al503

Best post of this thread. As with everything, there is a tradeoff. Lexus isn't going to spend all that money (direct injection, high compression ratio, etc.) on getting the class leading power output of a 3.5 just to starve it for air with the secondary filter.

I'm not saying you won't see avery slight gain but it's probably negligible and there must be a good reason they spent the money to engineer it in.

Cleric

If you mean Exhaust Gas Recirculation, aka EGR, then yes then this should not be near the filter, however vapors do exists within the crankcase and are often released back into the intake via Positive Crankcase Ventilation usually through a PCV valve. If you look at the stock intake pipe you will see a tube that that is attached to the intake pipe b/w the TB and Filter. The filter is there to prevent excess vapors from escaping back into the environment when the engine is off.

250for06

Wow i guess lexus should have hired you in designing this filter maybe they can get more that 305hp.
That filter is there for a reason and it's definately not because they want to restrict air flow and give you less horse power.

Hey people that want to do this MOD is fine, DO IT . but don't make DUMB arguement about giving you more horsepower.

Until you have dyno proven fact. you do not have my permission to take it off!!

tonyxcom

I'm just going to take my airbox off completely and put pantyhose (black, for the stock look) over the throttle body.

If you guys want to argue over a 10th of a horsepower, go ahead.

ba-b4

If you guys did the mod and looked at the 2ndary filter and saw the thickness you'd know that it's at least the difference between a clean and dirty stock filter and that's enough for me to warrant taking it off. Like I said I've never seen any other car with this 2ndary filter on the intake box lid before so you can't do any damage by removing it. Also what happens when your primary filter gets dirty and the dirt starts getting embedded into the 2ndary filter? This 2ndary filter was not meant to be removed because you have to snap off the clips to take it off so eventually all of you might have to take it off anyway lest you get that dirt into your intakes a few yrs down the road. I would even go far enough to say that this is a design flaw by lexus to not make the 2ndary filter removable.

Whether it's worth it or not I would say why not? As long as you don't crack the frame of that second filter you can put it back to stock and nobody will ever know the difference and it doesn't cost you a penny. The only reason maybe is because of the laziness factor. Honestly if some of you guys go through the trouble effort and spend hundreds of bucks to buy HKS/Blitz drop in filters and a smoother stock JoeZ tube I wouldn't know why you wouldn't do this easy mod that will guarantee you a bit better air flow. Actually if you got yourself a aftermarket drop in you'd be silly not to remove the 2nd filter because even if you have better flow through the HKS/Blitz the bottleneck would then be the 2nd filter right? Anyway every little bit helps however small cuz the effects are cumulative. And to you 250 owners you guys especially need every little bit you can get.

Tony1

Had I grew up and lived in Japan maybe they would have and by the way it's 306*HP not
305. I'm assuming this is your first car, but it's common knowledge that almost every car's air intake system is restricted to some extent, due to it's need to filter out airborne particles.. Taking out this 2nd filter (which no other car that I have seen has) will increase air flow FOR SURE. Now if you're arguing that no intake or no exhaust system will increase Hp, then I don't know what to tell you, But taking the 2nd filter will out will definatetly increase airflow, doesn't take a genius to figure that out, If you actually have seen this filter that is..

Lets Drive

iTrader: (3)

It appears you're right on both of your post. A quick search has shown its an emissions hydrocarbon filter, and is put in place to meet all current emissions standards, including those which will be phased in by 2007. It also assist Lexus in marketing the vehicle as an ultra low emissions vehicle.

The link below details some information on hydrocarbon filters.

This "hydrocarbon trap" is placed between a car’s air cleaner and engine where it can capture hydrocarbons that are escaping through the air intake. This position is desirable because the air intake system contributes as much as 50% of total evaporative emissions.

The trap adsorbs hydrocarbons that are emitted when the engine is stopped. Once the car is started and driven, the trap releases the hydrocarbons into the engine where they are burned. In this way, the new hydrocarbon trap continually regenerates itself.

http://www.engelhard.com/Lang1/xDocI...up1/SubSiteID0

Cleric

This is interesting logic. Just because no other car has this filter, no damage will come of it on this particular car?

How is this a design flaw? Is it because it actually serves a purpose that is perhaps greater than the 0.1 hp loss it may cause and is not meant to be removed?

Believe it or not, the dirtier the primary filter becomes, the less likely it will allow dirt particles to pass through.


All I will say is everyone has a right to do what they want to their $36K+ vehicle, but to just blurt out pure assumptions without good logic is sort of


Flowrate efficiency is dependent on many things. Filter surface area comes to mind and if the stock filters have adequate surface area to meet engine flow requirements over its entire operating range, then things such as filter thickness has no significance.

Cleric

Good find! This is exactly what I was referring too. Thanks.

4TehNguyen

iTrader: (1)

since it appears to be a filter does it get replaced eventually

Tony1

Actually now that i've read the last posts, along with the fact that it wasnt meant to be a "replaceable filter" seems to suggest that Lexus never had any intention of this 2nd filter
trapping any dirt particals that may have escaped the primary filter. Seems to be more of
an enviromental issue, now I'm def taking it off

ba-b4

Okay mr logic man if you don't want to take it off don't nobody is forcing you. If you looked at the thing you'd know that no damage would happen if you removed it. I can't prove it by any scientific means but if you had any common sense in you. Then you can tell taking this piece off won't hurt the car. I said it's a design flaw simply because it can't be removed to be cleaned or replaced. If you didn't eventually it'll get clogged with dirt over time so that'll mean replacing the airbox lid which I'm sure lexus service would be all the more happy to do for you at a price. Do what you guys want but for me taking this thing off seems like it will help more than hurt performance. If you guys care more about emissions then don't do it.

gsrthomas

iTrader: (1)

I will take mine out too when I get my new IS. Does the IS250 have this 2nd filter??

It clearly wont harm your engine if its intended for emissions.

javyLSU

iTrader: (21)

IMHO, it appears to me that this is not so much a "backup filter" as it is an "airbox lid" to keep particles and dirt out of the air intake box when removing it becomes necessary, or perhaps as has been mentioned already, an environmental/emissions feature.

Because of the fact that a dirty air filter allows LESS air and LESS dirt through (which is why changing it regularly is a gas-saving and performance enhancing measure), the idea of having a "backup filter" would be completely redundant unless this is a better grade filter, filtering out finer particles and is much, much more restrictive. Since this is non-replaceable, this REALLY wouldn't really make any sense at all - I know I'll be keeping mine on, at least until I know more facts...

Javier

ff_

Aftermarket intakes and exhaust systems don't make HP. The only thing in your car that makes power is the engine. Everything else just detracts from the engine's true potential.