"My Name Is Nobody" > wrote in message
news:qAVpj.2934$f73.1418@trndny08...
>
> "Ironrod" > wrote in message
> ...
> >
> > "Michael Johnson" > wrote in message
> > ...
> >> Ironrod wrote:
> >> > "Michael Johnson" > wrote in message
> >> > ...
> >> >> C. E. White wrote:
> >> >>> "Michael Johnson" > wrote in message
> >> >>> ...
> >> >>>
> >> >>>> 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.
> >> >>> 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, 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.
> >> >
> >> > 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.
> >
> > 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.
> >
> >
> Your example assumes that the clean filter provides ZERO restriction, that
> just isn't so.
>
>
No, I am saying that the restriction remains constant throughout its
service life, further that when the filter reaches the end of its service
life you will only feel it at the engines top end, remember in this example
I'm just talking about the air filter. Now when you take the entire intake
tract as a whole then the walls of my hypothetical corridor are by necessity
only as wide as the engine's air flow requirements need them to be. The
variable, of course, is the throttle plate which can only reduce the intake
restriction by a specific percentage determined by the engine load. Opened
wider the engine goes faster, closed it goes slower. Change the filter or
remove it entirely then the throttle plate must be adjusted (by means of
your foot) to restrict the air flow down to only the required amount. No
more no less.