed to be able to compensate for changes like increasing air filter restriction, drift in the response of the various sensors, altitude, etc. Compared to other changes over time, a minor increase in the flow restriction related to the air filter is trivial. Until you understand this, you'll continue to draw the wrong conclusion.

Ed

Ed, let it go. Mileage doesn't drop from a dirty filter at some magical point. It is a gradual reduction that gets progressively more noticeable as the filter collects more dirt.

BULLSHIT! Your theory is flawed, try some actual real world applications of it. Get back to us with your corrections...

Bullshit again, "Also included in this package is a new high flow conical filter assembly, custom filter shroud that separates it from the engine compartment heat, MAF mounting bracket, mounting hardware, installation tool and instructions. Dyno testing the 2005 GT has shown that the computer is so sensitive to airflow changes that a computer modification is necessary in order to control the air/fuel ratio at the proper level. Installing this air intake assembly on a 2005 GT without any tuning will result in a leaner-than-ideal 14:1 air/fuel ratio. While certainly not lean enough to cause engine durablility concerns, it is leaner than what is desired for optimum performance. Even when replacing the air filter ONLY to a higher flow assembly, the air/fuel ratio leans out at an alarming rate. This means that any 2005 Mustang owner who is interested in modifying their new car for better performance will have to use some form of tuning"

Heck, changes in the air filter are not close to the most

Until you actually move from the realm of theory into practical application, you'll never understand how it actually works.

Nice Fantasy Ed.

"Also included in this package is a new high flow conical filter assembly, custom filter shroud that separates it from the engine compartment heat, MAF mounting bracket, mounting hardware, installation tool and instructions. Dyno testing the 2005 GT has shown that the computer is so sensitive to airflow changes that a computer modification is necessary in order to control the air/fuel ratio at the proper level. Installing this air intake assembly on a 2005 GT without any tuning will result in a leaner-than-ideal

14:1 air/fuel ratio. While certainly not lean enough to cause engine durablility concerns, it is leaner than what is desired for optimum performance. Even when replacing the air filter ONLY to a higher flow assembly, the air/fuel ratio leans out at an alarming rate. This means that any 2005 Mustang owner who is interested in modifying their new car for better performance will have to use some form of tuning"

Do you have any actual real world data to support your position? Any at all? I'm talking real world automotive air flow data, not paragraphs of hot air.

It seems more like you don't get it. If the filter is clogged enough it can still restrict more than the throttle at part way.

Michael Johnson wrote in news:ioCdneZi4fV4qz_anZ2dnUVZ snipped-for-privacy@giganews.com:

I can see each side of this, and each argument makes sense in its own right. That said, the only thing that will put this to bed is honest, real world test results, which seem to be in short supply these days.

Agreed.

I think I said something similar to that several weeks ago....

There is plenty real world proof that:

1. Filters alone change the airflow restrictions in modern EFI cars enough to dramatically effect their horsepower and fuel mileage.
2. Filters alone can and do alter the airflow beyond the stock engine management computers ability to correct.

The real world results are overwhelming! None of them support Ed's misguided positions on this.

Tuning, needed or not? YES! I made the dyno runs like this, on the first car I installed the stock air box and ran it three times and then installed the Bullitt airbox and did the same. With both intakes I had the stock tune installed in the car. Sure enough with the stock airbox and tune it went rich down to the high 11's and low 12's like normal. When I installed the Bullitt airbox it went lean, very very lean, in the mid to high 14's. Yes, this intake requires a tune. Any tuner can verify this as well by looking at the stock Bullitt tune, which SCT has in their database, and noting that the MAF adjustments are different for the new Bullitt air box.

Again, I am not talking about some wildly contaminate filter. I am talking about a normally serviced filter. A filter that is so contaminated that it will significantly effect fuel economy will be outside the range the PCM can compensate for and in response, the PCM should turn on the check engine light.

I keep repeating I am not talking about some hypothetical case where the filter is absurdly contaminated. I am talking about normal filters, in normal sorts of use, replaced at the proper intervals - NOT SOME HYPOTHETICAL FILTER SO PLUGGED THAT IT IS MORE RESTRICTIVE THAN THE THROTTLE PLATE UNDER NORMAL DRIVING CONDITIONS.

And most especially I am talking about a comparison between a K&N filter and a standard paper filter in reasonable condition.

Ed

Tell me why you believe this to be true. Why is the PCM unable to correct the A/F ratio. Exactly why is the restriction imposed by the air filter uniquely different than the restriction imposed by the throttle plate. AND AGAIN, I AM NOT TALKING ABOUT SOME HYPOTHETICAL FILTER THAT IS ABSURDLY CONTAMINATED.

I have a hard time letting it go because you aren't getting it right. get it. Modern EFI feedback systems are designed to compensate for exactly the sort of gradual changes associated with things like changes in the restriction of an air filter, the drift of sensors like the MAF and TPS, etc. You seem to think that air filters become very restrictive over time. This is simply not true if they are serviced per the manufacturer's recommendations. We are talking about restrictions that range from less than 0.05 psi for a new filter to

0.5 psi for a heavily used filter (I'll bet you've never seen one this contaminated). This is a change on the order of tenths of a psi. At cruise the difference between atmospheric pressure and manifold pressure is in the rage of 5 to 8 psi. The air filter contributes less than 1% of this pressure drop, even for a restrictive filter. As I pointed out before, drift in the TPS sensor is on the order of +/-10%. If you doubled the pressure drop across the air filter, it will be an insignificant factor in the total pressure drop between the atmosphere and the cylinders. It is simply ridiculous to believe that the PCM can compensate for a 10% drift in the output of the TPS or the MAF sensors, but cannot handle a 1% drift in the restriction of the intake tract.

Ed

And I pointed you guys to the Consumer Reports article where they said a dirty air filter doesn't significantly affect fuel economy

or I even tracked down the source of the EPA claim that a dirty air filter could reduce fuel economy by up to 10% (it is based on data analysis by a company called Energy and Environmental Analysis, Inc.) I e-mailed the company and discovered they have no actual test data to back up this claim. They are basing it on studies of vehicles that failed the OBDII test because the check engine light was on. I've never claimed that a filter that was so restrictive that it turned on the check engine light would not affect fuel economy. I am only addressing reasonably contaminated air filters. And actually this thread got started because I disparaged the notion that K&N air filters can improve the fuel economy of a properly maintained modern fuel injected car.

Ed

IGNORING THE TRUTH WON'T MAKE IT GO AWAY ED!

Tuning, needed or not? YES! I made the dyno runs like this, on the first car I installed the stock air box and ran it three times and then installed the Bullitt airbox and did the same. With both intakes I had the stock tune installed in the car. Sure enough with the stock airbox and tune it went rich down to the high 11's and low 12's like normal. When I installed the Bullitt airbox it went lean, very very lean, in the mid to high 14's. Yes, this intake requires a tune. Any tuner can verify this as well by looking at the stock Bullitt tune, which SCT has in their database, and noting that the MAF adjustments are different for the new Bullitt air box.

Dyno testing the 2005 GT has shown that the computer is so sensitive to airflow changes that a computer modification is necessary in order to control the air/fuel ratio at the proper level. Installing this air intake assembly on a 2005 GT without any tuning will result in a leaner-than-ideal

14:1 air/fuel ratio. While certainly not lean enough to cause engine durablility concerns, it is leaner than what is desired for optimum performance. Even when replacing the air filter ONLY to a higher flow assembly, the air/fuel ratio leans out at an alarming rate.