Air filter and mpg.

What happened to you, guy? Did you fall asleep in 1974, just before the
development of the aneroidal alcomp, and not wake up until last year or
so, thus missing a couple of generations of closed-loop feedback
carburetors?

That's right. Once the ability of the ECM to compensate is exceeded, the
AFR will be wrong. And that's only just *one* of the mechanisms by which
fuel economy is reduced with a dirty filter.

 

The grandparent post described an open-loop situation and was equating
this to fuel injection using a MAF sensor.

So, what you are saying is that the mathematics done by the PCM are
somehow limited?

Remember, we are talking about putting LESS fuel into the engine.

 

....has nothing to do with your incorrect statements, which you are now
refusing ownership of. Interesting.

Oh, gee, yeah, gosh, what a silly statement for me to make. Glad you
caught me on that one. Obviously, the ECM has an unlimited ability to
compensate for any variable you care to name. No limits at all. *eyeroll*

What you are doing, Mr. Whoever, is yacking-off: typing to hear your
keyboard rattle.

 

And you accuse me of using hand-waving arguments?

 

Once again, you quote me out of context and use wild exaggeration to try
to make a point. My point was that the result of a dirty air filter is
that to maintain the correct A/F mixture, the amount of fuel to be
injected should be REDUCED.

Yes, I was a little careless in my writing, clearly: there are limits to
the PCM's mathematics. But to think that the small differences due to a
dirty air filter could not be with the range of calculations is frankly,
ridiculous.

 

And to put it as simply as I can, the resulting situation is that the
throttle position sensor is shouting "MORE FUEL! MORE FUEL!" and the MAF
sensor is screaming "LESS FUEL! LESS FUEL!" What does the PCM do in the
case of conflicting sensors? Depends on the programming. Since leaning
out an engine is potentially destructive, most PCMs will err on the side
of biasing the actual mixture closer to the default value, resulting in
a richer-than-optimum mixture and lower efficiency (but a protected
engine). At SOME point, its also going to result in an error code,
because the PCM can't tell if its looking at a restricted intake or a
sensor fault.

Its more a limit to what software can safely do in the case of
conflicting or abnormal combinations of sensor inputs.

 

Yes, I do.

 

I quote only what you write. If you dislike what I quote, you should've
written something different.

Wild exaggeration? What wild exaggeration would that be?

Yes, it should. Now, consider: When the ECM sees conflicting demands (for
less fuel from the MAF, for more fuel from the TPS), what happens?

Yes, you were. Also in your thinking.

 

But what about the O2 sensor? Dirty filters are not a transient effect so
the PCM should adjust the mixture bias based on the O2 sensor reading.

Just a thought: no-one has commented on my suggestion that there are much
greater differences in pressure drop across the filter from when it is
brand new to the first thousand miles than between end of service life
and some time after that. Clearly, the PCM has to and does accommodate
this.

 

Y'mean the one that's ignored during open-loop acceleration? Or some other
O2 sensor?

That's because it was, as you yourself admitted, nothing more than an
ignorant guess. You'll have to do better than ignorant guesses if you want
people to comment on what you say.

 

*cricket chirp*
*cricket chirp*
*cricket chirp*
*silence from Whoever's corner 'cause the answer to the question at the
bottom of this post is embarrassing to him*
*cricket chirp*
*cricket chirp*
*cricket chirp

 

YOU MUST NOT DO THAT

....otherwise somebody will bite your head off.


Write 100 lines "I must not be careless in writing"...

DAS

For direct contact replace nospam with schmetterling
---

[...]

[...]

 

Yes, I mean the one that affects LONG TERM TRIM. And hence affects the
amount of fuel injected during open loop conditions.

All right. Let me assert that it is true. What's your response?

 

Sorry to jump into this, but it seems like you are missing one thing in
your assertion that MPG doesn't suffer.

In the previous "one clean-filtered car vs. one dirty-filtered car"
example, you are not accounting for both cars doing the SAME WORK. In
this case, it must be assumed (because Daniel doesn't have all day to
write a voluminous and legally exacting example) that both cars are
keeping neck and neck throughout the trip. Whenever the dirty car
struggles and requires additional throttle angle over that of the clean
car (here's a tip: any non-slowing event), dirty boy's fuel delivery
volume is GREATER than clean boy's.

The dirty car has an efficiency problem which, strictly from an A/F
ratio standpoint, can be corrected with an ECM and sensors. WHEN
corrected, more fuel is required to achieve an identical power output
vs an identical setup equipped with a clean air filter.

Toyota MDT in MO

 

Nope, that's not what I'm saying.
Did you see the part where I mentioned that (for instance) Ford
MAF sensors up-date BARO readings at wide open throttle. If as
you claim you were involved in the design of such systems, you'd
know that wide open throttle represents -increased- pressure, not
reduced pressure as your reply states.

To a point, problem is, they do not have infinite ability to
compensate, and when they're lied to, problems occur.

Really? You read the post?

<snippage duly noted>

 

And if he's using a Macintosh...

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

 

Bzzt! When in open-loop mode, the O2S is ignored, therefore it has NO
effect on the amount of fuel injected during open-loop conditions. You
were obviously telling a fib when you claimed to have once designed EFI
systems and MAF sensors.

"Is not."

 

Naw, that's when Macintologists start preaching the Gospel According to
Jobs.

-DS (uses Macs...they're my computers, not my religion. They're still just
better, though! ;-) )

 

Y'know, Whoever is really not doing himself any favours by delaying his
response to the post below, for his stalling is giving me time to think of
other means by which clogged air filters reduce fuel economy. For example,
most vehicles sold in North America have automatic transmissions. Dirty
air filter --> less airflow through engine --> less power at any throttle
opening --> driver must push accelerator down farther to attain a given
acceleration --> automatic trans kicks down out of top gear and torque
converter unlocks more often --> reduced fuel economy.

Are we havin' fun yet?

 

And a modern transmission, adapting itself to the driving style it
thinks it's seeing, starts getting even quicker to downshift...