DC-RDX

I began driving a 2008 Black RDX Tech 3 months ago. I heard about the K&N High-Flow filter shortly after discovering the forum here, eager to see how the hell it was installed (if it was easy to do) and what I could expect form it. Unfortunately there wasn't really anybody around who had either purchased and installed one or likewise described how it affected the car on the road.

Well, I took it upon myself to do my own review. I drove the RDX "lightly" for the first two weeks for break in. After this time I began my "regular use" testing with the stock air filter for 1 month. During this time I recorded (via the car's computer) an average gas mileage of 18.6 MPG. I also specifically noted how the turbo kicked like a mule when it engaged over 2100 RPM and how I loved every second of driving it. After this period, I drove over to auto zone and picked up the K&N filter and installed it on the spot in the parking lot. I may have loved the RDX before, but now I lusted for it.

In comparison to the previous months, the RDX turbo no longer felt "forced". In previous situations where I expected the turbo to engage, I found I had to depress the accelerator more and more than I expected to elicit any kind of response. Even when it did respond, the impact felt somehow, lacking. Looking at the gauges closer, I noticed a phenomenon I hadn't really noticed since 7th grade physics classes. In the class we measured the amount of force and work required to pull several objects along the ground. We measured the force (in newtons) by attaching various objects to a spring gauge. During this time we measured not only the "constant" force required to drag an object, but also the initial force required to move it from its starting position Much like stepping on a spring scale, the needle would jump to a high reading before leveling off to a lower number.

On the RDX I saw the same phenomenon of "initial impact" in the use of the turbo. When the turbo engaged, the needle would spike as it pulled against the high resistance stock filter. However, once this initial impact was gone, the actual amount of air being pulled through would decrease, and the needle would fall on the gauge, having to constantly battle the lack of air flow. This initial force also resulted in a significant amount of turbo lag, in that the car would seem to suddenly jerk forward with torque as opposed to engaging smoothly. The K&N Filter resolved this problem rather elegantly. By allowing air to flow easier into the turbo there is almost a complete removal of turbo lag and resistance. Compared to stock it now spools quickly and without fuss or sudden jerking -- it's almost as if somebody had completely reworked the throttle while you were blinking. At highway speeds I found that the engine acceleration was silky smooth when passing cars, a powerful and increasing wave of torque rather than a sledgehammer. In addition, I began averaging an average MPG of 19.8, 1.2 over stock. As much as I wish I could provide meaningful figures for 0-60 times, I didn't have (and still don't have) a reliable and accurate way of measurement. Overall it seems the same (if not a bit faster), but again, that is not backed up in any way by measurable figures.

Now last week after driving with the K&N filter for a full month I replaced it again with the stock filter to take it in for service. Needless to say I had forgotten the limitations this placed on the car and found myself extremely wanting. I tried to see how long I could live with the stock filter after the service to see if the difference was really that noticeable.

One day.

I lasted for one day before throwing the stock air filter back into the garage and lovingly replacing the K&N.

So, in closing, I have found that the K&N High Flow Air Filter may not necessarily increase horsepower or 0-60 times, but it has had a marked increase on my gas mileage as well as the enjoyment I get out of everyday driving. If you are looking for an affordable and easy way to refine the drive of your RDX, I highly recommend it.

john50

Was this the K&N Typhoon Air Intake System, or just the high flow filter?

I understood that K&N and AEM had not produced a cold air intake system yet, but after seeing your report, I found the Typhoon system on K&N's website.

cwepruk

I have a K&N filter and removed all the junk before the airbox. it makes more noise. That is about it. I honestly couldn't feel a couple hp anyways.

Comparing your mileage to the mileage when brand new is a bit of a stretch too. My mileage improved decently after a few thousand miles. Right now, with the K&N in, all city driving, a few quick bursts, but mostly reserved driving, I'm getting 19 mpg.

cwepruk

And since I can't edit...

Here is the K&N "intake"

http://store.knfilters.com/search/pr...Prod=69-0017TS

Something like $320+ for a filter on a stick. A bit ridiculous. At least the CPE one replaces all the rubber tubing.

wwest

You do realize, do you not, that if the K&N has/had a higher intake resistance to airflow the results would be very much like you state...??

Higher restriction to airflow = improved MPG.

And that boost guage "spike" you see might very be due to an inrush of airflow from a freer flowing OEM filter and then the boost control activating to reduce the acceleration rate of the turbine.

Higher resistance K&N, less "inrush" airflow, nice and smooth(er), "throttled" turbine speed/boost rise.

crazycated

I just bought a K&N filter 33-2382 also and it works great you could just feel the difference in the power and how smooth it picks speed and also hear the air just rushing in if you don't have one you should get one it's better than a stock air filter .

wwest

before anyone buys a K&N "oil" type filter you should browse the internet regarding MAF/IAT module failures. Say Google for:

K&N MAF

Most modern day vehicles use a low mass, smallish "hot wire" mass airflow sensor. A very "high gain" temperature resistance coefficient sensor. This sensor is heated using a constant current flow and the level to which it is cooled by the intake airflow determines the signal level. In order for the MAF signal to be accurate the IAT, Intake Air Temperature, sensor is used to measure the temperature of the intake airflow.

Now, think of a freshly oiled, CAREFULLY oiled, K&N air filter in the (100 MPH..??) WIND TUNNEL of your intake at WOT and high engine RPM and the WICKING of oil from the filter that will undoubtedly occur.

It doesn't take very long to develop even a very slight coasting of oil on both the MAF and the IAT sensors and not long thereafter a coating of fine dust particles in top of that.

Now, anytime you ask for a level of torque for acceleration the emissions system will switch from the A/F mixture control oxygen sensor to the MAF/IAT and the now contaminated (insulated) sensors will NEVER indicate an intake airflow as high as actual. That will very likely result in knocking/ping due to a LEAN mixture, initially detected at a level below your hearing by the new wide bandwidth knock/ping sensors.

That, in turn, will result in degraded engine performance.

crazycated

So I guess your talking from experience right because I have been using K & N filters on various cars for 16 years and never had any problems or are you just saying this because it's something you read on some order article or think thats what's going to happened has it been tested thats accurate.

wwest

The only experience I have with HIGH FLOW (K&N..??) filters is the ones we have run at the 24 hours of Daytona the last 8 years, mostly in Porsche GT3s.

Otherwise just research, comprehensive reading and common sense.

GOTTSPD

So, you've run the rolex 24 hour race w/ K&N filters for 8 years now, but you're saying you are concerned about them damaging the engine? That strikes me as a contradiction....

wwest

Damaging the engine in 24 hours.....

NOT....!!

Contaminating the MAF/IAT in 24 hours....

NOT....!!!

Contaminating the MAF/IAt within 10,000 miles....

YES....!!!

Damaging the engine via DIRT in 40-50,000 miles....

YES...??

K&N filters make their reputation, justifiably so, in the days of carburation.

But they have no place in today's marketplace.

LuvMyRDX

Sold my Accord with 226k on it still running well. ~150k of that was with a K&N replacement element installed. No problems with oil build-up anywhere in the intake and I think 225k speaks for itself as far as damaging dirt getting into the engine. I've been using K&N's in just about everything I've owned the last 17 years from carb'd to fuel injected to direct injected diesel. No issues at any time with any of them. Maybe I'm lucky...who knows, but it's a pretty bold statement to say they don't belong in today's marketplace when millions of customers will beg to differ.

crazycated

I just think he's been reading to many articles in magazines unless he could say the he f*** up an engine by running the K&N filter from experience but sounds like a lot bull not common sense .

cwepruk

I've used them as well and as long as you don't overoil them, there usually aren't any issues. But you have to keep in mind, that the guy you are talking too said they have a higher resistance to airflow, yet he calls them high flow and uses them on his (??) Porsches. Contradiction much?

MMike1981

ok so what is the underlying point here?

filters lubed with oil will ruin an engine?

this guy talks out of his ass, lets just keep that in mind. if you know his post history you will now that some of this guy's ideas are out on mars.

so really tho, what is the underlying theme here? ALL/SOME/MOST ? oil lubed air filters are dangerous to an engine? I find that hard to believe.

my friends who have cars costing 6x's as much as an acura would contest that statement. Dont you think if such awful horrible results came from using K&N or a like product, consumers would know about it?

wwest

I said that K&N has a higher resistance to airflow...??

Where, when...??

If I did say that is was definitely a mistake on my part.

The Porsche use is by TeamSeattle Children's hospital racing guild and is only for the 24 hour period of the race. I would NEVER recommend consistent use of the K&N other than in the racing venue.

Personally were it solely my decision there would be no air filter use at all.

wwest

If you care to have a look at the K&N site and their attempt at rebutting this generally, widely and publically known, information adverse to K&N, you might come to realize that where there's smoke there is generally fire nearby.

"...this guy's ideas are out on mars..."

I wonder if Tom Edison often heard that statement, or one of like kind.

MMike1981

...and now he compares himself to edison.

the saga continues

MMike1981

a company trying to make claims of their product being better by refuting others? wow, amazing, ive never heard of such a ridiculous thing.

the way you are talking, you could take a look at every single item for sale and say wait a minute, if they are telling you one thing, there must be a fault! why should i buy this pilot pen vs this flare pen? mac vs pc? oil lubed vs reg?

cwepruk

Short memory?

MMike1981

its what happens when u get old. memory loss & cynical.

wwest

No, but my guess is that you do not know the meaning of "IF".

As in "if" the K&N has/had a higher intake resistance to airflow....

cwepruk

And then you went on a whole tirade correlating the original poster's K&N impressions to being more resistive to airflow including this:

and

Let alone pretending higher resistance to flow gives you better mileage.

wwest

If you don't believe that higher resistance to intake airflow will yeild improved FE then I would like to make a serious wager.

Right after I wire your throttle plate so it can't fully open.

cwepruk

Make the wager. Call on Audi and BMW who are removing their throttle plates (or having them wide open) at certain conditions to reduce pumping loses and improve efficiency.

wwest

Sure, tell me your "table limit" and we'll get together and write up the rule book.

But the rules will involve/require typical city stop and go and highway cruising and NO sustained race speeds or race track runs.

cwepruk

Good day.

wwest

Pumping losses...

I'm confident someone will correct me if I'm wrong on this...

Pumping losses are the result of the crankcase being at atmospheric pressure as the piston moves downward on the intake stroke while the piston top side has a vacuum or at least a partial vacuum.

If you happen to have a manual tire pump, say for a bicycle, you can replicate these pumping losses by blocking the pump's air inlet port (as in a fully closed throttle plate, or in the above BMW example, an intake valve not fully open or not reminaing open for the full duration of the intake cycle) as you "raise" the pump handle for the intake stroke.

The only way I know to eliminate those pumping losses, at least mostly so, is to allow the piston, during the intake stroke, to "pull in" a non-oxygen containing portion of "atmosphere", say PURE nitrogen, wherein both sides of the piston would remain mostly at atmospheric pressure and the fuel injection valves could remain fully closed.

Can someone help me out by explaining how/why BMW is eliminating pumping losses, even partially so, via using valve timing, a reduced valve opening period during the piston's intake stroke, vs simply using the throttle plate.

It seems to me that in either case you end up with a the same level of vacuum on the top side of the piston and atmospheric pressure on the bottom. In both cases the idea is to restrict the level of oxygen entering the combustion chamber/cycle in order to "throttle" the engine.

Note: It is my belief that pumping losses are not a major issue when operating at or near WOT "mode". Furthermore it is my understanding that pumping losses, along with frictional losses are the major contributers to poor FE at typical highway cruising speeds, and therefore OVERALL.

So let's apply the "ointment" where the "hurt" is.

wwest

Edited beyond 5 minutes..Pumping losses...

I'm confident someone will correct me if I'm wrong on this...

The major pumping losses are the result of the area under the "intaking" piston being at atmospheric pressure as the piston moves downward on the intake stroke while the piston top side has a vacuum, or at least a partial vacuum. Obviously a more important issue when operating at low or partial throttle openings, the clear majority of most of our driving time.

If you happen to have a manual tire pump, say for a bicycle, you can replicate these pumping losses by blocking the pump's air inlet port (as in a fully closed throttle plate, or in the above BMW example, an intake valve not fully open or not remaining open for the full duration of the piston's intake stroke) as you "raise" the pump handle for the pump's intake stroke.

The only way I know to eliminate those pumping losses, at least mostly so, is to allow the piston, during the intake stroke, to "pull in" a non-oxygen containing portion of "atmosphere", say PURE nitrogen, wherein both sides of the piston would remain mostly at atmospheric pressure and the fuel injection valves could remain fully closed. That is one of the purposes of EGR, Exhaust Gas Recirculation, allow the piston to "pull-in" at least a portion of "atmosphere" that contains little or no oxygen.

Can someone help me out by explaining how/why BMW is eliminating pumping losses, even partially so, via using valve timing, a reduced valve opening period during the piston's intake stroke, vs simply using the throttle plate.

It seems to me that in either case you end up with a the same level of vacuum on the top side of the piston and atmospheric pressure on the bottom for an equal level of engine performance, power production. In both cases the idea is to restrict the level of oxygen entering the combustion chamber/cycle in order to "throttle" the engine.

Note: It is my belief that pumping losses are not a major issue when operating at or near WOT "mode". Furthermore it is my understanding that pumping losses, along with frictional losses are the major contributers to poor FE at typical highway cruising speeds, and therefore OVERALL.

So let's apply the "ointment" where the "hurt" is.

MMike1981

West, we all must just be crazy.

other than racing, if you actually do it, do you work in a vehicle engineering field? what do you do with all this knowledge (im not agreeing that you are right) but seriously, where have you or will you apply this stuff, because honestly, either 99% of the ppl working in this field for a living and making & developing technologies for vehicles, according to you, at least inferred from your posts, are not only dead wrong, but crazy for even attempting.

where do you stand with automotive technology? so far, from something as simple as a CAI, all the way up to BMW's new tech....you are on the other side of the fence...why? dont you think if there were different ways or BETTER ways, these guys/corps would be pursuing them and doing it? what is the deal with you , seriously.

cwepruk

And what difference does it make if it's pure nitrogen vs regular air? Fuel injection valves? You mean injectors?

Pulling air though a restricted throttle plate requires more work for the engine which reduces efficiency slightly. Removing the throttle and controlling engine speed with variable valve timing/lift allows that restriction to be removed.

No one said all pumping losses were being eliminated either, just the portion caused by the throttle plate. Since most driving is done with 1/4 throttle or less (light acceleration and cruising for example) pumping losses are significant.

DC-RDX

Jesus Christ, would you all just let it go?

For fucks sake.

I concluded that I enjoyed the drive of the RDX better with the K&N filter. If you are concerned about fouling of the MAF due to over-oiling, then it can be cleaned. Quite easily. This thread is about opinions on the filter in the real world by people who have tried it.

Nobody gives a FLYING FUCK about your internet cock fight. Take it elsewhere.

wwest

***1:

First, let's assume there is NO throttle plate, NO way of metering, no way whatsoever, 100% nitrogen flow at local atmospheric pressure INTO the combustion chamber.

Now, if the intake were 100% nitrogen the engine would quickly stop running.

But now, if you could somehow "meter" an appropreate level of oxygen along with a totally UNRESTRICTED flow of nitrogen to attain the level of engine performance you desired at any given moment the pumping losses due to desparate atmospheric pressure differential would be TOTALLY eliminated.

***2:

"..pulling air through a restricted throttle plate requires more work for the engine..."

And if the "restriction" to intake airflow is imposed by a late opening or prematurely closed intake valve, what then..??

It seems to me that the only thing the BMW technique accomplishes is a reduction in the losses due to relatively minor level of turbulance caused by the (fully open ??) throttle plate.

***3:

For the majority of automotive engines, engines with a significant power "reserve", pumping losses are insignificant at WOT (virtually NO throttle plate airflow restriction) in comparison to idling or simply cruising along at a relatively constant speed.

wwest

***1:

No, my guess would be that only about 0.001% of ppl working in this field are designing and selling, or attempting to sell, "snake oil". How many of you today remember Andy Grannettli (sp)..??

***2:

I guess I simply do not believe that the actual intake airflow temperature from a CAI is really enough colder than the OEM intake to justify the cost. And if you check around the INTERNET for professionals that have actually made measurement of various CAI kit performance you will find that most have concluded that CAI's have ZERO benefit.

That all being said I quite firmly believe that even a marginally competent engineer designing a CAI would be certain sure it wasn't subject to radiant heating from the nearby HOT engine components.

***3:

I don't think I have said that the BMW technique isn't beneficial, just that it does NOTHING to reduce or alleviate engine pumping losses within the engine RPM and torque range of most importance in attaining improved FE

***4:

"..better ways..."

You make my point, thanks.

Nether CAI's nor K&N can be considered a "better way" which is exactly why the majority of "guys", nor corps, are not pursuing them.

***5:

"pursuing them...."

Along those lines I believe I am already on record stating that were I to design a CAI, then I would cut a hole in the hood immediately above the most downstream point possible, just upstream of the throttle plate, for an alternate airflow intake path. With/upon WOT I would use a servomotor to open a bypass for the normal intake filter and ducting allowing the intake airflow, UNRESTRICTED intake airflow, via the new duct routed to the hole in the hood. That would also give the driver all the intake NOISE s/he might desire.

That would also require a separate MAF/IAT module, mounted, and calibrated, to supply signal inputs to the engine ECU during the WOT periods.

A combined CAI, noisemaker, and a K&N substitute.

wwest

I was wrong, yet again.

A "take-off" on the BMW technique.

Pumping losses could be almost totally alleviated/limited on 4 cylinder engine by letting the cylinders fill, FULLY fill, no thottling of intake flow restriction at anytime. Then proportionally delay the closing of the intake valve into/during the compression stroke, simuilar to the Atkinson cycle. That would allow the (just prevously) fully filled cylinder's "charge" to be reduced, proportionally reduced, forced back into the intake, proportional to the engine power needs of the moment.

Note that for a 4 cylinder engine an opposite cylinder would be currently intaking air from that very same intake manifold in accordance with the power demands/needs of the moment. Anything other than 4 cylinders would require a method (2 cycle engine reed valve..??) to prevent reverse airflow, surge pulses, OUT of the intake manifold, "backwards" through the MAF/IAT module.

You could probably use the same technique with a 6 cyclinder engine provided it used the Miller cycle.

crazycated

Hey wwest why don't you just shut the f*** up you don't even own an RDX do you have anything else to do than post crap on all the threads you go on because sounds like crap nobody is trying to write a book on hear except you on every thread you go on keep it short it's just for chatting and comments not written a f***** book get the hint .

wwest

And guess what..??

You're one vote out of THOUSANDS.

01clsstock

lets make that 2 votes out of thousands

wspy

Lets make it 3.

And mines worth a THOUSAND!