You just don't get it Ed, certainly it's not different, but it is in addition to the throttle plate. It is an additional restriction! All filters cause a flow restriction, regardless of their flow capacities!
Exactly, and the entire intake system is an accumulative restriction, each individual restriction has it's own distinct effect. Simple airflow dynamics at work here.
EVERY SINGLE brand new clean air filter ADDS restriction to the system regardless of it flow rate abilities.
Yet...
"My Name Is Nobody" wrote in message news:629qj.3475$eD3.1942@trndny05...
I absolutely get it. Tell me why you think the filter restriction affects fuel economy more than the throttle plate.
And again, why do you seem to believe the restriction of a properly serviced air filter has a significant effect on fuel economy?
Absolutely true, but the restriction is trivial as far as it's effects the ability of the PCM to adjust the A/F Ratio. For a properly serviced air filter the pressure drop across the filter at WOT will be around 0.5 psi or less (for a stock engine). At part throttle operation, the pressure drop across the filter is likely to be in the hundredths of a psi range. The only time the small restriction of the air filter is going to be meaningful is when the throttle is wide open. Even then, the air filter restriction is likely to be less than a fraction of the total restriction from air intake to cylinder. Assuming the engine is in good condition and the PCM has completed a drive cycle so that it can learn the long term fuel trim, the A/F Ratio will not be out of the acceptable range even when running in open loop mode. PCMs incorporate long term fuel trim parameters to compensate for changes in engine parameters (sensor drift, air filter restriction, increased back pressure in the exhaust, increased flow from the PCV system, etc). The long term fuel trim is learned when the car is running in closed loop and is used to modify the original look-up table fuel delivery parameters. While in closed loop mode, the A/F ratio is continually adjusted based on the feedback from the O2 system. Closed loop mode is the primary operating mode of the vehicle, and the only one that really matters as far as average fuel economy is concerned. The time spent in open loop mode is trivial for most street vehicles.
One more time - I am not claiming that the filter restriction will not reduce maximum air flow and therefore possibly reduce maximum power. I agree that it may. I am only saying that a properly serviced air filter will not have a measurable effect on fuel economy. The change in the restriction of the air filter over time is an insignificant factor as far as the ability of the PCM to properly adjust the A/F Ratio is concerned.
Ed
To start with I have 70,000 miles of detailed records that say it does.
Again, I have 70,000 miles of detailed records that say it does.
It has nothing to do with wide open throttle! My car gained 2 miles per gallon from a simple filter element change, and like saw WOT for a total of
5 or 10 of those 70,000 miles.It was a bone stock engine.
BULLSHIT!
I'm sure it did by 20,000 - 70,000 miles at 70+ miles a day.
I am saying you are WRONG, My detailed records show the exact opposite to be true...
I am not wrong, at least in the general case. So why do you think there is a difference? What is your explantion? Do you think your PCM wasn't able to maintain the correct A/F ratio? Without seeing your data, and knowing what was changed, I can't say you are right or wrong for your specific situation. However, I keep records on all my vehicles, and I've never seen any indication in a change in fuel mileage related to changing air filters. Consumer Reports recently tested fuel economy "myths" and came to the same conclusion - dirty air filters (and I am talking about normally dirty filters, not some widly plugged filter) don't measurably effect fuel economy. The operating mode of modern fuel injection system is designed to handle changes in vehicle operating parameters and adjust the A/F ratio to the proper range (as determined by the vehicle manufacturer). If the system can't maintain the proper A/F ratio, then it should set the check engine light. If the A/F ratio is in the proper range, and assuming the vehicle is being operated in the same manner, the fuel economy should not change. If you are claiming that just changing the air filter significantly affected your fuel economy, then I would suspect that either something was wrong with your car, or that you changed your driving style.
Ed
The stock RD boxes were very restrictive and I had to replace the small jets with bigger ones (can't remember the sizes) also. I used two paper cone filters though, not K&N. That was my second Yamaha "Road Death" :)
Carbureted two stroke - not what I am talking about. Intake restrictions can definitely effect fuel economy of a carbureted engine, and when you are dealing with two strokes...who knows - they are extremely sensitive to changes to the air path.
Ed
In case you are intersted, you can see my fuel economy records at
Evidently so is a four stroke dual intake runner 4 valve per cylinder computer controlled EFI engine...
There is no reason that it should be. In fact, if the feedback system is functioning as designed there should be very little change in the A/F ratio no matter what you do to the intake. If the PCM can't maintain the proper A/F ratio, then it should set the check engine light.
Ed
BULLSHIT!
I've posted three different links to documented dyno tuning of new FORD cars with simple new air intake systems, that exceed the PCM's ability to properly adjust the air fuel ratio without changing the programming. There are many many more links showing the same. If indeed these peoples information (dyno charts with A/F ratios) indicating a filter changing DOES cause the PCM to run the air fuel ratio TOO LEAN, is held up against your undocumented insistences that the PCM can maintain the proper A/F ratio, seems like you are wrong.
You love to use that term, yet I would argue you keep dishing out the same references without really considering the facts. Tell me why you think just changing the air filter (not the complete air intake system) can effect fuel mileage. Two of your three references were ads, so you should view them with suspicious. All three were concerned with WOT performance, not normal everyday driving. Trying to predict changes in gas mileage based on WOT performance tests is risky at best.
The first reference you cite, really just an ad ,
Point 2 - I doubt if what they say is even true (or at least not in sense that you interpret it). The ad provided no numbers, it just made a BS statement - "Even when replacing the air filter ONLY to a higher flow assembly, the air/fuel ratio leans out at an alarming rate." What is the air filter assembly? Just the actual filter element, or everything in front of the throttle body? What is an alarming rate? How can "replacing the air filter assembly ONLY to a higher flow assembly" lean out the A/F ratio at an "alarming rate" when in the same article they claim that replacing the air filter assembly won't result in a mixture "lean enough to cause engine durability concerns." If there are no durability concerns (at WOT by the way) what the heck is "alarming."
Point 3 - Mostly the ad is talking about a complete intake system replacement, including the MAF. Certainly if you start screwing around with the MAF you may need to retune the PCM. I never made any claims about what happens when you do things like that. I am only talking about air filters in the OE intake assembly. Once you start screwing with the other components (particularly the MAF), all bets are off.
Your second reference was another thinly disguised ad
Point 2 - There are no charts showing that changing the air filter ALONE will cause the engine to run to lean. And although the charts do show changes in A/F ratio when the COMPLETE AIR FILTER ASSEMBLY is changed (again the charts are showing only WOT operation), I don't see anything alarming. Without data at part throttle operation and after the PCM has learned the long term fuel trim, I can't see where the information presented can be used to say anything about the effect changing the air filter has on fuel economy.
Point 3 - I suspect they did not bother to complete a drive cycle in between the tests. Unless you compete a drive cycle, the PCM does not have a chance to learn new long term fuel trim parameters. Since they are measuring things at WOT (i.e., not in feedback mode), you need to complete a drive cycle to make sure the PCM has learned the correct long term fuel trim so that the A/F ratio will be corrected for open loop operation.
Your third reference
Ed
OH Fer Crying out loud! I've told you no less than six times!!! Yes that term is perfectly applicable here. You are blowing smoke up everyone's ass on this issue, and somehow you expect no one will call you on your BULLSHIT!
I logged every single fuel fill up and all maintenance (all done by me)
75,000 miles on a new car, both before and after a simple air filter element change in the stock air box, with ZERO other changes.Before air filter element change 7~25,000 miles with a very consistent 24.5 mile per gallon fuel mileage. After air filter element change 25,000~75,000 miles with a very consistent
26.5 mile per gallon fuel mileage.All NORMAL everyday mixed highway / surface street commuter miles! Near ZERO WOT!
"My Name Is Nobody" wrote in message news:UL2rj.4$Uq4.2@trndny02...
Well, you have repeated the same claim six times. It would help if you posted your personal data that supports this claim. I have explained why the ads you referenced were irrelevant to the discussion.
You have never tried to explain why just changing the air filter should result in a large increase in fuel economy. You posted several thinly disguised ads that were testing things at WOT. They were not relevant to the discussion of the fuel economy of an otherwise stock vehicle's fuel economy in normal day to day operation. You also claimed you have personal documentation to support the idea. Maybe you do. Without the data and knowledge of what was changed, I cannot comment on your particular situation. I certainly would not dispute the data for your personal case. However, in general what your are claiming cannot be true. You must have some reason for believing that changing the air filter improved the fuel economy. Under normal driving conditions, the A/F ratio is adjusted by the PCM in response to the O2 sensor. No matter what happens in the intake system, the PCM should be able to adjust the A/F ratio back to the desired value. So I think it would be difficult to claim that changing the air filter changed the A/F ratio in a way that would significantly affect fuel economy. And unless you are at WOT, the restriction across the air filter is not a determining factor in intake system pumping losses. For a less than "maximum" power level, the air flow into the engine is controlled to less than maximum. It is the total restriction from the air intake to the back of the throttle plate that matters. It is largely not relevant whether the restriction is at the air filter or the throttle plate (unless you are at WOT). And again, the air restriction of a properly service air filter is trivial. One of your sources provides back up for this. See
Most of my vehicles have shown improvements in fuel economy over time as they have been broken in. My 2 Expeditions (a 1997 and a 2003). took the longest to achieve maximum fuel economy. The 1997 average 13.84 mpg for the first 25 k miles and 14.29 mpg for the next 25 k miles. The 2003 averaged
14.7 mpg for the first 25 k miles and 15.13 for the next 25 k miles. For both vehicles this represents about a 3% increase in fuel economy, and there were no changes other than routine maintenance. This is not as dramatic as your claimed 8% improvement, but I think you can get the idea that you might need to look closer at your data.I assume your data also shows a gradual decrease in fuel economy between air filter changes? Or is it your claim that you changed to the lower restriction filter, got a huge fuel economy improvement that you attributed to the filter, and that it stayed steady over time, showing no decline between air filter changes (or cleanings)? If it doesn't show a decrease between filter changes (or cleanings) why not? If you believe changing to low restriction air filter increased the fuel economy by 8%, you must also believe that the fuel economy decreases as the filter becomes contaminated. I've never seen any indication that this is the case for any of my modern vehicles (again my data is at
Finally, does your claim of an 8% improvement in fuel economy pass the reasonableness test? Do you thing Ford, or GM, or Toyota wouldn't change to an air filter that improved fuel economy by 8%? How great would that be in their drive to meet CAFE requirements?
Ed
conditions.
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.
Nobody" wrote in message news:XnAlj.5641$5h6.763@trndny09...
leaner-than-ideal
after about five minutes it becomes impossible to tell who is who. Its getting to be the same with this thread, A point that I think was overlooked is that nobody pointed out that at normal idle the intake is almost 100% restricted, (closed). The almost part being the small amount of air needed supply the idle circuit. The engine changes speed (RPM) by removing that restriction to allow for more air as the demand increases. Point of fact, if that restriction isn't there then the engine will continue to spin up until it self-destructs. You need restriction in order to control the engine output. Now while I've never measured it I would suspect that the intake is still restricted by over 90% even when cruising at 70. Mileage is not effected solely by air flow changes, what has to change is the air/fuel ratio. If sufficient air is flowing to feed the fire then you're golden. With current electronics measuring the air coming in, the exhaust going out and adjusting the fuel feed in between the air/fuel ratio is held static. Another misconception is that the engine has to work harder in order to suck the air through a dirty filter than it does through a clean one. It doesn't. (Hard to believe I know). The engine isn't sucking air through the filter, it is sucking it past the throttle plate, which is almost completely closed to start with. (If it wasn't the engine would spin up out of control.) Air flows across the filter as a result of the pressure drop. The amount of restriction needed to maintain a certain RPM at a certain load is fixed. Restriction of the air filter, intake, throttle body, manifold & outside pressure are all cumulative but overall pressure drop is the same for a specific load. An example, if you were measure the pressure drop between the outside air and just aft of the throttle body you would have a number that would directly correlate with how much effort the engine is expending to suck the air in. Remove the entire intake tract so there just a bare throttle body and take the measurement again you would still have the exact same number. In other words the engine worked just as hard to suck air through the intake as it did to suck it straight out of the atmosphere. The throttle would be slightly more closed to compensate for the loss of the restriction caused by the missing components but the overall result would remain the same.
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