Air filter and mpg.

Bzzt. Wrong. Try this document:
http://www.google.com/url?sa=t&ct=r...101.com/forms/h44.pdf&ei=IDwnQ-CuM8-YYYmbiIIO

From the document:
"Because Long FT is part of the basic injection duration, it affects
injection duration in closed and open loop"

See that: "it affects injection duration in ... open loop".

Now, as to your other comments. I do agree that if the dirty filter causes
the system to be in open loop mode longer, this will affect mpg, however,
I suspect that the impact of this is pretty small -- too small to be
noticed. How often do most drivers actually use WOT?

Regarding acceleration: if the gas pedal has to be depressed further (but
not into WOT), what is the difference? If it takes 4 seconds (say) to
accelerate onto an on-ramp, with clean or dirty filter, how is that any
different if the pedal is pushed down a little further? It's still 4
seconds under high acceleration.

Acceleration does not mean that the pedal is pushed down -- it means that
the car is changing velocity. It the velocity is changing at the same rate
with clean or dirty filter, then both conditions will be treated the same
by the PCM (both or neither will be high acceleration).

So, basically, while you have provided zero evidence about this, we
should believe you and not me?

 

Try reading again. I did not state that WOT = increased pressure. My point
is that the dirty filter is equivalent to a slightly closed throttle:
closed throttle = reduced (absolute) manifold pressure (it also
depends on engine speed, but for the sake of this limited discussion we
assume a constant speed)

But a dirty filter does not require infinite compensation. Remember, the
effect is to reduce peak air flow, and hence reduce the need for fuel. And
we are not talking about a situation that the PCM has detected a fault
condition.

Evidently, you did not read my initial post in which I concurred that a
dirty filter would affect performance.

 

Oh, gee, you read something on the interweb, therefore it's true. Sorry,
you'll have to do a *lot* better than that, mister "I used to design EFI
systems". Open-loop mode BY DEFINITION is a mode in which the O2S is
disregarded.

Very good. Very VERY good. Now, that wasn't so hard, was it?

Pretty much. You're the one who made the wild-assed guess and then, when
told that guesses don't cut the mustard, restated it as a factoid without
adding any support for the notion. That means *YOU* set the low level of
debate. That means all your factoid is worth is an "is not." If you want
people to engage your ideas in an adult fashion, you'll have to present
them in an adult manner, i.e., with support.

Toodles,

DS

 

aarcuda doesn't need my help, but I just can't pass up this beautiful gem:

Exactly. That's the problem -- you didn't state that WOT = increased
pressure.

But don't feel bad, you don't go away emptyhanded...you've won a
family-pak of Lee Press-On Nails, and a full container load of
Rice-a-Roni. It's the San Francisco treat!

Well, sure, Whoever, if you impose all sorts of spurious restrictions and
conditions on the discussion, you can appear to provide support for
whatever point you think you're making. Hell, restrict the discussion
enough and you might just be able to show that a dirty air filter
*increases* fuel economy in the 2.2 seconds immediately after engine
startup when ambient temperatures are between 20 and 21.5 Centigrade,
altitude is 2km above sea level, and the driver is smoking a Kool Filter
and listening to Steely Dan's "Peg" with the fader set so the sound comes
only through the left front speaker.

But your victory would be pyrrhic, for it would have nothing to do with
the real world.

Ah. Whoever said it, therefore it's true. *pfft*

 

MAF and throttle position BOTH have significant input to the ECU. MAF
tells the ECU how much air the engine is getting, and the TPS tells
the ECU how much you want it to get. Two different things.
Mixture is significantly richer at low RPM with the throttle wide open
than at high RPM with the throttle almost closed - but both can have
the same number of grams per second air flow.

 

Never heard of a feedback carb? They run closed loop with Lambda
correction. Never heard of a CV carb? They compensate for changes in
atmospheric pressure quite effectively and are basically Mass Airflow
Sensers.

Yes, and it's true = particularly when the vehicle is running open
loop more because of reduced power output.

 

Typo. I meant to write "I did not state the WOT != increased pressure"
< CR*P DELETED>

Can you take part in a discussion without resorting to insults and
ad-hominem?

 

I surely can. Can you answer my Mr. Green vs. Mr. Black scenario...?

 

Man - I'm disappointed - you missed the joke. I thought surely you'd
get it (and I'll quit calling you Shirley!). While he's *yacking-off*,
you're - wait for it - "macking-off".

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')

 

I was merely pointing out that you had it backwards.

No it isn't.
You can't claim one aspect of function and totally ignore the
others.

Sorry, "limited discussion' serves no useful purpose other than
to confuse the issue.

How dirty is dirty?

There are other effects which you're totally ignoring, or are
oblivious to.

That wasn't all of it.
"Driveability" covers a lot of ground.

 

For this to be relevant and lend any support to your argument,
open loop operation would have to have some authority on long
term fuel trim. It doesn't.

Quite often.
WOT on almost all systems is defined as any TPS voltage above 2.5
volts.
(that's roughly half throttle)

 

Naw, I didn't. I just didn't blurt out the punchline, is all.

"Maccin' off". There.

 

Apparently s/he's not one of those types who let facts stand in his/her
way.

Geeze, Neil, can't you have a debate without resorting to ad hominems and
gross exaggeration? ;-)

Dirty! Y'know, dirty!

 

The phrase "knows enough to be dangerous" comes to mind...

So much for the 'kinder, gentler' Neil.

Oh, *that* dirty!

 

At least I don't *think* he meant the dirty that comes between twenny-nine
and dirty-one.

 

I haven't read all the posts in this string, but I'd bet that once the
filter got too dirty for the computer to correct for, it would key the
check engine light and you'd store a code. Up to that point, you
should be fine, and mileage shouldn't be effected.

Marvin Stockman

 

....but you're sure you know the answer...

OK, that's an imaginative, special and unique guess. Thanks for
sharing it with us. Now, go look up the difference between "effect" and
"affect".

 

First, "dirty" needs to be defined! Is it "cosmetic" or
"restrictive"??? Highly significant differences!!!

Each air filter element is designed to support a particular service life
in its intended use, which can relate to some highly skewed filter sizes
versus engine air flow requirements. In the GM side of things, by
observation, a garden variety car which will see a lot of fleet (rent
car company) sales, can have a huge air filter element for a 3.1L V-6
whereas a 4.6L Northstar Cadillac will have a filter that's less than
1/2 that size.

There has been some informative discussions on engine air filters in the
www.bobistheoilguy.com message board website. Engine oil analysis (one
thing many participants on that board like to do) tends to support
higher silica levels in the oil of engines equipped with the beloved K&N
air filter elements. Another test reveals that the factory GM Duramax
air filter element flows better and has higher particle retention (in
standardized tests) than a K&N replacement element.

GM TSBs also mention the oil in the K&N fouling the computer sensors
downstream in the air flow from the K&N air filter too. A "fouled"
sensor that will throw a code too!

In general, a fresh air filter will always flow better than a "used"
one, the degree of longevity of the filter's higher flow life will
depend on the operational environment of the vehicle. It can also
depend on the filter media too. I was short on funds and bought a less
expensive filter (for the popular 13x3" open element air cleaner) and it
turned "dirty" quickly, yet the Fram I got to replace it is still
"white".

IF the filter element size/flow situation is on the smaller side of
things, a small amount of "wear" will put things into the "decreased
performance" area quickly (kind of like the 3.1L V-6 and Northstar V-8
illustration), but if the filter is oversized for the application (for
longer service life of the element), so how much of an affect the
"dirty" filter has on performance is highly variable and NOT
particularly related to brand or type (other than the oil issue
previously mentioned).

IF the filter element size/flow is on the "too small" side of things,
adding a higher flow element (i.e., K&N or Fram AirHog) might help
performance, BUT only if the orig setup is so far undercapacity that it
really makes a difference with the higher flow element.

"Dirty" air filters and performance and mpg? If the additionally
restricted air filter element will not flow enough air for the
particular throttle input, then more throttle input will be desired to
maintain a particular performance level of the vehicle. More throttle
input = more delta TPS signal = more fuel for a given result, even with
feedback loop operation of the fuel system. Just like in the "old
days", when lower manifold vacuum levels would kick in the "power
circuit" sooner than normal.

Fuel econony? We need to talk about cruise economy or city driving
economy, I suspect. At highway cruise, I suspect a dirty air filter
element would impact fuel economy very much, unless it was really
clogged up. In the city environemnt, where throttle position will
change much more frequently and accelerative bursts might be needed, I
suspect THAT's where you'll notice the difference in power and economy.

It's a given that the less throttle input it takes to achieve a desired
level of performance, fuel ecomomy will typically be better.

Many of the radio talk show hosts have to talk in generalitics more than
specifics. Giving the general listening public some general information
they can deal with in their daily lives is important, so what they say
in response to a question might not be applicable to all vehicles in all
situaitons per se. And the television car show operatives can also
"sell up" a particular product, which might well be an advertiser on
their show.

To me, the key thing is to consider their statements as "general"
statements rather than statements that would specifically apply to YOUR
vehicle only. End result, somebody somewhere will let a "service
professional" make a determination as to whether or not their air filter
element is "dirty" and needs changing. OR they'll check the restriction
gauge on their air filter housing (if equipped) to see if it's still
"green" or "red".

(Let the engine speed now return to idle!)

Enjoy!

C-BODY