Air filter and mpg.

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.

Reply to
Whoever
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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*

Reply to
Daniel J. Stern

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.

Reply to
nospam.clare.nce

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.

Reply to
nospam.clare.nce

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?

Reply to
Whoever

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

Reply to
Daniel J. Stern

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')

Reply to
Bill Putney

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.

Reply to
aarcuda69062

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

"Maccin' off". There.

Reply to
Daniel J. Stern

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!

Reply to
Daniel J. Stern

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

So much for the 'kinder, gentler' Neil.

Oh, *that* dirty!

Reply to
aarcuda69062

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

Reply to
Daniel J. Stern

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

Reply to
marvinstockman

...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".

Reply to
Daniel J. Stern

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

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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

Reply to
C-BODY

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