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Mustang GT and K&N air charger



 
 
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  #21  
Old January 16th 08, 05:05 AM posted to rec.autos.makers.ford.mustang
Michael Johnson
external usenet poster
 
Posts: 1,039
Default Mustang GT and K&N air charger

Gill wrote:
> Michael Johnson wrote:
>
>>> Exactly, I don't believe an air filter will change mileage. The auto
>>> makers would be on it and so would the rest of this small world.

>>
>> Ever notice that an engine running with a dirty filter sees a drop in
>> gas mileage? The same principle applies to an OEM filter verses a
>> filter that flows better (i.e. a K&N etc.). There are two things that
>> can happen when air flow through an engine is made more efficient.
>> One is an increase in horsepower and the second is an increase in
>> mileage. Sometimes both can happen simultaneously. If you don't
>> believe me then take your air filter and clog it up and run your car
>> for a tank of gas then put in a new one and see whats happens to your
>> gas mileage and power output. I'll bet the farm that they both will
>> see a substantial increase when a clean filter is installed.

>
> One of these days, the next time I have access to a flow bench at work,
> I may have to do some "all things equal side by side testing" of an OEM
> and K&N type filter. At a normal driving speed air flow.
>
> I must say though, adding the power pipe with a larger K&N than I had
> before, and mounting it in the fender sure helped clear some of the
> black smoke I had coming from the exhaust at WOT.


I don't think there will be much difference on a stock engine. Many
times people will open up the intake side and then do nothing to the
exhaust side. You can have the biggest diameter garden hose in the
world but one kink in the line brings the water flow to a crawl. The
same principle applies to an automobile engine.

My guess is that the claimed 15 hp increase K&N makes is on a car with a
blower, large diameter exhaust etc.
Ads
  #22  
Old January 16th 08, 01:27 PM posted to rec.autos.makers.ford.mustang
C. E. White[_1_]
external usenet poster
 
Posts: 933
Default Mustang GT and K&N air charger


"WindsorFox-{SS}-" > wrote in message
...

> Yes but I'd bet that by "dirty filter" they mean clogged. I can
> see Ed's point here but there is probably a point at which the clog
> becomes so bad the electronics can not compensate. I once bought a
> 1977 Thunderbird for $50. It would not start, the guy and 4 friends
> tried to get it started to get it home. When I went to get it I had
> a battery, some gas and tools. It was full of gas, I cranked,
> smelled gas and popped the hood. Took off the air breather and put
> it in the trunk, started it and drove home to all their amazement.
> Three months and $500 later I sold it for $4500. It had 267K miles
> on it. The buyer was still driving it 4 years later. P


Of course a 1977 Thunderbird had a carburetor...

Ed


  #23  
Old January 16th 08, 01:31 PM posted to rec.autos.makers.ford.mustang
Bob Willard
external usenet poster
 
Posts: 90
Default Mustang GT and K&N air charger

Michael Johnson wrote:

> C. E. White wrote:
>
>> "Michael Johnson" > wrote in message
>> news >>
>>>> Exactly, I don't believe an air filter will change mileage. The auto
>>>> makers would be on it and so would the rest of this small world.
>>>
>>> Ever notice that an engine running with a dirty filter sees a drop in
>>> gas mileage? The same principle applies to an OEM filter verses a
>>> filter that flows better (i.e. a K&N etc.). There are two things
>>> that can happen when air flow through an engine is made more
>>> efficient. One is an increase in horsepower and the second is an
>>> increase in mileage. Sometimes both can happen simultaneously. If
>>> you don't believe me then take your air filter and clog it up and run
>>> your car for a tank of gas then put in a new one and see whats
>>> happens to your gas mileage and power output. I'll bet the farm that
>>> they both will see a substantial increase when a clean filter is
>>> installed.

>>
>>
>> While this was certainly true with carbureted engines, there is no
>> reason to think this is the case for modern fuel injected engines. For
>> carbureted engines, a clogged air filter acts like a choke and
>> enriches the mixture because of the effect on air pressure in front of
>> the throttle plates. This reduces the fuel economy. In a modern fuel
>> injected engine, the mixture is not influenced in this way. The amount
>> of fuel injected is determined based on the MAF sensor and other
>> sensors. These sensors can't tell the difference between a restriction
>> to the flow related to the air filter and a restriction to the flow
>> related to the throttle plates. There is no difference as far as the
>> computer is concerned between the restriction of the air filter and
>> the restriction of the throttle plates. The engine speed / power
>> output is determined by the total intake restriction (intake tract
>> plus throttle opening). The only thing a slightly restricted air
>> filter does on a modern engine is require you to open the throttle a
>> slight amount more and reduce the maximum power output. The effect on
>> fuel economy for a modern engine is minimal. I won't claim it is zero,
>> but I doubt you would be able to tell the difference unless the filter
>> was absurdly restrictive.

>
>
> A dirty filter will lower gas mileage on EFI engines too. Instead of
> going into a long rebuttal I'll just provide a few links to some
> credible web sites.
>
> http://www.fueleconomy.gov/feg/maintain.shtml
> http://www.edmunds.com/reviews/list/...4/article.html
> http://tinyurl.com/2a9v2
> http://tinyurl.com/2hyeyx
> http://www.mass.gov/Eoca/docs/doer/pub_info/dt.pdf
>
> There are a huge number of sites stating that a dirty filter decreases
> mileage. There is more than just a MAF reading that the computer uses
> to determine the amount of fuel needed. Air density, throttle position,
> air temperature etc. also come into play. Excessive opening of the
> throttle plate on a fuel injected car also tells the computer the engine
> is under a greater load which effects how much fuel is delivered to the
> cylinders.
>
> I'm not saying a K&N filter will give a noticeable improvement in gas
> mileage over an OEM unit but with all things being equal the engine with
> a more efficient filter will perform better. Do you think an engine
> with a dirty air filter would pass an emissions test? If so then why not?


None of those sites listed states that the effect of a dirty air filter
on gas mileage applies to FI engines with MAF sensors. It seems rather likely
to me that those sites are merely repeating what was true with carburated
engines as still being true, without retesting or even remodeling.

Do you have any URLs for tests done with modern engines?
--
Cheers, Bob
  #24  
Old January 16th 08, 02:24 PM posted to rec.autos.makers.ford.mustang
C. E. White[_1_]
external usenet poster
 
Posts: 933
Default Mustang GT and K&N air charger


"Michael Johnson" > wrote in message
...

> A dirty filter will lower gas mileage on EFI engines too. Instead
> of going into a long rebuttal I'll just provide a few links to some
> credible web sites.
>
> http://www.fueleconomy.gov/feg/maintain.shtml
> http://www.edmunds.com/reviews/list/...4/article.html
> http://tinyurl.com/2a9v2
> http://tinyurl.com/2hyeyx
> http://www.mass.gov/Eoca/docs/doer/pub_info/dt.pdf


If by credible, you mean sites that are repeating their granddaddy's
advice, then I guess they qualify. Can you show me one that actual has
any data to support your claim? Or at least an explanation of why a
slightly restrictive air filter might reduce the fuel economy of a
modern fuel injected engine? These sites are just repeating the same
sort of maintenance information that has been out there for 70 years.
Things have changed.

> There are a huge number of sites stating that a dirty filter
> decreases mileage. There is more than just a MAF reading that the
> computer uses to determine the amount of fuel needed. Air density,
> throttle position, air temperature etc. also come into play.
> Excessive opening of the throttle plate on a fuel injected car also
> tells the computer the engine is under a greater load which effects
> how much fuel is delivered to the cylinders.


Sigh, if you are talking about a completely plugged air filter, I
agree that the fuel economy may be affected (heck it might actually
increase since the maximum engine power will be limited). However, for
a modern fuel injected car operated in a normal environment with a
filter changed at reasonable intervals the difference in fuel economy
between a "new" and "used" filter approaches zero. The same is true
for a proper paper filter and a K&N filter. The only sensor in front
of the throttle plate(s) is the MAF. It is called a Mass Air Flow
sensor because it is measuring the mass of air flowing through the
intact tract, not pressure or density, or temperature. The throttle
position sensor is at the throttle and measures it position. All of
the other sensors are behind the throttle plate. So think about what
the various sensors see when the filter is slightly more restrictive.
The MAF is measuring the mass of air flowing through the system. It
doesn't measure pressure, so it won't be affected because the flow is
reduced my a slightly higher restriction at the filter (we are talking
about tenths of a psi difference or less). If the filter is slightly
more restrictive, the throttle may need to be slightly more open to
achieve the same power output. And I mean slightly. Throttle position
sensors are not particularly precise. They are a gross position
indicator. I doubt the difference in the throttle opening related to a
slightly more restrictive filter is significant enough to affect the
engine parameters at all. All the other engine sensors are after the
throttle plate. They will not be affected by the restriction in the
air filter any more than by the much larger restriction of the
throttle plate. AND remember you have O2 sensors that feed data back
to the PCM that is used to correct for variations in the other
sensors. So even if the restriction of the air filter was severe
enough to affect the other sensors, the feedback from the O2 sensors
should allow the PCM to adjust the fuel trim to compensate.

> I'm not saying a K&N filter will give a noticeable improvement in
> gas mileage over an OEM unit but with all things being equal the
> engine with a more efficient filter will perform better. Do you
> think an engine with a dirty air filter would pass an emissions
> test? If so then why not?


As long as the filter is in good shape, it will have no significant
effect on the ability to pass an emissions test. See above for the
reasons. I won't argue that a K&N might provide a slight performance
increase at WOT. It very well might. But for anything but large
throttle openings, the throttle plate is by far the most significant
restriction in the intake tract. The filter is almost not there as far
as air flow is concerned until the throttle is nearly wide open.
Again, I am only talking about modern fuel injected engines. For older
carbureted engines, a restrictive air filter would definitely
significantly reduce fuel economy. And the situation is not clear to
me if you are talking about some of the early speed density type fuel
injection systems (systems without a MAF). For normal sorts of air
filter restriction the PCM of these types of systems would be able to
compensate for a restrictive air filter. However, for a very
restrictive filter, they may not. However, as far as I know, no one
has sold a car with a speed density only system for a decade.

By the way, the DIY Basics sight you referenced is loony
(http://tinyurl.com/2hyeyx). You should follow your vehicle
manufacturers replacement schedule for the air filter. I think that
sight must be run by filter manufacturers.

You should read these sites:

http://www.visteon.com/utils/whitepa...05_01_1139.pdf
http://www.filtercouncil.org/techdata/tsbs/89-3R3.html

Air filters (paper and K&N) are less efficient at removing dirt when
they are new. As the accumulate particles, the filtering efficiency
improves. So changing your filter too frequently (or cleaning your K&N
too often) can actually increase engine wear. You should also consider
that K&N filters loads up with dirt much faster than paper filters
(they have less dirt holding capacity). So while they may enjoy a flow
advantage when new (or when just cleaned), the advantage decreases
rapidly with time.

Ed


  #25  
Old January 16th 08, 02:39 PM posted to rec.autos.makers.ford.mustang
C. E. White[_1_]
external usenet poster
 
Posts: 933
Default Mustang GT and K&N air charger


"Michael Johnson" > wrote in message
...
> wrote:
>> On Jan 15, 1:23 pm, Michael Johnson > wrote:
>>> Gill wrote:

>>
>>> That's because the overall specific energy of E10 is less than
>>> pure
>>> gasoline. This is why going to biofuels is a horrible idea, IMO.
>>> We
>>> use up our top soil

>>
>> Using proper farming techniques, top soil will last forever.

>
> It just won't stay in the same place. Erosion from farms is far
> worse than from land development activities. Top soil can be
> depleted to the point it can't grow much which is why farmers so
> much fertilizer to their land.


Care to sight some back up for this. I suppose it might be true on a
total tonnage basis, but probably not on a per unit of land basis. My
farm has been in constant cultivation for over 300 years. I would
argue we add fertilizer to replace the nutrients removed when we
harvest crops. Some crops remove more nutrient than others. One of the
nice things about ethanol production is that it does not actually
increase the nutrient drain. Ethanol is carbon (from CO2) and hydrogen
(from H2O). After you make the ethanol, the dried mash can be used as
a high quality animal feed. The animal waste can be used as fertilizer
to return the nutrients to the soil (well except for those that are
used to make the meat and milk products humans consume).

>>> to fill our tanks and at the same time increase the cost of food
>>> substantially.

>>
>> No it won't. It'll promote farming, which in turn will keep our
>> top
>> soil from being paved over/ruined. To cut your food costs, just
>> cut
>> out the convenience -- i.e. eating out, packaged meals, etc.

>
> It has already increased food prices world wide. The UN's food
> budget is going through the roof because of the demand of biofuels.
>
>
http://yaleglobal.yale.edu/display.article?id=10167

The real problem is the increase in consumption of meat in developing
countries. And despite all the whining in that article, food prices
are not at "historic highs" if you correct them for inflation. In
fact, they are barely above depression era prices when corrected for
inflation. My Father was selling corn for over $3.50 a bushel in 1975.
I got that much for the first time this year. Given that almost
everything I buy cost three times as much now as it did in 1975, I am
not even close to making the kind of money from farming that my Father
did (despite farming almost twice as many acres and using half as much
labor).

Ed


  #26  
Old January 16th 08, 08:25 PM posted to rec.autos.makers.ford.mustang
Michael Johnson
external usenet poster
 
Posts: 1,039
Default Mustang GT and K&N air charger

C. E. White wrote:
> "Michael Johnson" > wrote in message
> ...
>> wrote:
>>> On Jan 15, 1:23 pm, Michael Johnson > wrote:
>>>> Gill wrote:
>>>> That's because the overall specific energy of E10 is less than
>>>> pure
>>>> gasoline. This is why going to biofuels is a horrible idea, IMO.
>>>> We
>>>> use up our top soil
>>> Using proper farming techniques, top soil will last forever.

>> It just won't stay in the same place. Erosion from farms is far
>> worse than from land development activities. Top soil can be
>> depleted to the point it can't grow much which is why farmers so
>> much fertilizer to their land.

>
> Care to sight some back up for this. I suppose it might be true on a
> total tonnage basis, but probably not on a per unit of land basis. My
> farm has been in constant cultivation for over 300 years. I would
> argue we add fertilizer to replace the nutrients removed when we
> harvest crops. Some crops remove more nutrient than others. One of the
> nice things about ethanol production is that it does not actually
> increase the nutrient drain. Ethanol is carbon (from CO2) and hydrogen
> (from H2O). After you make the ethanol, the dried mash can be used as
> a high quality animal feed. The animal waste can be used as fertilizer
> to return the nutrients to the soil (well except for those that are
> used to make the meat and milk products humans consume).


The very fact that the farmer has to add fertilizer to the soil means
the methods he deploys to grow crops depletes the topsoil of nutrients.
What happens to his crops if no fertilizer is added? The other
component is that typical modern farming techniques cause erosion on a
massive scale. Promoting biofuels just creates more tillable land and
more erosion and more demand for fertilizer. IMO, biofuels use more
energy than is practical for the amount of fuel produced. There are
much better energy sources like geothermal, tides, ocean currents, solar
etc. that have much better efficiency and MUCH LESS impact on the
environment. After all, one of the main points of using alternative
energy is to create less impact on the environment.

>>>> to fill our tanks and at the same time increase the cost of food
>>>> substantially.
>>> No it won't. It'll promote farming, which in turn will keep our
>>> top
>>> soil from being paved over/ruined. To cut your food costs, just
>>> cut
>>> out the convenience -- i.e. eating out, packaged meals, etc.

>> It has already increased food prices world wide. The UN's food
>> budget is going through the roof because of the demand of biofuels.
>>
>>
http://yaleglobal.yale.edu/display.article?id=10167
>
> The real problem is the increase in consumption of meat in developing
> countries. And despite all the whining in that article, food prices
> are not at "historic highs" if you correct them for inflation. In
> fact, they are barely above depression era prices when corrected for
> inflation. My Father was selling corn for over $3.50 a bushel in 1975.
> I got that much for the first time this year. Given that almost
> everything I buy cost three times as much now as it did in 1975, I am
> not even close to making the kind of money from farming that my Father
> did (despite farming almost twice as many acres and using half as much
> labor).


Our standard of living is higher now than in the depression or even
1975. If food prices climb substantially then our standard of living
declines. IMO, this is the real issue. Sure most of us can buy higher
priced food but then we have to drop something else off our wish list.
This will ripple through the economy and could have catastrophic
effects. Plus, poor people that barely make ends meet are the hardest
hit by increasing food prices. Having biofuels in my tank isn't worth
more people going hungry because the price of bread is too high for them
to buy it.
  #27  
Old January 16th 08, 09:35 PM posted to rec.autos.makers.ford.mustang
Michael Johnson
external usenet poster
 
Posts: 1,039
Default Mustang GT and K&N air charger

C. E. White wrote:
> "Michael Johnson" > wrote in message
> ...
>
>> A dirty filter will lower gas mileage on EFI engines too. Instead
>> of going into a long rebuttal I'll just provide a few links to some
>> credible web sites.
>>
>> http://www.fueleconomy.gov/feg/maintain.shtml
>> http://www.edmunds.com/reviews/list/...4/article.html
>> http://tinyurl.com/2a9v2
>> http://tinyurl.com/2hyeyx
>> http://www.mass.gov/Eoca/docs/doer/pub_info/dt.pdf

>
> If by credible, you mean sites that are repeating their granddaddy's
> advice, then I guess they qualify. Can you show me one that actual has
> any data to support your claim? Or at least an explanation of why a
> slightly restrictive air filter might reduce the fuel economy of a
> modern fuel injected engine? These sites are just repeating the same
> sort of maintenance information that has been out there for 70 years.
> Things have changed.


Maybe the way to do this is to find a web site that says a dirty air
filter will not decrease gas mileage on an EFI engine.

>> There are a huge number of sites stating that a dirty filter
>> decreases mileage. There is more than just a MAF reading that the
>> computer uses to determine the amount of fuel needed. Air density,
>> throttle position, air temperature etc. also come into play.
>> Excessive opening of the throttle plate on a fuel injected car also
>> tells the computer the engine is under a greater load which effects
>> how much fuel is delivered to the cylinders.

>
> Sigh, if you are talking about a completely plugged air filter, I
> agree that the fuel economy may be affected (heck it might actually
> increase since the maximum engine power will be limited). However, for
> a modern fuel injected car operated in a normal environment with a
> filter changed at reasonable intervals the difference in fuel economy
> between a "new" and "used" filter approaches zero. The same is true
> for a proper paper filter and a K&N filter. The only sensor in front
> of the throttle plate(s) is the MAF. It is called a Mass Air Flow
> sensor because it is measuring the mass of air flowing through the
> intact tract, not pressure or density, or temperature. The throttle
> position sensor is at the throttle and measures it position. All of
> the other sensors are behind the throttle plate. So think about what
> the various sensors see when the filter is slightly more restrictive.
> The MAF is measuring the mass of air flowing through the system. It
> doesn't measure pressure, so it won't be affected because the flow is
> reduced my a slightly higher restriction at the filter (we are talking
> about tenths of a psi difference or less). If the filter is slightly
> more restrictive, the throttle may need to be slightly more open to
> achieve the same power output. And I mean slightly. Throttle position
> sensors are not particularly precise. They are a gross position
> indicator. I doubt the difference in the throttle opening related to a
> slightly more restrictive filter is significant enough to affect the
> engine parameters at all. All the other engine sensors are after the
> throttle plate. They will not be affected by the restriction in the
> air filter any more than by the much larger restriction of the
> throttle plate. AND remember you have O2 sensors that feed data back
> to the PCM that is used to correct for variations in the other
> sensors. So even if the restriction of the air filter was severe
> enough to affect the other sensors, the feedback from the O2 sensors
> should allow the PCM to adjust the fuel trim to compensate.


Does an engine under a heavy load run richer than one that is under a
light load? The ECU has load tables that it uses to help calculate what
it believes the optimum air fuel ratio should be taking into account the
conditions it thinks the engine is operating under. What the computer
thinks is optimum isn't always 14.7:1. The computer expects the
operator to keep the filters fresh and a dirty air filter makes the ECU
think the engine is under a heavier load and thus changes the target A/R
to run richer than normal. This in turn reduces gas mileage. ECUs
aren't clairvoyant and can determine the degree to which an air filter
is dirty. It only takes the input from ALL the sensors and using
preprogrammed tables makes A/F adjustments (and many other) to the
conditions it perceives the engine to be operating under. Determining
engine load is a very important component is what it uses to set the
target A/F at any given moment. This is why they put throttle position
sensors on engines nowadays. The new Mustangs are somewhat different in
that there is no longer a direct wire connection to the throttle plate.
The computer senses the position of the accelerator pedal and then
sets the throttle opening accordingly.

I have a TwEECer chip in my '89 LX that lets me program almost all of
the EEC-IV operating parameters. I know load tables exist and they
affect A/F as do many other sensor readings. There is a lot more going
on in the ECU than reading air in and making a simple computation for
fuel required. Things like engine acceleration rate, load, etc. come
into play in a big way. When something like a dirty air filter causes
readings of the throttle position sensor to be out of the range it
expects for a given driving condition then gas mileage can, and will, be
affected. The computer doesn't know the air filter is dirty and tries
to run the engine in a manner that isn't optimum for gas mileage. It
thinks you are doing something like climbing a hill, or accelerating,
and delivers fuel accordingly.

The A/F doesn't remain constant across the entire load range an engine
can experience. As the load increases the target A/F decreases. This
is programmed into the load data tables of ECUs. If the A/F didn't
decrease then cylinder temperatures would get too high and start melting
things like piston tops.

To further make my point does an engine get better gas mileage going
downhill or uphill at the same speed? Is that because in one condition
the engine is under a heavier load than the other? If the rpm rate is
the same for each condition then why is the mileage different? It is
because the throttle has to be open more going uphill to get the air
necessary to make the power needed to overcome the elevation increase.
The data tables for engine load the computer uses are very specific to
the size of the throttle body put on the car. It relies on these tables
in conjunction with throttle position readings to determine what target
A/F is used from the load table. It also uses the O2 readings to fine
tune the A/F but only to meet the target A/F from the load table. A
dirty filter requires an increase in throttle opening which triggers the
computer to operate from the higher end of the load tables. Hence the
engine runs richer and gets lower mileage.

>> I'm not saying a K&N filter will give a noticeable improvement in
>> gas mileage over an OEM unit but with all things being equal the
>> engine with a more efficient filter will perform better. Do you
>> think an engine with a dirty air filter would pass an emissions
>> test? If so then why not?

>
> As long as the filter is in good shape, it will have no significant
> effect on the ability to pass an emissions test. See above for the


So if the filter is dirty enough then it will affect whether the
emissions test is passed? This means the A/F ratio isn't optimum,
doesn't it? If what you are saying is true then the computer should
compensate and make the A/F optimum thus allowing it to pass the test.

> reasons. I won't argue that a K&N might provide a slight performance
> increase at WOT. It very well might. But for anything but large
> throttle openings, the throttle plate is by far the most significant
> restriction in the intake tract. The filter is almost not there as far
> as air flow is concerned until the throttle is nearly wide open.
> Again, I am only talking about modern fuel injected engines. For older
> carbureted engines, a restrictive air filter would definitely
> significantly reduce fuel economy. And the situation is not clear to
> me if you are talking about some of the early speed density type fuel
> injection systems (systems without a MAF). For normal sorts of air
> filter restriction the PCM of these types of systems would be able to
> compensate for a restrictive air filter. However, for a very
> restrictive filter, they may not. However, as far as I know, no one
> has sold a car with a speed density only system for a decade.


You keep saying for "normal sorts of air filter restrictions" when a
restriction is a restriction. A filter just doesn't not affect mileage
one day and then suddenly becomes dirty enough to affect it the next.
It is a gradual progression that happens continuously and in most
circumstances is too slow for the driver to perceive.

Also, the basic operating parameters of an engine doesn't change because
it is fuel injected and computer controlled. The computer actually
mimics the old carburetors, governors, points etc. by using sensor
readings. The ECU controlling today's engines isn't a HAL 9000 that
thinks like a human. If it is getting garbage input from the sensors
then it spits garbage out to control the engine. The effect of a dirty
air filter on a fuel injected engine is the same as one with a
carburetor. On both engines the dirty filter puts the engine under load
and it is this that decreases gas mileage in both cases.


> By the way, the DIY Basics sight you referenced is loony
> (http://tinyurl.com/2hyeyx). You should follow your vehicle
> manufacturers replacement schedule for the air filter. I think that
> sight must be run by filter manufacturers.
>
> You should read these sites:
>
> http://www.visteon.com/utils/whitepa...05_01_1139.pdf


I searched the PDF for "gas mileage" "mileage" and "mpg" and got no
hits. It's a little too long for me to read through but it seems to
address filtering efficiency for removing particulates and not the
effect of dirty air filters on gas mileage.

> http://www.filtercouncil.org/techdata/tsbs/89-3R3.html


This also seems to be addressing filter efficiency for removing
particulates and not gas mileage efficiency.

> Air filters (paper and K&N) are less efficient at removing dirt when
> they are new. As the accumulate particles, the filtering efficiency
> improves. So changing your filter too frequently (or cleaning your K&N
> too often) can actually increase engine wear. You should also consider
> that K&N filters loads up with dirt much faster than paper filters
> (they have less dirt holding capacity). So while they may enjoy a flow
> advantage when new (or when just cleaned), the advantage decreases
> rapidly with time.


I have no doubt that a K&N filter lets more particulates by (and
therefore more air itself) than an OEM filter. Where the debate starts
is whether is has any appreciable impact on engine longevity for the
average vehicle. I believe it doesn't based on my own experience. My
'89 LX had had the same filter installed for over 130k miles and I had
the heads off at around 150k miles and saw no appreciable cylinder wall
wear. It also doesn't noticeably use any more oil than when it was new.

The air filter debate is similar to the synthetic verses conventional
oil debate. IMO, there is no appreciable difference in wear from using
any oil that is changed every 3,000-4,000 miles. The contaminants never
get a chance to build up in the oil to cause a problem whether the oil
is synthetic or conventional.
  #28  
Old January 16th 08, 11:28 PM posted to rec.autos.makers.ford.mustang
C. E. White[_2_]
external usenet poster
 
Posts: 617
Default Mustang GT and K&N air charger


"Michael Johnson" > wrote in message
...

> Does an engine under a heavy load run richer than one that is under a
> light load? The ECU has load tables that it uses to help calculate what
> it believes the optimum air fuel ratio should be taking into account the
> conditions it thinks the engine is operating under. What the computer
> thinks is optimum isn't always 14.7:1. The computer expects the
> operator to keep the filters fresh and a dirty air filter makes the ECU
> think the engine is under a heavier load and thus changes the target A/R
> to run richer than normal. This in turn reduces gas mileage.


Some of what you say is true, but your conclusion are wrong. As I said
before, the throttle position sensor is the only sensor that will even show
a minor variation as a result of a change in air filter restriction. And
throttle position sensors are not precise at all. They are gross indicators,
used primarily to communicate rapid changes in the throttle position (i.e.,
mashing down or letting up) so the PCM will be able to temporarily enrich
the mixture (mimicking the accelerator pump of a carbureted engine) or
change the IAC setting to prevent the engine from stalling as the speed
falls back to idle (like a dashpot).

> ECUs
> aren't clairvoyant and can determine the degree to which an air filter
> is dirty. It only takes the input from ALL the sensors and using
> preprogrammed tables makes A/F adjustments (and many other) to the
> conditions it perceives the engine to be operating under. Determining
> engine load is a very important component is what it uses to set the
> target A/F at any given moment. This is why they put throttle position
> sensors on engines nowadays. The new Mustangs are somewhat different in
> that there is no longer a direct wire connection to the throttle plate.
> The computer senses the position of the accelerator pedal and then
> sets the throttle opening accordingly.


Not just Mustangs are fly by wire. But again, you are missing the key truth.
An air filter, even a used one, is a minor restriction comapred to other
elements in the intake system. When crusing at a steady speed (say 60 mph),
the air drop across the engine air filter is going to be less than 0.3 psi.
The pressure drop across the throttle plate will be on the order of 7 psi.
The difference in pressure drop between a clean K&N filter and a reasonably
dirty paper filter is probably less than 0.1 psi. Is it your claim that this
small change is going to upset the PCM so much that it can't maintain the
proper fuel to air ratio? There will be a bigger difference in the pressure
after the air filter if you drive the car from sea level to the top of a
5000 ft mountain that any change in pressure related to normal changes in
the filter restriction. If you truly believe this, why doesn't installing a
K&N upset the PCM parameters?

> I have a TwEECer chip in my '89 LX that lets me program almost all of
> the EEC-IV operating parameters. I know load tables exist and they
> affect A/F as do many other sensor readings. There is a lot more going
> on in the ECU than reading air in and making a simple computation for
> fuel required. Things like engine acceleration rate, load, etc. come
> into play in a big way. When something like a dirty air filter causes
> readings of the throttle position sensor to be out of the range it
> expects for a given driving condition then gas mileage can, and will, be
> affected. The computer doesn't know the air filter is dirty and tries
> to run the engine in a manner that isn't optimum for gas mileage. It
> thinks you are doing something like climbing a hill, or accelerating,
> and delivers fuel accordingly.


Again, the throttle position sensor is just a gross indicator. The change in
the position of the throttle related to normal variations in air filter
restrictions will be trivial at cruise speeds. As the throttle angle changes
from 4 degrees to 90 degrees, the tps ratio of output voltage to input
voltage will go from around 0.2 to 0.98. The accuracy of the output is on
the order of +/- 20%. There is no way a reasonable change in the restriction
of the air filter is going to cause a greater change in the output of the
TPS than normal variations inherent in the design of the tps. Automotive
throttle position sensors are not highly accurate. And the PCM is able to
use the feedback from the O2 sensor to compensate.

> The A/F doesn't remain constant across the entire load range an engine
> can experience. As the load increases the target A/F decreases. This
> is programmed into the load data tables of ECUs. If the A/F didn't
> decrease then cylinder temperatures would get too high and start melting
> things like piston tops.
>
> To further make my point does an engine get better gas mileage going
> downhill or uphill at the same speed? Is that because in one condition
> the engine is under a heavier load than the other? If the rpm rate is
> the same for each condition then why is the mileage different? It is
> because the throttle has to be open more going uphill to get the air
> necessary to make the power needed to overcome the elevation increase.


Ths had nothing to do with wether or not the air filter restriction has any
affect on fuel economy.

> The data tables for engine load the computer uses are very specific to
> the size of the throttle body put on the car. It relies on these tables
> in conjunction with throttle position readings to determine what target
> A/F is used from the load table. It also uses the O2 readings to fine
> tune the A/F but only to meet the target A/F from the load table. A
> dirty filter requires an increase in throttle opening which triggers the
> computer to operate from the higher end of the load tables. Hence the
> engine runs richer and gets lower mileage.


The change in the throttle opening related to normal changes in air filter
restriction is trivial. You are talking about gross changes that are far
from normal.

>>> I'm not saying a K&N filter will give a noticeable improvement in gas
>>> mileage over an OEM unit but with all things being equal the engine with
>>> a more efficient filter will perform better. Do you think an engine
>>> with a dirty air filter would pass an emissions test? If so then why
>>> not?

>>
>> As long as the filter is in good shape, it will have no significant
>> effect on the ability to pass an emissions test. See above for the

>
> So if the filter is dirty enough then it will affect whether the
> emissions test is passed? This means the A/F ratio isn't optimum,
> doesn't it? If what you are saying is true then the computer should
> compensate and make the A/F optimum thus allowing it to pass the test.


Exactly. I can certainly imagine cases where a filter that is severely
contaminated could cause a modern fuel injected vehicle to fail an emissions
test, but this would be an exceptional case. For any reasonably well
maintained vehicle, with an air filter changed per the manufacturers
recommendations, you aren't going to fail an emissions test because of the
air filter. If you want to hypothesize a very restrictive filter, all bets
are off.

>> reasons. I won't argue that a K&N might provide a slight performance
>> increase at WOT. It very well might. But for anything but large throttle
>> openings, the throttle plate is by far the most significant restriction
>> in the intake tract. The filter is almost not there as far as air flow is
>> concerned until the throttle is nearly wide open. Again, I am only
>> talking about modern fuel injected engines. For older carbureted engines,
>> a restrictive air filter would definitely significantly reduce fuel
>> economy. And the situation is not clear to me if you are talking about
>> some of the early speed density type fuel injection systems (systems
>> without a MAF). For normal sorts of air filter restriction the PCM of
>> these types of systems would be able to compensate for a restrictive air
>> filter. However, for a very restrictive filter, they may not. However, as
>> far as I know, no one has sold a car with a speed density only system for
>> a decade.

>
> You keep saying for "normal sorts of air filter restrictions" when a
> restriction is a restriction. A filter just doesn't not affect mileage
> one day and then suddenly becomes dirty enough to affect it the next.
> It is a gradual progression that happens continuously and in most
> circumstances is too slow for the driver to perceive.


By normal, I mean real world situations. Again, if you want to theorize
about some wacky almost plugged filter, then all bets are off. Once again -
unless you are operating near wide open throttle, any restiriction in the
intake related to the air filter is trival compared to the restriction of
the throttle plate.

> Also, the basic operating parameters of an engine doesn't change because
> it is fuel injected and computer controlled. The computer actually
> mimics the old carburetors, governors, points etc. by using sensor
> readings. The ECU controlling today's engines isn't a HAL 9000 that
> thinks like a human. If it is getting garbage input from the sensors
> then it spits garbage out to control the engine. The effect of a dirty
> air filter on a fuel injected engine is the same as one with a
> carburetor. On both engines the dirty filter puts the engine under load
> and it is this that decreases gas mileage in both cases.


THINK!!!!!!!!!!!!!!!!!!!!!! Why does a dirty filter impose any more load on
an engine than a partially closed throttle plate. Do you understand
carburetors? Do you know why they have a choke plate in front of the
metering jets. Do you understand how the choke enriches the mixture. Can you
see why for a carbureted engine a dirty filter might act like a choke and
affect the mixture. Don't you understand that none of this applies to modern
fuel injected engines? Carburetors depend on the Bernoulli principal to
meter fuel. The fuel in the bowl is under atmospheric pressure. The pressure
in the venturies is related to the flow through the venturies. If you place
a restriction in front of the venturies, you will pull an artificially high
vacuum in the venturies (higher than created by the Bernoulli principal),
drawing more fuel into the air stream. Anything (like a choke, or a plugged
air filter) affects the balance between the pressure on the fuel in the fuel
bowl and the pressure in the venturies will affect the fuel to air ratio.
This is why a clogged air filter can greatly affect the fuel economy of a
carbureted engine. A fuel injected engine determines the amount of fuel my
measuring a lot of parameters. None of these parameters is going to be
significantly affected by normal variations in the filter restriction.

>> By the way, the DIY Basics sight you referenced is loony
>> (http://tinyurl.com/2hyeyx). You should follow your vehicle manufacturers
>> replacement schedule for the air filter. I think that sight must be run
>> by filter manufacturers.
>>
>> You should read these sites:
>>
>> http://www.visteon.com/utils/whitepa...05_01_1139.pdf

>
> I searched the PDF for "gas mileage" "mileage" and "mpg" and got no
> hits. It's a little too long for me to read through but it seems to
> address filtering efficiency for removing particulates and not the
> effect of dirty air filters on gas mileage.
>
>> http://www.filtercouncil.org/techdata/tsbs/89-3R3.html

>
> This also seems to be addressing filter efficiency for removing
> particulates and not gas mileage efficiency.


True. I just thought you might find it interesting. They were meant to
refute the idea that it was a good idea to change filters based on the
advise at the DIY Basics site you referenced. I thought it was bad advice.

>> Air filters (paper and K&N) are less efficient at removing dirt when they
>> are new. As the accumulate particles, the filtering efficiency improves.
>> So changing your filter too frequently (or cleaning your K&N too often)
>> can actually increase engine wear. You should also consider that K&N
>> filters loads up with dirt much faster than paper filters (they have less
>> dirt holding capacity). So while they may enjoy a flow advantage when new
>> (or when just cleaned), the advantage decreases rapidly with time.

>
> I have no doubt that a K&N filter lets more particulates by (and
> therefore more air itself) than an OEM filter. Where the debate starts
> is whether is has any appreciable impact on engine longevity for the
> average vehicle. I believe it doesn't based on my own experience. My
> '89 LX had had the same filter installed for over 130k miles and I had
> the heads off at around 150k miles and saw no appreciable cylinder wall
> wear. It also doesn't noticeably use any more oil than when it was new.
>
> The air filter debate is similar to the synthetic verses conventional
> oil debate. IMO, there is no appreciable difference in wear from using
> any oil that is changed every 3,000-4,000 miles. The contaminants never
> get a chance to build up in the oil to cause a problem whether the oil is
> synthetic or conventional.


This time I am not trying to debate how well a K&N filter "filters." I am
only arguing that there is no reason to expect a K&N filter to increase the
fuel economy of a modern fuel injected engine (compared to a paper filter in
reasonable condition).

Ed


  #29  
Old January 16th 08, 11:32 PM posted to rec.autos.makers.ford.mustang
Michael Johnson
external usenet poster
 
Posts: 1,039
Default Mustang GT and K&N air charger

Bob Willard wrote:
> Michael Johnson wrote:
>
>> C. E. White wrote:
>>
>>> "Michael Johnson" > wrote in message
>>> news >>>
>>>>> Exactly, I don't believe an air filter will change mileage. The
>>>>> auto makers would be on it and so would the rest of this small world.
>>>>
>>>> Ever notice that an engine running with a dirty filter sees a drop
>>>> in gas mileage? The same principle applies to an OEM filter verses
>>>> a filter that flows better (i.e. a K&N etc.). There are two things
>>>> that can happen when air flow through an engine is made more
>>>> efficient. One is an increase in horsepower and the second is an
>>>> increase in mileage. Sometimes both can happen simultaneously. If
>>>> you don't believe me then take your air filter and clog it up and
>>>> run your car for a tank of gas then put in a new one and see whats
>>>> happens to your gas mileage and power output. I'll bet the farm
>>>> that they both will see a substantial increase when a clean filter
>>>> is installed.
>>>
>>>
>>> While this was certainly true with carbureted engines, there is no
>>> reason to think this is the case for modern fuel injected engines.
>>> For carbureted engines, a clogged air filter acts like a choke and
>>> enriches the mixture because of the effect on air pressure in front
>>> of the throttle plates. This reduces the fuel economy. In a modern
>>> fuel injected engine, the mixture is not influenced in this way. The
>>> amount of fuel injected is determined based on the MAF sensor and
>>> other sensors. These sensors can't tell the difference between a
>>> restriction to the flow related to the air filter and a restriction
>>> to the flow related to the throttle plates. There is no difference as
>>> far as the computer is concerned between the restriction of the air
>>> filter and the restriction of the throttle plates. The engine speed /
>>> power output is determined by the total intake restriction (intake
>>> tract plus throttle opening). The only thing a slightly restricted
>>> air filter does on a modern engine is require you to open the
>>> throttle a slight amount more and reduce the maximum power output.
>>> The effect on fuel economy for a modern engine is minimal. I won't
>>> claim it is zero, but I doubt you would be able to tell the
>>> difference unless the filter was absurdly restrictive.

>>
>>
>> A dirty filter will lower gas mileage on EFI engines too. Instead of
>> going into a long rebuttal I'll just provide a few links to some
>> credible web sites.
>>
>> http://www.fueleconomy.gov/feg/maintain.shtml
>> http://www.edmunds.com/reviews/list/...4/article.html
>> http://tinyurl.com/2a9v2
>> http://tinyurl.com/2hyeyx
>> http://www.mass.gov/Eoca/docs/doer/pub_info/dt.pdf
>>
>> There are a huge number of sites stating that a dirty filter decreases
>> mileage. There is more than just a MAF reading that the computer uses
>> to determine the amount of fuel needed. Air density, throttle
>> position, air temperature etc. also come into play. Excessive opening
>> of the throttle plate on a fuel injected car also tells the computer
>> the engine is under a greater load which effects how much fuel is
>> delivered to the cylinders.
>>
>> I'm not saying a K&N filter will give a noticeable improvement in gas
>> mileage over an OEM unit but with all things being equal the engine
>> with a more efficient filter will perform better. Do you think an
>> engine with a dirty air filter would pass an emissions test? If so
>> then why not?

>
> None of those sites listed states that the effect of a dirty air filter
> on gas mileage applies to FI engines with MAF sensors. It seems rather
> likely
> to me that those sites are merely repeating what was true with carburated
> engines as still being true, without retesting or even remodeling.


These web sites were developed after EFI was common place. The .gov
site is from the US Dept. of Energy and is very current. The Edmunds
site is also very current. The last one is put up by the State of
Massachusetts. These aren't old out of date web sites. Do a Google
search and you'll have weeks of reading that tells you that dirty air
filters decrease gas mileage on ALL cars.

> Do you have any URLs for tests done with modern engines?


Try this one:
http://www.genuineservice.com/genuin...lt?page=Filter
Expand the link to "Do I need a new air filter?" Look at the third item
listed. Do you think this site is referring only to engines with
carburetors? Do you think Ford's Genuine Parts and Service web site is
giving out bogus information on this topic? Are the thousands of sites
saying dirty air filters decrease gas mileage all wrong. Can you find a
site that says dirty air filters DON'T decrease mileage? I can't
believe we are even arguing the point, to be honest.

  #30  
Old January 17th 08, 12:09 AM posted to rec.autos.makers.ford.mustang
WindsorFox[_4_]
external usenet poster
 
Posts: 234
Default Mustang GT and K&N air charger

C. E. White wrote:
> "WindsorFox-{SS}-" > wrote in message
> ...
>
>> Yes but I'd bet that by "dirty filter" they mean clogged. I can
>> see Ed's point here but there is probably a point at which the clog
>> becomes so bad the electronics can not compensate. I once bought a
>> 1977 Thunderbird for $50. It would not start, the guy and 4 friends
>> tried to get it started to get it home. When I went to get it I had
>> a battery, some gas and tools. It was full of gas, I cranked,
>> smelled gas and popped the hood. Took off the air breather and put
>> it in the trunk, started it and drove home to all their amazement.
>> Three months and $500 later I sold it for $4500. It had 267K miles
>> on it. The buyer was still driving it 4 years later. P

>
> Of course a 1977 Thunderbird had a carburetor...
>
> Ed
>
>


Doesn't matter, the way it was clogged nothing would have been able
to run.

--
"Yah know I hate it when forces gather in ma' fringe..." - Sheogorath

"Daytime television sucked 20 years ago,
and it still sucks today!" - Marc Bissonette
 




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