My oldest stepson wants to replace his 1995 Pontiac Firebird Formula's air filter with a K&N. Would this make the car get better or worse gas mileage? It seems as though the air-gas ratio would increase giving it more power but worse gas mileage. Maybe I'm wrong. Since it would allow the engine to breath better maybe this would improve the gas mileage.
At any rate, I'd like to know the truth about this before he drops any cash on the K&N. If it's going to make the car use even more gas than it already does, he'll probably drop the idea altogether.
Extremely doubtful that he would see a gain or loss in power or mileage. Try this test. Take the air filter completely out and drive it. It won't run any better or worse unless your current air filter is clogged and restrictive.
An air filter has nothing to do with fuel economy. The K&N will help the car to breath better, thus allowing it to perform better. Not to mention with cleaning, you will save on the cost of paper filters.
On a stock car, you might get .5 (1/2 of a HP) power increase at wide open throttle. That little amount of increased air flow will not cause the injectors to go richer then normal. Charles
I threw a K&N on my 01 Trans Am. Fuel economy change - negligible. (I track all my fuel mileage in a spreadsheet.) Performance - maybe a 1/2 tenth at the quarter mile. (13.11 NA, 12.18 with 100 shot... over 50 passes at the strip.)
Why spend the $50? Because a paper element was $25 and I was replacing it every year... so it's cheaper in the long run for a K&N for this car. (Wife's Beretta... not so - $50 for the K&N, $5 for the paper one.)
You car pretty much gets all the air it needs at normal throttle opening with the stock filter set up. Anything you do to increase air flow at less than full throttle is a waste, because the only real restriction is the throttle plate. Once you open the throttle all the way, then the K&N may help. But only if it really passes more air than the paper filter, and the throttle body is capable of passing that extra air into the engine. One side effect of the K&N is that because it does allow more air into the engine, it also allows more dirt. Which defeats the purpose of the air cleaner.
Different air cleaners have different amounts of resistance to airflow. If a K&N has less resistance (debatable) it can accomplish this a number of different ways. One way is making the filter media more permeable - which will let in more dirt. But, another way is if the permability of the media is the same, you can increase the area of it - ie: more pleats - which also reduces air resistance of the media. You can also use media that is designed differently. (probably more expensive than plain paper, of course)
In short, filters and their design are considerably more complicated than your making them out to be, and thus your rule of thumb is pretty useless.
To a certain point. Pleating simply increases the area of the filter, while adding more pleats might seem like a good way to go, what actually happens is that the box gets filled up and adding more pleats forces the pleats to close up and actually cuts down on the area available. Plus reducing the area that the dirt can sit on. So, you will find that a filter like that will plug up faster, and probably not pass enough more air to begin with to make a difference.
Dick is claiming the K&N lets in more dirt. I have no argument with that because I am not even talking about that.
What I am saying is that the rule of thumb the other respondent posted - which is that if the filter lets in more air it lets in more dirt - is a bunch of poppycock.
There is nothing in Dick's study that contradicts this or even addresses this issue.
As I said, better filter media could be designed that would allow greater airflow and remove just as much dirt. If you believe Dick's study, then the K&N filter doesen't use better filter media. But the K&N isn't the reference standard for filters. Just because this hypothetical better filter media might cost 20 times that of paper, doesen't mean it can't be designed.
I would invite you to look over the filter designs used in the Space Shuttle and other esoteric installations where cost is not an issue. I would bet that you will find that these filters do indeed have much better airflow than paper, and remove even more dirt, with a smaller media area. And undoubtedly they will cost
100 times that of paper, knowing the US Government. ;-)
Once again this depends on the area of the airbox. But don't you know that stacking air filters is a common trick in drag racing? Of course it's possible to do that when the filters are round and cover a carburetor.
I also said there are other ways than just increasing the pleats.
For another example of filter media, you can buy an electrostatic filter for your home furnace that uses a set of charged wires to apply a charge to the dirt as it passes through the filter, then attract the dirt to a plate where it is held. These filter out far smaller particles than paper can, and have much lower air resistance, with the downside that you have to wash them frequently, and of course you also need a power source.
A fact often overlooked by most people: The media it's self (cotton gauze type) is not only a better Media for filtration. The fact that it is a WET type filter also has something to do with filtration. This is often over-looked.
Paper Media filters are a low cost item. They let thru an "acceptable" around of dirt by Automobile Manufacture Standards. Washable, Reusable, Oiled Cloth Gauze type filters cost more to produce. Since the lower cost item good enough to keep an engine going 300K+, vehicle makers see no reason to use a higher maintenance, higher cost item. Which does make perfect economical since. They leave it to the consumer to choose the higher cost, and install it them self's. This is an item that will not void any US Automakers warrantee.
People also forget that such filters when used in high dust area's also require a Course Media filter. Else wise larger partials will clog the finer, oil impregnated media. Most Pre-Filters for the filers are made from Large cell foam rubber. The cell is the void, or air gap. Some small engines (Industrial & Lawn mowers) only use a Mid Size Cell Foam Rubber filter. Most of those are supposed to be oil coated. They are washable. The service life is anywhere from 2 years to 15 years. Yet they must be cleaned as part of preventative maintenance ever 25 to 500 hours (depending, some are recommend for 3 times what they should go).
Very few people do P-M on their vehicles, let alone equipment. They just run them till something breaks, wears out, or fails.
Another thing people often forget is High End air filters for automobile HVAC, Hospital HVAC, Building HVAC, and Residential HVAC are often made from woven fine media cloth fibers. Some have other fibers both natural and synthetic added to them to increase performance in one aspect or another. Where as the standard low end filters for these application are either woven fiberglass strands, or pleated paper elements. Charles
Of course, but given the modern car's lack of space, and small box for the filter, stacking them is not possible. On the other hand, manufacturers have done some interesting things. On a GM from the 60's there would be a round filter box with a short stub pointing off to one side. Today, the intake system consists of a tube mounted so that it takes in fresh air, feeding to the filter box, which is square. The box, of course, is connected to the throttle body. But what is interesting is that the air is fed into the top of the filter, so that a lot of surface area is available. Add pleating and the filter is actually a lot bigger than it would appear to be at first glance.
WRONG GM, Ford and Dodge have all issued statements about reusable oiled filters being a reason to void warrantee repairs. The oil coats sensors and causes problems.
This is incorrect. GM has bulletins out to the effect that an improperly oiled filter can cause problems that range from driveability problems to transmission failures. And will void the warranty.
Do you have a link to that? A TSB? I have a K&N on my TA - it's out of warranty, but I'm curious...
(Oh, and I put the K&N on because it's cheaper than throwing out a paper filter every year - in my case a K&N was only the price of two paper filters.)
Automatic Transmission Shift, Engine Drivability Concerns or Service Engine Soon (SES) Light On as a Result of the Installation of an Aftermarket Reusable, Excessively Oiled Air Filter TSB #04-07-30-013 - (03/05/2004)
Ok, is it possible to get the full text of the TSB? Here's the TSB listings for my car (01 Firebird TA, LS1 V8)
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TSB is NOT listed in there - which is interesting because I'd be willing to bet the F-Body has one of the highest percentage of owner modifications that violate the warranty.... (myself included.) I've had the MIL come on for O2 failure - but in my case I blame the nitrous instead of the K&N. Resetting the light worked and my new AutoTap sits unused...
An air filter will cause a transmission failure? Bull Shit!
Oil covered sensors? When GM stops using a Intake vented PVC system I might believe that.
Let them attempt to void a warrantee of mine or one of my customers for such shit. Ill go thru and find the cause of the failure, then get it re-instated. That's the time a tech tried to blame the use of Nitrous for repeated starter issues, and they voided a warrantee. The problem was a wiring issue that the dumb techs couldn't track. Charles
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