Mustang GT and K&N air charger

Until you quit quoting advertisements that are completely out of the range what I am talking about, you'll continue to be confused. See my other reply in this thread.

Ed

What truth?

I have never said a restricted air filter won't affect performance. I am strictly talking about fuel economy. As long as we aren't talking about some absurdly restricted filter, the filter throttles the maximum power of the engine, just like the throttle plate. There is no reason to think in the case of a modern fuel injected engine that a properly service air filter will reduce fuel economy any more than driving around at anything less than WOT. The air filter, intake piping, and throttle all work to limit maximum air flow through the engine. The fuel economy is not going to be affected just because the throttling occurs at the air filter instead of at the throttle plate. And again, I am only talking about modern feedback controlled fuel injected engines operating with an air filter that is not absurdly contaminated.

When you swapped air boxes, how did you measure the A/F ratio? Were you measuring it at wide open throttle? Did you complete a drive cycle so that the PCM could adjust the long term fuel trim to compensate for the changes in the system? The company who wrote the advertising you keep reposting claims that at 450 cfm the pressure drop through the stock Mustang GT air box is only 20 inches of water (see

). This is 0.7 psi. And this is for a flow rate of 450 cfm - well beyond the flow necessary to develop 250 hp. At a normal cruise the pressure drop is a fraction of this. Probably less than 0.1 psi. Atmospheric pressure at sea level is 14.7 psi. Atmospheric pressure at 5000 feet (Denver more or less) is 12.2 psi. You seem to think that the PCM can't adjust the A/F ratio if you reduce the pressure at the throttle plate by less than 1 psi, yet modern cars can easily handle the 2.5 psi drop associated with driving from sea level to Denver Colorado. Think about what you are claiming.

Why do you keep posting this advertisement. It is not even related to what I am talking about. Plus it contradicts itself. In one passage they are claiming that just installing an aftermarket air filter leans out the A/F ratio to an "alarming" degree, yet in another passage, they claim that replacing the complete air intake in front of the throttle body (including replacing the MAF with a large bore MAF) won't lean the engine enough to cause engine durability concerns. If installing a completely different MAF (one not calibrated for use with the PCM) and the complete induction tract doesn't lean the mixture enough to cause durability concerns, what in the world could be "alarming" about any change related to changing the air filter to a low restriction air filter. If you left the air filter out you wouldn't decrease the intact tract resistance my more than a few tenths of a psi at wide open throttle. At anything less that wide open throttle the difference will be close to nil. Just based on this one paragraph it is easy to see that this advertisement is poorly researched crap.

There are plenty of sources for information on air filter flow restrictions. Read a few and quit falling for this advertising crap.

From

: "Most engine manufacturers suggest a maximum allowable restriction between

15 inches and 20 inches of water (3.75 - 5.00 Kpa) for gas and LP engines, and from 20 inches to 30 inches of water (5.00 - 7.50 Kpa) for diesels. Exceeding these maximums will affect engine performance. " 20 to 30 inches of water is 0.7 to 1 psi. This is the maximum you should ever see under any condition if you follow the manufacturers recommended replacement intervals (I doubt most people ever get close to this).

includes a chart showing the increase in air filter restriction versus mileage. This chart is "typical" for diesel trucks, but it demonstrates that we are not talking about large difference in the pressure drop across filters (by the way, filter restriction is a much bigger issue for diesel engines, since they don't include throttle plates). The chart shows typical values for filter restriction ranging from 5 inches of water to 20 inches of water (and since this is a diesel engine chart, we are talking about pressure drops at much higher air flow rates than is typical for a gas vehicles cruising down the highway at part throttle). 5 inches of water is 0.03 psi. 20 inches of water is 0.7 psi.

From

and : "The differential pressure was measured between atmospheric and the pressure drop after the air filter in the stock airbox. The max pressure drop in this test was seen at only 7.0 inches of water or 0.25 psi. The factory airbox and piping with no filter yielded a pressure drop of 5.0 inches of water or

0.18 psi. That means that the worst filter in this test only caused a pressure drop of 0.07 psi."

Again, filters are not particularly restrictive....

See

Figure 14. This chart shows the increase in filter restriction versus contaminant loading for a long life air filter prototype in a fleet test. The pressure drop across the filter increases from 0.5 kPa (0.007 psi) to 2.5 kPa (0.362 psi) as the contamination increased by a factor of 5. Again, we are not talking about large changes in the pressure drop across an air filter during its normal service life. See The chart on this reference claims that a paper filter will flow 508 cfm with a pressure drop across the filter of 1.5" of water. A pressure drop of 1.5" of water is 0.054 psi! 508 cfm is well in excess of the flow rate needed for a stock Mustang to develop maximum power. What do you think the pressure drop will be across the filter when cruising at 65 mph? I am sure it will be way less than .05 psi. Do you honestly believe that removing an air filter with this sort of restriction will have any affect on the PCM? It you quadruple the restriction, do you think the PCM can't compensate to correct the A/F ratio? See . One of the charts on this page tracks the air filter pressure drop versus contamination. The chart ranges from 0 to around 1 psi for the test set-up employed.

I don't believe any properly serviced air filter will exhibit a pressure drop as great as 1 psi. Think about what this means....................

Explain to me how a change in the pressure drop across the air filter from a few hundredths of a psi to a few tenths of a psi at the maximum air flow rate (WOT). Then tell me how this is going to affect fuel economy when the air flow rate is a fraction of the WOT air flow rate.

Ed

I knew this was hopeless when he made the absurd assertion that you get more horsepower (which he incorrectly associates with fuel economy) just by changing the exhaust.

That's not true, there is a knee point in the curve. As long as the filter is capable of delivering more air than the engine is capable of demanding then the percentage of blockage is not a factor. Once the blockage exceeds a certain amount then you will experience a power roll off as you approach WOT. As far as mileage is concerned there should be little or no change, (at cruising speeds) as the fuel mixture is relatively constant because of the electronics.

The air filter is a restriction to air flow under ALL CONDITIONS. This is an undeniable fact. As it gets dirty is becomes a larger and larger restriction. This restriction affects performance under all conditions. How much varies with the conditions and the efficiency of the filter. An engine is an air pump. Anytime the pump can move more air it makes more power and becomes more efficient.

My truck did and I can actually feel the difference in my Mustang between 6" pipes off the mufflers and pipes that go all the way out the back.

Approach it this way, imagine walking down a hallway 10 foot square with its sides converging. As you move towards the end the corridor gets narrower until you can no longer pass. Now as long as you remain in the portion of the hallway that is as large or larger than you are, you can run back and forth at whatever speed you feel like. It won't be until you reach the point where your start rubbing up against the walls that your forward progress will be slowed. So goes the Air Filter, as it becomes dirtier the walls close in, so to speak, but still you can move about freely. It won't be until after the walls have narrowed to the point that you can no longer walk upright that your movement is significantly impeded.

Changing the exhaust can increase maximum power by lowering back pressure, although it might shift the peak torque curve, or even reduce the peak torque (even as it increases maximum horsepower). IC engines are air pumps. Anything you do to reduce the total resistance to flow from the air intake to the muffler exhaust can increase the maximum power. Air moves into the engine because of the pressure differential between the outside air and the gas in the cylinders. If you lower the pressure in the cylinders (by decreasing the exhaust back pressure) you can draw more air into the cylinder. More air in, equals more power out, assuming that the PCM can adjust the A/F ratio - which in can unless you do something really strange. However, adding duals does not always improve performance. Poorly designed duals may actually be worse than the OEM exhaust. And even if they increase the maximum horsepower, they may adversely affect performance and drivability under normal driving conditions by screwing up the torque curve (or even reducing horsepower). All too often people confuse increased noise with increased power.

Ed

Not until it reaches the point where it can no longer flow enough air to meet the engine's needs.

I made a similar mistake myself, I replaced the stock 2.25" pipes with 2.5". In a flat out drag race they could be said to be an improvement. In real world part throttle driving I discovered that I had lost a lot of low end torque, this really became apparent when driving along I 80 going to Reno NV. I found myself constantly downshifting on hills that previously the car could climb with no effort. (This blows the hell out of your mileage by the way.) It wasn't until I replaced the 2.5" mufflers with 2.25" that I regained that lost bottom end.

I agree completely, but I think we approach it wrong. Instead of conserving oil we should be using it as fast as possible. The quicker we burn it up the sooner we will be forced to find an alternative. All happens when we conserve is to pay more tomorrow for the same thing we could have bought for less today.

Ok who and what part of that kludge of text are you replying to??? Havn't you been here long enough to catch on??

Well I never saw anything like that. But I changed intake cam and heads shortly after on the Mustang. On my truck I went to an over all less restrictive exhaust and with the Volant air breather gained a bit. I estimate about 18HP give or take, but on the 04-06 modle there was a very poorly designed Y pipe. Of course it's obvious that the Titans do not start off with what Nissan says they do in the first place, much to the dismay of many a Hemi owner.

I can't claim to be totally blameless but he top posted so I top posted.

I can't claim to be totally blameless but he top posted so I top posted.

Your example assumes that the clean filter provides ZERO restriction, that just isn't so.

You keep saying "more efficient." In what way is it more efficient. I agree that a restrictive air filter can limit maximum power (by limiting MAXIMUM air flow). I do not agree that it will affect fuel economy to a measurable degree as long as it is not grossly restrictive (i.e., it has been serviced properly per the manufacturers design intent).

You just can't seen to get your arms around the idea that for a modern fuel injected engine the restriction imposed by the air filter is no different than the restriction imposed by the throttle plate. The entire intake tract restriction is what matters, not just the air filter. You also seem to have an exaggerated idea of how restrictive air filters may be when properly service. We are talking about differences of a few tenths of a PSI at the maximum flow rate. At cruise, the difference in restriction is trivial. Until you understand this, you will continue to draw bad conclusions. Modern feedback controlled EFI engines are easily able to adjust to compensate for all sorts of changes over time - changes in altitude and sensor drift being the most significant. When it comes to correcting the A/F ratio because of changes over time, the change in air filter restriction over time is so trivial it is below the noise range for other factors.

Ed

Hey LQQK!! PenisPill spammers are arrested....