Has anyone tried K&N Engine Air Filters?

FUD being?
Only had 23 years as a mechanic tells me foam filters are not good for road cars. Race cars use them but also have short between overhaul lives.
Toyota and every major manufacturer use paper element air filters. Who you going to believe, major auto manufacturers or a foam filter maker selling you a foam filter?
If you believe a foam filter manufacturer then why not Donaldson, a manufacturer of filters for heavy equipment. Have a look at how many foam filters the most respected manufacturer of filters in the world for heavy industrial machines and transport trucks make.
http://www.odms.net.au/files/organise/donaldsonfilters/product_file_attachment/7_13_42_Air%20Cleaner%20Element%20Booklet%20-%20F111080.pdf
Yep, none!!!

 

It's not a foam filter. 23 years as a mechanic and you've never seen one and don't know what they are??? I smell FUD...

 

As Clack of Click and Clack would say, Au Contraire, piston puss. Internal combustion piston engines are enhanced gas pumps. Anything that increases the efficiency of pumping gases increases the efficiency of utilization of the fuel used to power that pump. For instance, opening up the exhaust ports and passages will reduce the power needed to force out gas. Domed combustion chambers with opposed multiple valves eases the passage of intake and exhaust gases, reducing the power needed to draw in and expel gases.

Increasing engine function as a gas pump also increases efficiency of the engine as a power source.

The efficiency of the Prius Hybrid is most dependent on the ratio of ICU to electric motor use. That said, anything that increases the ICU as a gas pump and as a heat engine will increase the efficiency of the entire system. Increase of heat engine efficiency works when the ICU is a smaller heat sink to combustion conversion from heat energy to mechanical energy. That means running as hot as possible.

Why do you think Toyota invests in that coolant storage tank and pump? Why the huge plenum in the intake manifold? That's "race car" if I've ever built a race engine. Every dragster I've ever built engines for had NO cooling system except for the oil pump! I certainly wish I could have had an offset cylinder arrangement, like the Prius ICU, in the race engines I built. The closer to vertical the thrust from piston to crankshaft at combustion conversion the less energy wasted to cylinder wall forces!

The Prius ain't your father's race car. It's better!

 

In this case we aren't talking about changing the efficiency of pumping the gas, but the mass throughput. It is not more efficient to burn more gasoline. It does however provide more power. There are those who mistakenly assume a low DP filter is going to improve their mileage. Barring some sort of oddity with the set up it will not. But it does provide somewhat more air and power when called for.

Well, we aren't talking about changing the shape of the combustion chamber. And I've done exhaust mods. They gave the vehicle more power on the top end, but didn't help the low end--seat of the pants suggested I was losing low end torque and my runs confirmed it. It didn't help my fuel efficiency...nor did the air intake mod. But I did get considerably more horsepower overall and the vehicle still ran clean. Did the mods in stages, testing each (also had the ECU remapped but it was still CARB legal.) Changed tires and shocks/struts/sway bars/tower brace and made it a fun little car. Several times after running against some higher performance vehicles the other driver caught up wide eyed and asked, "what did you do to that thing?" ...looked bone stock and that was half the fun.

I was getting a lot more power, but burning more gas because I was making use of it very liberally. I haven't done that in years.

 

Sorry Shawn, I feel like a dill. I was thinking unifilter and FinerFilter not K&N. Believe it or not K&N filters were not all that popular in Australia when I was in the trade.

I don't like the idea of using a washable filter anyway but the K&N is most likely a better filter than unifilter. When it comes to protecting my several thousand dollar engine I'll buy the genuine filters.

 

So, increasing the efficiency of an ICE as a pump will not increase the efficiency of the ICE??? In the case of an ICE, pumping and converting the fuel/air mixture is mass throughput.

You must understand the concept of incremental saving.

Reducing air resistance in the intake stream reduces the power/energy needed to move the piston and create vacuum effects for "natural" aspiration. Providing the plenum in the intake manifold provides a dynamic storage chamber for the moving intake gas stream. Why do you suppose Toyota goes to that extra design, fabrication, and materials expense? To smooth out the otherwise violent pulsing in the intake gas stream, to reduce the power needed for normal aspiration, and to let the computer program have an easier job of reducing fuel use. That is the object of the exercise; to provide high fuel efficiency.

Ah, yes, the ego boost of the secret mod win. And here I thought we were talking about the usefulness of K&N filters to reduce intake air resistance and save money.
They do indeed reduce resistance to the passage of air in the intake stream, a generally good thing, but, most importantly, they also save the expense of 50K miles worth of service charges for paper filter replacement each time you remove, clean, and re-oil that permanent K&N filter on your engine.

And you bought a Prius...why? There is no such thing as direct throttle response in a Prius; throttle position is ALWAYS controlled by computer and throttle control modules. The pedal connects to an electrical device and through that to multiple computers, and all to provide high fuel efficiency along with excellent driving. We drive the equivalent of a mini Cray. All we can easily modify is mechanical efficiencies. For example, in the ICE we can use more efficient filters, in the tires we can use low drag tires.

 

Efficiency doesn't always mean fuel efficiency. One can create an efficiency measurement that is reversed of that. (My Tundra is much more efficient than my Prius in pulling air and gasoline through the engine...and that is not a good thing with respect to fuel efficiency.) The basic problem here is that you are mixing various efficiencies and treating them as all being the same, they are not.

Look, the principle is simple so I'm going to try to explain it to you one last time: 1. The control system is targeting a given air/fuel ratio. 2. Introducing more air doesn't change this ratio since the control system adjusts for the additional air (particularly with an MAF, but also with the O2 sensor in feedback.) 3. You still need the same amount of power to do the same task if driven the same way. (Obviously if you use full throttle acceleration you will take a hit and a greater one if more power is produced by the engine.) 4. Therefore, the combustion efficiency is not changed by the additional air.

What the availability of the additional air does for you is make more power available. It also can change the throttle response as a result on traditional linkages. With the throttle valve open the vehicle will pull harder or acccelerate better (because it is using more air and gas to increase power), but if you think there will be a fuel efficiency improvement as well, you are sadly mistaken.

Yes, and the efficiency for that at given power outputs is relatively fixed.

This has ABSOLUTELY nothing to do with the air input as controlled by the throttle and air filter. You are off in the weeds, just as you were with combustion chamber design. Sure they are important to improving combustion efficiency, but that is not what reducing restrictions prior to the throttle is about. My sports car had ECU controlled swirl control valves in the intake manifold to improve low load/low rpm operation and improve combustion efficiency in this range. Yet, that had next to nothing to do with air intake improvements before the throttle valve...except that to squeeze out a little more power from the engine at high rpm I would have had to pull those SCV valves as even fully open their presence was producing some restriction. I could have gotten more power on the high end and taken an efficiency/drivability hit on the low end.

There is a reason K&N doesn't make gas mileage improvement claims, but does make horsepower claims. Both can be easily measured. One could run the EPA cycle on a vehicle and dyno the car (as well as using time trials.) You can find the dyno results stock and with various K&N set ups. It makes more power. It doesn't produce better gas mileage. Why? Because the EPA cycle has prescribed acceleration and speed profile.

Look, I don't care if a mechanical/cable linkage, the ECU, leprechauns or aliens move the throttle valve to WOT. The fact is that once the throttle is full open (or at whatever its max limit is) the air that can pass through is greater if the intake restriction is less. And the ECU can definitely cope with different quantities of air and varying ambient pressure (weather or altitude induced.) So unless the ECU has a low upper limit on how much air and fuel it will allow, a vehicle will make more power with greater air pressure at the throttle chamber...until the pressure is high enough that the charge will detonate during the compression stroke.

I bought the Prius for fuel efficiency. My one concern before the test drive was that it might lack adequate power for passing/merging. As long as it could provide the basic acceleration requirements I was satisfied. So far that has not been a problem for me. If it does become one or I anticipate one (mountain driving), then a K&N will be first on my list give a small incremental bump.

And I can tell from observing other Prius drivers on the hills and entrance ramps around here, many are much more aggressive with the throttle than I am anymore. While I'm not using full throttle, some of them clearly are flogging every last bit out of it when accelerating.

 

Talking gobble-de-gook about fuel/air ratios and combustion efficiency does not change the fact that requiring LESS fuel by reducing operating power requirements is what K&N filters provide. Or don't you agree that providing lower operating power requirements is the object of many fuel efficiency mods?

WRONG!

The power required to operate the engine is a large part of the power produced by the engine. Anything that reduces the power required to OPERATE the engine improves the efficiency OF THE ENGINE! That includes gas pump efficiency as one of the many efficiencies that can be modified.

One corollary example from racing. The Chevy mouse motor had a high performance oil pump available as a heavy duty engine part, ostensibly for the truck line. That oil pump is perfectly adequate for the oiling requirements for any high performance modified Chevy rat motor, which it fits perfectly, and saves, at 8200 RPM in a 396, approximately 15 horsepower over the box stock rat motor oil pump! The savings on the 454 opened to 510 at 7200 rpm are equally spectacular.

15 horsepower more AT THE FLYWHEEL, dynamometer demonstrated, from the SAME fuel/air inputs because it costs less energy to lubricate the engine!

Do you understand now why reducing intake air flow resistance saves FUEL? For a given net power output the fuel required to run that air pump is lower! That's why the plenum, that's why four valves per cylinder, that's why a hemispherical combustion chamber, that's why the variable valve timing, and that's why you use low resistance K&N filters, to say nothing about the cash saved. This is the same size engine as the mid 60s VW. Getting a stock VW any where near 80 mph was almost impossible but I regularly take this Prius over 100 mph and get 28 MPG while doing it.

Not wasting fuel while pumping gas is a good thing.

 

rusty,

You are wrong about air "efficiency" in a throttle controlled system. You keep putting apples to oranges "comparisons" up. You can dismiss the correct analysis as "gobble-de-gook" but it only illustrates that you don't understand the system.

K&N's own claims, independent dyno tests, and real world results illustrate how incorrect you are about efficiency. I've done what I can to point out what you are missing in your reasoning, but if you want to continue tilting at windmills, good luck to you.

 

Amazing! So the throttle is what ultimately determines the efficiency of the system.

Every ICE has a throttle!

The efficiency of the system is NOT controlled by the throttle.

The throttle simply determines how much of the power potential of the system will be allowed at any given time.

The size, shape, and surface finish of the gas ports, the position and angle of stream flow of any fuel injectors or jets, the timing of valve opening and closing, the presence or absence of port boundary layer effects, the presence or absence of combustion chamber squish areas, and the presence or absence of extraneous air flow restrictions, all these are determinants, and enhancements, of efficiency. And what efficiency is that? Why that efficiency is the efficiency of the system as a gas pump, the MAJOR efficiency that counts in an ICE.

The thing is, K&N filters reduce extraneous air flow resistance, thereby contributing to ICE efficiency.

Ask someone who builds racing engines; their success in life depends on accurate knowledge of just such facts.

 

The only person saying that the throttle itself determines the efficiency is you.

Reducing "extraneous air flow resistance" does not help if you are AT THE SAME ENGINE LOAD! And why are you at the same engine load? Because you (or the ECU) are holding the throttle slightly more closed to produce the same power output. And what does that do? It provides the exact same intake manifold pressure as before which is why you have the same power output. "Efficiency" improvement gone. The increased pressure before the throttle is eaten by the throttle valve. That is its job.

Or let's take the other case: you get more power at a given throttle opening because you get more air, you but still use the accelerator the same way. What happens then? You accelerate faster...and that is not more efficient in most instances.

I take it you are not an engineer and don't have experience designing flow control loops (gas and liquid)?

 

For the first time you are correct!

I was too impacted with PTSD from the Korean War to sustain the concentration needed for the degree in physics I tried for. I just expressed my abilities other ways. For a time, I built unique engine combinations to various racing rules. I built championship NASCAR modified engines. I built championship AHRA and IHRA injected fuel dragster engines. At the time Adams and Enriques had NHRA injected fuel sewed up with their modified 315 CI Chrysler Hemi UPS truck engines. I modified heads for the Boston Shaker when it was still naturally aspirated and still from Alston, Mass. I modified cylinder heads for championship SCCA Formula VW and Formula Ford engines. I built championship SCCA 350 CI small block Corvette carburetted engines that were so efficient some drivers timed as fast as the fastest SCCA Corvettes with injected 427 CI big block engines over the same course.

No I'm not degreed. I'm a man who found out what it takes to make a good engine into a better engine, and made a good living at the time. It's just amazing what you can accomplish by reading the proper research reports and, after using Occam's razor, build accordingly. At one time that was the definition of an engineer. Does writing assembler for extremely compact machine code count?

Reducing power waste in any engine causes that engine to produce more usable power. You reduce power waste by reducing operating resistances, one of which is gas flow resistance.

Trying to blind 'em with science or baffle 'em with BS doesn't work. The proof is at the checkered flag, or the timing lights, or the lap counters. Or, in this case, at the gasoline pump AND the parts counter.

 

Sometimes you just can't teach an old dog new tricks, and this appears to be an example of that. You still don't appreciate the problem. You can't get the right answer if you can't understand the problem--that's my #1 rule for troubleshooting: define the actual problem first (frequently it differs from the problem one is initially asked to solve, that's where experience helps the most.) You keep going off on tangents and missing the core of the problem. Designing for power/acceleration is not designing for gas mileage. Sure getting more specific horsepower from a smaller block will give an advantage, we aren't talking about changing blocks or heads or any of the moving parts. We are talking about what is before the throttle valve. It's a different optimization and you are missing the key to doing that.

With respect to optimizing for mileage for the K&N the problem is this: You have fixed load and throttle controlling the air feed to generate that load. If you understand that, the answers become obvious.

With respect to optimizing for power/acceleration: The load is no longer fixed and it becomes a WOT problem. Different problem requiring a different analysis.

I've done what I can to explain it to you. K&N is careful not to make the claims you are making, while they do back the power claims. (If people buy the filters thinking they will get a mileage boost, that helps K&N, but they are careful not to say that...and at the same time careful not to disprove it because folks like you coming to the wrong conclusion can still generate more sales.) I have yet to see anyone do an EPA mileage test cycle with the K&N in a standard MAF/O2 sensor system and demonstrate greater mileage, although I have seen dyno results for power vs. rpm with/without. Notice the difference is that in the first the load is fixed, in the second the load is the max available at given rpm.

I have commented that you keep talking about parts AFTER the throttle. You are analyzing the wrong side.

So dazzle me here. Explain how in the world you are going to get greater efficiency at the same load with the K&N with the same pressure and temperature air in the intake manifold. Because that is exactly what the air filter/throttle are going to give you if you target the same acceleration and cruise speed. (Notice we aren't racing so holding the throttle at the same position does not apply.) Whatever vacuum there was before for the profile is what you will get again, but the throttle will be slightly more closed at this value. Net result is the same intake manifold pressure & temp. The mass meter reads the same flow rate. The injectors give the same pulse. The O2 sensor gives the same feedback as before. But the throttle position is slightly different.

So stop the hocus pocus, and give me some numbers to back your "efficiency" claim. I'm particularly interested in what you are going to use for the absolute pressure after the filter (K&N vs. stock--in front of the throttle valve) and after the throttle valve. This is where you are going to get in trouble...because you and I both know what is going to happen when you have the same throttle position. The engine will get a larger gulp of air and produce more power. Sounds great...until you realize that the power demand is the same (not running WOT). To get the same acceleration and cruise profile the driver will open the throttle less, producing the same load. And why? Because the engine is getting the same gulp of air as before--same pressure and temperature, same fuel pulse. The combustion will be unaffected by the change at a fixed load, as will the O2 sensor. All the parts you have been so concerned about see the same conditions as before. Efficiency as measured by gas mileage will be the same.

You aren't reduing power waste this way, because the throttle valve goes ahead and wastes it for you to produce the same load/acceleration. (If it didn't you would be running WOT whenever an ICE was running as a way to improve mileage--good luck with THAT!!!.) You've drawn the box incorrectly.

By your logic one should remove the throttle valve altogether, since it reduces "efficiency" and increases "gas flow resistance" by your definition.

 

I think to simplify, the throttle plate causes vastly more air restriction than the filters ever do unless they're very dirty.

Removing air restriction upstream doesn't help if the throttle is not open all the way because the throttle plate will introduce it's own restriction. With a wide-open throttle, you will get more power with the K&N, but WOT is a very inefficient way to run the Prius.

 

You are so wrong! An automobile is NOT a fixed load, it is a dynamic load. The size of the load has very little to do with general operating efficiency. But even then, it is a dynamic system with dynamic loads.

Your above sentences, taken together, is entirely gobbledegook.

The K&N filter works with a W(ide) O(pen) T(hrottle) or a partial throttle to reduce the dynamic load for any engine on which it is installed.

I repeat my very simple, easily understood Occam's razor analysis:
"Reducing power waste in any engine causes that engine to produce more usable power. You reduce power waste by reducing operating resistances, one of which is gas flow resistance."

In fact, show me the numbers that demonstrate no effects of flow resistance ahead of the throttle! If there is no effect then we never need change any filter no matter how clogged it gets.

DUH!

Even the simple matter of reducing pre-throttle flow resistance produces a power saving effect on the total system.

It's the grain of sand problem; displace it and the world changes. Change ANY element in a dynamic system and the effects are evident throughout the system.

Your insistence on disconnected analysis is leading you astray. No matter how small the effect, it is there. Claiming it is insignificant compared to the throttle plate is illogical. It's effect is real.

 

Um, trying to keep this civil and polite, here goes

I put a K&N/Downey intake kit on a 1990 Toyota 4Runner V6 I used to have. That year 4Runner had to suck all it's intake air around the driver side headlight bucket. The Downey kit bolted up to the factory mass air flow meter, a vane meter, and used a large conical K&N under the hood.

The fact Toyota designed an air intake system that had to suck all the combustion air through the headlight bucket, was pretty dumb. I didn't dyno it, but it did feel peppier, and sounded pretty cool too when I put my foot into it

By far, the most important gain for that 4Runner was putting in the Downey headers, which eliminated the poorly-designed factory crossover pipe. With the Borla cat-back, that rig actually *gained* around 2 mpg, and was way, way peppier

My FJ, I see no need to touch it. Factory stock, it has way more power than my old 4Runner ever did. Actually better fuel economy too. I have yet to see any reports from FJ owners who gained anything - except expense - putting on various cold air intake this, header that, cat-back whatever

I may put on a snorkle kit though. There are some advantages if you drive on gravel roads, as the FJ sucks all its intake air from over top of the passenger side wheelwell. It also looks pretty cool too

 

No, the dynamic load is unchanged if you are targeting the same acceleration. The dynamic load in this case won't differ either. That's what is wrong with your anaylsis. If you are accelerating at the same rate and cruising at the same rate, the throttle is going to adjust to provide the same load. You aren't heating or cooling the gas, or even changing its flow pattern inside the intake manifold. Both the filter and throttle valve are simple DP restrictions when you consider them.

You appear to be entirely unable to take your racing knowledge and apply it to a non-racing fuel efficiency problem. Unfortunately, it's not uncommon for talented techs (and some engineers) to be unable to make such a transition for different types of optimization.

Nope, but your statement above just illustrates an inability to apply your knowledge to a different system.

The difference between us is that I understand what you are saying and don't need to dismiss it (other than to explain how you are misapplying portions), but you don't understand what I'm saying, so to you it is "gobbledegook." You conceded as much with your "mini-Cray" comment.

 

My suggestion to you, read Hobbit.

Prius heat-efficiency mods

Read both the first and second versions. Then, think about exactly WHY Toyota designed in a system to keep engine temperature as high as possible at all times.

Cool air and ram air intakes to NOT increase fuel mileage. High temperatures do increase fuel mileage and reduce emissions, as does ANY attempt to reduce energy waste. In the midget displacement system of the Prius, heat is one of the largest energy wastes, along with others, one of which is the minuscule energy waste caused by systemic intake flow resistances.

Anything that reduces energy waste in the Prius increases fuel efficiency. That, after all, is one of the major aims of the Prius system; lower costs to both the wallet and the atmosphere. Speaking of which, K&N filters help both.

 

Just follow rusty's advice and pull out that pesky throttle valve to get rid of that "systemic flow resistance." :cheer2: Sheesh... some people never learn.

 

I was specifically referring to a 1990 V6 4Runner. The intake and especially the passener side exhaust crossover pipe, was very poorly engineered by Toyota. The crossover pipe had many sharp bends, and really held back that 3.0 V6

Folks who bothered to dyno that vintage 4Runner with the Downey intake and Downey header kit, with Borla catback - same kits I had installed in mine - gained upwards of 76 HP and had a much broader torque band, compared to stock. As I didn't have to put my foot into it so much, that was how I gained 2 mpg

With the FJ, imho there is nothing to be gained by catbacks, headers, CAI, etc. If you examine the headers and especially exhaust crossover, Toyota has clearly learned from their early mistakes. Despite the FJ being heavier than a 1990 4Runner, with a much larger V6, it has much better useable power, and better fuel economy

About the only thing I can see doing to my FJ is putting in the snorkle kit. It looks cool, much in character with the FJ design, and would prevent dust ingestion on gravel roads. The stock location is in the front passenger wheelwell.

After driving through flooded streets this summer, at perhaps too high a speed, there was evidence of water in the airduct and filter housing of my FJ. Apparently, the drain holes worked, as I'm pretty sure I would have been aware of water ingestion into my motor

With the Prius, I don't see how adding a different air filter or a cai would help matters. Perhaps if one bypassed the tb heater, but this should never be done in a freezing climate as the throttle blade could ice and stick. That's why TB's are now heated with engine coolant