Rx400h K&n Air Filter Installation

[tommygunn]

I just installed a K&N air filter on our 2008 RX400h (I personally feel they do make a difference, and this is the fourth car I have added one to). I have a question though, for those who have added one as well. Normally when installing the filter, it just drops into place with the bottom of the filter dropping into the airbox. The airflow enters the top of the filter and flows through. With the 400h, the bottom of the filter inserts into the bottom of the air filter box. To me this seems like the reverse of previous vehicles, as air flow comes into the bottom of the unit and exits through the top of the filter. But it fits like a glove; whereas when reversed (like previous cars); the filter will not fit. Any answers would be appreciated.

[Gryphon]

I just installed one. It only fits one way.

Tom

[NeoN]

hey i installed one a while ago, i would take out the stock restrictive filter, both of them and i think install it face down, like the other guy said, it only fits one way., dont force it in like i would do lol

[Gryphon]

Neon, are you referring to the second "filter" that sits behind the primary air filter? Did you remove that one too? If so, how is it held in?

Tom

[RXREY]

Can I simply take out the second air filter? The first one comes out very easily but the second one is pretty well stuck in there and I don't want to force anything until one of you tells me how and or if I should. Rey

[RXREY]

I saw the K&N air filter for about $44. but it also states that it is for 2007-08. I have an 06, why would it be different for the newer years? Rey

[RXREY]

I just installed a K&N air filter on our 2008 RX400h (I personally feel they do make a difference, and this is the fourth car I have added one to). I have a question though, for those who have added one as well. Normally when installing the filter, it just drops into place with the bottom of the filter dropping into the airbox. The airflow enters the top of the filter and flows through. With the 400h, the bottom of the filter inserts into the bottom of the air filter box. To me this seems like the reverse of previous vehicles, as air flow comes into the bottom of the unit and exits through the top of the filter. But it fits like a glove; whereas when reversed (like previous cars); the filter will not fit. Any answers would be appreciated.

It doesn't make it louder does it? The last thing I want is for this great car to be loud! Did you take off the second air filter as NeoN suggested? Rey

[wwest]

I just installed a K&N air filter on our 2008 RX400h (I personally feel they do make a difference, and this is the fourth car I have added one to). I have a question though, for those who have added one as well. Normally when installing the filter, it just drops into place with the bottom of the filter dropping into the airbox. The airflow enters the top of the filter and flows through. With the 400h, the bottom of the filter inserts into the bottom of the air filter box. To me this seems like the reverse of previous vehicles, as air flow comes into the bottom of the unit and exits through the top of the filter. But it fits like a glove; whereas when reversed (like previous cars); the filter will not fit. Any answers would be appreciated.

It doesn't make it louder does it? The last thing I want is for this great car to be loud! Did you take off the second air filter as NeoN suggested? Rey

Other than LOUDER is there another "advantage" to one of these aftermarket "free-flow" engine intake filters..??

[riwyle]

I just installed a K&N air filter on our 2008 RX400h (I personally feel they do make a difference, and this is the fourth car I have added one to). I have a question though, for those who have added one as well. Normally when installing the filter, it just drops into place with the bottom of the filter dropping into the airbox. The airflow enters the top of the filter and flows through. With the 400h, the bottom of the filter inserts into the bottom of the air filter box. To me this seems like the reverse of previous vehicles, as air flow comes into the bottom of the unit and exits through the top of the filter. But it fits like a glove; whereas when reversed (like previous cars); the filter will not fit. Any answers would be appreciated.

It doesn't make it louder does it? The last thing I want is for this great car to be loud! Did you take off the second air filter as NeoN suggested? Rey

Other than LOUDER is there another "advantage" to one of these aftermarket "free-flow" engine intake filters..??

Might give you a slightly faster quarter mile on the drag strip. If not into racing, I see no advantage other than helping the economy by spending more money.

[Gryphon]

Rey. to answer your questions about K&N air filters:

1. They have a lifetime warranty, which means you will only buy one for the life of the vehicle. In lieu of replacing them, you service them by cleaning with either K&N's filter cleaner, or a household degreaser. They you re-oil them lightly with K&N filter oil (red).

2. On some vehicles they do increase fuel mileage and/or performance slightly, but don't expect huge differences. Specifically, on a Porsche 968, several enthusiasts have documented around 5-10 HP gains with careful dynomometer comparisons.

3. They make the engine slightly louder, mainly at full throttle. I somewhat like the slightly more throaty sound on my RX.

4. K&N claims that their filters catch finer particles than stock filters. I don't know if this has been measured, and the results will obviously vary depending on which stock filter they are being compared to.

Tom

[RX400h]

It's very tough to have better filtration AND higher flow. I've used K&N filters for over 20 years and in every case, hydrocarbon concentration in each of the cars, steadily increased. If you want all-out performance and accumulate low miles every year, I don't blame anyone for going with a hi-flow filter. However, if you want your vehicle to last 200,000 miles and you do pile on the miles, stick with the OEM filter.

How can you tell if your filter is letting in more dirt? Get an oil analysis while you have the stock filter in-place and do the same after a time while running the high-flow filter. If the dirt level is higher after the same number of miles, you'll know what the likely culprit is.

[wwest]

It's very tough to have better filtration AND higher flow. I've used K&N filters for over 20 years and in every case, hydrocarbon concentration in each of the cars, steadily increased. If you want all-out performance and accumulate low miles every year, I don't blame anyone for going with a hi-flow filter. However, if you want your vehicle to last 200,000 miles and you do pile on the miles, stick with the OEM filter.

How can you tell if your filter is letting in more dirt? Get an oil analysis while you have the stock filter in-place and do the same after a time while running the high-flow filter. If the dirt level is higher after the same number of miles, you'll know what the likely culprit is.

Okay, first of all, and I think all would agree, the only advantage for any "free-flow" intake air filter occurs ONLY at WOT and fairly high engine RPM, LOADED engine RPM. Otherwise the throttle plate itself is the major obstruction to HIGH VOLUME intake airflow.

So.

If a free-flow intake air filter is so desireable why hasn't someone designed an intake bypass that opens an intake path around the filter with WOT...??

You would then have the advantages, long engine life, of the OEM filter but still have that extra 5-10 HP (whatever, at least the THRILL of the intake noise/sounds) with WOT.

I rather doubt that street use of any vehicle would allow enough WOT, filter bypass, to compromise the engine life.

[wwest]

Oh, lets not forget that your RX400h engine is already derated via factory "tuning" (de-tuning..??) and therefore NEVER reaches its full potential for HP/torque to begin with. That may mean the engine never breathes heavy enough to take advantage of ANY free-flow aftermarket intake air filter.

[RX400h]

It's very tough to have better filtration AND higher flow. I've used K&N filters for over 20 years and in every case, hydrocarbon concentration in each of the cars, steadily increased. If you want all-out performance and accumulate low miles every year, I don't blame anyone for going with a hi-flow filter. However, if you want your vehicle to last 200,000 miles and you do pile on the miles, stick with the OEM filter.

How can you tell if your filter is letting in more dirt? Get an oil analysis while you have the stock filter in-place and do the same after a time while running the high-flow filter. If the dirt level is higher after the same number of miles, you'll know what the likely culprit is.

Okay, first of all, and I think all would agree, the only advantage for any "free-flow" intake air filter occurs ONLY at WOT and fairly high engine RPM, LOADED engine RPM. Otherwise the throttle plate itself is the major obstruction to HIGH VOLUME intake airflow.

So.

If a free-flow intake air filter is so desireable why hasn't someone designed an intake bypass that opens an intake path around the filter with WOT...??

You would then have the advantages, long engine life, of the OEM filter but still have that extra 5-10 HP (whatever, at least the THRILL of the intake noise/sounds) with WOT.

I rather doubt that street use of any vehicle would allow enough WOT, filter bypass, to compromise the engine life.

...probably, liability reasons is my guess. many folks install electric exhaust cutouts to bypass their mufflers, but this really doesn't harm the engine. In fact, some new cars come with a similar type of bypass that is activated by throttle position.